azaserine and Cell-Transformation--Neoplastic

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

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 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 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

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

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 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

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 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