azaserine and Pancreatic-Neoplasms

We investigated short (6 months) and long (12 months) term inhibitory effects of low (200 ppm) and high (400 ppm) dosages of acetylsalicylic acid (aspirin) on exocrine pancreatic carcinogenesis. It is known that exocrine pancreatic carcinogenesis can be detected by the presence of atypical acinar cell foci (AACF) in pancreas. We investigated possible inhibitory effects of acetylsalicylic acid in an azaserine-treated rat model. AACF were produced in rats by injection with azaserine according to previous studies. Our findings showed that the number, volume and diameter of pancreatic AACF were reduced after acetylsalicylic acid application. These observations suggest that acetylsalicylic acid may exert a protective effect against neoplastic development of pancreatic acinar cells in azaserine injected rats. Our findings corroborate reports in the literature concerning the effects of aspirin in reducing neoplastic development.

Topics: Acinar Cells; Animals; Anti-Inflammatory Agents, Non-Steroidal; Anticarcinogenic Agents; Aspirin; Azaserine; Carcinogens; Colorectal Neoplasms; Disease Models, Animal; Humans; Male; Pancreas, Exocrine; Pancreatic Neoplasms; Rats; Rats, Wistar

Topics: 4-Hydroxyaminoquinoline-1-oxide; Aging; Animals; Azaserine; Cocarcinogenesis; Diet; Disease Models, Animal; Ethionine; Gonadal Steroid Hormones; Nitrosamines; Pancreatic Neoplasms; Precancerous Conditions; Vitamins

In order to understand the evolution, histogenesis, and biological behaviour of exocrine pancreatic carcinoma, some reproducible experimental models have been developed in certain rodent species. To date, more than 16 chemicals, many of them structurally unrelated, have been shown to induce pancreatic tumors. Although some of these chemicals appear species specific in their effect on the pancreas, others have been shown to be capable of inducing pancreatic tumors in more than one species. In hamsters, the administration of diisopropylnitrosamine or its oxidized metabolites leads to the development of ductal adenocarcinomas that histologically resemble human pancreatic carcinomas. The histogenesis of the ductal type of adenocarcinoma in hamsters is complex, and appears to involve both the duct cells and dedifferentiated acinar cells. All pancreatic tumors in rats develop from acinar cells showing variable degrees of differentiation, regardless of the type of carcinogen used. The type of pancreatic lesions that develop in mice are also of acinar cell origin. In guinea pigs the tumors are adenocarcinomas of the ductal type and are shown to be derived from dedifferentiated acinar cells that have undergone duct-like transformation. Irrespective of the type of tumor that develops in these experimental animals, all of these models can be successfully used to evaluate the various modifying (risk) factors and biological behaviour of these neoplasms.

Topics: 4-Hydroxyaminoquinoline-1-oxide; 9,10-Dimethyl-1,2-benzanthracene; Animals; Azaserine; Carcinogens; Corn Oil; Cricetinae; Disease Models, Animal; Guinea Pigs; Hypolipidemic Agents; Mice; Nitrosamines; Nitrosourea Compounds; Pancreatic Neoplasms; Rats

A morphologically distinctive type of pancreatic acinar cell foci, different from hyperplastic nodules and adenomas, in rats has been recognized for two decades. The lesions have been observed to occur spontaneously and to be induced experimentally. They consist of enlarged acinar cells with abundant cytoplasm of altered staining characteristics and prominent nuclei. There is, however, a wide divergence of opinion among investigators regarding the nature of the lesions. As a result of different interpretations and classifications, many terms have been given to them. Based on morphologic characteristics, the author has designated the lesions as hypertrophic foci, a descriptive morphological term. The biologic significance with particular reference to age and the relationship with acinar cell neoplasia is discussed. Also included in the review are similar lesions in other rodent species.

Topics: 2-Acetylaminofluorene; 4-Hydroxyaminoquinoline-1-oxide; Age Factors; Animals; Azaserine; Cell Nucleolus; Cell Nucleus; Cricetinae; Endoplasmic Reticulum; Female; Golgi Apparatus; Male; Mitochondria; Muridae; Pancreatic Neoplasms; Rats; Sex Factors; Species Specificity

Topics: Animals; Azaserine; Carcinogens; Carcinoma; Cell Transformation, Neoplastic; Cells, Cultured; Diet; Disease Models, Animal; Female; Male; Microscopy, Electron; Pancreatic Neoplasms; Sex Factors; Time Factors

Topics: 4-Hydroxyaminoquinoline-1-oxide; Adenocarcinoma; Aminoquinolines; Animals; Azaserine; Carcinoma; Cricetinae; Neoplasms, Experimental; Nitrosamines; Pancreatic Neoplasms

Hydatid cyst is a zoonotic infestation caused by Echinococcus granulosus, and it is known that some parasites found in humans cause cancer in humans or some may have a protective effect against cancer. Cancer is one of the most serious health problems of today and it has been shown in some studies that parasites such as Echinococcus granulosus can have an inhibitory effect. The aim of this study was determined as whether Echinococcus granulosus has an inhibitory effect on exocrine pancreatic cancer with the help of the azaserine-rat model used in different cancer studies.  Material and Methods: During experimental process a total of 45 male Wistar rats used, 14-day-old male Wistar rats were divided into groups according to the experimental protocol, administered azaserine injection protocol or kept as a control group without azaserine injection. Animals are grouped as Group 1, Control Group (group not treated with Azaserine and not injected with protoscolex.) (E-A-) (n=7); Group 2, Group injected with (IP) Azaserine only (30mg/kg) (E-A+)  (n=8);Group 3, Group injected (IP) with protoscolex suspension of 1 cc only (E+A-) (n=15);Group 4, Group injected both Azaserine (IP) and protoscolex suspension (IP) (E+A+) (n=15). Atypical Acinar Cell Foci (AACF) load in the exocrine pancreas of each rat was measured quantitatively with the help of a video image analyzer and the AACF load was calculated with the help of a mathematical model. Results: Findings showed that the Atypical Acinar Cell Foci (AACF) burden was statistically significantly lower in the Azaserine+ protoscolex (Azaserine-injected-protoscolex-implanted) rat group compared to the other groups, suggesting that Echinococcosis in the azaserine-rat model could inhibit the development of precursor foci of neoplastic changes in the exocrine pancreas. Conclusion: The most significant aspect of our study is that it contributes new insights into the controversy that Echinococcosis suppresses pancreatic cancer.

Topics: Animals; Azaserine; Echinococcosis; Echinococcus granulosus; Humans; Male; Pancreas; Pancreatic Neoplasms; Rats; Rats, Wistar

High-fat diet has been considered a risk factor for the development of pancreatic cancer. It is also shown to significantly impact composition and dysbiosis of gut microbiota in both humans and animals. However, there is little information on the effect of high-fat diet on the development of pancreatic cancer or upon the gut microbiota of patients with pancreatic cancer in humans or animal models.. In this study, the effect of high-fat diet on cancer pathology and the gut microbiota was investigated by a carcinogen-induced pancreatic cancer mouse model.. Compared with carcinogen alone, mice with high-fat diet and carcinogen showed more obvious pathological changes in pancreatic tissue; increased levels of proinflammatory cytokine tumor necrosis factor-α, interleukin-6, interleukin-10, and carbohydrate antigen 242; and increased expression of cancer-associated biomarkers mucin-4 and claudin-4 in pancreatic tissue. Moreover, there is a significant change in the gut microbiota between the carcinogen group and the carcinogen with high-fat diet group. We identified that Johnsonella ignava especially existed in the carcinogen with high-fat diet group, which may contribute to pancreatic cancer development.. Our results revealed that high-fat diet changed the composition of the gut microbiota and was involved in carcinogen-induced pancreatic cancer progression.

Topics: Animals; Azaserine; Bacteria; Carcinogens; Claudin-4; Cytokines; Diet, High-Fat; Disease Models, Animal; Drug Synergism; Feces; Female; Gastrointestinal Microbiome; Gastrointestinal Tract; Humans; Mice, Inbred C57BL; Mucin-4; Pancreatic Neoplasms; RNA, Ribosomal, 16S; Sequence Analysis, DNA

We investigated whether the acrylamide formed during cooking carbohydrate-rich foods at high temperatures causes neoplastic changes in rat pancreas. Azaserine, which is an amino acid derivative that has the ability to initiate neoplastic changes in rat pancreas, was injected into 14-day-old male rats once a week for three weeks. Acrylamide was given to both azaserine-injected and non-injected rats at doses of 5 and 10 mg/kg/day in drinking water for 16 weeks after which tissue slides were prepared from the pancreata. Pancreas weights and body weights of rats treated with azaserine and acrylamide together increased significantly compared to the other groups. Moreover, the size, average diameter and volume of atypical acinar cell foci that developed in the pancreata of rats treated with azaserine and acrylamide together increased significantly compared to rats treated with either azaserine or acrylamide alone and control groups. Atypical acinar cell adenoma or adenocarcinoma was not observed in the pancreata of rats in any group.

Topics: Acrylamide; Adenocarcinoma; Animals; Azaserine; Body Weight; Carcinogenicity Tests; Male; Organ Size; Pancreas, Exocrine; Pancreatic Neoplasms; Rats; Rats, Wistar

We studied the eco-toxic and carcinogenic effects of a commonly used 2,4-D acid iso-octylester herbicide on rat liver and pancreas. The rats in Group 1 were fed a standard feed and the rats in Group 2 were fed with standard feed to which was added 200 mg/kg/day 2,4-D acid iso-octylester for 16 weeks. Azaserine, 30 mg/kg/body weight, was injected into rats of Groups 3 and 4 to investigate the effects of 2,4-D acid iso-octylester on the development of neoplasms. After feeding the rats with neoplasms in Group 4 with food including 200 mg/kg/day 2,4-D acid iso-octylester for 16 weeks, an autopsy was carried out on all animals. We found that 2,4-D acid iso-octylester caused the formation of atypical cell foci (ACF) in the pancreata and livers of rats. ACF that were formed experimentally by exposure to azaserine had increased diameter, volume and number of atypical cell foci/mm(2) and mm(3) after exposure to 2,4-D acid iso-octylester. Our observations indicated that this herbicide potentially is a cancer initiator.

Topics: 2,4-Dichlorophenoxyacetic Acid; Animals; Azaserine; Carcinogens; Cocarcinogenesis; Herbicides; Liver; Liver Neoplasms, Experimental; Male; Pancreas; Pancreatic Neoplasms; Rats; Rats, Wistar; Secretory Vesicles

In humans, initial events of pancreatic carcinogenesis remain unknown, and the question of whether this cancer, which has a ductal phenotype, exclusively arises from duct cells has been raised. Previous studies have demonstrated that transgenic expression of the CCK2 receptor in acinar cells of ElasCCK2 mice plays a role in the development of pancreatic neoplasia. The aim of our study was to examine initial steps of carcinogenesis in ElasCCK2 mice, adding a supplementary defect by using a chemical carcinogen, azaserine. Results of posttreatment sequential immunohistochemical examinations and quantifications demonstrate that mice responded to azaserine. Transition of acinar cells into duct-like cells expressing Pdx1 and gastrin, as well as proliferation of acinar cells, were transiently observed in both transgenic and control mice. The carcinogen also induced formation of preneoplastic lesions, adenomas, exhibiting properties of autonomous growth. Importantly, expression of the CCK2 receptor increased the susceptibility of pancreas to azaserine. Indeed, treated ElasCCK2 mice exhibited larger areas of pancreatic acinar-ductal transition, increased cellular proliferation as well as larger adenomas areas vs. control mice. These amplified responses may be related to auto/paracrine stimulation of CCK2 receptor by gastrin expressed in newly formed duct-like cells. Our results demonstrate that activation of CCK2 receptor and azaserine result in cumulative effects to favor the emergence of a risk situation that is a potential site for initiation of carcinogenesis.

Topics: Adenoma; Animals; Antimetabolites, Antineoplastic; Azaserine; Bromodeoxyuridine; Carcinogens; Carcinoma, Acinar Cell; Cell Proliferation; Coloring Agents; Homeodomain Proteins; Homozygote; Immunohistochemistry; Inflammation; Lymphocytes; Mice; Mice, Transgenic; Pancreatic Neoplasms; Phenotype; Precancerous Conditions; Receptor, Cholecystokinin B; Receptors, G-Protein-Coupled; Risk; Time Factors; Trans-Activators; Transgenes

The presence of gastrin and cholecystokinin-2 (CCK2) receptors in human preneoplastic and neoplastic gastrointestinal lesions suggests a role in cancer development. In addition to the growth-promoting action of gastrin, recently a role of the cholecystokinin-2/gastrin receptor (CCK2-R) modulating cellular morphology in cultured epithelial cells has been shown. Here, we have investigated in transgenic (ElasCCK2) mice whether ectopic expression of human CCK2-R in the exocrine pancreas affected epithelial differentiation. Cellular localization of cell adhesion molecules, differentiation markers, and transcription factors was determined using immunofluorescence techniques. Before tumor formation, expression and subcellular localization of proteins of the adherens junction complex, differentiation markers, and transcription factors were altered in ElasCCK2 exocrine pancreas, indicating an evolution from an acinar to a ductal phenotype. Loss of cell polarity, defective secretion, and loss of intercellular adhesion in acini of ElasCCK2 mice was confirmed by ultrastructural analysis. Finally, expression of the transgene in mice treated with the carcinogen azaserine resulted in enhanced size of preneoplastic lesions as well as an increased degree of acinar-ductal transdifferentiation. Thus, these data represent the first evidence for the CCK2-R modulating intercellular adhesion and cell fate in vivo and show that these alterations may contribute to enhanced sensitivity of ElasCCK2 pancreas to chemical carcinogens.

Topics: Animals; Azaserine; Carcinogens; Cell Adhesion; Cell Differentiation; Cell Transformation, Neoplastic; Islets of Langerhans; Mice; Mice, Transgenic; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Receptor, Cholecystokinin B; Transgenes

The progression of azaserine-induced rat pancreatic adenocarcinoma (AC) was characterised using quantitative and semiquantitative immunohistochemistry for proliferating cell nuclear antigen (PCNA), basement membrane laminin (BML) and trypsinogen (TG). Samples were taken 5-20 months after initiation. High PCNA-labelling indices (PCNA LIs) were measured 5 months after the induction of atypical acinar cell nodules (AACNs), which decreased later and stagnated until a further decline in the month 10 adenomas. Then a second premalignant proliferative wave was observed (month 13) within the adenoma stage. Later, in month 20 differentiated ACs PCNA LIs fell to the host tissue level but were found highest in the month 20 anaplastic ACs indicating a switch to malignant proliferation. Month 20 invasive ACs showed a number of separate proliferative foci. In early AACNs, BML decreased and remained low till the local maximum in the month 13 adenoma. Invasive ACs did not express BML. Month 5 AACN and differentiated AC were TG deficient but anaplastic AC regained its TG expression. However invasive AC was again TG negative. These results are discussed in combination with our previous data on progressional changes of autophagic capacity and microvessel densities.

Topics: Adenocarcinoma; Adenoma; Animals; Azaserine; Biomarkers, Tumor; Carcinogenicity Tests; Cell Count; Disease Progression; Fluorescent Antibody Technique, Indirect; Laminin; Male; Pancreatic Neoplasms; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Trypsinogen

The present study was performed to investigate the influence of fish oil on the genotoxic effects of azaserine, using the formation of micronucleated erythrocytes as a measure for the degree of initiating potency and the number and size of putative preneoplastic pancreatic atypical acinar cell foci (AACF) as a measure for the actual number of initiated cells. Male Wistar rats were treated twice i.p. with 30 mg azaserine per kg body weight to induce AACF. During the initiation/early promotion phase the rats were maintained on diets containing 5 wt% vegetable oil (safflower and high-oleic sunflower oil), 25 wt% vegetable oil, 25 wt% fat (15% vegetable oil + 10 wt% fish oil), or 25 wt% fat (5% vegetable oil + 20 wt% fish oil), respectively. One day after carcinogen treatment, the numbers of micronucleated polychromatic erythrocytes were determined in blood smears obtained from 10 animals per group. Each high-fat diet resulted in higher percentages of micronucleated polychromatic erythrocytes than the low-fat diet. Dietary fish oil did not significantly influence the number of micronucleated cells. Two weeks after carcinogen treatment, the diets containing fish oil were replaced by the diet containing 25% vegetable oil, and the animals were further maintained for about 14 wk. Pancreatic tissue slides were microscopically evaluated for the number and size of AACF. Dietary fish oil caused an increase in the number and size of AACF, although a clear dose-effect relationship was absent. It was concluded that a high level of dietary fish oil, when given during the induction/early promotion phase, enhances azaserine-induced pancreatic carcinogenesis in rats.

Topics: Animals; Azaserine; Dietary Fats, Unsaturated; Docosahexaenoic Acids; Drug Combinations; Eicosapentaenoic Acid; Erythrocytes; Female; Fish Oils; Male; Micronuclei, Chromosome-Defective; Pancreatic Neoplasms; Plant Oils; Precancerous Conditions; Rats; Rats, Wistar

The knowledge of alterations in regulation of autophagy during tumorigenesis may also help our understanding of its normal control. We established an experimental system and reported recently that autophagic capacity, measured as the cell's capability of increasing segregation (formation of autophagosomes) and subsequent degradation of cytoplasmic quanta were highly increased in premalignant nodule cells 6 months after initiation by azaserine in the rat pancreas in vivo. In the present study, we followed changes of these autophagic functions throughout the tumour progression. We carried out electron-microscopic morphometrical analysis of the expansion of autophagic vacuole compartment and subcompartments induced by vinblastine (an in vivo segregation enhancer), as well as their regression upon segregation-inhibitor cycloheximide post-treatment. Premalignant tumour samples were taken at month 5, month 8 (nodules), month 10 and month 15 (adenomas) after initiation. In all these stages, a highly increased and varying autophagic capacity was found compared with the host tissue. The basal (non-stimulated) autophagic compartment was measurable only at month 5 and month 15, and its regression upon cycloheximide was consistent with increased basal autophagic activity. Compared with the host tissue, autophagic capacity profoundly decreased in the differentiated and anaplastic adenocarcinomas at month 20, when, surprisingly, cycloheximide was unable to inhibit segregation. Our conclusion is that down-regulation of the cycloheximide sensitive segregation and a partly compensatory up-regulation of an alternative pathway of segregation might occur along with malignant transformation.

Topics: Adenocarcinoma; Adenoma; Animals; Autophagy; Azaserine; Cell Cycle; Cell Division; Disease Progression; Male; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Wistar; Time Factors; Vinblastine

Previous studies in our laboratory demonstrated that pancreatic carcinomas in rodents express receptors for the peptide hormone gastrin that are not present in normal adult pancreas. In view of an abundant literature suggesting that gastrin may promote growth of various gastrointestinal tissues and tumors, the effect of hypergastrinemia on the process of pancreatic carcinogenesis was evaluated.. Rats received subcutaneous injections of the pancreatic carcinogen azaserine at 19 and 26 days of age. Starting at 12 months of age, animals were randomized to treatment with the proton pump inhibitor lansoprazole or vehicle by gavage for 6 months. At autopsy, pancreatic wet weight normalized to body weight was recorded, as well as the number of benign and malignant pancreatic lesions.. Serum gastrin levels were determined by radioimmunoassay and showed a greater than two-fold increase in lansoprazole-treated animals. Pancreatic wet weight in hypergastrinemic rats was increased compared to controls (p <0.05). Premalignant lesions such as acidophilic atypical acinar cell foci, adenomas, heterogeneous phenotypic populations of nodules within nodules, and carcinoma-in-situ were not increased in the hypergastrinemic group. Likewise, there was no difference in the incidence of invasive carcinoma in hypergastrinemic animals (10%) compared to controls (5.7%).. Hypergastrinemia stimulated an increase in pancreatic weight, but did not stimulate development of premalignant lesions or progression to cancer in the azaserine model of rat pancreatic acinar cell carcinoma.

Topics: 2-Pyridinylmethylsulfinylbenzimidazoles; Adenoma; Animals; Anti-Ulcer Agents; Azaserine; Carcinoma in Situ; Carcinoma, Acinar Cell; Disease Models, Animal; Gastrins; Lansoprazole; Male; Omeprazole; Organ Size; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Lew

The literature contains many controversial or unclearly defined opinions about the risk of development of carcinoma of the exocrine part of the pancreas in patients with chronic pancreatitis. This and our own clinical observations based on analysis of patients with chronic pancreatitis treated surgically (anastomotic and resectional procedures) formed the background to an experimental study to define the risk of carcinogenesis in the course of chronic pancreatitis in rats.. In Wistar rats with chronic pancreatitis induced by etionine and then exposed to carcinogenic action of azaserine, proliferation, adenomas and acinic cell carcinomas of the exocrine part of the pancreas were diagnosed; the carcinomas were transplantable. In rats treated with azaserine only, benign proliferative lesions and adenomas were found. The presence of the p53 mutation protein was observed in carcinomatous pancreatic cells in malignant lesions of the pancreas in primary and transplantable cancers, but was not detected in benign proliferative lesions and adenomas. Chronic pancreatitis in Wistar rats predisposes the exocrine part of pancreas to malignant transformation. Growth of cancers of the exocrine part of the pancreas in male rats, but not in female rats, suggests hormonal determination of experimental pancreatic cancer.. Results demonstrate that chronic pancreatitis in rats predisposes to malignant proliferative lesions, including acinic cell carcinoma. Expression of the protein product of p53 gene mutations correlated with neoplastic transformation of pancreas preceded by chronic pancreatitis, and was also detected in transplantable tumours.

Topics: Animals; Azaserine; Cell Transformation, Neoplastic; Chronic Disease; Female; Male; Neoplasm Transplantation; Pancreatic Neoplasms; Pancreatitis; Rats; Rats, Wistar; Tumor Suppressor Protein p53

The ubiquitin (Ub)-proteasome proteolytic system is highly selective, and the specific proteins involved in cell division, growth, activation, signaling and transcription are degraded at different rate depending on the physio-pathological state of the cell. Ubiquitination serves first of all as a signal for protein degradation of short-lived and abnormal proteins under several stressful conditions. The immunocytochemical localization of Ub in some malignant tumours has recently been presented and differences in Ub expression has been observed during malignant transformation. Change in the level of Ub and Ub-conjugated proteins might reflect a higher metabolic-catabolic ratio in neoplastic cells. Most studies have been focused on the malignant stage of tumour progression, and only a few papers have dealt with the change in Ub and Ub-protein conjugates level during the whole progression. To address this problem, we applied an azaserine-induced pancreatic carcinogenesis model, in which premalignant and malignant stages were investigated throughout the progression. The level of Ub immunoreactivity was measured in nucleus and cytoplasm by electron microscopic immunocytochemical and morphometrical methods. We found a significant increase of Ub level in the nucleus and the cytoplasmic area in premalignant atypical acinar cell nodule (AACN) cells and in malignant adenocarcinoma in situ (CIS) cells at month 20 after initiation.

Topics: Adenocarcinoma; Adenoma; Animals; Azaserine; Carcinoma in Situ; Cell Nucleus; Cysteine Endopeptidases; Cytoplasm; Immunohistochemistry; Male; Multienzyme Complexes; Neoplasm Proteins; Pancreatic Neoplasms; Precancerous Conditions; Proteasome Endopeptidase Complex; Rats; Rats, Wistar; Ubiquitin

Growth regulation is a crucial event in tumour progression. Surprisingly, relatively few papers have dealt with the catabolic side of regulation, and there are practically no data regarding the autophagic process during tumour development. We approach this problem by morphometrical investigation into the possible changes of autophagic activity during the progression of rat pancreatic adenocarcinoma induced by azaserine. In the present study, autophagic capacity of the azaserine-induced premalignant and malignant cells were characterised and compared to the respective host tissue cells of the rat pancreas and to the acinar cells in other stages of tumour development. Using vinblastine (VBL) as an enhancer, and cycloheximide (CHI) as an inhibitor of autophagic segregation we observed that autophagic capacity of premalignant cells (month 6 and 10 after initiation) is much higher than in the host tissue cells. We found a sharp decrease in self-digesting capacity in adenocarcinoma cells (month 20) where VBL induced a minimal accumulation of autophagic vacuoles which was, surprisingly, not inhibited by CHI, i.e. the CHI-sensitive regulatory step was lost. The changes in autophagic capacity are probably associated to specific steps of tumour progression in our system.

Topics: Adenocarcinoma; Adenoma; Animals; Autophagy; Azaserine; Carcinoma in Situ; Cycloheximide; Male; Pancreatic Neoplasms; Rats; Rats, Wistar; Time Factors; Vinblastine

Although angiogenesis is considered to be indispensable for continuous tumour growth, only very few studies have been published performing microvessel quantification during tumour progression. We measured the tumour vascularity in different stages of rat pancreatic carcinogenesis induced by azaserine and promoted by raw soya flour-containing pancreatotrophic diet. Besides the tumour samples taken at 6 (atypical acinar cell nodules), 15 (adenomas) and 20 (localised adenocarcinomas) months after carcinogen initiation, we also investigated 3 control groups: tumour-bearing host tissue of azaserine-treated rats and normal tissue of untreated rats kept on standard or pancreatotrophic diet. In contrast with the usual microvessel counting on hot spots, we determined microvascular surface density (Sv) and volume density (Vv) by electron microscopic morphometry. There was no significant difference in these respect between the control groups. At month 6 after the azaserine induction Sv and Vv showed slight, nonsignificant decrease as compared to the host control. Both values remained unchanged until the 15th month and increased significantly by the 20th month. These results may indicate comparable growth rate of tumour and new microvessels in the premalignant stages of carcinogenesis while a more intense angiogenesis than tumour growth afterwards.

Topics: Adenocarcinoma; Animals; Azaserine; Male; Microcirculation; Neovascularization, Pathologic; Pancreatic Neoplasms; Rats; Rats, Wistar; Time Factors

The majority of human pancreatic adenocarcinomas display a ductal phenotype; experimental studies indicate that tumors with this phenotype can arise from both acinar and ductal cells. In normal pancreas acinar cells, the pancreas transcription factor 1 transcriptional complex is required for gene expression. Pancreas transcription factor 1 is a heterooligomer of pancreas-specific (p48) and ubiquitous (p75/E2A and p64/HEB) basic helix-loop-helix proteins. We have examined the role of p48 in the phenotype of azaserine-induced rat DSL6 tumors and cancers of the human exocrine pancreas. Serially transplanted acinar DSL6 tumors express p48 whereas DSL6-derived cell lines, and the tumors induced by them, display a ductal phenotype and lack p48. In human pancreas cancer cell lines and tissues, p48 is present in acinar tumors but not in ductal tumors. Transfection of ductal pancreas cancers with p48 cDNA did not activate the expression of amylase nor a reporter gene under the control of the rat elastase promoter. In some cell lines, p48 was detected in the nucleus whereas in others it was cytoplasmic, as in one human acinar tumor. Together with prior work, our findings indicate that p48 is associated with the acinar phenotype of exocrine pancreas cancers and it is necessary, but not sufficient, for the expression of the acinar phenotype.

Topics: Adenocarcinoma; Amino Acid Sequence; Animals; Antimetabolites, Antineoplastic; Azaserine; Cell Differentiation; Disease Models, Animal; Helix-Loop-Helix Motifs; Humans; Molecular Sequence Data; Pancreas; Pancreatic Neoplasms; Phenotype; Rats; RNA, Messenger; Transcription Factors; Tumor Cells, Cultured

Although cellular autophagy is recognized as a major pathway of macromolecular catabolism, little data are available regarding its activity or regulation in tumor cells. We approach this problem by morphometrical investigation into the possible changes in autophagic activity during progression of rat pancreatic adenocarcinoma induced by azaserine and promoted by a raw soya flour-containing pancreatotrophic diet. In the present study, the autophagic capacity of the carcinogen-induced premalignant atypical acinar nodule cells was characterized and compared with controls (normal tissue of rats kept on standard laboratory or pancreatotrophic diet and host tissue of the premalignant nodules of the azaserine-treated rats). Given for 90 min, vinblastine, an enhancer of autophagic segregation (i.e. formation of autophagic vacuoles), caused a one to two orders of magnitude larger expansion of the autophagic compartment in atypical nodule cells than in the controls. Then a 20 min blockade of segregation by cycloheximide led to regression of the autophagic compartment, which was barely measurable or moderate in the controls but exceeded 50% in the premalignant cells. At the same time, the cytoplasmic volume fraction of early autophagic vacuoles regressed to a near zero value in each cell type. Expansion and regression rates of these nascent vacuoles showed that both segregation and degradation were 6-20 times faster in the nodule than in normal tissue cells. These results show that the autophagic capacity of the premalignant cells in our system is greatly increased, possibly making these cells unusually sensitive to up-regulation of their self-digesting activity in response to different extracellular signals or drugs.

Topics: Adenocarcinoma; Animals; Autophagy; Azaserine; Male; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Wistar

The effects of galanin on pancreatic carcinogenesis induced by azaserine and on the norepinephrine concentration in the pancreas were investigated in male Wistar rats. Rats were given weekly injections of 10 mg/kg body weight of azaserine for 25 weeks and 8 microg/kg body weight of galanin in depot form every other day for 62 weeks. Azaserine-induced pancreatic lesions were examined with hematoxylin and eosin and histochemical techniques. In week 62, quantitative histological examination showed that prolonged administration of galanin significantly reduced the number and size (as percent of parenchyma) of adenosine triphosphatase-positive pancreatic lesions, which are correlated closely with the ultimate development of pancreatic cancer. The number of pancreatic adenocarcinomas in rats treated with galanin was significantly less than in controls. Galanin also significantly decreased the bromodeoxyuridine-labeling index of azaserine-induced pancreatic lesions and the norepinephrine concentration in the pancreas. Our findings indicate that galanin inhibits pancreatic carcinogenesis and that such inhibition may be related to the suppression of sympathetic nervous system activity and subsequently to the inhibition of cell proliferation in neoplastic lesions of the pancreas.

Topics: Animals; Anticarcinogenic Agents; Azaserine; Body Weight; Bromodeoxyuridine; Carcinogens; Galanin; Male; Norepinephrine; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Wistar

The purpose of this study was to describe the inoculation technique and patterns of growth as well as to characterize typical histological features of Lewis rat subcutaneous and intrapancreatic tumors, induced by inoculation of cultured pancreatic cancer cells (DSL-6A/C1). Subcutaneous inoculation of cultured cells produced a solid tumor that was a locally invasive, well- to moderately differentiated ductal adenocarcinoma. Tumor take was 100% in animals 5 weeks of age; tumor growth was consistent and predictable and a tumor volume of approximately 1 cm3 was reached in 8 weeks. After intrapancreatic transplantation the tumors showed the same histological features as subcutaneous tumors. During inoculation carcinoma cells easily spread around the injected area, and after 2 weeks both pancreatic tumors and superficially infiltrating carcinomas were found in the liver and spleen and around the peritoneum. Tumor take was 60% and tumor growth was somewhat indefinite and unpredictable in the pancreas. However, by reducing the injected carcinoma cell volume and solving the technical problems, 100% tumor take was achieved. The tumor volume reached 2 mm3 during 2 weeks and larger tumors showed a tendency for invasion. According to our results, subcutaneous as well as intrapancreatic tumor induction with cultured cells offers a model for pancreatic cancer studies.

Topics: Adenocarcinoma; Animals; Azaserine; Lymphocytes, Tumor-Infiltrating; Male; Neoplasm Invasiveness; Neoplasm Transplantation; Pancreatic Neoplasms; Plasma Cells; Rats; Rats, Inbred Lew; Skin; Tumor Cells, Cultured

To investigate the effects of increasing concentrations of cholecystokinin octapeptide (CCK-8) on a pancreatic acinar adenocarcinoma.. Growth of the tumour was estimated in vivo on rats bearing a subcutaneous pancreatic carcinoma, and in vitro on primary cultured tumour cells. CCK receptors were characterized by binding assays.. CCK-8, administered for 12 successive days, exerted a biphasic action on tumour growth: a dose-dependent stimulation with low doses (0.1 and 0.5 microg/kg) and inhibition with high doses (2 and 4 microg/ kg) as shown by respective increases and decreases in tumor volume, protein, RNA and amylase contents. In cell cultures, [3H]thymidine incorporation was dose-dependently increased with 10-(10) to 10(-8) M CCK-8 and inhibited with 10(-7) M. Both effects were completely suppressed by the CCK-receptor antagonists CR 1409 and L 364,718 (10(-4) M). Binding studies showed the overexpression of two classes of CCK-A receptors of low and high affinity when compared to the normal pancreas which was less sensitive to CCK-8.. CCK-8 exerts a biphasic growth response on the acinar pancreatic carcinoma, mediated by two classes of CCK-A receptors overexpressed in the tumour.

Topics: Animals; Azaserine; Carcinoma, Acinar Cell; Cell Division; Dose-Response Relationship, Drug; Iodine Radioisotopes; Pancreatic Neoplasms; Radioligand Assay; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin; Sincalide; Tumor Cells, Cultured

5'-Deoxy-5'-methylthioadenosine phosphorylase (MTAP) is involved in the salvage of adenine and methylthio moieties of 5'-deoxy-5'-methylthioadenosine, a byproduct of polyamine synthesis, to adenine nucleotides and methionine, respectively. The gene encoding MTAP, MTAP, is frequently codeleted along with the tumor suppressor gene p16 in malignant cells bearing homozygous deletions in the chromosome 9p21 region. p16-, MTAP- malignant cells have been shown to be more susceptible to the purine de novo inhibitory actions of antifolates such as methotrexate than are p16+, MTAP+ cells. To understand the underlying mechanism, we reintroduced MTAP activity into two p16-, MTAP- cell model systems, the MiaPaCa-2 and PANC-1 human pancreatic carcinoma cell lines, by transfection with MTAP cDNA. It was found that transfection with MTAP cDNA (i) restored both the MTAP-dependent adenine and methionine salvage pathways, (ii) decreased the rates of purine de novo synthesis (18-47% lower than the wild-type or sham-transfected counterparts), and (iii) decreased cellular sensitivity to the antipurine-related growth-inhibitory actions of methotrexate and azaserine. These data support the hypothesis that operation of the MTAP-dependent adenine salvage pathway renders MTAP+ cells less dependent on de novo purine synthesis and hence less susceptible than MTAP- malignant cells to the growth-inhibitory actions of agents (e.g. antifolates) whose mechanism of action in part involves the de novo purine pathway. These findings provide a theoretical basis for the relatively selective action certain antifolates may have against MTAP-deficient malignancies.

Topics: Adenosine; Antimalarials; Antimetabolites, Antineoplastic; Azaserine; Biomarkers, Tumor; Cell Count; Deoxyadenosines; DNA, Complementary; Dose-Response Relationship, Drug; Humans; Methionine; Methotrexate; Pancreatic Neoplasms; Purine-Nucleoside Phosphorylase; Purines; RNA, Messenger; Thionucleosides; Tumor Cells, Cultured

In the present study the effects of dietary galactooligosaccharide (GOS) on dietary fat-promoted pancreatic carcinogenesis in azaserine-treated rats were investigated. The aims of this study were to determine 1) whether GOS acts as an inhibitor of pancreatic carcinogenesis and 2) whether GOS interacts with dietary fat-promoted pancreatic tumor development. Four groups of 39 azaserine-treated rats were maintained on different experimental diets that were formulated as follows: 4.3 wt% fat-8.3 wt% GOS (low fat-low GOS), 3.5 wt% fat-27.4 wt% GOS (low fat-high GOS), 15.5 wt% fat-9.5 wt% GOS (high fat-low GOS), and 14.3 wt% fat-28.6 wt% GOS (high fat-high GOS). Autopsies were performed after 6 months (9 animals/group) and 12 months (30 animals/group). Five rats per group were treated with bromodeoxyuridine before autopsy. Parallel sections of the pancreas were stained with hematoxylin and eosin or with hematoxylin and a monoclonal antibody against bromodeoxyuridine and examined by light microscopy. A high-fat diet caused a significant decrease, whereas a diet high in GOS caused a significant increase, in absolute and relative weight of the cecum content. A high level of dietary fat caused a highly significant increase in multiplicity and incidence of pancreatic (pre)neoplastic lesions after 6 and 12 months of feeding. A high level of GOS in the diet did not influence the number of atypical acinar cell nodules or the tumor incidence in comparison with controls. Dietary fat and dietary GOS caused a significant increase in cell proliferation in atypical acinar cell nodules after six months. It was concluded that dietary GOS has no modulating effect on pancreatic carcinogenesis in azaserine-treated rats or on the tumor-promoting effect of a high-fat diet.

Topics: Animals; Azaserine; Cecum; Cell Division; Diet; Dietary Fats; Eating; Energy Intake; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Wistar; Trisaccharides; Weight Gain

In the present study the putative chemopreventive effect of dietary fish oil (MaxEPA) on azaserine-induced pancreatic carcinogenesis in rats was investigated. Groups of rats were maintained on a semipurified low-fat (LF; 5 wt%) diet or on semipurified high-fat (HF; 25 wt%) diets containing 5 wt% linoleic acid (LA) and including 0.0, 1.2, 2.4, 4.7, 7.1 or 9.4 wt% MaxEPA. Animals fed a HF diet developed significantly higher mean numbers of atypical acinar cell nodules (AACNs), adenomas and carcinomas than animals fed a LF diet. Dietary MaxEPA caused a significant (P < 0.01) dose-related increase in mean number of AACNs (0.5 < phi < 3.0 mm). The mean number of adenomas and carcinomas remained similar among the groups. Cell proliferation was significantly lower in AACNs from animals fed HF containing 9.4% MaxEPA in comparison with HF without MaxEPA and with LF. LA levels had increased and arachidonic acid (AA) levels had decreased in blood plasma and pancreas with increasing dietary MaxEPA. Feeding MaxEPA resulted in significant decreases in 6-keto-prostaglandin (PG) F1 alpha (P < 0.05) and PGF2 alpha (P < 0.01) in non-tumorous pancreas, whereas PGE2, PGF2 alpha and thromboxane B2 (TXB2) levels were significantly (P < 0.001) higher in pancreatic tumour tissue than in non-tumorous pancreatic tissue. It is concluded that (i) dietary MaxEPA enhances dose-relatively growth of putative preneoplastic AACNs in the pancreas of azaserine-treated rats; (ii) dietary MaxEPA inhibits the conversion of LA to AA, as well as the conversion of AA to TXB2 or PGF2 alpha in non-tumorous pancreatic tissue; (iii) the high levels of PGE2, PGF2 alpha and TXB2 in pancreatic adenocarcinomas indicate a possible role for these eicosanoids in modulation of tumour growth.

Topics: Animals; Anticarcinogenic Agents; Azaserine; Body Weight; Carcinogens; Cell Division; Cocarcinogenesis; Dietary Fats, Unsaturated; Docosahexaenoic Acids; Drug Combinations; Drug Synergism; Eating; Eicosapentaenoic Acid; Fatty Acids; Fatty Acids, Omega-3; Female; Fish Oils; Liver; Organ Size; Pancreatic Neoplasms; Precancerous Conditions; Pregnancy; Prostaglandins; Rats; Rats, Wistar

In a previous short-term study (4 months) we found that Sandostatin, when administered prophylactically, inhibited growth of putative pre-neoplastic ductular lesions induced in hamster pancreas by N-nitrosobis(2-oxopropyl)amine (BOP), but not of acinar lesions induced in rat pancreas by azaserine. The present long-term (12 months) study was carried out to investigate the effects of Sandostatin (3 microgram/day), alone and in combination with orchiectomy, on pancreatic carcinogenesis in azaserine-treated rats and BOP-treated hamsters. In order to mimic therapy in humans, treatment of the animals started 4 months after the last injection with carcinogen, when (pre)neoplastic lesions had already developed. After treatment with Sandostatin for 8 months, rats developed fewer pancreatic atypical acinar cell nodules and tumours than those not treated with Sandostatin. Moreover, multiplicity of (pre)neoplastic acinar lesions was also lower in orchiectomized rats than in intact rats. However, Sandostatin treatment did not enhance the inhibitory effect of surgical castration on pancreatic carcinogenesis in rats. In hamsters that were both orchiectomized and treated with Sandostatin, the development of borderline lesions was significantly inhibited, whereas such an effect was not present in hamsters that were either surgically castrated or treated with Sandostatin alone. In Sandostatin-treated hamsters a significantly lower number of microcarcinomas was found than in hamsters not treated with Sandostatin. The present findings suggest that Sandostatin, particularly in combination with surgical castration, might be of therapeutic value for treatment of ductular pancreatic tumours.

Topics: Animals; Anticarcinogenic Agents; Azaserine; Body Weight; Carcinogens; Combined Modality Therapy; Cricetinae; Male; Mesocricetus; Microscopy; Nitrosamines; Octreotide; Orchiectomy; Organ Size; Pancreas; Pancreatic Neoplasms; Pituitary Gland; Rats; Rats, Wistar; Testis

The hormone gastrin is thought to stimulate the growth of certain pancreatic carcinoma cell lines. We have previously detected the presence of the gastrin receptor in rat pancreatic carcinoma cell lines but not in normal rat pancreas. We had not, however, previously demonstrated that gastrin receptor is expressed in pancreatic carcinomas developing in the rat in vivo. Therefore, in the present study, we examined rat pancreatic tissue at various stages in azaserine-induced pancreatic carcinogenesis for gastrin binding and for the presence of gastrin receptor mRNA to determine the temporal expression pattern of the gastrin receptor during the in vivo development of pancreatic cancer. Autoradiography of pancreatic tissue using (125)I-gastrin-17-I from all azaserine-treated and control animals at 2, 4, 8, and 12 months of age demonstrated no specific gastrin binding. At 18 months of age, normal pancreas, azaserine-induced premalignant pancreatic nodules, and internodular pancreas demonstrated no specific gastrin binding. One of three azaserine-treated animals developed an area of pancreatic acinar cell carcinoma at 18 months of age which exhibited significant specific gastrin binding of 141.8 - 32.8 fmole/gm of tissue. Southern blot analysis of pancreatic RNA isolated from animals at 12 months of age revealed no gastrin receptor mRNA; however, by 18 months of age, gastrin receptor mRNA was present in all azaserine-treated animals but absent in control animals. In summary, specific gastrin binding is present in in vivo azaserine-induced pancreatic acinar cell carcinoma but absent in normal pancreas and azaserine-induced premalignant pancreatic nodules. Gastrin receptor mRNA is first expressed in azaserine-treated rat pancreas at some point between 12 and 18 months of age. These results demonstrate that expression of gastrin receptor is altered in azaserine-treated rat pancreas and may play a role in the development of pancreatic cancer.

Topics: Animals; Autoradiography; Azaserine; Base Sequence; Carcinogens; Carcinoma, Acinar Cell; DNA Primers; Gastrins; Gene Expression; Male; Molecular Sequence Data; Pancreas; Pancreatic Neoplasms; Polymerase Chain Reaction; Precancerous Conditions; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin; RNA, Messenger

In the present study, the expression of the epidermal growth factor receptor (EGFR) was investigated in putative preneoplastic and neoplastic acinar cell lesions induced in the rat pancreas by azaserine, using Northern blotting, in situ hybridisation (ISH) and immunohistochemistry. EGFR protein levels were decreased in putative preneoplastic eosinophilic acinar cell lesions (atypical acinar cell nodules, AACN) in comparison with normal acinar cells of the pancreas. However, EGFR mRNA expression correlated positively with the volume of AACN in pancreatic homogenates and ISH showed equal or stronger EGFR mRNA expression in AACN than in the surrounding normal acinar cells. Neither EGFR protein nor EGFR mRNA was detected in more advanced lesions such as acinar adenocarcinomas (in situ). Moreover, EGFR protein expression showed an inverse relationship with the mitotic rate of the acinar cells. These findings suggest that down-regulation of EGFR at the protein level may abrogate negative constraints on cell growth, which may stimulate the development of putative preneoplastic AACN to more advanced lesions and, ultimately, acinar adenocarcinomas.

Topics: Animals; Azaserine; Blotting, Northern; Carcinogens; ErbB Receptors; Immunohistochemistry; In Situ Hybridization; Neoplasm Proteins; Pancreatic Neoplasms; Precancerous Conditions; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; RNA, Messenger

The effect of a calcium channel blocker, verapamil, on cholecystokinin (CCK)-enhancement of pancreatic carcinogenesis induced by azaserine was investigated in Wistar rats. During and after 25 weekly injections of azaserine, each rat received alternate-day injections of CCK-octapeptide (CCK-8) and/or verapamil. Carcinogen-induced pancreatic lesions staining for mu class glutathione S-transferase (GST-mu) were examined histochemically at week 62. Prolonged administration of CCK-8 significantly increased the number and area as a percentage of parenchyma of GST-mu-positive lesions. Concomitant administration of verapamil significantly attenuated the enhancing effect of CCK-8. These findings indicate that calcium may play an important role in CCK-enhancement of pancreatic carcinogenesis.

Topics: Animals; Azaserine; Calcium Channel Blockers; Cholecystokinin; Drug Synergism; Glutathione Transferase; Male; Pancreatic Neoplasms; Rats; Rats, Wistar; Verapamil

In the present study the effects of 0.1 or 1.0 g beta-carotene/kg diet (L beta C or H beta C) and 1.0 mg or 2.5 mg selenium/kg diet (LSel or HSel), as well as combinations of the respective low and high concentrations of beta-carotene and selenium (LMix or HMix) on the initiation/early promotion phase or on the late promotion phase of pancreatic carcinogenesis in azaserine-treated rats, were investigated using cell proliferation and volumetric data of atypical acinar cell foci (AACF) as parameters. The present results indicate chemopreventive effects of dietary selenium, dietary beta-carotene and of their combination on the development of acinar pancreatic lesions induced in rats by azaserine. The inhibitory effect was most pronounced when beta-carotene and/or selenium were added to the diets during the late promotion phase of the carcinogenic process, although inhibition was also observed with these compounds when they were added to the diets during the first 5 weeks of the study only (initiation/early promotion phase). Neither in the initiation/early promotion phase nor in the late promotion phase was a dose-related trend observed. The multiplicities of AACF with a diameter over 1.0 mm and of carcinomas in situ (CIS), as well as the incidence of CIS were not significantly different among the groups. However, in the late promotion experiment a dose-related decline in multiplicity could be observed in the selenium supplemented groups and in the groups receiving combinations of beta-carotene and selenium. Cell proliferation in azaserine-induced AACF, as estimated by the bromodeoxyuridine (BrdU) labeling index, was significantly higher in H beta C, HSel, LMix and HMix groups (initiation/early promotion phase) as well as in H beta C, LSel, HSel, LMix and HMix groups (late promotion phase) than in high fat controls. From the present results it can be concluded that: (i) beta-carotene and selenium have inhibitory effects on pancreatic carcinogenesis induced in rats by azaserine; (ii) the most clear effects were observed when selenium was given as such, or in combination with beta-carotene during the late promotion phase; and (iii) beta-carotene and selenium stimulate cell proliferation in AACF.

Topics: Analysis of Variance; Animals; Anticarcinogenic Agents; Azaserine; beta Carotene; Body Weight; Carcinogens; Carotenoids; Diet; Feeding Behavior; Female; Organ Size; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Wistar; Selenium

The effects of prolonged administration of the diuretic amiloride on pancreatic carcinogenesis induced by azaserine and on the labeling index of carcinogen-induced pancreatic lesions were investigated in Wistar rats. Rats were given 25 weekly injections of 10 mg/kg body weight azaserine and also 5 mg/kg body weight amiloride every other day until the end of the experiment at week 62. Carcinogen-induced pancreatic lesions were examined by histochemical techniques and were classified as ATPase-positive or ATPase-negative. In week 62, quantitative histologic analysis showed that prolonged administration of amiloride significantly reduced the number and size (as percent of parenchyma) of ATPase-positive pancreatic lesions, which are closely correlated with the subsequent development of pancreatic cancer. Amiloride also significantly decreased the labeling index of carcinogen-induced pancreatic lesions, but not of the surrounding acinar cells. In contrast, amiloride has no significant influence on the number and size of ATPase-negative pancreatic lesions. These findings indicate that amiloride inhibits pancreatic carcinogenesis, and that this effect may be related to the reduction of ATPase-positive lesions and to amiloride's inhibition of cell proliferation in neoplastic lesions of the pancreas.

Topics: Adenosine Triphosphatases; Amiloride; Animals; Anticarcinogenic Agents; Azaserine; Biomarkers, Tumor; Body Weight; Carcinogenicity Tests; Carcinogens; Male; Mitotic Index; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Wistar

The peptide hormone cholecystokinin (CCK) has been shown to stimulate the growth of azaserine-induced preneoplastic nodules in the rat pancreas. Previously, our labortory demonstrated by classical binding studies that CCK receptors are overexpressed in azaserine-induced rat pancreatic neoplasms. In the present study, we utilized autoradiography to determine the temporal course of this increased receptor binding. Male Lewis rats were given azaserine or saline injections and sacrificed at 2, 4, 8, 12, and 18 months of age. Pancreatic tissue was harvested and autoradiography using 125l-labeled. CCK-8 was performed. Densitometry measurements of azaserine-induced pancreatic nodules, internodular pancreas, and normal pancreatic tissue (from saline-treated controls) of each age group were taken with an image analyzer. There was no statistically significant difference in CCK binding to internodular pancreas and normal pancreas at any age. At 2 months of age, there was no significant increase in CCK binding to azaserine-induced pancreatic nodules. However, at 4, 8, 12, and 18 months of age there was significantly greater CCK binding to azaserine-induced pancreatic nodules than to both internodular pancreas and normal pancreas (p < 0.001 for all groups). At 18 months of age, one azaserine-treated animal developed a pancreatic acinar cell carcinoma, which likewise exhibited significantly greater CCK binding than internodular pancreas or normal pancreas (p < 0.001 for both). These findings demonstrate increased CCK binding in azaserine-induced preneoplastic pancreatic nodules and pancreatic acinar cell carcinoma, compatible with our previous demonstration of receptor overexpression in these tissues. Increased CCK binding first becomes apparent by 4 months following exposure to azaserine. These result suggest that overexpression of CCK receptors, located specifically on preneoplastic and neoplastic pancreatic lesions, results in increased CCK binding and is involved in the mediation of CCK-stimulated growth during azaserine-induced pancreatic carcinogenesis.

Topics: Animals; Autoradiography; Azaserine; Densitometry; Iodine Radioisotopes; Male; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin; Sincalide

The biochemical and pharmacological characteristics of specific binding sites for gastrin-releasing peptide (GRP) were investigated in normal exocrine pancreas and in an azaserine-induced pancreatic carcinoma in the rat, under similar experimental conditions. Cells from both types of tissues contained rapid, reversible, temperature-dependent, and highly specific binding sites for GRP. Scatchard analysis of equilibrium data obtained with normal and tumor plasma membranes indicated a single class of high-affinity sites (KD = 0.42 +/- 0.06 and 0.35 +/- 0.05 nM, respectively), but the number of GRP receptors was significantly different (Bmax = 31 +/- 4.5 and 189 +/- 20 fmol/mg protein, respectively). Binding of 125I-GRP1-27 was sensitive to GTP analogues, suggesting that the GRP receptor is functionally linked to a guanyl regulatory protein; however, the wheat germ agglutinin-agarose purified receptor had lost this G-protein activity. Cross-linking of 125I-GRP1-27 either to normal and neoplastic cells or to crude membranes, solubilized membrane proteins, and partially purified receptors revealed the presence of a specific MW 75-kDa polypeptide. N-Glycanase treatment reduced this apparent MW to about 45 kDa. Together, these data suggest that normal and tumor pancreatic cells contain a specific GRP receptor that is expressed more on malignant pancreatic tissues.

Topics: Animals; Azaserine; GTP-Binding Proteins; Pancreas; Pancreatic Neoplasms; Radioligand Assay; Rats; Rats, Inbred Lew; Receptors, Bombesin

Expression of transforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF) was studied in normal pancreatic tissue and in (pre)neoplastic pancreatic lesions of azaserine-treated rats. They were given either a low fat, high fiber (low caloric) diet, to inhibit carcinogenesis, or a low fat diet combined with injections of the cholecystokinin analog caerulein to enhance carcinogenesis. The control groups, maintained on a low fat diet, were injected with azaserine or were not treated at all. Autopsy was performed at 6 and 15 months after the last azaserine injection. After both 6 and 15 months immunohistochemistry revealed a weak expression of EGF and TGF-alpha peptides in the acinar cells, and a stronger expression in the ductular and centroacinar cells. TGF-alpha peptide expression was reduced in both putative preneoplastic and neoplastic acinar cell lesions, but no differences in EGF peptide expression were observed between the various stages of exocrine pancreatic carcinogenesis. After 16 months an increase in TGF-alpha mRNA due to treatment with azaserine was detected by semi-quantitative PCR in total pancreatic homogenates, whereas EGF mRNA expression had decreased. TGF-alpha mRNA levels in macroscopically isolated tumors were significantly lower, but EGF mRNA levels were significantly higher, than in total pancreatic homogenates from azaserine-treated rats. Furthermore, EGF and TGF-alpha mRNA levels in isolated tumors did not differ significantly from mRNA levels in non-carcinogen-treated rats. Neither with immunohistochemistry nor with PCR were differences in EGF or TGF-alpha expression observed due to either inhibition or stimulation of carcinogenesis. It is concluded that putative preneoplastic acinar cell lesions induced in rat pancreas by azaserine may develop into acinar adenocarcinomas independently of TGF-alpha and EGF. The results suggest involvement of these growth factors at the early stage of the carcinogenic process, during the initiation of normal acinar cells into putative preneoplastic cells. However, modulation of azaserine-induced pancreatic carcinogenesis by cholecystokinin or a low fat, high fiber (caloric restricted) diet appeared not to be regulated by EGF or TGF-alpha.

Topics: Animals; Azaserine; Base Sequence; Body Weight; Carcinogens; Ceruletide; Cocarcinogenesis; Diet, Fat-Restricted; Dietary Fiber; Drug Synergism; Energy Intake; Epidermal Growth Factor; Immunohistochemistry; Male; Molecular Sequence Data; Organ Size; Pancreas; Pancreatic Neoplasms; Polymerase Chain Reaction; Rats; Rats, Wistar; RNA, Messenger; Transforming Growth Factor alpha

The present 12-month study was carried out to investigate the effects of the aromatase inhibitor aminoglutethimide, alone and in combination with orchiectomy, on pancreatic carcinogenesis in azaserine-treated rats and N-nitrosobis(2-oxopropyl)-amine-treated hamsters. Treatment of the animals started 4 months after the last injection with the carcinogen. They were surgically castrated and/or treated with aminoglutethimide. Aminoglutethimide-treated rats developed less pancreatic tumours than did untreated controls. Multiplicity of (pre-)-neoplastic acinar lesions was lower in orchiectomized rats than in intact rats. Inhibition of pancreatic carcinogenesis was most pronounced in rats that were both orchiectomized and treated with aminoglutethimide. These effects were statistically significant after 8 months, but not after 4 months, of treatment. In hamsters, aminoglutethimide showed an enhancing rather than an inhibitory effect on the formation of ductular pancreatic tumours. Castration appeared to have no effect on the development of N-nitrosobis(2-oxopropyl)amine-induced ductular lesions in the pancreas, either alone, or in combination with aminoglutethimide. The present findings indicate that aminoglutethimide, alone and in combination with surgical castration, might be of value for the treatment of pancreatic acinar tumours, whereas the usefulness of aminoglutethimide for treatment of ductular adenocarcinomas of the pancreas is somewhat doubtful.

Topics: Aminoglutethimide; Animals; Antineoplastic Agents; Azaserine; Body Weight; Combined Modality Therapy; Cricetinae; Male; Mesocricetus; Orchiectomy; Organ Size; Pancreatic Neoplasms; Rats; Rats, Wistar

Gut peptides are involved in the growth and carcinogenesis of the exocrine pancreas of rats after treatment with azaserine. However, little is known about the influence of azaserine on expression of gut peptide receptors in the pancreas of the rat. Cholecystokinin, bombesin, somatostatin, secretin, and vasoactive intestinal peptide receptors were therefore visualized and quantified by storage phosphor autoradiography in pancreata of either saline control or azaserine-treated rats. As expected, putative preneoplastic lesions were formed in the pancreata of the azaserine-treated but not in the control animals. The pancreata of control rats contained receptors for cholecystokinin, bombesin, somatostatin, secretin, and vasoactive intestinal peptide. Cholecystokinin receptors were of the A-type and showed, in contrast to the other receptors, a heterogeneous expression due to variability of the high-affinity receptors. In the pancreata of azaserine-treated animals a significantly increased binding capacity of high-affinity receptors fro cholecystokinin was found not only in atypical acinar cell nodules but also in non-nodular pancreas when compared to pancreas of control rats (P < 0.05). Neither atypical acinar cell nodules nor non-nodular pancreas of rats treated by azaserine were shown to possess receptors for the other four types of gut peptide receptors. The spectrum of peptide receptors in pancreas of control and azaserine-treated rats in this study may help to understand the mechanism whereby gut hormones may modulate pancreatic carcinogenesis.

Topics: Animals; Azaserine; Pancreas; Pancreatic Neoplasms; Rats; Rats, Wistar; Receptors, Peptide

Keratin is a member of the intermediate filament family in epithelial cells. Two-dimensional gel electrophoresis of different epithelial cells has shown 20 different keratin polypeptides. Therefore, mapping of the keratin polypeptides can be used to define a specific tissue.. Cytokeratin expression was investigated by using monoclonal antibodies in human surgical specimens and autopsy material of pancreatic, gastric, liver, and colon carcinomas and cholangiocarcinomas, and their metastasis to lymph nodes and liver was examined. In addition, rat acinar cell carcinomas were used to compare cytokeratin expression in ductal vs. acinar cell pancreatic carcinomas.. Human pancreatic ductal carcinomas expressed keratins 7, 8, 18, and 19, whereas the majority of rat acinar carcinomas did not express keratins typical for ducts in rat pancreas. The keratin patterns of gastric and colon carcinomas were identical with keratins 8, 18, and 19. In contrast, hepatocellular carcinomas expressed the same keratin pattern as pancreatic acinar carcinomas with keratins 8 and 18, whereas cholangiocarcinomas expressed keratin 7, 8, 18, and 19, similar to pancreatic ductal carcinomas. Metastasis of pancreatic ductal and colon carcinomas retained their keratin patterns.. Keratin polypeptide typing of unknown malignant cells can be a useful tool for cell identification.

Topics: Animals; Azaserine; Carcinoma, Acinar Cell; Carcinoma, Ductal, Breast; Colonic Neoplasms; Epithelium; Gastrointestinal Neoplasms; Humans; Immunohistochemistry; Intermediate Filaments; Keratins; Male; Neoplasms, Experimental; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Stomach Neoplasms

In the present study the modulating effects of dietary fish oil (MaxEPA) on unsaturated fat-promoted pancreatic carcinogenesis in azaserine-treated rats were investigated. Three groups of 20 rats (each group comprised five saline-treated and 15 azaserine-treated animals) were fed an AIN76-based purified diet containing (i) 5 wt% fat, (ii) 25 wt% fat including 5 wt% linoleic acid or (iii) 25 wt% fat including 5 wt% linoleic acid and 9.4 wt% (20 cal%) MaxEPA for 6 months. The number and size of pancreatic atypical acinar cell foci was significantly higher (P < 0.01) in azaserine-treated animals maintained on a high fat diet than in those fed a low fat diet. MaxEPA did not influence the promoting effect of the high fat diet. The labeling index of atypical acinar cell foci in animals maintained on both a low fat or a high fat/MaxEPA diet was significantly (P < 0.01) lower than that in rats fed a high fat diet without MaxEPA. The linoleic acid concentration was higher, whereas the arachidonic acid concentration was lower, in blood plasma and to a lesser extent also in the pancreas of animals given MaxEPA in comparison with the other groups. Furthermore, animals fed MaxEPA showed lower 6-keto-prostaglandin F1 alpha, prostaglandin F2 alpha and thromboxane B2 levels, but not prostaglandin E2 levels in pancreatic tissue in comparison with the other groups. It is concluded that a high fat diet containing 5 wt% linoleic acid has a strong promoting effect on pancreatic carcinogenesis in azaserine-treated rats. Dietary MaxEPA did not influence the promoting effect of unsaturated fat on pancreatic carcinogenesis, although it caused a decrease in both cell proliferation in atypical acinar cell foci and prostaglandin levels in the pancreas.

Topics: Animals; Anticarcinogenic Agents; Azaserine; Body Weight; Cell Division; Dietary Fats; Eating; Fatty Acids; Fish Oils; Linoleic Acid; Linoleic Acids; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Prostaglandins; Rats; Rats, Wistar

Topics: Animals; Azaserine; Carcinogens; Cell Division; Cholecystokinin; Male; Pancreas; Pancreatic Neoplasms; Peptide Fragments; Precancerous Conditions; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin; Sincalide; Tetragastrin

Physical activity (exercise) is a lifestyle factor that has received little attention with regard to its role in the etiology and/or prevention of cancer. These studies examined the effects of treadmill exercise on the early stages of pancreatic carcinogenesis initiated by azaserine in rats. Male Lewis rats were treated with azaserine at 2 weeks of age and weaned to experimental protocols at 3 weeks of age. Two experiments were undertaken; treadmill exercise began at 6 weeks of age (Experiment 1) or at 13 weeks of age (Experiment 2). Rats were exercised for 15-20 min/day and for 3-5 days/week. Treadmill speed and angle of incline were adjusted to afford a range of exercise intensities. The development of putative preneoplastic lesions of the pancreatic acinar cells (henceforth termed foci) was evaluated by quantitative stereological analysis using light microscopy. In Experiment 1, exercise resulted in a known paradoxical reduction in food intake by about 15% of the intake of the sedentary group fed ad libitum. The burden of azaserine-induced foci was decreased by approximately 37%, and this was attributed to the well known effects of reduced caloric intake in these young, rapidly growing rats. In Experiment 2, the higher intensity treadmill exercise group had an increased focal burden, compared to their sedentary pair-fed controls. Importantly, this enhancement occurred despite a reduction in food intake and body fat stores in this treadmill exercise group. These experiments demonstrate that exercise may suppress or promote carcinogenesis, depending upon the stage in the life cycle of the animal.

Topics: Aging; Animals; Azaserine; Body Weight; Carcinogens; Diet; Energy Intake; Energy Metabolism; Female; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Physical Conditioning, Animal; Rats; Rats, Inbred Lew

It has been suggested that linoleic acid (LA) is responsible for the promoting effect of dietary polyunsaturated fat on pancreatic carcinogenesis via an accelerated prostaglandin synthesis, caused by metabolism of LA-derived arachidonic acid in (pre)neoplastic tissue. The purpose of the present study was to investigate whether dietary LA is the cause of pancreatic tumor promotion by a high fat diet. Five groups of 30 azaserine-treated rats and 5 groups of 30 N-nitrosobis(2-oxopropyl)amine-treated hamsters were maintained for 6 months (rats) and 12 months (hamsters) on high fat (25 weight %) AIN diets containing 2, 4, 6, 10, or 15 weight % LA. The results indicated that the strongest enhancing effect on the growth of pancreatic (pre)neoplastic lesions in rats and hamsters was obtained with 4 and 2 weight % of dietary LA, respectively. At higher LA levels the tumor response seemed to decrease rather than increase. In both rats and hamsters the fatty acid profiles of blood plasma and pancreas showed an accurate reflection of the dietary fatty acid profiles: a proportional increase in LA levels was observed in plasma and pancreas with increasing dietary LA. In both species plasma and pancreatic AA levels remained constant, except for arachidonic acid levels in rat plasma, which significantly increased with increasing dietary LA levels. Fatty acid profiles in hamster pancreatic tumors did not differ from fatty acid profiles in nontumorous pancreatic tissue from hamsters fed the same diet. Prostaglandin (PG) E2, 6-keto-PGF1 alpha, PGF2 alpha, and thromboxane B2-concentrations in nontumorous pancreatic tissue were similar among the diet groups. Ductular adenocarcinomas from hamster pancreas showed significantly higher levels of 6-keto-PGF1 alpha, PGF2 alpha, and thromboxane B2, but not of PGE2 in comparison with nontumorous pancreas. It is concluded that the strongest pancreatic tumor promotion by dietary LA is 4 weight % in rats and 2 weight % or less in hamsters, and that PGs may be involved in the development of ductular adenocarcinomas induced in hamster pancreas by N-nitrosobis(2-oxopropyl)amine.

Topics: Animals; Arachidonic Acid; Azaserine; Carcinogens; Cricetinae; Dietary Fats; Fatty Acids; Linoleic Acid; Linoleic Acids; Male; Mesocricetus; Microsomes; Nitrosamines; Pancreas; Pancreatic Neoplasms; Plant Oils; Precancerous Conditions; Rats; Rats, Wistar; Reference Values; Safflower Oil; Species Specificity; Sunflower Oil

Although the etiology of pancreatic cancer is largely unknown, diet-associated factors may play a role. Male Sprague-Dawley rats (14 d of age) were given a single injection of either saline or azaserine and were weaned (21 d) to diets with either adequate (30 micrograms/g) or low (9 micrograms/g) zinc, with or without 1.0 g/100 g active trypsin inhibitor in the form of soybean trypsin inhibitor concentrate. Experimental diets were fed for 14 wk. Regardless of dietary zinc status, diets with soybean trypsin inhibitor concentrate caused hyperplasia and/or hypertrophy of the pancreas. Pancreatic zinc content was not different among groups. Low dietary zinc levels did not affect total body growth rate or serum zinc concentration. Tibia zinc was also used as an indicator of zinc status. Tibia zinc concentration was lower in rats fed diets low in zinc relative to adequate zinc diets. Azaserine-induced acidophilic foci were larger and more numerous when soybean trypsin inhibitor concentrate was present in the diet regardless of dietary zinc level. Thus, low zinc does not exacerbate the soybean trypsin inhibitor concentrate effects that promote pancreatic cancer.

Topics: Animals; Azaserine; Body Weight; Diet; Male; Nutritional Status; Organ Size; Pancreatic Neoplasms; Rats; Rats, Sprague-Dawley; Trypsin Inhibitors; Zinc

The role of duct cells in the histogenesis of pancreatic carcinoma was studied using a propagable cultured pancreatic duct epithelial cell line derived from a Fischer-344 rat. Tumorigenic transformation was induced by treatment with two experimental pancreatic carcinogens, azaserine and streptozotocin, or spontaneously using a 'selective' culture condition. Tumors arising from spontaneously transformed cells were anaplastic carcinomas, while those from streptozotocin-transformed cells were well or moderately differentiated ductal adenocarcinomas. Azaserine-treated cells produced moderately to poorly differentiated adenocarcinomas. Ultrastructural evidence of acinar or endocrine differentiation was absent. The biochemical phenotypes of representative tumor cell lines established from these tumors were studied. As compared to the parental cell line which expressed high activity of carbonic anhydrase (CA) and negligible activity of gamma-glutamyl transpeptidase (GGT), the tumor cell lines displayed variably increased levels of GGT, and a diminution or loss of CA activity. The tumor cell lines also showed heterogeneity in proto-oncogene and growth factor/receptor expression. The transforming growth factor-alpha mRNA expression was increased in all tumor cell lines, especially in those induced by azaserine. In contrast, mRNA expression of epidermal growth factor receptor was markedly down-regulated in all tumor cell lines. All chemically induced tumor cell lines showed marked overexpression of the c-myc and c-Ki-ras mRNAs, whereas the spontaneously transformed tumor cell line showed only a significant overexpression of the c-Ki-ras. Point mutation of this proto-oncogene at codons 12, 13 or 61 was absent. The results show that azaserine and streptozotocin are potent carcinogens in vitro for cultured rat pancreatic duct epithelial cells, and the phenotype of the tumors is modulated by the method or agent used for their transformation.

Topics: Animals; Azaserine; Blotting, Northern; Carcinogens; Cell Adhesion; Cell Cycle; Cell Division; Cell Line; Cell Transformation, Neoplastic; Epithelium; ErbB Receptors; gamma-Glutamyltransferase; Genes, myc; Genes, ras; Male; Microscopy, Phase-Contrast; Neoplasm Transplantation; Pancreatic Ducts; Pancreatic Neoplasms; Rats; Rats, Inbred F344; RNA, Messenger; Streptozocin; Transforming Growth Factor alpha

Using receptor binding assays, we have previously demonstrated the overexpression of the high-affinity cholecystokinin (CCK) receptor and the novel expression of the gastrin (CCK-B) receptor in the azaserine-induced rat pancreatic carcinoma DSL-6. Since cDNA of both the CCK-A receptor (classical pancreatic CCK receptor) coding region and the CCK-B receptor coding region have recently been cloned and sequenced, we investigated the expression of messenger RNA of these receptors in DSL-6 pancreatic carcinoma. Our results showed that the 32P-labelled cDNA probe of the CCK-A receptor coding region hybridized with an approximately 2.7 kb mRNA from both DSL-6 pancreatic carcinoma and normal rat pancreas. However, the relative expression of the CCK-A receptor mRNA in DSL-6 pancreatic carcinoma was approximately 8-fold of that in normal rat pancreas. The 32P-labelled cDNA probe of the CCK-B receptor coding region hybridized with an approximately 2.7 kb mRNA from DSL-6 pancreatic carcinoma; no hybridizing mRNA could be identified from normal rat pancreas. In summary, the CCK-A receptor mRNA is overexpressed approximately 8-fold and the gastrin (CCK-B) receptor mRNA is novelly expressed in DSL-6 pancreatic carcinoma as compared to normal rat pancreas. These results further confirm our previous findings based on receptor binding assays. The gene overexpression of the CCK-A receptor and the novel gene expression of the gastrin (CCK-B) receptor may be generated by alterations in gene regulation during carcinogenesis, and may play an important role in promoting tumor growth.

Topics: Animals; Azaserine; Blotting, Northern; Carcinoma; Male; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin; RNA, Messenger

Cholecystokinin (CCK-A) and gastrin (CCK-B) receptors have been demonstrated in the azaserine-induced rat pancreatic carcinoma DSL-6. In order to determine at what stage in azaserine-induced pancreatic carcinogenesis gastrin (CCK-B) receptors are first expressed, we examined the binding of [125I]gastrin-I to normal rat pancreas, azaserine-induced premalignant pancreatic nodules, grossly normal internodular pancreas, and DSL-6 carcinoma. We observed that specific gastrin binding was absent in normal pancreas, premalignant nodules, and internodular pancreas, and also reconfirmed our previous report of marked overexpression of gastrin (CCK-B) receptors in the DSL-6 carcinoma. Specific cholecystokinin (CCK) binding was present in all pancreatic tissue types tested. Therefore, we conclude that the presence of gastrin (CCK-B) receptors in the azaserine-induced pancreatic carcinoma DSL-6, in contrast to their absence in premalignant nodules, suggests that the expression of the gastrin (CCK-B) receptor may be important in the transformation from premalignant nodules to pancreatic cancer.

Topics: Animals; Azaserine; Cell Transformation, Neoplastic; Gastrins; Male; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin; Sincalide

Cholecystokinin (CCK) has been shown to stimulate the growth of both normal pancreas and azaserine-induced putative preneoplastic pancreatic lesions in the rat. The present study was performed to determine whether these effects are mediated by way of CCK-A receptors, CCK-B receptors, or both. Sixteen-day-old male Lewis rats were given i.p. injections of azaserine at 30 mg/kg body weight. Starting on day 21, rats were given s.c. injections, 5 days/week for 16 consecutive weeks, of either (a) CCK octapeptide (nonselective CCK agonist) (2.50 micrograms/kg body weight, n = 17), (b) tert-butyloxycarbonyl-Trp-Lys(epsilon-N-2-methylphenylaminocarbonyl++ +)-Asp- (N-methyl)-Phe-NH2 (highly selective CCK-A agonist) (1.84 micrograms/kg body weight, n = 18), (c) [(2R,3S)-beta-MePhe28,N-MeNle31]CCK26-33 (highly selective CCK-B agonist) (2.40 micrograms/kg body weight, n = 18), or (d) normal saline solution (control, n = 17). Rats were subsequently sacrificed, pancreatic weights were determined, and quantitative morphometric analysis of atypical acinar cell foci and nodules was performed. Both CCK octapeptide and the selective CCK-A agonist tert-butyloxycarbonyl-Trp-Lys(epsilon-N-2- methylphenylaminocarbonyl)-Asp-(N-methyl)-Phe-NH2 stimulated pancreatic growth and the development of acidophilic atypical acinar cell foci and nodules. Furthermore, the effect produced by the selective CCK-A agonist tert-butyloxycarbonyl-Trp-Lys(epsilon-N-2- methylphenylaminocarbonyl)-Asp-(N-methyl)-Phe-NH2 was greater than that produced by CCK octapeptide. In contrast, the selective CCK-B agonist [(2R,3S)-beta-MePhe28,N-MeNle31]CCK26-33 had no effect. These findings suggest that the growth of putative preneoplastic lesions (acidophilic atypical acinar cell foci and nodules) in the rat pancreas during the early stages of azaserine-induced pancreatic carcinogenesis is mediated specifically by way of CCK-A receptors.

Topics: Animals; Azaserine; Cholecystokinin; Chronic Disease; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Pancreatitis; Peptide Fragments; Precancerous Conditions; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin; Sincalide; Tetragastrin

Two cell lines were derived from a transplantable acinar cell carcinoma that had been established from a primary carcinoma of the pancreas in an azaserine-treated Lewis rat. The cultured tumor cells initially produced amylase, but production of exocrine enzymes ceased after 1-2 weeks in culture. The cultured cells were tumorigenic in Lewis rats, and one line produced solid tumors composed of ductlike structures surrounded by dense fibrous tissue. The second cell line produced partially solid and partially cystic tumors with a mixed phenotype of squamous, mucinous, and glandular areas when it grew in vivo following regrafting. Both cell lines lost structural and immunohistochemical acinar cell markers while acquiring duct cell markers during culture and regrafting. These studies provide strong support for the hypothesis that ductlike carcinomas can arise from neoplastic pancreatic acinar cells in rats.

Topics: Animals; Azaserine; Carcinoma, Intraductal, Noninfiltrating; Cell Line; Cells, Cultured; Immunohistochemistry; Microscopy, Electron; Neoplasm Transplantation; Pancreatic Ducts; Pancreatic Neoplasms; Phenotype; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin

In two experiments, the effects of caloric restriction during the postinitiation phase of pancreatic carcinogenesis were evaluated. Male Lewis rats were given injections of azaserine at 14 days of age and weaned to the postinitiation test protocols at 21 days of age. In the first experiment, the caloric content of the diets was restricted by 10, 15, 20, and 30% of the intakes of the ad libitum-fed rats. A sixth group was fed diet ad libitum for only 5-6 h/day; i.e., they were "meal-fed". The development of putative preneoplastic lesions (henceforth termed foci) was evaluated by quantitative stereological (morphometric) analysis of the pancreas. Caloric restriction during the 4-month postinitiation phase resulted in a significant reduction in focal development beginning at 10% caloric restriction and increasing with more severe restriction. The caloric intake of the meal-fed group closely matched the caloric intake of the 10 or 15% caloric restriction groups and the focal response of the meal-fed rats was similar to the groups restricted in calories by 15 to 20%. In the second experiment, rats were initiated with azaserine and weaned to one of four groups: ad libitum; meal-fed; meal-fed for 2 months and ad libitum thereafter; or ad libitum for 2 months and meal-fed thereafter. Foci were evaluated at 2 and 4 months; neoplasm incidence and multiplicity were determined at 14 months postinitiation. Compared to the ad libitum group, the meal-fed group had significantly fewer foci at all times of evaluation and significantly fewer neoplasms. When rats were meal fed for 2 months and then switched to ad libitum feeding for the remainder of the experiment, the focal outcome at 4 months was similar to the group meal fed for all 4 months; and at 14 months the neoplastic outcome was intermediate between the ad libitum and the meal-fed group. Intervention in the ad libitum feeding regimen at 2 months by meal feeding for the remainder of the experiment resulted in a significant decrease in the focal and neoplastic development, as compared to the group fed ad libitum continuously. These two intervention groups were intermediate in response between the meal-fed and ad libitum-fed groups. These results indicate that the postinitiation phase of pancreatic carcinogenesis can be modulated by relatively simple dietary interventions such as moderate caloric restriction.

Topics: Animals; Azaserine; Body Weight; Dose-Response Relationship, Drug; Energy Intake; Male; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Time Factors

The role of cholecystokinin (CCK) has been explored in pancreatic carcinogenesis following pancreatobiliary diversion (PBD), using the specific CCK receptor antagonist CR-1409. Male Wistar rats (n = 80) weighing 70-100 g were given weekly i.p. injections of azaserine (30 mg kg-1 week-1) for 3 consecutive weeks. One week later animals were randomised to receive either PBD or sham PBD and thereafter to receive s.c. injections of either saline or CR-1409 (10 mg kg-1 day-1, 5 days a week). Six months after operation surviving rats were killed as follows: sham + saline 20, PBD + saline 19, sham + CR-1409 14, PBD + CR-1409 11. Cardiac blood was taken for CCK assay and the pancreas was excised for wet weight measurement and quantitative estimation of atypical acinar cell foci (AACF), the precursor of carcinoma. PBD reduced median body weight (3-20% less than shams) but trebled the absolute and relative pancreatic weights (P < 0.001). CR-1409 blunted this adaptive response to PBD, reducing absolute pancreatic weight by 35% (P < 0.005). PBD quadrupled circulating CCK concentrations, regardless of the antagonist treatment. Acidophilic AACF occurred only in rats with PBD. CR-1409 markedly reduced the number of observed acidophilic AACF by 90% (P < 0.001) and the number of foci per pancreas by 93% (P < 0.001). Moreover, CR-1409 reduced the mean focal diameter of each lesion by 18% (P < 0.005), the mean focal volume by 58% (P < 0.05) and the percentage of pancreas occupied by acidophilic foci by 95% (P < 0.001). PBD enhances pancreatic carcinogenesis by causing hypercholecystokininaemia, and CR-1409 largely inhibits this enhancement.

Topics: Animals; Azaserine; Biliopancreatic Diversion; Body Weight; Cholecystokinin; Cocarcinogenesis; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Proglumide; Rats; Rats, Wistar

The effects of pancreaticobiliary diversion (PBD) and gastric fundectomy on the pancreas in azaserine-treated rats were studied over 14 months. Sham-operated azaserine-treated animals served as controls. A significant increase in pancreatic weight and total DNA and protein content was found in PBD-operated and fundectomized animals. DNA flow cytometry showed a significantly increased ratio of tetraploid to diploid cells in pancreatic tissue in both experimental groups. Mean values of all these variables were significantly higher after PBD than after fundectomy. Acidophilic atypical acinar cell foci of the pancreas were observed in all of the experimental and 75% of the control animals. The volume density of these foci was significantly higher in each experimental group than in the controls. The volume density, radioactive thymidine labeling index, and mitotic index of the foci were significantly higher after PBD than after fundectomy. Changes consistent with pancreatic adenoma were diagnosed in the PBD group only. It is concluded that not only PBD with endogenous hypercholecystokininemia, but also fundectomy with endogenous hypergastrinemia lasting about half of the life span in rats, induces pancreatic hypertrophy and enhances the development of precancerous pancreatic changes after azaserine treatment. In comparison with PBD, fundectomy caused less pronounced changes and no observable neoplasia.

Topics: Animals; Azaserine; Bile Ducts; Cholecystokinin; DNA; Gastric Fundus; Male; Pancreatic Ducts; Pancreatic Neoplasms; Rats; Rats, Wistar

Pancreatic nodules were produced in rats by either feeding raw soya flour alone or by injection of azaserine plus raw soya flour feeding. The resulting nodules were studied to determine whether there was any functional difference between this tissue and the relatively normal internodular pancreas. Tissue DNA and trypsin content were significantly elevated in nodules compared to the adjacent tissue. With fasting, protein and enzyme content increased significantly and equally in both nodular and internodular tissues. RNA levels fell significantly and the decrease was more pronounced in nodular tissue. The responsiveness of the multinodular pancreas to cholecystokinin was examined by measuring pancreatic secretion basally and in response to cholecystokinin. Both the volume and protein content secreted by the multinodular pancreas were greatly elevated above control levels. When corrected for pancreatic weight, the difference remained significant and appeared to be due to increased basal secretion by the nodular pancreas. These studies demonstrate that azaserine-raw soya flour induced nodules are functionally efficient. Furthermore, the secretory response to cholecystokinin of these nodules is equal to or higher than that of normal tissue.

Topics: Amylases; Animals; Azaserine; Cholecystokinin; Fasting; Male; Pancreas; Pancreatic Neoplasms; Rats; Rats, Wistar; Trypsin

Cholecystokinin and bombesin have been shown to promote pancreatic growth and development of azaserine-induced acidophilic atypical acinar cell nodules in rat pancreas after treatment for 16 weeks. Lorglumide, a specific cholecystokinin receptor antagonist, inhibited the stimulating effect of cholecystokinin, but not of bombesin. The present study was carried out to determine effects of cholecystokinin and bombesin, alone and in combination with lorglumide, on pancreatic growth and carcinogenesis after chronic treatment. The animals were killed 8 months after the start of treatment. Growth of the pancreas and the development of acidophilic atypical acinar cell nodules in exocrine pancreas was enhanced significantly by both cholecystokinin and bombesin, but the number of carcinomas was increased only by bombesin. Lorglumide inhibited the effects of cholecystokinin on both pancreatic growth and on the development of acidophilic nodules. The effects of bombesin on pancreatic growth and development of pancreatic lesions, except for adenomas, were not inhibited by lorglumide.

Topics: Animals; Azaserine; Bombesin; Carcinogens; Cholecystokinin; Drug Synergism; Male; Pancreatic Neoplasms; Proglumide; Rats; Rats, Wistar; Receptors, Cholecystokinin

Studies were undertaken to evaluate the effects of caloric restriction on voluntary exercise in a rat model of pancreatic cancer. Suckling male Lewis rats were initiated with 3 doses (30 mg/kg body weight) of the pancreatic carcinogen azaserine. At 28 days of age they were weaned to one of four experimental protocols; namely, sedentary/ad libitum fed, voluntary exercise/ad libitum fed, sedentary/food restricted, and voluntary exercise/food restricted. Voluntary exercise was provided by free access to running wheels fitted with odometers. Food restriction was intended to be mild, at less than 10% reduction of ad libitum intake. Putative pre-neoplastic pancreatic foci were identified microscopically at 4 months post-azaserine treatment. As previously shown, food restriction led to increased wheel activity, but the increased activity could not be maintained beyond the first half of the post-initiation treatment phase. Additionally, the extensive wheel running occurred only when available food was restricted by greater than 10%. Exercise per se had a lesser effect compared to food restriction on pancreatic tumorigenesis.

Topics: Analysis of Variance; Animals; Azaserine; Food Deprivation; Male; Pancreatic Neoplasms; Physical Conditioning, Animal; Rats; Rats, Inbred Lew; Volition

Many reports have emphasized the role of gastrin as a growth factor for normal gastrointestinal mucosa and gastrointestinal cancers. Recent studies have pointed out that this peptide acts also as a growth factor for the pancreatic cancer cell line AR42J. This effect is mediated by gastrin [cholecystokinin (CCK)-B] receptors. In the present study, we investigated gastrin (CCK-B) receptor expression in the azaserine-induced rat pancreatic carcinoma DSL-6, comparing it to normal rat pancreas, and we also characterized CCK receptor subtypes in this tumor. The results showed that there is extensive gastrin binding to the DSL-6 pancreatic carcinoma. No evidence of specific gastrin binding to normal pancreas was found. Analysis of the ability of gastrin-17-I to inhibit 125I-gastrin-I binding demonstrated that gastrin bound to a single class of receptors with a Kd of 0.21 +/- 0.04 nM and a binding capacity of 184 +/- 29 fmol/mg protein. 125I-Gastrin-I binding was inhibited by the specific CCK-B receptor antagonist L365,260 approximately 40 times more effectively than by the specific CCK-A receptor antagonist L364,718. Analysis of the ability of cholecystokinin octapeptide (CCK-8) to inhibit 125I-Bolton-Hunter-CCK-8 binding revealed two CCK binding sites, i.e., a high affinity site and a low affinity site. The observed binding affinities of CCK-8 were then introduced into the computer analysis of the dose-inhibition curve of the ability of gastrin-17-I to inhibit binding of 125I-Bolton-Hunter-CCK-8, which was significantly better fit by a three-site model than by a two-site model. The three sites meet the criteria for CCK-B, high affinity CCK-A, and low affinity CCK-A receptors. The binding capacity of CCK-B receptors constitutes 34% of the total high affinity CCK binding sites. This study demonstrated that DSL-6 pancreatic carcinoma expresses three subtypes of CCK receptors. Gastrin (CCK-B) receptors, which were not detected in normal rat pancreas, constitute about one third of the total high affinity CCK receptors. We suggest that novel expression of gastrin (CCK-B) receptors may be generated by gene mutation or amplification during carcinogenesis and may play an important role in promoting tumor growth.

Topics: Animals; Azaserine; Gastrins; Male; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Receptors, Cholecystokinin; Sincalide

The results of a previous 4-mo study in azaserine-treated rats and BOP-treated hamsters indicated that orchiectomy inhibited pancreatic growth and development of putative preneoplastic lesions in the exocrine pancreas of rats but not hamsters. This 12-mo study was carried out to investigate the effects of orchiectomy, alone and in combination with testosterone, and of treatment with cyproterone acetate on pancreatic carcinogenesis in azaserine-treated rats and BOP-treated hamsters. Treatment started 4 mo after injection of the carcinogen. In orchiectomized rats, pancreatic wt was lower than in controls, whereas pancreatic wt of orchiectomized rats treated with testosterone was similar to that of controls. Both orchiectomy and cyproterone acetate caused a decrease in body wt gain and had an inhibitory effect on pancreatic carcinogenesis. Testosterone treatment did not influence the inhibitory effects of orchiectomy on body wt gain and on pancreatic carcinogenesis. In hamsters, neither orchiectomy, alone or in combination with testosterone, nor cyproterone acetate (CA) affected pancreatic growth or pancreatic carcinogenesis. This study indicates that testosterone plays a minor role in the development of pancreatic tumors induced in rats by azaserine but not in that of pancreatic tumors induced in hamsters by BOP.

Topics: Animals; Azaserine; Body Weight; Cricetinae; Cyproterone; Cyproterone Acetate; Growth Substances; Male; Mesocricetus; Nitrosamines; Orchiectomy; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains; Specific Pathogen-Free Organisms; Testosterone

The controversial issue of enhanced pancreatic carcinogenesis following partial gastrectomy has been explored in male Wistar rats (n = 40) weighing 250-300 g. Animals were randomised to receive either 60% distal gastrectomy with Roux-en-Y reconstruction or gastrotomy and resuture (control). Immediately after operation each group was further divided into two subgroups, receiving i.p. injections of either saline or azaserine (30 mg kg-1 wk-1 for 3 weeks). At 15 months blood was obtained at 0, 5, 15 and 30 min after a fatty meal for cholecystokinin (CCK) assay; rats were then killed. Pancreatic wet weight was measured, and histological sections were examined for atypical acinar cell foci (AACF), the putative precursor lesion of carcinoma. There were no significant differences in body weight or pancreatic weight between controls and rats with gastrectomy. Only azaserine-treated rats had acidophilic AACF. Partial gastrectomy substantially increased the number of acidophilic AACF per pancreas (median 26.05 vs 2.09; P less than 0.005), with a 9-fold increase in their volume (P less than 0.005). Basal and postprandial plasma CCK concentrations were higher after gastrectomy than in controls (P less than 0.05). Partial gastrectomy has an enhancing effect on azaserine-induced pancreatic carcinogenesis, probably by means of increased CCK release.

Topics: Anastomosis, Roux-en-Y; Animals; Azaserine; Cholecystokinin; Dietary Fats; Follow-Up Studies; Gastrectomy; Male; Neoplasms, Experimental; Organ Size; Pancreas; Pancreatic Neoplasms; Postoperative Complications; Precancerous Conditions; Rats; Rats, Inbred Strains; Stomach

Cholecystokinin (CCK) is a growth factor for normal pancreas. Numerous studies also suggest that CCK promotes pancreatic carcinogenesis in the rat. Our previous studies suggested that growth of preneoplastic pancreatic foci was stimulated by CCK more than that of normal pancreas. We hypothesized that such differential growth might be due to increased numbers of CCK receptors in neoplastic tissue. Azaserine-induced pancreatic carcinoma (DSL6) had an increased high-affinity CCK receptor binding capacity of 122 +/- 23 (SD) fmol/mg protein compared to 12 +/- 2 fmol/mg protein in normal pancreas (P less than 0.001). The Kd of the high-affinity site was 0.33 +/- 0.04 nM for carcinoma and 0.46 +/- 0.08 nM for normal pancreas (P less than 0.01). The amount of cholecystokinin octapeptide (CCK-8) bound to high-affinity receptor was 8.6 +/- 1.9 fmol/mg protein for DSL6 compared to 0.6 +/- 0.2 fmol/mg protein in normal pancreas (P less than 0.001). Azaserine-induced premalignant nodules were compared to remaining internodular pancreas. Nodules demonstrated a mean high-affinity CCK receptor binding capacity of 38 +/- 9 fmol/mg protein compared to 6 +/- 3 fmol/mg protein in internodular pancreas (P less than 0.001). The amount of CCK-8 bound to high-affinity receptor was 3.1 +/- 0.8 fmol/mg protein in nodules compared to 0.6 +/- 0.3 fmol/mg protein in internodular pancreas (P less than 0.001). Overexpression of high-affinity CCK-8 receptor in premalignant and malignant azaserine-induced tumors may result in a growth advantage relative to normal pancreas.

Topics: Animals; Azaserine; Binding, Competitive; DNA, Neoplasm; Hydrogen-Ion Concentration; Male; Pancreatic Neoplasms; Precancerous Conditions; Rats; Receptors, Cholecystokinin; Sincalide; Succinimides; Temperature; Time Factors

The role of cholecystokinin in dietary fat-promoted pancreatic carcinogenesis was investigated in azaserine-treated rats, using lorglumide, a highly specific cholecystokinin-receptor antagonist. The animals were killed 8 months after the start of treatment. Cholecystokinin, but not dietary unsaturated fat, increased pancreatic weight. Rats treated with cholecystokinin developed more acidophilic atypical acinar cell nodules, adenomas and adenocarcinomas than control animals. Rats maintained on the high-fat diet developed significantly more adenomas and adenocarcinomas than controls given a diet low in unsaturated fat. Lorglumide largely inhibited the enhancing effect of cholecystokinin, but not of dietary fat, on pancreatic carcinogenesis indicating that it is unlikely that the promoting effect of dietary unsaturated fat on pancreatic carcinogenesis is mediated via cholecystokinin.

Topics: Animals; Azaserine; Body Weight; Cholecystokinin; Dietary Fats; Liver; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Proglumide; Rats; Rats, Inbred Strains; Receptors, Cholecystokinin

The effects of treatment with the somatostatin analogue Sandostatin, separately and in combination with surgical castration, on the development of azaserine-induced lesions in rat pancreas and N-nitrosobis(2-oxopropyl)amine (BOP)-induced lesions in hamster pancreas were investigated. The animals were divided in 4 groups and treated as follows: (a) controls, injected s.c. with saline solution (0.9% NaCl); (b) orchiectomy directly after the last treatment with carcinogen; (c) Sandostatin (SMS 201-995) subcutaneously; (d) orchiectomy followed by treatment with Sandostatin. No significant suppressive effects on plasma EGF or IGF-I concentrations were noted after Sandostatin treatment, but plasma gastrin levels decreased slightly in the rats, not in the hamsters. In rats, Sandostatin treatment enhanced rather than inhibited growth of acidophilic atypical acinar cell nodules. In hamster pancreas, by contrast, Sandostatin inhibited the development of putative pre-neoplastic ductular lesions. There was no interaction between treatment with Sandostatin and surgical castration. It was concluded that Sandostatin, when administered prophylactically, has an inhibitory effect on the growth of putative pre-neoplastic ductular, but not acinar, lesions.

Topics: Animals; Azaserine; Carcinogens; Cricetinae; Drug Interactions; Eating; Growth Substances; Guinea Pigs; Hormones; Male; Mesocricetus; Nitrosamines; Octreotide; Orchiectomy; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

This study investigates digestive and lysosomal enzyme secretion of azaserine-induced pancreatic acinar carcinomas in response to cholecystokinin in rats. After 15-20 months of treatment, 95% of the animals developed pancreatic acinar carcinomas encompassing more than 90% of the tissue. In anesthetized rats basal trypsin output was significantly elevated in the tumor group despite diminished fluid secretion. There was a linear correlation between tumor size and basal amylase and trypsin secretion. Intravenous infusion of cholecystokinin (25 IDU.kg-1.h-1) induced a significantly lower secretion of fluid per gram pancreas, as well as decreased amylase and trypsin output, in the tumor group compared with the control group. Plasma amylase and lipase levels were significantly elevated in the tumor group under both basal and stimulated conditions. The output of the lysosomal enzymes beta-D-glucuronidase and alpha-D-glucosidase was significantly increased in the tumor group under background secretin infusion. Additional cholecystokinin infusion caused a sharp increase in glucuronidase output in this group with only minimal increase in controls. Glucosidase output increased similarly in both groups. Amylase, lipase, and trypsin tumor tissue concentrations were markedly reduced by 85%, 90%, and 87%, respectively. It was concluded that the decreased secretory response of digestive enzymes may result from decreased synthesis, lowered storage capabilities, and/or a decreased/increased responsiveness to cholecystokinin. Increased glucuronidase secretion may reflect an augmented cell turnover of malignant tissue.

Topics: Adenoma; alpha-Glucosidases; Amylases; Animals; Azaserine; Carcinoma; Cholecystokinin; Food, Formulated; Glucuronidase; Lipase; Lysosomes; Male; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Secretin; Trypsin

The alpha, mu and pi classes of glutathione S-transferase (GST) were evaluated as early immunocytochemical markers for the development of atypical foci within the pancreases of azaserine treated rats. Changes detected with haematoxylin and eosin (H&E) were compared with those detected by immunocytochemistry using antibodies raised against each class of GST. All foci detected with H&E staining were classified as acidophilic atypical acinar cell nodules (AACN), which have previously been reported in this model. All of these AACN overexpressed GST mu. However, 64% of foci detected with GST mu staining had not been identified as AACN during a prior examination with H&E. Re-evaluation of the H&E sections revealed that some of these foci showed subtle morphological changes which are indicative of AACN. In many cases, however, no morphological difference could be seen with H&E staining. We conclude that immunocytochemical staining for GST mu is a more reliable and sensitive method than H&E for detecting the early stages of azaserine-induced foci. Furthermore, we suggest that studies on the incidence and growth of these foci can be shortened considerably if GST mu staining is used in conjunction with H&E.

Topics: Animals; Azaserine; Biomarkers, Tumor; Eosine Yellowish-(YS); Glutathione Transferase; Hematoxylin; Isoenzymes; Male; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains; Staining and Labeling

Diets enriched with fat, especially unsaturated fat, promote experimental pancreatic carcinogenesis, but little is known of the effects of individual fatty acids. The effect of stearic and oleic acid on pancreatic fatty acids and atypical acinar cell nodules (preneoplastic lesions) was studied in 14-day-old weanling male Leeds strain rats (n = 60) given the carcinogen azaserine. Rats were allocated to one of six groups: untreated controls (n = 10), 20% stearic acid diet (n = 10), 20% oleic acid diet (n = 10), carcinogen alone (n = 10), carcinogen plus 20% stearic acid diet (n = 10) or carcinogen plus 20% oleic acid diet (n = 10). Azaserine was administered by intraperitoneal injection in a dose of 30 mg/kg at 2, 3 and 4 weeks of age. When total lipid extracts of pancreas were examined, there was an increase in stearic acid in the stearic acid fed group and an increase in oleic acid in the oleic acid fed group, irrespective of carcinogen treatment. The relative content of all other pancreatic fatty acids was suppressed by feeding oleic acid. At 26 weeks, the number and volumetric indices of pancreatic atypical acinar cell nodules was increased only in rats given azaserine and oleic acid. The enhancing effect of oleic acid on pancreatic carcinogenesis may be associated with pancreatic fatty acid changes.

Topics: Animals; Azaserine; Dietary Fats; Drug Synergism; Fatty Acids; Male; Oleic Acids; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains; Stearic Acids

We studied the effects of hormonal manipulation by orchiectomy, alone or in combination with the aromatase inhibitor aminoglutethimide (AGT), and by luteinizing hormone-releasing hormone agonist (LH-RH-A) (goserelin) treatment on the development of early putative (pre)neoplastic lesions induced in the pancreas of rats and hamsters by azaserine and N-nitrosobis(2-oxopropyl)amine respectively. Treatment of the animals started 1 week after the last injection with carcinogen and continued for 4 months. Orchiectomy caused a significant inhibition of growth of acidophilic atypical acinar cell nodules in the rat model, whereas surgical castration did not show an effect in the hamster model. In rats, but not in hamsters, orchiectomy resulted in a significant decrease in body weight and in absolute, but not relative pancreatic weight. Treatment of the animals with AGT or goserelin did not cause a significant effect on the development of either putative preneoplastic acinar lesions in rat pancreas or early ductular lesions in hamster pancreas. Hamsters showed clearly higher plasma epidermal growth factor (EGF) and insulin-like growth factor 1 (IGF-1) concentrations than rats, while plasma testosterone levels were significantly lower. Plasma EGF and IGF-1 levels decreased with increasing age in both control and treatment groups. Compared to controls there were no clear unequivocal effects of treatment on EGF, IGF-1 and gastrin levels. Plasma testosterone levels decreased by orchiectomy and LH-RH-A treatment. In rats hormone-induced effects on food intake and altered nutritional status might be important with respect to the development of carcinogen-induced preneoplastic pancreatic lesions.

Topics: Aminoglutethimide; Animals; Azaserine; Body Weight; Buserelin; Carcinogens; Cricetinae; Epidermal Growth Factor; Gastrins; Goserelin; Male; Mesocricetus; Nitrosamines; Orchiectomy; Organ Size; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains; Somatomedins; Testosterone

A study was made on the effects of long-term dietary administration of beta-carotene, vitamin C, vitamin E and selenium, either alone or in combination, on azaserine-induced pancreatic carcinogenesis in rats. Male Wistar rats were given two i.p. injections of 30 mg azaserine per kg body weight at 19 and 26 days of age. The rats were allocated to eight groups of 40 animals each and were fed an AIN-76 diet rich in saturated fat (20% lard), either as such or after supplementation with beta-carotene, vitamin C, beta-carotene + vitamin C, vitamin E, selenium, vitamin E + selenium, or the combination of all micronutrients investigated. Fifteen months after the last treatment with azaserine the survivors were killed. The pancreata were examined for the number and size of advanced putative preneoplastic lesions and the number of neoplasms as well. Rats maintained on a diet high in either beta-carotene, vitamin C or selenium developed significantly less atypical acinar cells nodules, adenomas and carcinomas as compared to controls. The number of tumour-bearing animals was significantly lower in the groups fed the diet high in beta-carotene or selenium. In animals of the group given a diet high in all micronutrients investigated, both the number and incidence of pancreatic tumours was lower than in all other groups. It was concluded that selenium, beta-carotene and vitamin C, alone as well as in combination, have an inhibitory effect on pancreatic carcinogenesis induced in rats by azaserine.

Topics: Animals; Ascorbic Acid; Azaserine; beta Carotene; Body Weight; Carotenoids; Diet; Drug Combinations; Liver; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains; Regression Analysis; Selenium; Vitamin E

The effect of neurotensin on pancreatic carcinogenesis induced by azaserine was investigated in Wistar rats. Rats were given weekly injections of 10 mg/kg body weight of azaserine for 25 weeks and 200 micrograms/kg body weight of neurotensin in depot form every other day for 62 weeks. Carcinogen-induced pancreatic lesions were examined by histochemical techniques, and were classified as ATPase-positive or ATPase-negative. In week 62, quantitative histological analysis showed that prolonged administration of neurotensin significantly reduced the volume (as percent of parenchyma) of ATPase-positive pancreatic lesions, which are closely correlated with the ultimate development of pancreatic cancer. Histologically, pancreatic adenocarcinomas occurred at a significantly lower rate in rats treated with neurotensin than in untreated rats. Administration of neurotensin also significantly decreased the labelling indices of carcinogen-induced pancreatic lesions, but not of the surrounding acinar cells. These findings indicate that neurotensin inhibits pancreatic carcinogenesis, and that this may be related to the reduction of ATPase-positive lesions and to the inhibition of cell proliferation in neoplastic lesions of the pancreas.

Topics: Animals; Azaserine; Body Weight; Male; Neurotensin; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains; Time Factors

The kinetics of induction and growth of acinar cell lesions has been investigated in rat pancreas after a single dose of the carcinogen azaserine. The time--response relationship was studied in male Wistar-related rats given a single i.p. injection of 30 mg L-azaserine/kg body weight at 18 days of age. Rats were killed between 4 and 78 weeks after treatment and ATPase-stained pancreas sections were quantitatively evaluated for the number and size of acidophilic, ATPase-positive and basophilic, ATPase-deficient foci. The number of acidophilic foci remained constant from 8 weeks onwards, while the number of basophilic foci slightly increased with time. The size of both acidophilic and basophilic foci increased throughout the experimental period. Due to two times higher number/cm3 and faster growth of the acidophilic foci, four times more acidophilic than basophilic focus tissue was present at the end of the experiment. Progression of acidophilic foci to adenomas and carcinomas was occasionally seen at later time points (greater than 34 weeks) in this rat strain. The dose--response relationship was studied in male and female Sprague--Dawley rats given a single i.p. injection of 0-45 mg azaserine/kg body weight at 19 days of age. Rats were autopsied at 17 weeks after treatment, and pancreas sections were quantitatively evaluated after ATPase histochemistry. The relationship between dose and number of foci was linear up to 30 mg/kg azaserine for both acidophilic and basophilic foci in males and females. For each individual dose, the number of foci induced was the same in males and females, and there were two to three times more acidophilic than basophilic foci. The percentage of pancreatic tissue occupied by focus tissue was 1.75 times higher in males, pointing to a higher growth-potential of acidophilic foci in males than in females. The first-order dose--response kinetics indicate that the conversion of a normal acinar cell into a focus-forming cell occurs by one specific azaserine-mediated rare event, occurring probably at the genetic level of the target cell.

Topics: Adenosine Triphosphatases; Animals; Azaserine; Dose-Response Relationship, Drug; Female; Kinetics; Male; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains; Sex Factors

The effect of tetragastrin on pancreatic tumors induced by azaserine was investigated in Wistar rats. Rats were given 25 weekly injections of 10 mg/kg body weight of azaserine and 1 mg/kg body weight of tetragastrin as a suspension in olive oil every other day. Carcinogen-induced pancreatic lesions were examined by histochemical techniques, and were classified as ATPase-positive or ATPase-negative. In week 62, quantitative histological analysis showed that prolonged administration of tetragastrin had little or no influence on the number and size of the carcinogen-induced pancreatic lesions, although it caused significantly increased cell proliferation, indicated by a greater labelling index of the pancreatic acinar cells.

Topics: Adenosine Triphosphatases; Animals; Azaserine; Body Weight; Cell Division; Gastrins; Male; Mitotic Index; Organ Size; Pancreatic Neoplasms; Rats; Rats, Inbred Strains; Tetragastrin

Studies were undertaken to evaluate the effects of exercise on the development of pancreatic cancer. Exercise is one life-style factor that has received little attention with regard to its role in the etiology of cancer. Male Lewis and female F344 rats were initiated with azaserine during the suckling period and weaned to the experimental protocols. Food and water were available ad libitum. A purified diet of 20% unsaturated fat was fed to both the sedentary and exercise groups. Rats of the exercise group had free access to voluntary exercise wheels. At approximately 2 and 4 months postinitiation, pancreases were evaluated for the number and size of azaserine-induced putative preneoplastic foci by quantitative stereology. Voluntary exercise activity peaked at approximately 2 months postinitiation with a gradual decline in activity there-after. Male Lewis rats averaged 0.95 +/- 0.13 km/day (SE) and female F344 rats averaged 2.73 +/- 0.26 km/day of voluntary wheel running. Compared with the sedentary groups, male Lewis and female F344 rats with access to the running wheels had significantly smaller foci at 4 months postinitiation. Azaserine-induced foci were evaluated in the male Lewis rats at both 2 and 4 months postinitiation. At 4 months postinitiation, the size and growth rate (as measured by [3H]thymidine autoradiography) of foci were less in the rats with access to the exercise wheels. No differences were observed at 2 months postinitiation. Access to voluntary exercise reduced the growth rate of azaserine-induced pancreatic foci. The effect occurred late in the postinitiation phase and was not directly related to the extent of running activity early in the postinitiation phase.

Topics: Animals; Azaserine; Disease Models, Animal; Female; Male; Pancreatic Neoplasms; Physical Conditioning, Animal; Rats; Rats, Inbred F344; Rats, Inbred Lew; Time Factors

Dietary fat has been shown to enhance pancreatic carcinogenesis. Uncertainty still exists whether the amount of linoleic acid or the amount of fat is the main determining factor. In the present study the effects of a high lard, a low lard, a linoleic acid supplemented low lard and a laboratory chow diet were investigated on the development of (pre)neoplastic pancreatic lesions in rats treated with azaserine. The rats were killed 15 months after carcinogen treatment and the pancreata were examined for the number and size of putative preneoplastic lesions and for the occurrence of neoplasms. The linoleic acid supplemented low lard group showed a significantly increased number of basophilic foci as compared to the low lard group. Rats maintained on the linoleic acid supplemented diet or the laboratory chow developed significantly less atypical acinar cell nodules larger than 1.0 mm in diameter and adenocarcinomas as compared to the high lard group. Animals maintained on the low lard diet developed significantly less adenocarcinomas than rats on the high lard diet did. Overall, the number of benign and malignant pancreatic tumours was consistently higher in the high lard group and consistently lower in the linoleic acid supplemented low lard group than the number of these types of tumours in the low lard group, with the exception of the number of carcinomas in situ, which was lower in the high lard group. The laboratory chow group showed a significant lower number of atypical acinar cell nodules with a diameter over 1.0 mm and a lower number of adenocarcinomas as compared to both the high lard and the low lard group. It is concluded that a diet high in saturated fat has a promoting and that laboratory chow has an inhibitory effect on pancreatic carcinogenesis in azaserine-treated rats.

Topics: Animals; Azaserine; Body Weight; Diet; Dietary Fats; Eating; Incidence; Linoleic Acid; Linoleic Acids; Liver; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Benzyl acetate was found to induce liver tumours and gastric squamous neoplasms in mice in a chronic bioassay conducted through the National Toxicology Program. An increased incidence of acinar cell adenomas of the pancreas of F344 rats was noted in the bioassay, but the significance of these lesions was confounded because the benzyl acetate was given by gavage in corn oil. The use of corn oil as a vehicle has been shown to enhance the growth of such lesions in the rat pancreas. The current studies were undertaken to evaluate benzyl acetate alone as an initiator and promoter of carcinogenesis in the pancreas. Alkaline elution analysis of acinar cell DNA showed no evidence of damage 1 hr after administration of benzyl acetate. Significant stimulation of growth of azaserine-induced foci was observed in a 6-month study, and a low but significant incidence of carcinoma in situ was observed in rats fed benzyl acetate in the diet for 2 yr. These experiments suggest that benzyl acetate is a weak promoter of the growth of carcinogen-induced and spontaneous pre-neoplastic foci in the pancreas.

Topics: Adenoma; Animals; Azaserine; Benzyl Compounds; Chi-Square Distribution; Corn Oil; DNA; Kidney; Kidney Failure, Chronic; Male; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred F344

We examined the pattern of expression of several proto-oncogenes during nonneoplastic growth and in acinar cell neoplasms in the rat pancreas. The levels of c-myc, c-raf-1, and c-Ki-ras mRNAs were increased in regenerating pancreata following surgical partial pancreatectomy and following administration of camostat. We also investigated proto-oncogene expression associated with the progression of pancreatic cancers in azaserine-treated rats. Injection of a single dose (30 mg/kg) of azaserine (O-diazoacetyl-L-serine) to 14-d-old rats leads to a variety of neoplastic lesions in the rat pancreas. Total RNA was isolated from lesions in various stages of tumor progression, including adenomas, carcinomas in situ, and invasive carcinomas. We observed increased expression of c-myc, c-raf-1, and c-Ki-ras in azaserine-induced adenomas and carcinomas. Actin expression was also increased in these tissues, whereas amylase expression was variable. However, when compared to the normal growing pancreas, the level of proto-oncogene expression in the adenomas and carcinomas was disproportionate to the degree of cellular division in those tissues. Thus, the alterations induced by azaserine apparently caused a deregulated increase in expression of cellular oncogenes associated with growth regulation.

Topics: Adenoma; Animals; Azaserine; Blotting, Northern; Carcinoma; Cell Cycle; Esters; Gabexate; Gene Expression; Guanidines; Mitotic Index; Pancreas; Pancreatic Neoplasms; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-myc; Proto-Oncogene Proteins c-raf; Proto-Oncogene Proteins p21(ras); Proto-Oncogenes; Rats; Rats, Inbred Lew; Regeneration; RNA, Neoplasm

Putatively preneoplastic, pancreatic atypical acinar cell foci (AACF) and nodules (AACN), collectively termed atypical acinar cell lesions (AACL), were induced in male Lewis rats by L-azaserine (300 mg/kg body weight [bw] in divided doses). Rats given carcinogen and then fed a lipotrope deficient (LD) diet developed a significantly greater number of larger lesions than animals fed complete diet throughout the experiment. It is suggested that lipotrope deficiency plays a promoting role in this model of pancreatocarcinogenesis. Ultrastructural morphometric studies of AACF, when compared to control tissues, revealed the following significant results: 1) a decrease in surface area of cell cytoplasm with no change in nuclear area, and hence increased nucleus/cytoplasm (N/C) ratio; 2) a reduction in size and uniformity of zymogen granules; and 3) an increase in number of granules per microns 2 of cell. The results suggest that arrested development of the AACF cells is associated with reduced cytoplasm and zymogen production per cell. AACL may be eosinophilic due to an overall increased concentration of zymogen in these hyperplastic lesions and not because individual acinar cells in the AACL contain an increased amount of zymogen or are "zymogen-rich," as has been reported.

Topics: Animals; Azaserine; beta-Lipotropin; Cell Transformation, Neoplastic; Choline Deficiency; Cytoplasmic Granules; Diet; Enzyme Precursors; Folic Acid Deficiency; Male; Methionine; Microscopy, Electron; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Lew; Vitamin B 12 Deficiency

The effects of cyclosporine (CsA), an immunosuppressive agent, on azaserine-induced pancreatic carcinogenesis in rats were investigated using the short-term assays of the quantitation of atypical acinar cell foci. Male Lewis rats at 14 days of age were given a single intraperitoneal injection of azaserine (30 mg/kg). At 25 days of age, the treated rats were weaned and divided into two groups fed either basal diet or the same diet containing 0.011% CsA. Saline-injected rats were also fed the CsA diet. Rats were killed 4 months after azaserine injection and acidophilic and basophilic foci in the pancreas were quantified. The pancreas of the rats given saline injection and maintained on the CsA diet showed no significant histological alterations. The dietary CsA after the injection of azaserine markedly reduced the number of both acidophilic and basophilic foci. It is concluded that addition of CsA to the diet inhibits the growth of initiated cells to form foci in the pancreas of azaserine-treated rats. The experimental model is useful in analyzing the modifying role of this immunosuppressant in the induction and growth of epithelial cell tumors.

Topics: Animals; Azaserine; Cyclosporins; Male; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Thymus Gland

In the rat, when pancreatic growth is stimulated there is an increased incidence of spontaneous pancreatic neoplasms and marked potentiation of the pancreatic carcinogen azaserine. Since previous studies showed that cholestyramine caused pancreatic growth in this species we have now studied the effect of azaserine in rats fed soya flour diets containing cholestyramine. Two groups, each of eight rats, were fed either heated soya flour (HSF) or raw soya flour (RSF). Two further groups, each of 12 rats, received the same diets containing 2% cholestyramine (HSF + C, RSF + C). In each group, four rats received azaserine (30 mg/kg i.p.) and the remainder saline, weekly, for the first 5 weeks. Animals were killed after 24 weeks and pancreatic growth and the number and size of pancreatic neoplastic nodules was measured. RSF caused a significant increase in pancreatic weight, protein, RNA and DNA, compared with HSF and cholestyramine caused a further significant increase in pancreatic weight, protein and RNA but not DNA. Azaserine did not affect pancreatic growth. In azaserine-injected rats significantly more nodules were seen and the nodules were larger and the tumour burden greater in rats fed HSF + C than in rats fed HSF alone. However, the nodule count and other nodule parameters were not significantly different in RSF and RSF + C fed rats. It is concluded that 2% cholestyramine enhances pancreatic growth when added to soya flour diets and in rats fed HSF it potentiates the action of azaserine on the pancreas. It does not increase the potentiation of azaserine seen with RSF up to 24 weeks.

Topics: Animals; Azaserine; Cholestyramine Resin; DNA; Drug Synergism; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Plant Proteins, Dietary; Proteins; Rats; Soybean Proteins

Dietary administration of dehydroepiandrosterone (DHEA) (0.6%) or butylated hydroxytoluene (BHT) (1%) during or subsequent to two i.p. injections of azaserine (30 mg/kg body wt) resulted in significant alteration of yield of preneoplastic lesions in both pancreas and liver. While concomitant application appeared not to have any effect on subsequent development of glutathione S-transferase P form (GST-P) positive hepatocellular lesions in either case, BHT and to a lesser extent also DHEA reduced initiation of pancreatic acinar carcinogenesis. Both BHT and DHEA were associated with significant increase in GST-A form positive pancreatic foci when administered after cessation of carcinogen treatment while clearly inhibiting liver lesion development. The results point to a marked differential in the response of the liver and pancreas to external stimulus with regard to preneoplastic focal lesions while demonstrating significant second stage promotion of pancreatic acinar carcinogenesis by BHT and DHEA.

Topics: Animals; Azaserine; Butylated Hydroxytoluene; Dehydroepiandrosterone; Liver Neoplasms; Male; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains

The effects of coffee and dietary fat (alone and in combination) on the development of preneoplastic lesions in exocrine pancreas were investigated in rats and hamsters, treated with azaserine or N-nitrosobis(2-oxopropyl)amine, respectively. The animals were given the respective diets (5% or 25% corn oil) and coffee (instead of drinking water) within one week after the treatment with carcinogen. At four months postinitiation, the pancreata were quantitatively examined for the number and size of preneoplastic foci. In rats, coffee alone inhibited growth of acidophilic foci and, moreover, slightly inhibited the positive modulating effect of fat on growth of these foci, pointing to a negative rather than a positive interaction between these two life-style factors. In hamsters, coffee alone enhanced growth of cystic foci, whereas fat alone enhanced growth of ductular foci. An interaction between fat and coffee on pancreatic carcinogenesis in hamsters could not be demonstrated.

Topics: Animals; Azaserine; Body Weight; Carcinogens; Coffee; Cricetinae; Dietary Fats; Drug Interactions; Male; Nitrosamines; Organ Size; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains; Specific Pathogen-Free Organisms; Time Factors; Weaning

The effect of chronic coffee ingestion on dietary fat-promoted pancreatic carcinogenesis was investigated in rats and hamsters. Rats were given a single i.p. injection of 30 mg azaserine per kg body weight at 19 days of age. Hamsters were injected s.c. with 20 mg N-nitrosobis(2-oxopropyl)amine (BOP) per kg body weight at 6 and 7 weeks of age. The animals were fed a semi-purified diet high in unsaturated fat (25% corn oil) either in combination with coffee or not. Coffee was provided instead of drinking water. A separate group maintained on a diet low in unsaturated fat (5% corn oil) was included as extra controls. The rats and hamsters were given their diets and coffee after treatment with carcinogen. Terminal autopsy of rats was 15 months after azaserine treatment and of hamsters 12 months after the last injection with BOP. In rat pancreas, the numbers of adenomas and carcinomas were significantly lower in the group maintained on the combination of a high-fat diet and coffee than in the high-fat group without coffee, while in the latter group the number of adenomas and carcinomas had significantly increased as compared to the low-fat controls. In hamsters, the number of ductal/ductular adenocarcinomas had significantly increased in the high-fat group as compared to the low-fat controls. The inhibitory effect of coffee on dietary fat-promoted pancreatic carcinogenesis was also noticed in this species but was less pronounced than in rats. It was concluded that chronic coffee consumption has an inhibitory effect on dietary fat-promoted pancreatic carcinogenesis in rats and hamsters. More research is needed to elucidate the mechanism by which coffee (constituents) modulates carcinogenesis.

Topics: Adenocarcinoma; Animals; Azaserine; Cocarcinogenesis; Coffee; Cricetinae; Dietary Fats; Male; Mesocricetus; Nitrosamines; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Effects of sex steroids on pancreatic carcinogenesis during the early stage were studied in azaserine-treated rats of both sexes. Fischer rats were given weekly i.p. injections of azaserine (30 mg/kg) [CAS:115-02; diazoacetate serine(ester)] at 2 and 3 weeks of age and were divided into six groups. Castration, ovariectomy, and s.c. implantations of either a 0.3-mg or a 1.0-mg 17 beta-estradiol (CAS:50-28.2; estradiol) pellet were performed at 7 weeks of age. The groups were as follows: group 1, intact male; group 2, castrated; group 3, castrated plus 0.3 mg estradiol; group 4, castrated plus 1.0 mg estradiol; group 5, ovariectomized; and group 6, intact female. Rats were killed 4 months after the last injection of azaserine. Azaserine treatment induced atypical acinar cell foci and nodules (AACN) in both sexes. The acidophilic AACN are considered preneoplastic lesions. An apparent sex difference was observed; the number of acidophilic AACN was greater in male rats than in female rats. Castration caused a significant decrease in both the serum testosterone levels and the number of acidophilic AACN, which were comparable to those in ovariectomized female rats. Furthermore, when estradiol treatment was administered to the castrated male rats, a linear decrease in the number of acidophilic AACN and an elevation in the serum estradiol levels were observed and were dose dependent. There were also positive relationships between estradiol treatments and the mean pituitary and pancreas weights. These results showed that estradiol treatment and the drop in testosterone levels caused by castration were highly effective in inhibiting the development and growth of preneoplastic lesions of the pancreas of the rats treated with azaserine. This estradiol effect was dose dependent. The present study, therefore, provides evidence that estrogen may act as an inhibitor and androgen as a promoter in the early stage of pancreatic carcinogenesis in rats.

Topics: Animals; Azaserine; Castration; Estradiol; Female; Male; Mammary Glands, Animal; Organ Size; Pancreas; Pancreatic Neoplasms; Pituitary Gland; Precancerous Conditions; Rats; Rats, Inbred F344; Testosterone

Feeding of raw soya flour or other trypsin inhibitors such as camostate is a well-established method for promoting growth of (pre)neoplastic foci induced in the exocrine pancreas of rats by azaserine. The effect of trypsin inhibitors is thought to be mediated through an increased release of cholecystokinin. Using the specific cholecystokinin receptor antagonist lorglumide (CR-1409), we performed a 16-wk study to investigate the potential of this drug in inhibiting growth of putative preneoplastic foci and to determine whether and to what extent cholecystokinin is responsible for the effect of trypsin inhibitors on pancreatic growth. After initiation with 30 mg/kg of azaserine at 19 days of age, six groups of 15 rats each received one of the following treatments: camostate, cholecystokinin-8, or gelatin control, either or not in combination with CR-1409, once daily, 3 days wk for 16 wk. Plasma cholecystokinin levels, measured 30 min after the stimulus, were similar after camostate and cholecystokinin octapeptide administration. After 16 wk the pancreata were removed, weighted, and quantitatively analyzed for the number and size of putative preneoplastic foci by light microscopy. Both camostate and cholecystokinin octapeptide stimulated pancreatic growth and development of acidophilic putative preneoplastic foci, whereas growth of basophilic putative preneoplastic foci was inhibited by camostate but stimulated by cholecystokinin. CR-1409 almost completely abolished the effect of cholecystokinin and was found to cause a significant decrease in the effects of camostate. It is concluded that (a) cholecystokinin plays a significant role in camostate-stimulated growth of acidophilic putative preneoplastic foci in rat pancreas and (b) CR-1409 inhibits growth of putative preneoplastic foci induced in rat pancreas by azaserine and hence may be of potential value for the treatment of pancreatic cancer in humans.

Topics: Animals; Azaserine; Cholecystokinin; Esters; Gabexate; Glutamine; Guanidines; Male; Pancreatic Neoplasms; Precancerous Conditions; Proglumide; Rats; Rats, Inbred Strains; Receptors, Cholecystokinin; Sincalide; Trypsin Inhibitors

We examined the effect of varying the ratio of dietary omega-3 (omega 3) to omega-6 (omega 6) on the development of pancreatic preneoplastic lesions in male Wistar rats given azaserine at 14 days of age. As the ratio of dietary omega 3 to omega 6 fatty acids increased in a diet totaling 20% by weight of fat, the development of preneoplastic atypical acinar cell nodules (AACNs) at 4 months after dosing with azaserine decreased significantly. In addition, serum levels of prostaglandin thromboxane B2, prostaglandin E2, and 6-keto-prostaglandin F1 alpha decreased significantly. The fatty acid composition of the rbc membrane was also significantly influenced by the ratio of dietary omega 3 to omega 6 fatty acids. In a second experiment, we examined the effect of dietary intervention with a different type of fat (corn oil or menhaden oil) 2 months into the 4-month postdosing period on AACN development at the end of the post-dosing period. Intervention of the omega 6 fatty acid-rich diet with the omega 3 fatty acid-rich diet significantly decreased focal development. The opposite was true when intervention involved substituting the omega 3 fatty acid-rich diet with the omega 6 fatty acid-rich diet.

Topics: Animals; Azaserine; Cell Membrane; Corn Oil; Dietary Fats, Unsaturated; Dose-Response Relationship, Drug; Erythrocytes; Fatty Acids; Fatty Acids, Unsaturated; Fish Oils; Male; Pancreatic Neoplasms; Precancerous Conditions; Rats

The binding patterns of the lectin Ulex Europaeus-I (UEA-I) to pancreatic cells of Wistar rats from TNO, in azaserine-induced acinar cell lesions, was examined by peroxidase-conjugated UEA-I. In the normal rat, acinar cells showed this lectin binding to luminal and intracytoplasmic cell membranes. Four different types of acinar cell nodules could be distinguished in this rat treated with azaserine. Acinar cell lesions, types 1-3, showed stronger lectin binding than was seen in normal tissue, whereas in type 4 lesions acinar cells showed similar or weaker binding than did the normal cells. In type 1 lesions, UEA-I binding was restricted to the luminal and intracytoplasmic cell membranes. Strong basolateral cell membrane binding not seen in the normal and type 1 or type 4 lesions was characteristic for type 2 lesions. Type 3 lesions were considered as the intermediate between type 1 and type 2. Comparison of histocytologic and UEA-I binding patterns demonstrated that type 1 lesions correspond to 'acidophilic nodules', type 2 to 'well- to moderately differentiated carcinoma', type 3 to 'in situ carcinoma' and type 4 to 'basophilic nodules'. Based on this classification, all 'nodules within nodules' observed in the pancreases of azaserine-treated rats were of malignant types. The present study indicates that UEA-I binding is a useful marker to differentiate between the benign and malignant lesions induced in rat pancreas by azaserine.

Topics: Animals; Azaserine; Biomarkers, Tumor; Cell Membrane; Cytoplasm; Glycoconjugates; Histocytochemistry; Lectins; Male; Pancreas; Pancreatic Neoplasms; Plant Lectins; Rats; Rats, Inbred Strains

Chemoprevention by a synthetic retinoid, selenium, and these agents in combination during the postinitiation stages of carcinogenesis induced in rats by azaserine was evaluated. Male Lewis rats were given three weekly injections of 30 mg/kg azaserine while being fed a purified diet. One week after completion of carcinogen treatment, groups of rats were switched to the purified diet supplemented with either a retinoid, N-(2-hydroxyethyl)retinamide, at a level of 0.5 or 1 mmol/kg diet, or with 5 ppm sodium selenite, or with a combination of retinoid and selenium. One year after the diet change, the incidence of pancreatic and other neoplasms was determined by autopsy and histologic study. The incidence of pancreatic carcinoma (including carcinoma-in-situ, CIS) among nonretinoid-treated controls was 68%. Since the dietary supplements were fed after completion of exposure to the carcinogen, the effects on both pancreatic and liver carcinogenesis were exerted during the postinitiation phase of carcinogenesis. As in previous studies, the retinoid inhibited the progression of pancreatic carcinogenesis in a dose-related fashion. Selenium alone had no effect. However, the combination of retinoid plus selenium was more effective than retinoid alone, although the increase in inhibition was not large. The retinoid was also found to inhibit liver carcinogenesis induced by azaserine. Selenium, either alone or in combination with retinoid, was ineffective. Finally, testicular atrophy, noted as a toxic effect of retinoids in other studies, was not observed in this work.

Topics: Animals; Azaserine; Drug Synergism; Food, Fortified; Liver Neoplasms, Experimental; Male; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Retinoids; Selenium

The effects of dietary camostate (FOY-305), a synthetic trypsin inhibitor, on the early stages of pancreatic carcinogenesis in the rat were studied because of earlier reports that feeding soy bean trypsin inhibitor stimulated growth and promoted carcinogenesis in the pancreas of rats. These effects are attributed to excess secretion of cholecystokinin, a trophic hormone for pancreatic acinar cells. Camostate has been shown to induce pancreatic enlargement in rats by the same mechanism. In preliminary experiments, pancreatic growth was studied in adult Fischer 344 (F344) and Lewis rats fed camostate mixed in the diet to define a level that induced pancreatic hypertrophy and hyperplasia. As little as 0.02% fed 3 days per week was effective. In a second experiment, F344 rats were injected with azaserine and thereafter were given camostate by gavage 5 days a week until autopsy 18 weeks later. In a third experiment, azaserine-treated Lewis rats were fed camostate in the diet 3 days a week for 8 or 16 weeks until autopsy. In the latter two experiments the number and size of atypical acinar cell foci and nodules (AACN) were measured in pancreas sections. Growth of acidophilic AACN was stimulated in camostate-fed groups; both the number and the size were increased in comparison with the control groups. The data suggest a promoting effect of dietary camostate on the growth of azaserine-induced preneoplastic lesions in the pancreas of both rat strains. The number of basophilic AACN was decreased in camostate-fed Lewis rats suggesting that the camostate diet also affected the phenotype of the carcinogen-induced AACN.

Topics: Animals; Azaserine; Carcinogens; Cell Division; Diet; Esters; Gabexate; Guanidines; Pancreas; Pancreatic Neoplasms; Protease Inhibitors; Rats; Rats, Inbred F344; Rats, Inbred Lew

Topics: Animals; Azaserine; Humans; Immunohistochemistry; Keratins; Pancreas; Pancreatic Neoplasms; Peptides; Rats

The biochemical and histochemical measurement of the enzyme gamma-glutamyltransferase (GGT) was undertaken in normal rat pancreas and in rat pancreas containing azaserine-induced preneoplastic nodules. A steady decrease in pancreatic GGT activity was observed in the normal animals as they aged from 5 to 34 weeks. The azaserine-induced nodules contained a lower average GGT activity than the control pancreas although a 10-fold variation was noted in the GGT activity of individual nodules. A significant increase in concentrations of both reduced glutathione and oxidized glutathione was noted in pancreatic nodules from azaserine-treated rats compared to concentrations found in both control pancreas from untreated rats and internodular pancreas from azaserine-treated rats. A pancreatic acinar cell carcinoma contained low GGT activity--similar to that found in large nodules and about 10% of the level found in control pancreas. Pancreatic GGT levels were higher in 5- and 7-week-old rats fed chow than in rats fed a purified diet, but this effect of chow was not observed at 34 weeks of age. Feeding a purified diet supplemented with a retinoid, N-2-hydroxyethylretinamide (2-HER), for a period of 2 weeks did not influence the GGT activity level in either normal pancreas or in the azaserine-induced nodules. While decreased GGT activity does not serve as a marker for all atypical acinar cell nodules, deficient activity with concomitant increased glutathione levels appears to correlate generally with increased growth potential.

Topics: Animals; Azaserine; Diet; gamma-Glutamyltransferase; Glutathione; Male; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Lew

The utility of gamma-glutamyltranspeptidase (gamma-GTP) as an enzyme marker during pancreatic acinar cell carcinogenesis in rats was assessed by measuring its enzyme-histochemical performance in pancreatic acinar cell lesions induced by 4-hydroxyaminoquinoline 1-oxide (4-HAQO) and/or azaserine in partially-pancreatectomized Fischer 344 and Wistar rats. Rats were given a single intravenous injection of 4-HAQO (10 or 7 mg/kg body weight) 3 days after partial pancreatectomy followed by intraperitoneal injections of azaserine (30 mg/kg) once a week for 10 weeks, or the same treatment without azaserine. The animals were sacrificed at 3, 6, 10, 12 and 18 months. 4-HAQO predominantly induced basophilic foci in Fischer rats, while in Wistar rats acidophilic foci and acidophilic hyperplastic nodules were predominant. A preferential enhancement of the induction of acidophilic foci and hyperplastic nodules was exhibited in Fischer rats following co-administration with azaserine. Normal acinar cells were positive for gamma-GTP. 90 to 100% of basophilic foci were either negative or slightly positive for gamma-GTP, whilst 68 to 98% of acidophilic foci were positive. The gamma-GTP activities of acidophilic hyperplastic nodules were more variable between nodules than within nodules, and either co-administration of azaserine or extension of experimental duration time appeared to increase the gamma-GTP positive nodules. Between the gamma-GTP positive and decreased nodules, no histological but some morphometrical differences were observed. As far as the nodules induced by 4-HAQO in Fischer rats were concerned, all of the gamma-GTP decreased nodules had thin fibrous capsules and exhibited ultrastructurally more atypia than the positive ones. Present study thus revealed that gamma-GTP is neither a useful nor invariable enzyme marker during pancreatic acinar cell carcinogenesis in rats.

Topics: 4-Hydroxyaminoquinoline-1-oxide; Animals; Azaserine; Body Weight; Cell Transformation, Neoplastic; gamma-Glutamyltransferase; Histocytochemistry; Hyperplasia; Male; Microscopy, Electron; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred F344; Rats, Inbred Strains

The incidence of carcinoma of the pancreas is higher among men than women. It is also higher among male than female carcinogen-treated rats. The role of testosterone in this preferential induction of pancreatic cancer was evaluated in a rat model of pancreatic carcinogenesis. Two-week-old Lewis rats were treated with a single injection of azaserine. At weaning (3 weeks), rats were divided into five groups as follows: females; intact males; sham-operated males; orchiectomized males; and orchiectomized males plus testosterone. Four months after administration of azaserine, quantitative histologic analysis of atypical acinar cell foci and nodules of the pancreas showed that in female and orchiectomized male rats, foci and nodules were smaller and less numerous than in intact males. Testosterone treatment partly reversed the effect of orchiectomy. This suggests that the susceptibility of male rats to induction of pancreatic carcinomas by azaserine is at least partially mediated by testosterone. Estrogen and testosterone receptors were assayed, but high-affinity receptors characteristic of gonadal tissues were not detected in normal pancreas or in a transplantable azaserine-induced acinar cell carcinoma. Thus, the effect of testosterone in the pancreas may depend on steroid-binding proteins of another type, or may be indirectly mediated.

Topics: Animals; Azaserine; Body Weight; Carcinoma; Female; Male; Neoplasm Transplantation; Orchiectomy; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Receptors, Androgen; Receptors, Estrogen; Testosterone

Studies were undertaken to characterize the growth of the azaserine-induced putative preneoplastic lesions in rats and to determine if a single dose of azaserine would be carcinogenic. Male Lewis rats were given a single i.p. injection of 30 mg L-azaserine/kg body weight at 7 weeks of age. A purified diet was fed throughout the study. Rats (10-12 per group) were autopsied at 6, 9, 12, 15 and 18 months post-initiation, and pancreases were quantitatively evaluated to characterize the growth of acidophilic and basophilic foci and nodules (henceforth called foci), and the incidence of neoplasms. All azaserine-treated rats had foci, and at all times approximately equal numbers of acidophilic and basophilic foci were present in the pancreas. The number of basophilic foci increased with time, and while their size also increased, the change was small compared with the increase in size of the acidophilic foci. Conversely, all acidophilic foci appeared to be present by 6-9 months, and their size greatly increased with time. The data suggest that virtually all foci persist rather than regress or remodel. At 9 months the incidence of carcinoma in situ was 30% and by 18 months there was a 100% incidence of pancreatic cancers (58% carcinoma in situ and 42% carcinoma).

Topics: Animals; Azaserine; Carcinoma; Carcinoma in Situ; Male; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Lew

The growth of azaserine-induced foci and nodules in a 4-month experiment and the incidence of carcinomas in a 15-month experiment were greater in LEW/CrlBR inbred rats fed a purified diet (AIN-76A) than in rats fed a natural-ingredient diet (chow). Addition of a mixture of several solvents to either diet reduced the incidence of adenocarcinomas in the pancreas in the long-term study but failed to reduce the number or size of pancreatic atypical acinar cell foci in the experiments of 4 months and 6 months (chow only) duration. Apparently, some component of the solvent mixture inhibits a late stage in the development of pancreatic carcinoma. Glyceryl monooleate and propylene glycol are implicated as the components of the mixture most likely to be responsible for the inhibitory effect, but neither the identity of the critical component nor the mechanism of the inhibition is known. The solvent mixture also contained ethanol and trioctanoin.

Topics: Animals; Azaserine; Diet; Ethanol; Glycerides; Male; Pancreatic Neoplasms; Pharmaceutical Vehicles; Polyethylene Glycols; Rats; Rats, Inbred Lew

This study was designed to analyze the effect of two pancreaticotrophic peptides on pancreatic carcinogenesis in the azaserine-rat model. The rats were treated with bombesin or caerulein for 16 weeks after initiation with azaserine. Two-week-old Lewis rats were given injections of a single dose of azaserine (30 mg/kg) and the control pups received an injection of saline. They were divided into ten groups for peptide treatment as follows: Group 1, azaserine-saline; Group 2, azaserine-bombesin, 10 micrograms/kg; Group 3, azaserine-bombesin, 30 micrograms/kg; Group 4, azaserine-caerulein, 5 micrograms/kg; Group 5, azaserine-caerulein, 15 micrograms/kg; Group 6, control-saline; Group 7, control-bombesin, 10 micrograms/kg; Group 8, control-bombesin, 30 micrograms/kg; Group 9, control-caerulein, 5 micrograms/kg; and Group 10, control-caerulein, 15 micrograms/kg. At 3 weeks of age, they were weaned. Peptides or saline were injected 3 consecutive days a week for 16 weeks. Rats were autopsied 4 months after the administration of azaserine. Pancreatic weight was increased by bombesin and decreased by caerulein treatment. Quantitative histological analysis of azaserine-induced atypical acinar cell nodules in the pancreas showed that the size and number of atypical acinar cell nodules were increased in both bombesin- and caerulein-treated groups. Thus, these peptides appear to stimulate the growth of preneoplastic acinar cell lesions.

Topics: Animals; Azaserine; Bombesin; Ceruletide; Drug Interactions; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Previous reports have shown that pancreatic cancer was induced preferentially in male versus female azaserine-treated rats. This study was designed to determine the importance of estrogen and testosterone in this phenomenon. Fischer (F344) rats received a single injection of azaserine (30 mg/kg) at 21 days of age. At 28 days of age, they were weaned and divided into 12 groups of 9-10 rats as shown below. Surgery (castration or sham operation) was performed at 4 weeks of age. All drugs (estradiol, the antiestrogen tamoxifen, testosterone propionate and/or the antiandrogen flutamide) were administered, starting at weaning, in 3-week timed-release pellets until autopsy. Rats were killed 4 months after the administration of azaserine. The pancreas was weighed and prepared for quantitative histologic analysis of atypical acinar cell nodules (AACNs) which are putative preneoplastic lesions. Both number and size of AACNs were analyzed. In intact female rats, AACN burden was smaller than in intact males (P less than 0.05). Ovariectomy increased the AACN burden (P less than 0.05), while estradiol or tamoxifen treatments to ovariectomized females resorted the burden to control levels (P less than 0.05). Testosterone with tamoxifen treatment to ovariectomized females led to a significant increase in AACN burden over control values. In intact male rats, orchiectomy decreased the AACN burden (P less than 0.05). In orchiectomized rats, testosterone treatment slightly increased the AACN burden, flutamide treatment alone increased this parameter (P less than 0.05) but flutamide with estradiol decreased the AACN burden (P less than 0.01). These data strongly support the hypothesis that sex steroids play a major role in the higher incidence of pancreatic cancer in male versus female rats.

Topics: Animals; Azaserine; Castration; Estradiol; Female; Flutamide; Male; Organ Size; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred F344; Sex Factors; Tamoxifen; Testosterone

We have previously shown that rats fed raw soya flour (RSF) for more than four months develop hyperplastic foci of pancreatic acinar cells, which undergo malignant change if feeding RSF is continued throughout the life of the animals. The tendency to undergo malignant change is augmented by the additional use of a genotoxic carcinogen such as azaserine. The present study has sought to examine the reversibility of the focal neoplastic change in the pancreas. Rats fed RSF for 24 weeks and then given a diet not containing soya flour (NSC) had a normal pancreas when killed after 60 weeks of study. When RSF was fed for only 36 weeks, however, some of the rats developed pancreatic cancer even though the diet had been switched to NSC. Similarly, while azaserine in the dose used in the present study does not produce pancreatic cancer in our strain of Wistar rats, coincident administration of RSF for 12 weeks (but not for six weeks) resulted in progression to pancreatic adenoma. Although change from RSF to NSC after 30 weeks resulted in rapid reduction in pancreatic weight and content of RNA, neoplastic foci persisted and became frankly malignant. We conclude that phenotypic reversion to normal of the RSF diet- and azaserine-treated rat pancreas is only possible if RSF alone is fed continuously for not more than about 24 weeks or six weeks if the rats have been exposed to a pancreatic initiating carcinogen.

Topics: Adenoma; Animals; Azaserine; Diet; Flour; Glycine max; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Both dietary unsaturated fat and raw soybean products are known to enhance pancreatic carcinogenesis when fed during the postinitiation phase. A comparison of these two dietary components was made to evaluate the relative potency of each ingredient for enhancing pancreatic carcinogenesis and to determine if this enhancement was correlated with an increase in plasma cholecystokinin (CCK) levels. Male Wistar rats were initiated with a single dose of azaserine (30 mg/kg body weight) at 14 days of age. The rats were weaned to test diets formulated from purified ingredients. Dietary protein at 20% by weight was either casein or soy protein isolate (heat treated or raw). Corn oil was the unsaturated fat of major interest and it was fed at either 5 or 20% by weight. Pancreases were quantitatively evaluated for carcinogen-induced lesions at 2- and 4-month postinitiation. In a second experiment designed to closely mimic the above experiment, rats were implanted with cannulae which allowed plasma to be repetitively sampled over a 2.5-week period during which the test diets were fed. Plasma was collected both prior to introduction of the test diets and afterwards. Plasma CCK was measured by a specific radioimmunoassay. Both the 20% corn oil diet and the raw soy protein isolate diet enhanced pancreatic carcinogenesis. The effects of the raw soy protein isolate on the growth of the carcinogen-induced lesions were significantly greater than the effects of the 20% corn oil diet. Plasma CCK values were not elevated in the rats fed the 20% corn oil diet, but they were significantly elevated in the rats fed the raw soy protein isolate. Heat-treated soy protein isolate neither enhanced carcinogenesis nor elevated the plasma CCK level. This study demonstrates that certain plant proteins enhance the growth of carcinogen-induced pancreatic foci and that this effect is considerably greater than the enhancement by high levels of dietary unsaturated fat. Furthermore, the enhancement by the raw soy protein isolate may be mediated by CCK; but this does not appear to be the mechanism by which the unsaturated fat, corn oil, enhances pancreatic carcinogenesis.

Topics: Animals; Azaserine; Cholecystokinin; Dietary Fats; Fatty Acids, Unsaturated; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Plant Proteins, Dietary; Rats; Rats, Inbred Strains; Soybean Proteins

Enzyme-histochemical investigation of pancreatic carcinogenesis in male Wistar rats treated at the age of 19 days by a single dose of 30 mg azaserine/kg body wt led to the detection of a new 'marker' for the recognition of foci of atypical acinar cells: the Mg2+-dependent ATPase. The two well-known populations of pancreatic atypical acinar cell foci, classified histologically as basophilic and acidophilic foci, showed a decreased and strongly increased ATPase reaction, respectively. The enhanced enzyme activity of the acidophilic foci has been characterized as unspecific nucleoside polyphosphatase. To validate the new marker, comparative quantitative evaluation was performed on haematoxylin and eosin-stained paraffin sections and ATPase-stained cryostat sections of the same pancreata of 25 azaserine-treated rats. Evaluation of basophilic ATPase-deficient foci of small diameter was more reproducible in haematoxylin and eosin-stained sections, while small acidophilic strongly ATPase-positive foci could be detected more reliably by the ATPase staining technique. The number of foci/cm3 pancreas was similar for both staining techniques above a focus diameter of about 100 microns for basophilic foci and 200 micronfor acidophilic foci. There were more acidophilic than basophilic foci/cm3 pancreas, and the acidophilic foci had significantly larger mean focal diameters than the basophilic foci. Together with the strong acidophilic staining of the latter emerging adenoma, this suggests that the acidophilic foci represent a neoplastic cell population progressing eventually to pancreatic carcinoma. The new 'marker' enzyme ATPase may greatly facilitate further investigations into the role of these putative preneoplastic lesions in pancreatic carcinogenesis.

Topics: Adenosine Triphosphatases; Animals; Azaserine; Pancreatic Neoplasms; Precancerous Conditions; Rats; Staining and Labeling; Substrate Specificity

Azaserine (CAS: 115-02-6), streptozocin (CAS: 18883-66-4; streptozotocin), and N-nitrosobis(2-oxopropyl)amine [(BOP) CAS: 60599-38-4] produce different types of pancreatic tumors in rodents. We have investigated the toxic effects of these compounds on pancreatic tissues from Wistar rats and Syrian hamsters. Inhibition of protein synthesis was used as a measure of toxicity. Pancreatic islets and acinar cells from rat and hamster were labeled with [3H]leucine for 60 minutes in vitro in the presence of the various carcinogens. Azaserine, which produces acinar cell tumors in the rat, inhibited synthesis by all tissues; rat acinar cells, however, were most sensitive. Glutamine, but not serine, provided some protection against azaserine toxicity. Streptozocin inhibited synthesis by islets of both species and acinar cells from hamster; islets were the most sensitive. BOP and N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine, which induce ductal tumors in the hamster, had no effect on any of the tissues examined. These results indicate that the specificities of the cellular toxicities of the pancreatic carcinogens parallel, to some degree, their tumorigenic effects.

Topics: Animals; Azaserine; Carcinogens; Cricetinae; Glutamine; Leucine; Male; Mesocricetus; Nitrosamines; Pancreatic Neoplasms; Protein Biosynthesis; Rats; Rats, Inbred Strains; Streptozocin; Tritium

The effect of dietary fat and ethanol and their interactions on the development of putative, preneoplastic foci in exocrine pancreas was investigated in rats and hamsters. Rats were given a single i.p. injection of 30 mg azaserine per kg body wt at 19 days of age. Hamsters were injected s.c., with 20 mg N-nitrosobis(2-oxopropyl)amine (BOP)/kg body wt at 6 and 7 weeks of age. The animals were fed a low fat (LF) control diet (5% corn oil) or a high fat (HF) diet (25% corn oil). Ethanol was provided in drinking water at a 15% (w/v) concentration. The animals were given the respective diets and ethanol after the treatment with carcinogen. At 4 months post-initiation, the pancreata were quantitatively examined for the number and size of preneoplastic foci. In rats, acidophilic as well as basophilic foci were subject to modulation by HF and ethanol. The results point to a specific promoting effect of unsaturated fat on the growth potential of azaserine-induced acidophilic acinar cell foci in rat pancreas. There was no evidence of an interaction between HF and ethanol as far as acidophilic foci are concerned. Evaluation of the number and size of the basophilic foci demonstrated an enhancing effect of ethanol on the modulation of pancreatic carcinogenesis by fat, pointing to a possible interaction between these two lifestyle factors. This suggestion was supported by the finding that six out of 20 rats in the HF with ethanol group exhibited a carcinoma in situ, whereas in the HF and in the ethanol group such an advanced lesion was found in one animal only. Unlike in rats, ethanol had no modulating effect on number and growth of putative, preneoplastic lesions in hamsters, either in combination with LF or in combination with HF. A HF diet, however, caused a significant increase in number as well as an increase in percentage of pancreatic tissue occupied by early lesions induced in hamster pancreas by BOP.

Topics: Adenosine Triphosphatases; Animals; Azaserine; Body Weight; Cricetinae; Dietary Fats; Eating; Ethanol; Male; Mesocricetus; Nitrosamines; Organ Size; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains

Azaserine induced two phenotypically different populations of foci, namely, acidophilic and basophilic foci. The effects of dietary modification during the post-initiation phase of carcinogenesis were examined. A diet of 20% (w/w) unsaturated fat (unsat) compared to a 20% saturated fat (sat) diet or a control diet (5% unsaturated fat) increased the number of acidophilic foci, as well as the thymidine labeling index (LI) of their nuclei. While the basophilic foci are carcinogen-induced and at 2.5 mo post-initiation have a similarly high growth rate to the acidophilic foci, this rate is not sustained as indicated by examination of both the LI and mean size of foci at 4 mo post-initiation.

Topics: Animals; Azaserine; Body Weight; Dietary Fats; Fatty Acids, Unsaturated; Male; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Lew

The response of LEW and F344 strain rats to the pancreatic carcinogen azaserine was compared using the size and number of azaserine-induced acidophilic acinar cell foci and nodules as parameters in a 4-month experiment. A second experiment compared the effect of corn oil intake by gavage and dietary routes on the growth of azaserine-induced pancreatic lesions in LEW rats. A third experiment tested the activity of benzyl acetate in regard to its ability to induce acinar cell foci or to promote the growth of such foci in azaserine-treated rats. The results showed that equivalent doses of azaserine induce two to seven times more foci in LEW than in F344 rats, and that LEW rats have a higher incidence of "spontaneous" foci than F344 rats. Azaserine-treated LEW rats that were given 5 mL corn oil/kg body weight 5 days per week by gavage developed more acinar cell foci than rats fed a basal diet (chow). Addition of an equivalent amount of corn oil to chow had a similar effect of enhancing the development of foci. Rats of neither strain developed acinar cell foci when benzyl acetate was given by gavage or in the diet nor was there evidence that benzyl acetate has a significant effect on the development of foci in azaserine-treated rats. These studies also demonstrate that the azaserine/rat model of pancreatic carcinogenesis which was developed in LEW rats can be adapted for use with F344 rats.

Topics: Animals; Azaserine; Benzyl Compounds; Corn Oil; Disease Models, Animal; Male; Pancreatic Neoplasms; Plant Oils; Rats; Rats, Inbred F344; Rats, Inbred Lew; Species Specificity

Acinar cells were isolated by enzymatic digestion from normal pancreas and from azaserine-induced atypical acinar cell nodules and a transplantable acinar cell carcinoma. Normal acinar cells were predominately binuclear, with abundant cytoplasm. They were 10-24 micron in diameter, with a size distribution skewed toward smaller sizes but with a peak at 18 micron. Cells were isolated from 41 enucleated nodules varying in weight from 1.1 to 200 mg. These cells were predominantly mononuclear, with a more uniform size than normal cells and a peak at 9 micron diameter. Cells from all nodules studied were grossly similar, and there was no relation between nodule size and the degree of mononucleation. Cells from the transplantable tumor were small, with little cytoplasm, and were almost exclusively mononuclear. The extent of binucleation in normal and microscopic atypical acinar cell nodules was also studied in sections from the pancreas of rats injected with azaserine 4 months before killing. Nuclear and cell counts in these sections confirmed that binucleation is more frequent in normal than in nodule tissue. These studies emphasize the high degree of binucleation found in normal pancreatic acinar cells. They demonstrate the feasibility of using cell separation techniques to obtain preparations of acinar cells from normal and neoplastic pancreatic tissue for studies of functional and morphological differences in these cells.

Topics: Animals; Azaserine; Cell Nucleus; Cell Separation; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Lew

The effects of feeding mice raw or heated soy flours or casein in the presence and absence of injected azaserine were investigated over a period of 18 months. Although the feeding of raw soy flour (compared with heated soy flour or casein) caused a significant inhibition of growth and an enlargement of the pancreas, there was no macroscopic evidence of pancreatic nodules in any of the six experimental groups. Microscopic examination of the pancreas revealed a somewhat higher (not significant) incidence of atypical acinar cell nodules in all animals injected with azaserine, but this difference was little influenced by the diets themselves. We concluded that raw soy flour itself has no carcinogenic effect on the mouse pancreas and does not enhance the sensitivity of the mouse pancreas to azaserine. Thus, it cannot be assumed that the appearance of pancreatic nodules constitutes an obligatory sequela of pancreatic hypertrophy and/or hyperplasia in all species of animals.

Topics: Animals; Azaserine; Body Weight; Diet; Eating; Flour; Glycine max; Hot Temperature; Mice; Organ Size; Pancreas; Pancreatic Neoplasms; Time Factors

Continuous administration of a diet consisting of raw soya flour produces pancreatic cancer in rats and sensitises the rat pancreas to the action of genotoxic carcinogens. We have therefore studied the effects of continuous feeding of diets containing lesser amounts of raw soya flour (5%, 25% and 50%) and feeding raw soya flour intermittently (2 days each week). The study has shown that a diet containing as little as 5% raw soya flour stimulates focal proliferation of the pancreatic acinar cells and sensitises to the action of azaserine. Similarly, intermittent feeding of raw soya flour induced focal proliferation of the acinar pancreas and, when 100% raw soya flour diet was fed for 2 days each week, resulted in the development of pancreatic cancer in some of the rats. We conclude that raw soya flour must be excluded from the diets of rats used in toxicological and carcinogenicity studies.

Topics: Adenoma; Animals; Azaserine; Diet; Flour; Glycine max; Male; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Foods containing soybean products have been shown to modify the biochemical and physiological status of the pancreas of several species of experimental animals. Recently, these products have been implicated as a factor in the causation of pancreatic neoplasms. Extensive experimental studies into the possible mechanisms need to be undertaken. Experimental details of a rat/azaserine model for the study of pancreatic carcinogenesis are reviewed. Emphasis is given to the quantitative components of this model and the adaptation of this model to the two-stage (initiation-promotion) concept of carcinogenesis. Particular attention is devoted to considerations of the experimental diets. Application of these concepts to the study of the postinitiational effects of raw and heated soybean protein isolate with and without the addition of high levels of unsaturated fat were undertaken. The results indicate that raw soybean isolate enhanced the growth of azaserine-induced pancreatic foci; whereas, a high level of unsaturated fat had a minimal effect. The effects of the soybean isolate were abolished by heat treatments, but the effects of the unsaturated fat would not be expected to be abolished by similar treatment with heat.

Topics: Animals; Azaserine; Carcinogens; Dietary Fats; Dietary Proteins; Disease Models, Animal; Nutritional Physiological Phenomena; Pancreatic Neoplasms; Plant Proteins, Dietary; Rats; Soybean Proteins

The effects of intervention by diets with high or low levels of dietary fat on the development of preneoplastic pancreatic lesions were examined. Wistar rats were treated ip at 14 days of age with a 30-mg/kg dose of L-azaserine [CAS: 115-02-6; diazoacetate serine (ester)] and weaned onto the test diets. Animals fed 5% corn oil had fewer preneoplastic lesions compared to animals fed 20% corn oil throughout the 4-month posttreatment period. The strong response observed in rats fed 20% corn oil could be markedly reduced by intervention with a 5% corn oil diet halfway through the posttreatment period. Similarly, the low response in animals fed 5% corn oil could be markedly elevated by intervention with a high-fat diet. These results provide evidence for the hypothesis that tumor development may be modified by dietary means.

Topics: Animals; Azaserine; Corn Oil; Dietary Fats; Female; Male; Oils; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains

The effect of dietary intake of fish (menhaden) oil and fish (cod) protein on the development of pancreatic preneoplastic lesions was examined in male Wistar rats. Fourteen-day-old animals were given a single ip injection of 30 mg L-azaserine/kg body weight [CAS: 115-02-6; diazoacetate serine (ester)]. At 21 days of age they were weaned and maintained on dietary treatment for 4 months. Fish protein did not appear to produce a significantly different preneoplastic response when compared to casein as a protein source. However, a 20% menhaden oil diet, rich in omega 3 fatty acids, produced a significant decrease in the development of both the size and number of preneoplastic lesions when compared to a 20% corn oil diet rich in omega 6 fatty acids. This study provides evidence that fish oils, rich in omega 3 fatty acids, may have potential as inhibitory agents in cancer development.

Topics: Animals; Azaserine; Caseins; Corn Oil; Dietary Proteins; Female; Fish Oils; Fish Products; Male; Oils; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred Strains

The ingestion of high levels of fats, especially unsaturated fats, has been shown to enhance carcinogenesis in a variety of experimental model systems. Recently attention has focused upon the unsaturated linoleic fatty acid (18:2 omega 6) as a key component for this postinitiation enhancement. We have investigated the dose-effect relationship of this essential fatty acid (EFA), in a well-characterized experimental model of pancreatic cancer. Male Lewis rats were given injections i.p. of azaserine (30 mg/ kg) at 14 days of age. The pups were weaned to test diets that contained 20% total dietary fat with EFA compositions varying from 0.5 to 11.5% of the diet. After 4 months of feeding these 20% fat diets, the pancreases were evaluated in situ for grossly visible tumors and microscopically for the number and size of the azaserine-induced, putative preneoplastic lesions (foci). Grossly visible tumors increased significantly in number as the EFA content of the diet increased. Two populations of microscopic foci were observed in these azaserine-initiated rats; namely, acidophilic foci and basophilic foci. Quantitative stereological analyses of these foci revealed that the acidophilic population of foci increased in both number and size as the EFA content of the diet increased. This increase was particularly apparent from 4.4 to 8.5% dietary EFA content. The basophilic population showed no similar response to increasing dietary EFA. These results indicate that the minimum dietary EFA required for enhancement of azaserine-induced, pancreatic carcinogenesis by a high fat diet lies in the range of 4 to 8%.

Topics: Animals; Azaserine; Basophils; Cocarcinogenesis; Dietary Fats; Dose-Response Relationship, Drug; Fatty Acids, Essential; Male; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Lew

The effects of melphalan were studied in rats fed raw soya flour and injected with azaserine in order to determine the suitability of this experimental model for testing drugs potentially useful for the treatment of pancreatic cancer. While melphalan did not prevent or delay the development of pancreatic cancer in these rats, the drug significantly lessened the number and size of the premalignant proliferative lesions in the pancreas. It seems that the model is useful both for testing potentially useful therapeutic agents and for analysing some of the processes involved in the development of pancreatic cancer.

Topics: Animals; Azaserine; Body Weight; Disease Models, Animal; Male; Melphalan; Nucleic Acids; Organ Size; Pancreas; Pancreatic Neoplasms; Proteins; Rats; Rats, Inbred Strains

Focal proliferative changes in the acinar cells of the pancreas of rats have been induced by several systemically administered carcinogens including azaserine, N-nitrosobis(2-oxopropyl)amine, N-nitroso-(2-hydroxypropyl) (2-oxopropyl)amine, and N delta-(N-methyl-N-nitrosocarbamoyl)-L-ornithine (MNCO). Foci, nodules, and adenomas induced by these carcinogens are usually made up of atypical-appearing acinar cells that maintain a high degree of differentiation, but a minority of these lesions exhibit anaplastic cellular changes that suggest the development of malignant potential. Such anaplasia may occupy the whole of smaller lesions or may occur as a secondary focal change within larger nodules or adenomas. Many foci and nodules per pancreas have been induced by single or multiple exposures to these known genotoxic carcinogens, but relatively few of them develop into carcinomas. Azaserine and MNCO have induced acinar cell carcinomas in rats. Those induced by azaserine have exhibited a broad spectrum of histologic variants, including ductlike cystic, and undifferentiated patterns. Higher doses of MNCO have induced a second pattern of change in the pancreatic lobules of rats, which includes cystic and tubular ductlike structures that have been called cystic and tubular ductal complexes. MNCO has also induced focal acinar cell lesions, cystic and tubular ductal complexes, and adenocarcinomas in the pancreas of Syrain golden hamsters. In this species, ductal complexes are much more numerous than are proliferative lesions of acinar cells, and the histologic appearance of the carcinomas is ductlike. Hyperplasia and atypical changes were also seen in the epithelium of the intralobular ducts of hamsters.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Azaserine; Carcinogens; Cell Transformation, Neoplastic; Cricetinae; Nitrosamines; Nitrosourea Compounds; Pancreatic Neoplasms; Rats; Rats, Inbred Lew

Pancreatic acinar cell hyperplastic lesions and neoplasms in rats and humans were studied for their nuclear DNA content by microspectrophotometry. Atypical hyperplastic acinar cell lesions induced in rats by azaserine displayed a wide range of DNA contents, 1.5-8C for those composed of acidophilic-type cells and 1.5-9C for those of basophilic-type cells compared with the euploid pattern of 1.5-5C in acinar cells in normal pancreas. The modal DNA values of rat acinar cell adenomas were distributed over an even wider range of 2-11C. In human pancreas, hyperplastic acinar cell lesions composed of eosinophilic-type cells displayed a slightly wider range of DNA content (1.5-8C) than that in surrounding normal acinar cells (1.5-5C). The DNA histograms of basophilic acinar cell lesions were of an aneuploid pattern (2-12C) similar to that of an acinar cell carcinoma (2-15C). These findings demonstrate that acinar cell hyperplastic lesions in rats and humans have an altered genetic complement and suggest that they probably are precursor lesions for acinar cell neoplasms.

Topics: Adenoma; Animals; Azaserine; DNA; DNA, Neoplasm; Humans; Hyperplasia; Male; Pancreas; Pancreatic Neoplasms; Ploidies; Precancerous Conditions; Rats; Rats, Inbred ACI; Spectrophotometry

Effects of the dietary phenolic antioxidants butylated hydroxyanisole [(BHA) CAS: 25013-16-5; (1,1-dimethylethyl)-4-methoxyphenol] and butylated hydroxytoluene [(BHT) CAS: 128-37-0; 2,6-di-tert-butyl-p-cresol] on pancreatic tumorigenesis were examined. Male LEW inbred rats were given injections of 30 mg azaserine [CAS: 115-02-6; diazoacetate (ester) serine] per kg body weight once a week for 3 weeks and maintained on either a control diet or 0.45% BHA- or 0.45% BHT-supplemented control diet throughout the initiation and post-initiation phases of the experiment. At 4 months post initiation, pancreatic tissue sections were quantitatively examined for the number and size of preneoplastic foci. BHT and BHA treatments reduced the number of acidophilic foci per pancreas by 32 and 48%, respectively, but were without effect on focal size. By contrast, basophilic foci were not subject to modulation by these antioxidants. A constellation of enzyme activities involved in carcinogen inactivation and known to be perturbed by antioxidant treatment was examined in liver and pancreas. The hepatic activities of glucose-6-phosphate dehydrogenase, glutathione reductase, and glutathione-S-transferases were markedly elevated while catalase and superoxide dismutase activities were unchanged. Glutathione peroxidase activity was diminished. In the pancreas, only glutathione peroxidase activity was affected, and it was reduced in both the BHA and BHT treatment groups. Although the pancreas is refractory to the enzyme inductive effects of these antioxidants, morphometric analysis of foci demonstrated chemoprevention by BHA and BHT of azaserine-induced foci. Whether this reduction reflected inhibition of an initiation, postinitiation , or a combination of effects was not known.

Topics: Animals; Antioxidants; Azaserine; Butylated Hydroxyanisole; Butylated Hydroxytoluene; Drug Interactions; Food Additives; Liver; Male; Pancreas; Pancreatic Neoplasms; Phenols; Rats; Rats, Inbred Lew; Time Factors; Weaning

The usefulness of a short-term azaserine [CAS: 115-02-6; diazoacetate serine (ester)]-rat model for the screening of retinoids (known chemopreventive agents) and the effect of two retinoids on the growth of azaserine-induced, presumptive preneoplastic foci of acinar cells were examined. At 14 days of age, male Lewis rats were each given injections of a single dose of 30 mg azaserine/kg body weight. These rats were weaned to test diets to which retinoids were added. At 4 months post initiation, pancreata were examined by quantitative stereologic methods to determine number and mean size of foci. Two phenotypically different populations of foci were observed and characterized as acidophilic or basophilic. Retinylidene dimedone and N-2-hydroxyethylretinamide decreased the number and size of the acidophilic foci but not the basophilic foci. The inhibition of growth of the acidophilic foci correlates well with the known effects of these retinoids in long-term carcinogenicity studies.

Topics: Animals; Azaserine; Dose-Response Relationship, Drug; Male; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Retinoids; Tretinoin

Multiple and single intraperitoneal injections of azaserine in male Wistar/Lewis rats induced a 100% incidence of atypical acinar cell foci. The foci were histologically classified into one of two populations, basophilic or acidophilic. The number and size of transections of the foci in tissue sections were determined. By means of known mathematical relationships, focal transectional data were transformed into three-dimensional data (i.e., foci/unit volume, foci/pancreas, mean diameter and volume of foci, and focal volume as percentage of pancreas volume). In general, initiation with azaserine resulted in more acidophilic than basophilic foci. An increase in the azaserine dose from 10 to 30 mg/kg resulted in the initiation of more acidophilic and basophilic foci. Over a 6-month period following initiation, basophilic foci showed a small increase in number and no increase in size. In these same pancreases, acidophilic foci significantly increased in both number and size. A promoter of pancreatic carcinogenesis (20% unsaturated fat diet) enhanced the number and percentage of the pancreas volume occupied by acidophilic foci. This modulator of the postinitiation phase of pancreatic carcinogenesis did not have a significant effect on the basophilic foci. Unlike the basophilic foci, the acidophilic foci show considerable growth potential and appear to be responsive to modulators of carcinogenesis. Further study of this population of carcinogen-induced pancreatic foci is warranted.

Topics: Animals; Azaserine; Dietary Fats; Injections, Intraperitoneal; Male; Neoplasms, Experimental; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Rat acinar cells in the azaserine-induced hyperplastic nodules or adenomas in the siderotic pancreas produced by repeated iron injections were found to be resistant to iron accumulation. These iron-resistant acinar cell lesions coincided rather well with the lesions having markedly decreased activity of gamma-glutamyl transpeptidase. These properties of the acinar cells could be useful for the identification of early lesions in pancreatic carcinogenesis.

Topics: Adenoma; Animals; Azaserine; Ferric Compounds; gamma-Glutamyltransferase; Histocytochemistry; Hyperplasia; Iron; Male; Nitrilotriacetic Acid; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred ACI

Chemoprevention by synthetic retinoids of the progression of carcinomas of the pancreas induced in rats by azaserine was evaluated. Lewis rats were given five weekly injections of azaserine, 30 mg/kg, while being fed a chow diet. Two weeks after completion of carcinogen treatment, groups of rats were fed the chow diet supplemented with four different retinoids at the level of 0.5 to 2 mmol/kg of diet for 1 year. The incidence of pancreatic and other neoplasms was determined by autopsy and histological study. The incidence of localized pancreatic carcinoma among male and female non-retinoid-treated controls was 25 and 17%, respectively. No invasive or metastatic carcinomas were found in the control group. The combined incidence of localized and invasive pancreatic carcinomas among male and female rats treated with retinoids was: N-(4-pivaloyloxyphenyl)retinamide, 4 and 0%; N-(2-hydroxypropyl)retinamide, 14 and 6%; N-(3-hydroxypropyl)retinamide, 16 and 4%; and N-(2,3-dihydroxypropyl)retinamide, 12 and 6%. High- and low-dose groups are combined in this summary of data. Thus, there was a trend towards fewer pancreatic carcinomas among all retinoid-treated groups. The reduction in incidence was significant in both male and female rat groups given N-(4-pivaloyloxyphenyl)retinamide and N-(2,3-dihydroxypropyl)retinamide. The principal evidence of retinoid toxicity was growth failure, which was most severe in animals treated with N-(4-pivaloyloxyphenyl)retinamide, and testicular atrophy, which was most severe among male animals treated with N-(3-hydroxypropyl)retinamide. Among the females, groups treated with three of the four retinoids showed a dose-related increase in incidence of hepatocellular carcinomas. Since the retinoids were fed after the completion of exposure to the carcinogen, the effects on both pancreatic and liver carcinogenesis were exerted during the postinitiation phase of carcinogenesis.

Topics: Animals; Atrophy; Azaserine; Body Weight; Cocarcinogenesis; Diet; Female; Liver Neoplasms; Male; Neoplasms, Experimental; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Sex Factors; Testis; Vitamin A

We have assessed the influence of an attack of acute pancreatitis on the incidence of experimentally induced pancreatic cancer in rats. A low-protein diet plus repeated injections of DL-ethionine produced acute pancreatitis in rats. The animals were then fed either a diet of raw soya flour or a non-soya-containing diet and given repeated injections of azaserine, a weak pancreatic carcinogen. The rats that had recovered from acute pancreatitis developed pancreatic cancer, whereas those without previous pancreatitis did not. We conclude that the interaction of recovery from acute pancreatitis with a pancreatic carcinogen predisposes to pancreatic cancer in rats.

Topics: Acute Disease; Animals; Azaserine; Dietary Proteins; Ethionine; Glycine max; Male; Pancreatic Neoplasms; Pancreatitis; Rats; Rats, Inbred Strains

Topics: Animals; Azaserine; Carcinogens; Diet; Flour; Glycine max; Male; Neoplasms, Experimental; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Chemoprevention by retinoids of the progression of carcinomas induced in rats by azaserine was evaluated. Wistar/Lewis rats were given 15 weekly injections of azaserine, 10 mg/kg, while fed a chow diet; after the completion of carcinogen treatment, they were fed a chow diet supplemented with four different retinoids at the level of 0.5 to 2 mmol/kg diet for 1 year. The incidence of neoplasms was determined by autopsy and histological study. The incidence of pancreatic carcinoma among a male positive control group (azaserine treated, but not retinoid treated) was 42%. The incidence of pancreatic carcinoma among male rats treated with retinoids was: N-2-hydroxyethylretinamide, 6%; N-4-propionyloxyphenylretinamide, 17%; and retinylidene dimedone, 12%. The incidence in rats fed these three retinoids was significantly (p less than 0.05) below the control group incidence. Thus, these three retinoids appeared to be effective in inhibiting the progression of pancreatic carcinomas in the azaserine-induced model. A similar trend was demonstrated in females, but statistical significance was shown only in rats fed N-2-hydroxyethylretinamide. A fourth retinoid, N-4-carboxyphenylretinamide, was more toxic and less effective in chemoprevention. Since retinoids were fed after exposure to carcinogen, the effect was exerted during the postinitiation phase of carcinogenesis. The ratio of invasive pancreatic carcinomas to localized carcinomas (carcinoma in situ) was clearly higher among non-retinoid-treated rats than among those treated with retinoids. This is consistent with retarded progression in the retinoid-treated groups.

Topics: Animals; Azaserine; Female; Liver Neoplasms; Male; Neoplasm Metastasis; Neoplasms, Experimental; Pancreas; Pancreatic Neoplasms; Rats; Vitamin A

Pancreatic carcinomas have been induced in Wistar and W/LEW rats by administration of total azaserine doses of 150-520 mg/kg by injection or oral routes over periods of 5-52 weeks. The latent period for development of invasive carcinomas was 1-2 years, but focal abnormalities in acinar cells appear earlier. The incidence of carcinomas varied with total dose, route, and schedule of azaserine administration. The spectrum of histologic patterns of the carcinomas included well and poorly differentiated acinar cell, ductlike, and undifferentiated carcinomas. Rats fed a purified diet developed more pancreatic neoplasms than rats fed a commercial laboratory chow. Selective feeding of these diets during the administration of carcinogen and following completion of carcinogen treatment indicated that the inhibitory effect of chow on pancreatic carcinogenesis was exerted during the postinitiation phas. Supplementation of diet with 0.025% retinyl acetate during the postinitiation phase also inhibited the progression of azaserine-induced lesions in the pancreas.

Topics: Adenocarcinoma; Animals; Azaserine; Carcinoma; Cell Transformation, Neoplastic; Cytoplasmic Granules; Diet; Diterpenes; Enzyme Precursors; Male; Neoplasms, Experimental; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Rats, Inbred Strains; Retinyl Esters; Vitamin A

Topics: Animals; Azaserine; Carcinoma; Disease Models, Animal; Female; Humans; Male; Neoplasms, Experimental; Pancreatic Neoplasms; Rats; Rats, Inbred Lew

Previously, the induction of pancreatic carcinogenesis in the rat using azaserine has involved a multiple-dose treatment protocol. The objective of the present study was to determine the effect of multiple azaserine treatments on pancreatic DNA synthesis and to develop a protocol for a single-dose initiation of pancreatic carcinogenesis by azaserine in the rat. Pancreatic DNA synthesis in young rats, which was determined by measuring the amount of [3H]-thymidine incorporation into DNA, was found to be elevated at 4.3 weeks of age and to decrease to a baseline level by 6.3 weeks. Treatment of 4-week-old rats with azaserine resulted in a dose-dependent inhibition of [3H]-thymidine incorporation into both pancreatic and liver DNA. Maximum inhibition was seen at 10 mg/kg body weight. This inhibition was followed by a gradual return of incorporation to normal values over a 48 h period. One week following pretreatment with four weekly injections of azaserine at 30 mg/kg, [3H]-thymidine incorporation into pancreatic and liver DNA was significantly elevated, suggesting that multiple injection protocols caused enhanced DNA synthesis which could have a co-carcinogenic and/or promotional effect. Single-doses of azaserine (10, 30 and 60 mg/kg) given at 7 weeks of age caused the appearance of more atypical acinar cell nodules (AACN) than when given at 5 weeks of age. The most effective dose was 30 mg/kg. Using alkaline elution, we determined that this response was due to the occurrence of more DNA damage in the 7-week-old animals. Thus, these results demonstrate a rationale for the use of single-dose initiation protocols in the pancreas. An effective single-dose protocol for induction of AACN in azaserine-treated rats fed semi-synthetic diet is presented.

Topics: Animals; Azaserine; Carcinogens; DNA; Food, Formulated; Male; Neoplasms, Experimental; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Lew; Rats, Inbred Strains

Rats have been fed for up to 2 years with either raw soya flour or control diets of heated soya flour or rat chow not containing soya flour. In addition, the rats received weekly injections of either a weak pancreatic carcinogen (azaserine) or control injection of saline. We found that rats fed a diet of raw soya flour and given weekly injections of azaserine developed benign and malignant neoplasms of the pancreas earlier in life and much more frequently than rats given raw soya flour alone, whereas azaserine alone in the dose used in this study did not produce pancreatic cancer. We conclude that raw soya flour sensitizes the pancreas to the action of azaserine.

Topics: Animals; Azaserine; Drug Interactions; Glycine max; Male; Neoplasms; Organ Size; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

One hour following intraperitoneal injection of the pancreatic and liver carcinogen azaserine, 10 mg/kg (0.06 mmol/kg), DNA damage is present in both pancreas and liver of Wistar/Lewis rats as determined with alkaline sucrose gradients. Single injections (0.06 mmol/kg) of either of 2 structural analogues of azaserine, 6-diazo-5-oxo-L-norleucine (DON) and ethyl diazoacetate (EDA), do not damage pancreatic or liver DNA. EDA administered at 0.5 mmol/kg damages liver DNA, but not pancreatic DNA. Total radioactivity in pancreas and liver of Wistar rats 1 h after intravenous injection of [14C]azaserine, (10 microCi/kg), is 2.8 and 1.3 times respectively, the level of 14C-activity in pancreas and liver following injection [14C]EDA. Three to four times as much [14C]EDA localizes in the liver of Wistar rats as in the pancreas. Azaserine (0.06 mmol/kg weekly for 6 weeks) induces atypical acinar cell nodules (AACN) in pancreas of Wistar/Lewis rats. DON (0.06 mmol/kg weekly for 6 weeks) induces an elevated incidence, but low number of AACN in pancreas. EDA (0.10 mmol/kg weekly for 6 weeks) does not induce pancreatic AACN.

Topics: Animals; Azaserine; Azo Compounds; Carcinogens; Diazonium Compounds; Diazooxonorleucine; DNA; Liver; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Diet has been shown to modulate the incidence of a wide variety of chemically induced cancers in animals. Various diets fed either during the initiation stage or the postinitiation (promotion) stage of carcinogenesis were evaluated for their ability to modulate the incidence of pancreatic cancer. Male Wistar/Lewis rats were treated with multiple injections of the pancreatic carcinogen, azaserine, during a 6- to 7-week-long initiation phase and were autopsied after a postinitiation phase of 34 or 44 weeks. The following diets were evaluated for their effects on the incidence of pancreatic neoplasms during each stage of carcinogenesis: high saturated fat; two high unsaturated fats (corn oil and safflower oil); low protein; and caloric restricted. A purified control diet was fed during that stage when the test diets were not fed. The incidence of pancreatic adenomas and adenocarcinomas was evaluated by light microscopy. Feeding of the caloric-restricted diet during the initiation phase suppressed the pancreatic neoplasm incidence. None of the ther diets tested had an effect on the incidence of pancreatic cancer during the initiation phase. During the postinitiation phase, both high-unsaturated-fat diets but not the high-saturated-fat diet significantly elevated the pancreatic neoplasm incidence. The low-protein and caloric-restricted diets had no effect on the neoplasm incidence when fed during the postinitiation phase. Thus, diets high in unsaturated fat appear to promote pancreatic carcinogenesis in the azaserine-treated rat while a diet high in saturated fat failed to show a similar degree of enhancement of pancreatic carcinogenesis.

Topics: Adenocarcinoma; Animals; Azaserine; Cocarcinogenesis; Dietary Fats; Fats, Unsaturated; Male; Neoplasms, Experimental; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Because diet has been shown to modulate the incidence of a wide variety of chemically induced cancers in experimental animals, various dietary constituents were evaluated for their ability to modulate the incidence of pancreatic exocrine cancer in male Wistar/Lewis rats given injections of the pancreatic carcinogen, azaserine. Ten different diet regimens were fed. The incidence of pancreatic cancers in rats fed a control diet was compared to that in groups fed diets formulated to evaluate the effect of caloric restriction, high protein, low protein, low fat, cyclopropenoid fatty acids, lipotrope deficiency, high unsaturated fat, and high saturated fat. The incidence of pancreatic adenomas and carcinomas was evaluated by light microscopy. The number of pancreatic neoplasms was reduced in carcinogen-treated groups which were underfed the control diet or fed the diet high in protein. Pancreatic carcinogenesis appeared to be enhanced in two groups which were fed diets containing 20% corn oil, i.e., high in unsaturated fat; whereas, the group fed a diet high in saturated fat had the same incidence of neoplasms as did the group fed the control diet. The pancreatic neoplasms from groups in which the incidence was enhanced by diet showed less evidence of acinar cell differentiation and displayed diverse histological types. In the lipotrope-deficient group, there was a significantly increased incidence of hepatocellular carcinoma; however, a low incidence of liver tumors was encountered in all other dietary groups.

Topics: Adenocarcinoma; Adenoma; Animals; Azaserine; Cocarcinogenesis; Diet; Dietary Fats; Energy Intake; Fatty Acids, Unsaturated; Male; Neoplasms, Experimental; Pancreatic Neoplasms; Rats

Pancreatic tumorigenesis of azaserine by a single intraperitoneal (i.p.) injection after partial pancreatectomy in male Wistar rats was studied. Pancreatic lesions developed in all rats 52 weeks after the administration of azaserine at doses of 50 mg (Group 1) or 100 mg/kg body wt (Group 2). Histologically, there were hyperplastic nodules in 4 of 12 rats and 4 of 7 rats, in Groups 1 and 2, respectively, adenomas 100% in both groups, and adenocarcinomas 2 of 7 rats of Group 2. It appears that pancreatic regeneration induced by partial pancreatectomy enhances the azaserine tumorigenesis.

Topics: 4-Hydroxyaminoquinoline-1-oxide; Adenocarcinoma; Adenoma; Animals; Azaserine; Carcinogens; Hyperplasia; Injections, Intraperitoneal; Male; Pancreas; Pancreatectomy; Pancreatic Neoplasms; Rats; Regeneration; Time Factors

Inbred W/LEW rats and noninbred CD-1 mice were compared for responsiveness to induction of pancreatic adenocarcinomas by azaserine. At 1 year following the first of 15 weekly ip injections of 10 mg azaserine/kg body weight, the rats had a pancreatic adenoma incidence of 71% (12/17) and a pancreatic adenocarcinoma incidence of 35% (6/17), with 1 invasive adenocarcinoma. The mice showed none of these advanced lesions, although numerous pancreatic atypical acinar cell nodules (AACN) were present. An examination of the number and size of the AACN showed the rats to hve more and larger AACN thatn did the mice. The concentration of [14C]azaserine and/or its metabolites was greater in rat pancreas than in mouse pancreas. Alkaline sucrose gradients were used to compare azaserine-induced pancrewtic and liver DNA damage in W/LEW and F344 rats, the CD-1 mouse, the Syrian golden hamster, and the strain 13 guinea pig. DNA damage was detected 1 hour following azaserine administration in both pancreata and livers of all animals tested and persisted for at least 1 week in the pancreata of all animals except the CD-1 mouse; however, neither the degree nor persistence of DNA damage accurately reflected the differing responsiveness of these species to induction of pancreatic AACN or neoplasms by azaserine.

Topics: Adenocarcinoma; Adenoma; Animals; Azaserine; Carcinogens; DNA; Liver; Liver Neoplasms; Lung Neoplasms; Mice; Neoplasms, Experimental; Pancreas; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

Glycoproteins and lipids of rat pancreatic acinar cell carcinomas maintained in nude mice and in cell culture, were analyzed. The tumor contained significantly elevated levels of glycoproteins when compared with their normal counterparts. SDS-PAGE of tumor glycoproteins revealed that there were increased amounts of small molecular weight glycoproteins and the tumor also contained a 51,000 dalton glycoprotein which was not detected in the pancreas, liver or the sera of the control animals. The tumor in nude mice and cancer cells in culture had decreased lecithins and triglycerides, and increased amounts of free fatty acids, and both free and esterified cholesterols. The results indicate that altered glycoprotein and lipid compositions represent some of the characteristic features of the acinar cell carcinoma.

Topics: Animals; Azaserine; Carcinoma; Cells, Cultured; Cholesterol; Glycoproteins; Lipids; Molecular Weight; Pancreatic Neoplasms; Rats

The response of two rodents to azaserine carcinogenicity for the pancreas was evaluated. Mystromys albicaudatus was not responsive; however, Mastomys natalensis developed large numbers of atypical acinar cell nodules and several adenomas in a 6-month study. Mastomys is the most responsive of several animals in which azaserine has been studied as a pancreatic carcinogen.

Topics: Adenoma; Animals; Azaserine; Neoplasms, Experimental; Pancreatic Neoplasms; Precancerous Conditions; Rodentia

Two pancreatic adenocarcinomas which had been induced in Wistar/Lewis rats by azaserine treatment were transplanted into rats of the same strain by subcutaneous and intraperitoneal injection of minced tumor. Subsequently, we have serially transplanted into non-radiated recipients. Transplanted tumors have maintained evidence of acinar cell differentiation including the presence of zymogen granules in tumors studied by electron microscopy, and of lipase, amylase and trypsin activity in the supernatant of tumor homogenates. Histologically, the tumors vary from poorly differentiated solid carcinomas to well differentiated variants which form acini. Transplanted tumors are locally invasive and have metastasized to lung and liver in some recipients.

Topics: Adenocarcinoma; Animals; Azaserine; Neoplasm Transplantation; Neoplasms, Experimental; Pancreatic Neoplasms; Rats; Transplantation, Homologous

Topics: Animals; Azaserine; Body Weight; Carcinogens; Carcinoma, Hepatocellular; Choline; Diet; Liver; Liver Neoplasms; Male; Neoplasms, Experimental; Organ Size; Pancreas; Pancreatic Neoplasms; Rats

The effect of azaserine on the pancreatic tumorigenesis of 4-hydroxyaminoquinoline 1-oxide (4-HAQO) after partial pancreatectomy in rats was studied. Pancreatic acinar cell carcinomas were produced in 7 out of 10 rats (70%), which received 7 mg/kg body wt. 4-HAQO 3 days after partial pancreatectomy, followed by 10 weekly injections of 30 mg/kg body wt. azaserine. Partial pancreatectomy enhanced the carcinogenesis of 4-HAQO, which was further promoted by azaserine.

Topics: 4-Hydroxyaminoquinoline-1-oxide; Aminoquinolines; Animals; Azaserine; Carcinoma; Drug Synergism; Male; Neoplasms, Experimental; Pancreas; Pancreatectomy; Pancreatic Neoplasms; Rats; Regeneration

Topics: Adenocarcinoma; Adenoma; Animals; Azaserine; Ethionine; Male; Pancreas; Pancreatectomy; Pancreatic Neoplasms; Rats; Regeneration

Subtoxic doses of azaserine induced atypical acinar cell nodules (AACN) in the pancreases of outbred Wistar rats, inbred W/LEW and F344 rats, and outbred Charles River CD-1 albino mice 4-6 months after initiation of treatment in the growing animal. These AACN apparently represented preneoplastic lesions, some of which have the potential to develop into adenomas or adenocarcinomas. Wistar and W/LEW rats were highly responsive to nodule induction; AACN developed in about 90% of the outbred Wistar rats and in all of the W/LEW rats tested. F344 rats were less susceptible and developed about 10% as many AACN as the Wistar rats. Female rats developed approximately half as many AACN as males. The mouse was intermediate in response between the F344 and the two Wistar rats. Syrian golden hamsters and strain 13 guinea pigs were relatively unresponsive. These studies of azaserine-induced AACN provided a basis for selection of carcinogenic azaserine regimens and suggested that the young male W/LEW rat was the most sensitive of the animals studied.

Topics: Animals; Azaserine; Cricetinae; Disease Models, Animal; Female; Guinea Pigs; Male; Mesocricetus; Mice; Neoplasms, Experimental; Pancreatic Neoplasms; Precancerous Conditions; Rats; Rats, Inbred F344; Rats, Inbred Lew; Sex Factors; Species Specificity

Rats were treated with raw soya flour to produce pancreatic hypertrophy and also received azaserine, a pancreatic carcinogen. The combined treatment resulted in the development of large numbers of hyperplastic nodules in the acinar tissue of the rat pancreas. We conclude that the pancreas of the rat stimulated to proliferate by raw soya flour provides a sensitive model for detecting and studying pancreatic carcinogens.

Topics: Animals; Azaserine; Cell Division; Glycine max; Hyperplasia; Male; Neoplasms, Experimental; Pancreatic Neoplasms; Precancerous Conditions; Rats

The efficacy of various azaserine treatment durations was evaluated with respect to induction of atypical acinar cell nodules in Wistar rat pancreas and was related to animal age and rate of pancreatic DNA synthesis during growth. The sensitivity to nodule induction was maximal in postnatal rats when the rate of pancreatic DNA synthesis was high, whereas treatment of weanlings was less effective and treatment of mature rats was least effective. When weaned growing rats were given 1, 3, or 5 weekly injections of 30 mg azaserine/kg, the number of nodules induced was proportional to the number of injections. A single dose at this level did not induce detectable pancreatic necrosis or inflammation; therefore, DNA synthesis due to regeneration was probably not a major factor in the initiation of nodules. We concluded that multiple daily injections of [3H]thymidine during the first or second postnatal week provided DNA of sufficiently high specific activity for use in DNA repair and biochemical toxicity studies.

Topics: Aging; Animals; Azaserine; DNA; Female; Male; Neoplasms, Experimental; Pancreas; Pancreatic Neoplasms; Precancerous Conditions; Rats; Thymidine

Development of a model of carcinoma of the pancreas in rats was approached by attempting to identify chemicals that (a) behave as mutagens and (b) localize in the pancreas following systemic administration; and then to study the effects of long-term administration. Azaserine was selected because it behaves as a direct-acting mutagen in two bacterial test systems and because tissue distribution studies showed concentration especially in kidney and pancreas. Groups of rats have been given i.p. injections once or twice weekly for 6 months, and rats have been autopsied after 6 to 18 months. During the first year pancreases developed (a) nodules of atypical exocrine cells which seem to represent hyperplastic foci and (b) encapsulated adenomas. After 1 year most pancreases from treated rats are diffusely abnormal and contain many hyperplastic nodules and adenomas, while more than one-quarter have had pancreatic adenocarcimona. Metastases have been observed in lymph nodes, liver, and lung. No carcinomas or adenomas have been observed in control rats. No other organ shows as high an incidence of involvement as pancreas, but renal neoplasms were frequent. Studies with another chemical O-(N-methyl-N-nitroso-beta-alanyl)-L-serine, are at an earlier stage. The tissue distribution of radioactivity following injection of a 14C-labeled sample is similar to that of azaserine; however, this compound is not a direct-acting bacterial mutagen. Rats treated for 6 months twice weekly i.p. have a higher incidence of nodules of atypical acinar cells than did controls, although the number of nodules per rat is few. No adenomas or carcinomas have been found during 13 months of the study. We conclude that azaserine is a carcinogen in rats and causes major abnormalities of growth and differentiation of the exocrine pancreas, including adenocarcinoma in some rats. O-(N-Methyl-N-mitroso-beta-alanyl)-L-serine had less effect than azaserine on pancreatic growth and differentiation.

Topics: Adenocarcinoma; Adenoma; Animals; Azaserine; Dipeptides; Disease Models, Animal; Hyperplasia; Injections, Intraperitoneal; Kidney Neoplasms; Mutagens; Neoplasm Metastasis; Neoplasms, Experimental; Nitrosamines; Pancreas; Pancreatic Neoplasms; Rats; Salmonella typhimurium; Serine

Topics: Adenoma; Animals; Azaserine; Carcinogens; Hyperplasia; Injections, Intraperitoneal; Neoplasms, Experimental; Pancreas; Pancreatic Neoplasms; Rats