methylnitronitrosoguanidine and Cocarcinogenesis

Helicobacter pylori infection is well accepted to be a very important factor for the development of gastric carcinogenesis in the human stomach. In Mongolian gerbils treated with chemical carcinogens, H. pylori infection enhances glandular stomach carcinogenesis, and eradication of infection and results in curtailment of enhancing effects, particularly at early stages of associated inflammation. A high-salt diet exacerbates the effects of H. pylori infection on gastric carcinogenesis, and these two factors act synergistically to promote the development of gastric cancers in this animal model. However, the bacterium exerts the greater effects. Early acquisition significantly increases gastric chemical carcinogenesis in Mongolian gerbils, as compared to later infection. While heterotopic proliferative glands, hyperplastic and dilated glands localized beneath the muscularis mucosae, frequently develop with H. pylori infection alone in this animal model, they obviously regress on eradication, suggesting a relation to severe gastritis, rather than a malignant character. Furthermore, endocrine cells, positive for chromogranin A, are observed in the heterotopic proliferative glands, in contrast to cancerous lesions which lack endocrine elements. In conclusion, H. pylori is not an initiator, but rather a strong promoter of gastric carcinogenesis, whose eradication, together with reduction in salt intake, might effectively prevent gastric cancer development.

Topics: Adenocarcinoma; Animals; Cocarcinogenesis; Disease Models, Animal; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Humans; Methylnitronitrosoguanidine; Methylnitrosourea; Precancerous Conditions; Sodium Chloride, Dietary; Stem Cells; Stomach Neoplasms

Topics: 9,10-Dimethyl-1,2-benzanthracene; Actins; Animals; Carcinoma, Squamous Cell; Cell Transformation, Neoplastic; Cocarcinogenesis; DNA; Gene Expression Regulation, Neoplastic; Matrix Metalloproteinase 3; Metalloendopeptidases; Methylnitronitrosoguanidine; Mice; Neoplasm Metastasis; Neoplasm Proteins; Neoplasms, Multiple Primary; Papilloma; Skin Neoplasms; Tetradecanoylphorbol Acetate; Ubiquitins

Topics: 2-Acetylaminofluorene; Animals; Cocarcinogenesis; Diet; Disease Models, Animal; Disease Susceptibility; Environment; Glutathione Transferase; Liver Neoplasms, Experimental; Methylnitronitrosoguanidine; Nitrosamines; Precancerous Conditions

Topics: 1,2-Dimethylhydrazine; Adult; Animals; Azoxymethane; Cholesterol; Cholesterol, Dietary; Cholestyramine Resin; Cocarcinogenesis; Colonic Neoplasms; Diagnosis-Related Groups; Dietary Fats; Dimethylhydrazines; Disease Models, Animal; Epidemiologic Methods; Humans; Methylnitronitrosoguanidine; Methylnitrosourea

We propose that SF derived from normal-appearing biopsies of ACR gene carriers exist in an initiated state as the result of a dominant mutation. Based on our studies with the ACR cell system, we further suggest that, although an initiated state is essential to cancer development, not all initiated cells necessarily develop into cancerous cells. The genetic makeup of an initiated cell has been established through linkage between abnormal phenotypic markers and pedigree profiles and through cell hybridization, including initial analysis of gene products. We believe that it is consistent with an autosomal dominant trait. In contrast, cells from patients who are homozygous for chromosomal breakage syndromes, including those with xeroderma pigmentosum, represent an experiment of nature which presumably underlies factors associated with cancer promotion in humans. We have demonstrated that ACR cells can be differentially transformed by oncogenic viruses, a carcinogen (MNNG), and gamma-ray irradiation, and that they can proliferate in vitro after exposure to a tumor promoter (TPA. This simple experimental model provides a novel system for the study of tumor promotion in vitro. We further suggest that, through the use of TPA, various stages associated with cancer development in humans, i.e., initiation through promotion and progression, can be identified in vitro. Attempts to apply these results in vivo are currently in progress. The apparent susceptibility of ACR cells to further transformation by oncogenic viruses and chemical and physical agents indicates that genetic information residing within these cells, probably in the form of a relatively limited and specific number of DNA sequences associated with the ACR mutation, renders them more sensitive to these three distinct classes of carcinogens. We submit that, through our tests on SF, and ACR gene carriers within recognized ACR clusters can be diagnosed at present with sufficient certainty to warrant immediate action. In addition, it seems that the time has arrived for a major undertaking to screen for persons who are likely to be at increased risk of cancer, perhaps through walk-in clinics. An underlying assumption in these studies is that predisposition to cancer, in general, is associated with an autosomal dominant trait in obligatory heterozygote gene carriers.

Topics: Actins; Adenoma; Antigens, Neoplasm; Carcinogens; Cell Transformation, Neoplastic; Cell Transformation, Viral; Cells, Cultured; Cholesterol; Cocarcinogenesis; Colonic Neoplasms; Cytoskeleton; Disease Susceptibility; Genes, Dominant; Humans; Kirsten murine sarcoma virus; Methylnitronitrosoguanidine; Mitochondria; Models, Biological; Mutation; Plasminogen Activators; Prognosis; Rectal Neoplasms

The fish liver has been the main subject of the biomonitoring and laboratory studies dealing with environmental carcinogenesis. The foci of cellular alterations are accepted pre-neoplastic hepatic lesions, and histopathology is the primary tool for their characterization. Despite its potential, using stereology to study quantitatively nuclear features of those lesions has not been evaluated. Herein, we estimated the volume density and the volume-weighted volume of the nucleus of normal and preneoplastic hepatocytes, using stereology and the brown trout (Salmo trutta f. fario) as model. In the hepatocarcinogenesis protocol the N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was used as initiator, and the 17-β estradiol (E2) as promoter. Three groups of 30 animals were considered: negative controls (non-exposed), initiator exposed and initiator plus promoter exposed. Estimates of both stereological parameters were significantly higher in preneoplastic hepatocytes, also showing an excellent discriminatory power when used to differentiate those hepatocytes from the normal ones. Besides, in the normal parenchyma the two parameters also differed among the three tested groups. The exposure to MNNG and/or to E2 leaded to modifications in the hepatocyte nuclei that could be unbiasedly quantified with two stereological parameters. We showed that quantitative nuclear morphology represents a valuable auxiliary tool in assessing hepatocarcinogenesis in fishes.

Topics: Animals; Cell Nucleus; Cell Nucleus Size; Cocarcinogenesis; Estradiol; Hepatocytes; Liver Neoplasms, Experimental; Methylnitronitrosoguanidine; Precancerous Conditions; Trout

Previously, we reported that perfluorooctanoic acid (PFOA) promotes liver cancer in a manner similar to that of 17β-estradiol (E2) in rainbow trout. Also, other perfluoroalkyl acids (PFAAs) are weakly estrogenic in trout and bind the trout liver estrogen receptor. The primary objective of this study was to determine whether multiple PFAAs enhance hepatic tumorigenesis in trout, an animal model that represents human insensitivity to peroxisome proliferation. A two-stage chemical carcinogenesis model was employed in trout to evaluate PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorooctane sulfonate (PFOS), and 8:2 fluorotelomer alcohol (8:2FtOH) as complete carcinogens or promoters of aflatoxin B(1) (AFB(1))- and/or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced liver cancer. A custom trout DNA microarray was used to assess hepatic transcriptional response to these dietary treatments in comparison with E2 and the classic peroxisome proliferator, clofibrate (CLOF). Incidence, multiplicity, and size of liver tumors in trout fed diets containing E2, PFOA, PFNA, and PFDA were significantly higher compared with AFB(1)-initiated animals fed control diet, whereas PFOS caused a minor increase in liver tumor incidence. E2 and PFOA also enhanced MNNG-initiated hepatocarcinogenesis. Pearson correlation analyses, unsupervised hierarchical clustering, and principal components analyses showed that the hepatic gene expression profiles for E2 and PFOA, PFNA, PFDA, and PFOS were overall highly similar, though distinct patterns of gene expression were evident for each treatment, particularly for PFNA. Overall, these data suggest that multiple PFAAs can promote liver cancer and that the mechanism of promotion may be similar to that of E2.

Topics: Aflatoxin B1; Alkanesulfonic Acids; Animals; Caprylates; Carcinogenicity Tests; Cocarcinogenesis; Decanoic Acids; Endocrine Disruptors; Fluorocarbons; Gene Expression; Gene Expression Profiling; Hydrocarbons, Fluorinated; Liver Neoplasms, Experimental; Methylnitronitrosoguanidine; Oligonucleotide Array Sequence Analysis; Oncorhynchus mykiss; Real-Time Polymerase Chain Reaction

Combination treatment with sodium nitrite (NaNO(2)) and ascorbic acid (AsA) is well known to promote forestomach carcinogenesis in rats and weakly enhance esophageal carcinogenesis under acid reflux conditions. Nitric oxide generation and oxidative DNA damage are considered to be related to the enhancement of carcinogenesis. The purpose of the present study was to investigate whether oxidative DNA damage-associated genotoxicity and tumor initiating potential are involved in the carcinogenesis. In the bacterial reverse mutation assay using Escherichia coli deficient in the mutM gene encoding 8-hydroxydeoxyguanosine (8-OHdG) DNA glycosylase, the combination with NaNO(2) and AsA increased the mutation frequency dramatically, slight increase being evident in the parental strain. In vivo, a significant increase in 8-OHdG levels in the rat forestomach epithelium occurred at 24 h after combined treatment. Six-week-old F344 male rats were given drinking water containing 0.2% NaNO(2) and a diet supplemented with 1% AsA in combination, or the chemicals individually or basal diet alone for 12 weeks. After an interval of 2 weeks, they received 1% butylated hydroxyanisole in the diet for promotion until the end of weeks 52 and 78. Although one squamous cell carcinoma was observed in the combined group, there was no significant variation in tumor development among the groups. The study indicated that the combination of NaNO(2) with AsA induces genotoxicity due to oxidative DNA damage in vitro, and elevates 8-OHdG levels in the forestomach epithelium, but lacks initiating activity in the rat two-stage carcinogenesis model.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Antioxidants; Ascorbic Acid; Butylated Hydroxyanisole; Carcinogens; Cocarcinogenesis; Deoxyguanosine; Disease Models, Animal; DNA Damage; DNA, Bacterial; Drug Therapy, Combination; Escherichia coli; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Mutagens; Organisms, Genetically Modified; Oxidation-Reduction; Oxidative Stress; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach Neoplasms

To determine whether chronic exposure to DMBA or MNNG in combination with or without UVB exposure would induce skin carcinomas in swine.. Eight gilts were exposed to 100 mJ of UVB in their left side, allowed to recuperate, and divided into two groups. Each gilt received identical high doses (DMBA 50 microM; MNNG 250 mM), low doses (DMBA 500 nM; MNNG 2.5 mM), carrier (DMSO), or nothing added treatments in the UVB and non-UVB sides. Animals were exposed weekly for 30 weeks and skin samples collected at 10, 20, and 30 weeks from initiation of exposure. An additional sample was collected 16 weeks following cessation of exposure. All samples were scored for dermal morphology, including intracellular epidermal edema, intercellular epidermal edema, papillary dermal edema, perivascular infiltrates, pyknotic stratum basale cells, collagen necrosis, and epidermal-dermal separation, and the data were analyzed by ANOVA. MNNG and UVB light had a significant effect on epidermal thickness and the number of cell layers. The greatest increase in epidermal thickness occurred from 20 weeks to 30 weeks in the UVB plus MNNG treatment. Treatment with MNNG resulted in intracellular and intercellular epidermal edema, dermal edema, and dermal inflammation at both the low and high doses of MNNG. In contrast, all the morphological evaluations of the DMBA treatments were less severe than the MNNG.. Our findings show that although chronic exposure to MNNG and DMBA, with or without UVB exposure, caused severe to mild dermatopathological changes, neither resulted in the development of skin carcinomas. These results indicate that at least with respect to responses to DMBA and MNNG, the swine model mimics more closely the responses seen in human skin.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Analysis of Variance; Animals; Cocarcinogenesis; Female; Methylnitronitrosoguanidine; Neoplasms, Radiation-Induced; Skin; Skin Neoplasms; Swine; Ultraviolet Rays

Elevated polyamine levels as a consequence of targeted overexpression of ornithine decarboxylase (ODC) to murine skin enhance susceptibility to tumorigenesis in this tissue. A possible mechanism for the enhanced susceptibility phenotype is an increased sensitivity of tissues with elevated polyamine levels to the mutagenic action of carcinogens. To test this hypothesis, a transgenic mouse model containing the Big Blue transgene and also expressing a K6/ODC transgene was developed. Incorporation of the K6/ODC transgene into the Big Blue model did not affect the spontaneous lacI mutant frequency in either skin or epidermis of the double-transgenic mice. After skin treatment with single doses of either 7,12-dimethylbenz[a]anthracene or N-methyl-N'-nitro-N-nitrosoguanidine, however, the mutant frequency was significantly increased in the skin of double-transgenic Big Blue;K6/ODC mice compared to Big Blue controls. The increases in mutant frequency were clearly due to ODC transgene activity, since treatment of mice with the ODC inhibitor, alpha-difluoromethylornithine, completely abolished the difference in mutant frequencies between double-transgenic and Big Blue mice. These results demonstrate that intracellular polyamine levels modulate mutation induction following carcinogen exposure.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinogens; Cocarcinogenesis; Methylnitronitrosoguanidine; Mice; Mice, Transgenic; Mutagenesis; Mutation; Ornithine Decarboxylase; Ornithine Decarboxylase Inhibitors; Polyamines; Skin Neoplasms

The effect of prolonged administration of iron chelator phenanthroline on sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and the labeling and apoptotic indices in the gastric cancers was investigated in Wistar rats. After 25 weeks of carcinogen treatment, the rats were given chow pellets containing 10% sodium chloride and intraperitoneal injections of phenanthroline at doses of 15 or 30 mg/kg body weight every other day. At week 52, feeding of sodium chloride significantly increased the incidence of gastric cancers, as compared with the control group. Prolonged injections of phenanthroline at both doses significantly reduced the incidence of gastric cancers, which was enhanced by oral supplementation with sodium chloride. Phenanthroline at both doses significantly decreased the labeling index of gastric cancers, which was enhanced by sodium chloride, and significantly increased the apoptotic index of gastric cancers, which was lowered by sodium chloride. In vitro examination using electron spin resonance revealed that sodium chloride promotes the production of hydroxyl radical during Fe(2+) oxidation by Fenton's reaction. These findings suggest that enhancement by sodium chloride of gastric carcinogenesis may be mediated by hydroxyl radicals.

Topics: Adenocarcinoma; Animals; Antigens, Neoplasm; Apoptosis; Cell Division; Cocarcinogenesis; Drug Synergism; Electron Spin Resonance Spectroscopy; Hydroxyl Radical; Iron Chelating Agents; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Oxidation-Reduction; Phenanthrolines; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Sodium Chloride, Dietary; Stomach Neoplasms

Helicobacter pylori (Hp) is thought to be a stomach carcinogen from epidemiological findings. To determine the effects of infection with the bacteria on experimental carcinogenesis, a study of the glandular stomach of Mongolian gerbils (MGs) was performed. Male MGs were treated with N-methyl-N'-nitro-N-nitrosoguanidine followed by inoculation with Hp or infected with Hp followed by N-methyl-N'-nitro-N-nitrosoguanidine administration. Animals were killed at week 50, and their excised stomachs underwent microbiological and histopathological examinations. In addition, a serological investigation was performed. The incidences of adenocarcinomas were significantly higher in animals treated with 60 or 300 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine for 10 weeks followed by Hp inoculation or Hp followed by 20 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine for 30 weeks than in the respective controls. Moreover, tumour-bearing animals had higher titres of anti-Hp antibodies than tumour-free animals. Of interest was the finding that a dose of 100 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine given to infected gerbils eradicated the Hp in about half the animals, with a concomitant reduction in the promoting effect. No tumours were found in animals infected with Hp without N-methyl-N'-nitro-N-nitrosoguanidine or non-treated gerbils. Hp infection enhances glandular stomach carcinogenesis in MGs treated with N-methyl-N'-nitro-N-nitrosoguanidine. Animals with high titres of anti-Hp antibodies are at greatest risk of developing neoplasms.

Topics: Adenocarcinoma; Animals; Antibodies, Bacterial; Carcinogens; Cell Differentiation; Cocarcinogenesis; Drug Administration Schedule; Edema; Gastric Mucosa; Gastritis; Gastrointestinal Hemorrhage; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Hyperplasia; Male; Metaplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Specific Pathogen-Free Organisms; Stomach Neoplasms; Stomach Ulcer; Time Factors

The modifying effects of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a mutagenic by-product in chlorinated water, on the development of glandular stomach cancers were investigated in Wistar rats. A total of 120 males, 6 weeks of age, were divided into six groups. After initiation with 100 ppm N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) solution and 5% NaCl diet for 8 weeks, 30 rats each in groups 1-3 were given MX in the drinking water at concentrations of 30, 10, or 0 ppm for the following 57 weeks. Ten animals each in groups 4-6 were administered the MX without prior carcinogen exposure. There were no statistical significant differences in final body weights between the groups. The incidences and multiplicities of adenocarcinomas in the glandular stomachs were significantly higher (P < 0.05) in the initiated 30 ppm MX group than those in the MNNG/NaCl group. The incidences of atypical hyperplasias in the glandular stomachs were also significantly increased (P < 0.05 or 0.01) by the MX treatments. With their multiplicity, the effects were clearly dose dependent. Interestingly, the 30 ppm MX alone itself induced atypical hyperplasias in the pylorus, although the incidences and severity were low. Moreover, MX showed a tendency to enhance the development of intrahepatic cholangiocellular tumors and thyroid follicular cell tumors in the MNNG-treated animals. The results of the present study thus indicate that MX exerts promoting effects when given during the postinitiation phase of two-stage glandular stomach carcinogenesis in rats.

Topics: Adenocarcinoma; Adenocarcinoma, Follicular; Adenoma, Bile Duct; Animals; Bile Duct Neoplasms; Bile Ducts, Intrahepatic; Body Weight; Carcinogens; Cholangiocarcinoma; Cocarcinogenesis; Fibrosis; Furans; Hyperplasia; Male; Methylnitronitrosoguanidine; Mutagens; Organ Size; Precancerous Conditions; Pylorus; Rats; Rats, Wistar; Stomach; Stomach Diseases; Stomach Neoplasms; Thyroid Neoplasms; Water Pollutants, Chemical

Induction of unscheduled DNA synthesis (UDS) in hairless mouse epidermis by six chemicals was determined in an in vivo-in vitro assay by using a liquid scintillation counting method. Test chemicals were applied once onto two areas of the back of female hairless mice after stripping of the stratum corneum with adhesive tape to enhance skin penetration. After exposure, the skin samples were taken and cultured in a medium containing [3H]thymidine with or without hydroxyurea (HU, an inhibitor of replicative DNA synthesis). DNA of the epidermis was extracted, and incorporation of [3H]thymidine into DNA and the DNA content was determined with a liquid scintillation counter and a fluorescence spectrophotometer, respectively. Induction of UDS by chemicals was judged by calculation of the UDS index [(the ratio of DNA synthesis in the presence of HU to that in its absence) x 100]. A good correlation between UDS induction and organ specificity of carcinogens was observed. 4-Nitroquinoline 1-oxide, a skin carcinogen used as a positive control, induced a dose-dependent increase in the UDS index of approximately 12-fold at 2 hr after exposure, while 1,2-epoxydodecane, a non-skin carcinogen applied as a negative control, did not increase the UDS index. Four other skin carcinogens induced dose-dependent increases in the UDS index; N-methyl-N'-nitro-N-nitrosoguanidine and diepoxybutane at 2 hr after exposure, and 7,12-dimethylbenz[a]anthracene and benzo[a]pyrene at 24 hr after exposure. The results suggest that UDS is a good marker of the genotoxicity of skin carcinogens.

Topics: 4-Nitroquinoline-1-oxide; 9,10-Dimethyl-1,2-benzanthracene; Animals; Benzo(a)pyrene; Carcinogens; Cocarcinogenesis; DNA; DNA Damage; Dose-Response Relationship, Drug; Epoxy Compounds; Female; Hydroxyurea; Methylnitronitrosoguanidine; Mice; Mice, Hairless; Quinolones; Skin

An animal model of stomach carcinogenesis was established using Mongolian gerbils with N-methyl-N-nitrosourea (MNU) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) as the carcinogens. In addition, the sensitivity of these gerbils to Helicobacter pylori (H. pylori) was confirmed. One hundred and sixty specific pathogen-free male MGS/Sea animals, 7 weeks old, were treated with MNU in the drinking water (30 ppm for alternate weeks to give 10 weeks exposure, or 10 ppm or 3 ppm for 20 weeks continuous exposure), or given MNNG in the drinking water at 400 ppm or 200 ppm for 20 weeks, or orally inoculated with ATCC43504 H. pylori (1.7 x 10(8) CFUs/animal). Adenocarcinomas in the glandular stomach were found in 2 out of 12 effective animals (2/ 12) treated with 30 ppm MNU at week 20, although all were dead or moribund by week 30 due to MNU toxicity. At week 50, the incidences of gastric adenocarcinomas in groups treated with 10 ppm MNU, 3 ppm MNU, 400 ppm MNNG, and 200 ppm MNNG were 2/21 (9.5%), 1/23 (4.3%), 7/ 11 (63.6%), and 1/10 (10.0%). The lesions were generally well differentiated, although poorly differentiated adenocarcinoma was also found in a single gerbil in each of the 10 ppm MNU and 400 ppm MNNG groups. In control animals no tumors were found. In the infection study, the animals were killed at week 20, and H. pylori was detected in all cases, causing multiple erosions with marked inflammatory cell infiltration in the lamina propria and submucosa, and frequent formation of lymphoid follicles. Thus, MNU and MNNG in the drinking water induced neoplastic lesions in the glandular stomach epithelium of H. pylori-sensitive gerbils.

Topics: Adenocarcinoma; Administration, Oral; Animals; Carcinogens; Cocarcinogenesis; Disease Models, Animal; Disease Susceptibility; Drinking; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Methylnitrosourea; Stomach Neoplasms; Water

The modifying effects of Chelidonium majis L. (Papaveraceae) herb extract (CH), an analgesic traditionally prescribed for gastric and duodenal ulcer patients, on gastric tumor development were studied in rats given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Sixty-four male 6-week-old Wistar rats were used. Group 1 rats were initially given MNNG (200 mg/kg b.w.) by gavage at days 0 and 14 as well as saturated sodium chloride solution (S-NaCl, 1 ml per rat) every 3 days during weeks 0-3 (six times), and then placed on basal diet containing 0.1 or 0.2% CH for 16 weeks from week 4. Rats of Group 2 and 3 were treated with MNNG together with S-NaCl or saline (0.9% NaCl, 1 ml per rat), respectively, timed as in Group 1 but without further treatment. All surviving animals were killed at week 20 and histopathologically investigated. In the glandular stomach, the number of preneoplastic pepsinogen 1 altered pyloric glands (PAPGs) in the MNNG + S-NaCl-->CH (0.1%) group (Group 1) was significantly smaller than in the MNNG + S-NaCl group (Group 2) (P < 0.02). The incidences of forestomach neoplastic lesions (papillomas and squamous cell carcinomas) also showed a tendency to decrease with the CH treatment. The results thus indicate that CH exerts inhibitory effects on glandular stomach carcinogenesis in the rat, so that it may have potential as a chemopreventive agent for stomach cancer in man.

Topics: Animals; Anticarcinogenic Agents; Body Weight; Carcinogens; Cocarcinogenesis; Hyperplasia; Male; Methylnitronitrosoguanidine; Organ Size; Pepsinogens; Plant Extracts; Plants, Medicinal; Precancerous Conditions; Pyloric Antrum; Rats; Rats, Wistar; Saline Solution, Hypertonic; Stomach; Stomach Neoplasms

The effects of cytotoxic monochloramine on the development of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in Wistar rats. After oral administration of drinking water containing the carcinogen and regular chow pellets for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without s.c. injection of taurine, until the end of the experiment in week 52. Treatment with both ammonium acetate and sodium hypochlorite significantly increased the incidence of gastric cancers in week 52, while the concomitant use of taurine with ammonium acetate and sodium hypochlorite significantly attenuated the enhanced gastric carcinogenesis. Spectrophotometric examinations revealed that taurine scavenged monochloramine. These findings suggest that Helicobacter pylori-associated gastric carcinogenesis may be mediated by monochloramine.

Topics: Animals; Body Weight; Chloramines; Cocarcinogenesis; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sodium Acetate; Sodium Hypochlorite; Stomach Neoplasms; Taurine

To develop mouse strains useful for studies of susceptibility and resistance to the induction of skin tumors, three new inbred SENCAR strains were independently derived by random inbreeding of outbred SENCAR mice. Characterization of these mice for sensitivity to skin tumor development indicated that mice of all three strains displayed increased sensitivity to initiation by 7,12-dimethylbenz[a]anthracene (DMBA), urethane, or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA). Promotion by mezerein as well as carcinogenesis by repeated treatment with DMBA or MNNG produced papillomas with a high frequency of conversion to squamous cell carcinomas (SCCs). Compared with outbred SENCAR mice, development of both squamous papillomas and carcinomas was increased at least two-fold by all protocols tested. The F1 hybrid between SENCARA/Pt males and resistant BALB/cAnPt females was resistant to the induction of both papillomas and SCCs after initiation by 2 microg of DMBA and promotion by 20 weekly applications of 2 microg of TPA. Papillomas developed in all of the SENCARA/Pt mice, none of the BALB/cAnPt mice, and 12% of the F1 progeny. Thus, at these doses of initiator and promoter, resistance was incompletely dominant in the F1 hybrid. However, the responsiveness of the F1 mice could be increased substantially by increasing the dose of the promoter.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinogens; Carcinoma, Squamous Cell; Cocarcinogenesis; Disease Susceptibility; Diterpenes; Female; Male; Methylnitronitrosoguanidine; Mice; Mice, Inbred BALB C; Mice, Inbred SENCAR; Papilloma; Phenotype; Sensitivity and Specificity; Skin Neoplasms; Terpenes; Urethane

The incidence of gastric remnant cancer after surgery for gastric malignancies has been increasing. The interval between previous operations and the diagnosis of gastric remnant cancer, location of cancer development, and histologic type were different from those after surgery for benign diseases. However, very little is known about the reasons for these differences. Patients with gastric cancer already have cancer-related gastric mucosal changes at gastrectomy, and they undergo a wide range of dissection of nerve distribution to the stomach due to lymph node dissection. Therefore, the effects of preliminary administration of a carcinogenic agent and denervation of the gastric mucosa on tumorigenesis in the gastric remnant were investigated.. Using male Wistar rats, N-methyl-N'-nitro-N-nitroguanidine (MNNG; 50 mg/L) was given in drinking water for 10 weeks. The animals were then assigned into four groups of those undergoing Billroth I (B-I) gastrectomy or Billroth II (B-II) gastrectomy, with and without denervation. Subdiaphragmatic truncal vagotomy was performed in the denervated group. Thirty weeks after gastrectomy, the following investigations were performed: histologic examination and periodic acid-Schiff-Alcian blue (PAS-AB) staining of the gastric mucosa by immunohistochemistry of proliferating cell nuclear antigen (PCNA).. In macroscopic findings, the groups undergoing nitrosoguanide (NG) gastrectomy with denervation showed a significant increase in the development of whitish, nodular changes in the gastric body. These changes mainly consisted of intestinal metaplasia in microscopic findings. In the NG gastrectomy group, the cancer developed at a lower rate of incidence at the anastomotic site and in the gastric body (1 of 11 rats and 1 of 11 rats, respectively). Conversely, a higher incidence of cancer development (5 of 13 rats) in the gastric body was observed in the group that underwent NG gastrectomy with denervation. Furthermore, the denervation group showed a significant increase in the PCNA labeling index and a distinct increase in the staining of Alcian blue positive mucin in the mucosa of the gastric body. The cancers that developed in the gastric body showed horizontal growth and were accompanied by intestinal metaplasia. In contrast, the cancers that developed in the gastric stumps showed downward growth, and were always accompanied by adenocystic proliferation, but not intestinal metaplasia.. Different processes of carcinogenesis in the gastric remnant are postulated after the surgery for gastric malignancies. The developed cancer is defined by its location and the gastric mucosal changes that developed at the time of gastrectomy.

Topics: Animals; Carcinogens; Cell Cycle; Cocarcinogenesis; Dose-Response Relationship, Drug; Female; Gastrectomy; Gastric Stump; Humans; Male; Methylnitronitrosoguanidine; Nitrosourea Compounds; Rats; Rats, Wistar; Stomach Neoplasms

The effect of ethanol (EtOH) on esophageal cell proliferation and the development of esophageal cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in shrews were investigated. Sequential histological examination was done, and cell proliferation was assessed by BrdU labeling. At 5 weeks of age, animals were given tap water, 2% EtOH, 50 ppm MNNG, or 50 ppm MNNG plus 2%, 5% or 10% EtOH in the drinking water. Administration of 10% and 5% EtOH simultaneously with MNNG caused death in 40% (10/25) within 4 days and in 20% (6/30) within 7 days respectively, whereas other treatment were well tolerated with no sudden deaths. Administration of 2% EtOH for 30 weeks caused a 2-fold increase, and that of MNNG caused a 4.5-fold increase in the proliferation index of the basal cells of the esophagus compared with control shrews, and MNNG plus 2% EtOH caused a 5.5-fold increase. In MNNG-treated shrews, with or without 2% EtOH administration, sequential histological examination of esophageal tissue revealed a similar change; dysplasia appeared at 30 weeks of age, squamous cell carcinoma occurred at 35 weeks of age, and the depth of invasion extended to adventitia at 45 weeks of age. These finding indicate that treatment with 2% EtOH promoted the proliferation of esophageal basal cells but did not alter the tumor induction period and did not have tumor-promoting activity. EtOH per se was not carcinogenic; no tumors were seen in shrews not administered MNNG.

Topics: Animals; Carcinogens; Cell Division; Cocarcinogenesis; Disease Models, Animal; Esophageal Neoplasms; Esophagus; Ethanol; Female; Methylnitronitrosoguanidine; Shrews

In this study, we investigated the carcinogenic response of transgenic mice carrying the human prototype c-Ha-ras gene, namely Tg rasH2/CB6F1 mice, to various genotoxic carcinogens and compared it with that of control non-transgenic CB6F1 mice (non-Tg mice). The present studies were conducted as the first step in the evaluation of the Tg rasH2/CB6F1 mouse as a model for the rapid carcinogenicity testing system. Short-term (< or = 6 months) rapid carcinogenicity tests of various genotoxic carcinogens, 4-nitroquinoline-1-oxide, cyclophosphamide, N,N-diethylnitrosamine, N-methyl-N-nitrosourea, N-methyl-N'-nitro-N-nitrosoguanidine and methylazoxymethanol, revealed that Tg rasH2/CB6F1 mice are more susceptible to these genotoxic carcinogens than control non-Tg mice. Tg rasH2/CB6F1 mice developed tumors more rapidly compared with non-Tg mice. Malignant tumors were observed only in the carcinogen-treated Tg rasH2/CB6F1 mice, but not in non-Tg mice treated with the same carcinogens. Each carcinogen induced tumors in corresponding target tissues of the Tg rasH2/CB6F1 mice. Only a very few lung adenomas but no other tumors were seen as spontaneous tumors during the 6 months of carcinogenicity tests. These results demonstrate that more rapid onset and higher incidence of more malignant tumors can be expected with high probability after treatment with various genotoxic carcinogens in the Tg rasH2/CB6F1 mice than in control non-Tg mice. The Tg rasH2/CB6F1 mouse seems to be a promising candidate as an animal model for the development of a rapid carcinogenicity testing system.

Topics: 4-Nitroquinoline-1-oxide; Animals; Carcinogenicity Tests; Carcinogens; Cocarcinogenesis; Cyclophosphamide; Diethylnitrosamine; Female; Genes, ras; Humans; Male; Methylazoxymethanol Acetate; Methylnitronitrosoguanidine; Methylnitrosourea; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Transgenic; Neoplasms, Experimental

The effects of combined administration of NaCl and the ornithine decarboxylase (ODC) inhibitor 1,3-diaminopropane (DAP) on the incidence and number of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and on the ODC activity of the gastric wall and the labeling index of the gastric mucosa were investigated in inbred Wistar rats. Rats were given drinking water with or without 2.5 g/l DAP and chow pellets with and without 10% NaCl ad libitum after 25 weeks of oral administration of MNNG. At week 52 feeding 10% NaCl resulted in significant increases in the incidence of gastric cancers, in the ODC activity of the antral portion of the gastric wall and in the labeling index of antral epithelial cells. Administration of both NaCl and DAP significantly reduced the enhancements by NaCl of gastric carcinogenesis, ODC activity of the antral wall and the labeling index of antral epithelial cells. These results suggest that inhibition of ODC attenuates NaCl enhancement of gastric carcinogenesis and that enhancement by NaCl of gastric carcinogenesis is mediated by polyamine biosynthesis.

Topics: Animals; Carcinogens; Cocarcinogenesis; Diamines; Drug Interactions; Enzyme Inhibitors; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Ornithine Decarboxylase; Ornithine Decarboxylase Inhibitors; Rats; Rats, Wistar; Sodium Chloride; Stomach; Stomach Neoplasms

Rats carrying the Eker tumor susceptibility mutation are genetically predisposed to renal cell carcinoma. Rats heterozygous for the Eker mutation (Eker carriers) develop multiple bilateral renal cell carcinomas by the age of 1 year. Using an in vitro rat kidney epithelial (RKE) transformation assay developed in our laboratory, proximal tubule cells derived from known Eker rat carriers (+/ek) and non-carriers (+/+) were exposed to the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), to determine if cells derived from Eker carriers were more susceptible to in vitro transformation than cells derived from non-carrier animals. The percent transformation frequency following MNNG treatment was 7.5-fold higher in cells derived from carrier animals when compared to cells from non-carrier animals. This increased susceptibility to transformation due to inheritance of the Eker mutation is consistent with a predisposition resulting from inactivation of a tumor suppressor gene. The increased susceptibility of kidney epithelial cells carrying the Eker mutation may prove useful in the further development of the RKE transformation assay as a sensitive tool to identify potential renal carcinogens. In addition, because transformation frequency in the RKE assay measures a very early step in multistage transformation, these results also suggest that alterations (by Loss of Heterozygosity or mutation) at the Eker tumor susceptibility locus are an early event in the development of renal tumors in the rat.

Topics: Animals; Carcinoma, Renal Cell; Cell Transformation, Neoplastic; Cocarcinogenesis; Epithelial Cells; Epithelium; Female; Kidney Neoplasms; Kidney Tubules; Male; Methylnitronitrosoguanidine; Mutation; Rats; Rats, Mutant Strains

The influence of different doses of sodium chloride (NaCl) on glandular stomach carcinogenesis was examined in male outbred Wistar rats after initiation with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Rats were given 100 p.p.m. MNNG in their drinking water for 8 weeks and then fed a diet supplemented with NaCl at doses of 10, 5, 2.5 or 0% for the next 82 weeks. The administration of 10% and 5% NaCl significantly enhanced the development of gastric adenocarcinomas and adenomas in a dose-dependent manner. Similar but non-significant tendencies for increase were also seen in the group given 2.5% NaCl compared to the MNNG-alone group values. Clear linear correlations between incidences of adenocarcinomas and/or adenomas and the concentration of supplemented NaCl were found. Mesenchymal tumors were also induced in the stomach of rats given MNNG, although the incidence was not statistically different between groups. Independent of the MNNG treatment, urinary lipid peroxidation levels were significantly increased in the NaCl-treated groups as compared to the control values. Thus, the results in the present study indicate that NaCl exerts dose-dependent tumor promoting activity on gastric carcinogenesis in rats, even at doses as low as 2.5%, when given after MNNG initiation.

Topics: Adenocarcinoma; Adenoma; Animals; Cocarcinogenesis; Dose-Response Relationship, Drug; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

We have studied the effect of intragastric instillation of 4.5 M NaCl on cell proliferation and carcinogen penetration into the forestomach of Wistar rats at different time intervals after salt exposure. Cells in the S-phase were labelled by incorporation of bromodeoxyuridine and located after immunohistochemistry. N-[3H]Methyl-N'-nitro-N-nitrosoguanidine ([3H]MNNG) was used as the carcinogen and penetration of [3H]MNNG to proliferative cells was determined by autoradiography. The number of cells in S-phase per millimetre epithelium length 12 h and 24 h after salt exposure (32.2 +/- 11.9 and 20.6 +/- 7.4) was significantly higher than in the control animals (9.4 +/- 3.6). No increase in cell proliferation occurred during the first 2 h after salt exposure. Microscopy also revealed oedema in the lamina propia. The forestomach blood flow was not influenced by the application of hypertonic saline. [3H]MNNG at a concentration of 40 micrograms/ml did not penetrate to the proliferative cells in the forestomach and no effect of salt pretreatment on carcinogen penetration was seen. The low penetration of [3H]MNNG to proliferative cells in the forestomach epithelium may explain why this concentration of MNNG given in drinking water over several weeks usually does not induce squamous cell carcinomas in the forestomach. The previously observed cocarcinogenic effect of salt on squamous cell cercinogenesis in the upper gastrointestinal tract could be due to the observed increase in cell proliferation after salt exposure.

Topics: Animals; Autoradiography; Body Water; Cell Division; Cocarcinogenesis; Gastric Mucosa; Hypertonic Solutions; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; S Phase; Sodium Chloride; Stomach; Stomach Neoplasms

N-Methyl-N-nitro-N'-nitrosoguanidine (MNNG) is a gastric carcinogen in several animal species and has been used in a number of systems to dissect the co-carcinogenic potential of various compounds in the induction of gastric adenocarcinoma. Recent epidemiological evidence suggests that Helicobacter pylori may play a role as a co-carcinogen in the etiology of this tumor in humans and we have been interested in developing an animal model to study this possibility. A related organism, H. mustelae, naturally colonizes the ferret stomach and causes persistent chronic gastritis. The pathology elicited by H. mustelae in ferrets has many similarities with the human disease including different stages of multifocal atrophic gastritis which underlie the gastric ulcer and gastric carcinoma syndrome. There is little evidence, however, demonstrating the susceptibility of ferrets toward chemical carcinogenesis. We have consequently undertaken a study to ascertain whether 10 6-month-old female ferrets given a single oral dose of MNNG (50-100 mg/kg) would develop adenocarcinoma of the stomach. Five age-matched unmanipulated control animals were included for comparative purposes. All 15 ferrets were infected with H. mustelae. Nine of 10 ferrets dosed with MNNG developed gastric adenocarcinoma (29-55 months after dosing), while none of the five historical control ferrets examined an average of 63 months after the initiation of the study developed gastric tumors. By comparison, we have not observed gastric adenocarcinoma, nor has it been reported, in > 10 years of observation of untreated ferrets naturally infected with H. mustelae. The H. mustelae-infected ferret, with demonstrated susceptibility to a gastric carcinogen, plus the recent availability of specific pathogen-free ferrets, should now allow longitudinal studies in vivo to probe the role of Helicobacter in the development of gastric cancer.

Topics: Adenocarcinoma; Animals; Biopsy; Cocarcinogenesis; Disease Models, Animal; Female; Ferrets; Gastritis; Helicobacter Infections; Longitudinal Studies; Methylnitronitrosoguanidine; Pyloric Antrum; Stomach; Stomach Neoplasms

Helicobacter pylori was implicated in gastric carcinogenesis through the induction of metaplasia of the gastric mucosa. In this experiment a co-carcinogenic effect of H. pylori on chemically induced gastric carcinogenesis was examined. Wistar WKY male rats received drinking water containing 50 mg/l of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and intragastric administration of 10(6) to 10(8) colony forming unit of H. pylori thrice a week for 40 weeks. Thus, 3 groups were assigned as Group I; MNNG alone, Group II; MNNG + vehicle, and Group III; MNNG + H. pylori (n = 30, each). At autopsy, 9 rats (30%) had 7 glandular stomach and 3 duodenal tumors in Group I, and 10 rats (33%) had 8 glandular stomach and 2 duodenal tumors in Group II, whereas in Group III 4 rats (13%) had 2 glandular stomach and 2 duodenal tumors (chi 2 = 4.257, P < 0.15 for the incidences of glandular stomach tumors among 3 groups). The finding seems to suggest that H. pylori has an ambitendency in the gastritis-metaplasia-carcinogenesis sequence as a promoter for the induction of the predisposing mucosa and as an inhibitor against certain carcinogens.

Topics: Animals; Cocarcinogenesis; Duodenal Neoplasms; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred WKY; Stomach Neoplasms

Appreciable yields of cutaneous mast cell tumors were induced in a two-stage skin carcinogenesis protocol comprising N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) initiation followed by 12-O-tetradecanoylphorbol-13-acetate (TPA) promotion in 4 of 5 strains of mice. Only female mice of each of the 5 strains were studied. The incidences of benign and/or malignant lesions differed considerably between strains; 27% in DBA/2, 22% in BDF1, 11% in BALB/c, 10% in CDF1 and 0% in C57BL/6 mice and no mast cell tumors were detected in any of the strains when treated with the initiator alone. First found in a DBA/2 mouse at week 50, most tumors were observed after 100 weeks of promotion, and were usually small in size (less than 2 mm in diameter) and predominantly located within the corium, although they occasionally extended into the subcutaneous tissue. Histologically, the benign mast cell tumors were composed of non-encapsulated, well circumscribed densely packed sheets of discrete cuboidal or rhomboid cells. Metachromatic granules were clearly visible in the cytoplasm by Toluidine Blue staining. Two of the tumors induced in DBA/2 mice were diagnosed as malignant mast cell tumors on the twin bases of cellular atypia and deep infiltration into the muscular layer. The cutaneous mast cell tumors were constantly accompanied by subepidermal mast cell aggregations which were also commonly observed in tumor-free skin of mice receiving the initiation-promotion procedure.

Topics: Animals; Cell Aggregation; Cocarcinogenesis; Female; Mast Cells; Mast-Cell Sarcoma; Methylnitronitrosoguanidine; Mice; Mice, Inbred Strains; Skin Neoplasms; Species Specificity; Tetradecanoylphorbol Acetate

Topics: Cocarcinogenesis; Fabaceae; Gastrointestinal Neoplasms; Humans; Methylnitronitrosoguanidine; Mutagenicity Tests; Plants, Medicinal; Salmonella typhimurium; Sodium, Dietary

The effects of diethylmaleate (DEM), previously demonstrated to inhibit butylated hydroxyanisole (BHA)-induced forestomach hyperplasia, on BHA promotion of forestomach carcinogenesis in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were examined. Groups of male 6-week-old F344 animals were given a single i.g. administration of 150 mg/kg body weight MNNG and starting 1 week later administered powdered diet containing 1% BHA plus 0.2% DEM, 1% BHA, 0.2% DEM or basal diet alone for 51 weeks. Further groups of rats were treated with 1% BHA plus 0.2% DEM, 1% BHA, 0.2% DEM or basal diet alone without MNNG pretreatment. Histopathological assessment of lesions at week 52 revealed enhancement of MNNG-initiated papilloma (100 versus 50%) and squamous cell carcinoma (100 versus 0%) development by BHA as compared to controls. Additional treatment with DEM, however, significantly reduced the relative incidences of carcinoma in situ (0 versus 35.7%) and squamous cell carcinoma (35.7 versus 100%), as well as BHA-induced forestomach hyperplasia with or without prior MNNG treatment. The results thus clearly demonstrate that DEM acts as a potent antagonist to BHA-promotion of rat forestomach carcinogenesis.

Topics: Animals; Butylated Hydroxyanisole; Cocarcinogenesis; Male; Maleates; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms

The effects of bombesin on the incidence, number, histological type, and depth of involvement of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in male Wistar rats. Rats received alternate-day s.c. administration of 20 or 40 micrograms/kg body weight of bombesin in depot form after p.o. treatment with the carcinogen for 25 weeks. Prolonged administration of bombesin at 40 micrograms/kg led to a significant increase in the incidence and number per rat of gastric cancers of the glandular stomach at Week 52. In rats that had received alternate-day injections of 20 micrograms/kg of bombesin, the number of gastric cancers per rat, but not the incidence of cancer, was significantly more than in untreated rats. However, bombesin at both dosages did not affect the histological appearance of the lesions or their depth of involvement. At Weeks 30 and 52, norepinephrine concentrations in the fundic and antral portion of the gastric walls and labeling indices in the antral and fundic mucosae were significantly higher in rats treated with bombesin at both dosages than in untreated rats. These findings indicate that bombesin enhances gastric carcinogenesis after administration of N-methyl-N'-nitro-N-nitrosoguanidine is stopped and that this effect may be related to its effects in increasing tissue norepinephrine concentrations in the stomach wall and increasing cell proliferation in the gastric mucosa.

Topics: Animals; Bombesin; Cocarcinogenesis; Drug Administration Schedule; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Norepinephrine; Rats; Rats, Inbred Strains; Stomach Neoplasms

We examined the tumor-promoting activity of sodium taurocholate in the remnant stomach of rats. Ninety male Wistar rats, 8 weeks of age, were separated into four groups. In group I, the rats were given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at a concentration of 83 mg/l in drinking water for 15 weeks, and distal partial gastrectomy was performed by Roux-en-Y procedure to prevent duodenal reflux into the remnant stomach. Thereafter, a diet containing 0.25% sodium taurocholate was given for 43 weeks. The group II rats were given MNNG and gastrectomy and were then given the usual commercial diet. The rats in group III were given gastrectomy and sodium taurocholate and no previous administration of MNNG. Only MNNG was given to the rats in group IV. The incidence of malignant tumors in the remnant stomach was 40.9% (9/22), 27.3% (6/22), and 0% (0/22) in groups I, II, and III, respectively, while the incidence in the area corresponding to the remnant stomach (control) was 8.3% (2/24) in group IV. The difference in tumor incidence was statistically significant (P less than 0.05) between groups I and IV but not between groups II and IV, and not between groups I and II. Six of nine tumors in group I and all six tumors in group II were located in the anastomotic area. These results suggest that sodium taurocholate promotes tumor production in the remnant stomach, and that the surgical procedure may well be associated with this enhanced tumor occurrence.

Topics: Animals; Cocarcinogenesis; Gastrectomy; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms; Taurocholic Acid

The influence of bile acids on the development of remnant gastric carcinoma was examined by investigating the incidence of carcinogenesis in noninbred male Wistar rats treated orally with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; CAS 70-25-7; 1-methyl-3-nitro-1-nitrosoguanidine) and fed a diet containing 1% cholesterol. The high-cholesterol diet did not influence the incidence of carcinoma in the nongastrectomized, MNNG-treated groups of rats. However, in the gastrectomized groups, the incidence of carcinoma was significantly higher in the group given the high-cholesterol diet (60.6%) than in the group given a normal diet (35.5%). Histologically undifferentiated adenocarcinoma was recognized more frequently in the high-cholesterol-diet group. Three gastrectomized rats not treated with MNNG but fed the high-cholesterol diet developed remnant gastric carcinoma (13%), whereas none of the rats given the normal diet did. Because the fecal excretion of bile acids increased significantly in the rats fed the high-cholesterol diet and the gastroduodenal reflux of bile acids was probably accelerated, the increase in the incidence of carcinogenesis in the remnant stomach was considered to be the result of the increase in the reflux of bile acids evoked by a high-cholesterol diet.

Topics: Animals; Bile Acids and Salts; Cholesterol, Dietary; Cocarcinogenesis; Female; Gastrectomy; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

This paper describes factorial experiments designed to determine whether two carcinogens that act on different organ systems act synergistically to produce cancers in Fischer 344 rats. Four carcinogens, N-methyl-N'-nitrosoguanidine (MNNG), N-butanol-N-butylnitrosamine (NBBN), nitilotriacetic acid (NTA), and dipentylnitrosamine (DPN) were studied in pairwise combinations. Each of the six possible pairs was studied by means of a 4 X 4 factorial experiment, each agent being fed at zero and at three non-zero doses. Methods of analysis designed explicitly for this study were derived to study interaction. These methods were supplemented by standard statistical methods appropriate for single agent studies. Antagonism was demonstrated in some chemical mixtures containing NTA. Other chemical mixtures did not interact. Findings for male and female animals were generally, but not always, in agreement.

Topics: Animals; Butylhydroxybutylnitrosamine; Carcinogens; Cocarcinogenesis; Data Interpretation, Statistical; Drug Interactions; Female; Kidney Neoplasms; Liver Neoplasms, Experimental; Male; Methylnitronitrosoguanidine; Nitrilotriacetic Acid; Nitrosamines; Rats; Rats, Inbred F344; Sex Factors; Stomach Neoplasms; Urinary Bladder Neoplasms

The effect of caerulein on the incidence and histology of gastric adenocarcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine was investigated in inbred Wistar rats. Prolonged alternate-day administration of caerulein at 10 micrograms/kg body weight after treatment with the carcinogen for 20 weeks significantly increased the incidence and number of adenocarcinomas of the glandular stomach. Histological examination showed that treatment with caerulein had no influence on the histology of induced adenocarcinomas. Furthermore, administration of caerulein resulted in a significant increase in the bromodeoxyuridine-labeling indices of the antral mucosa but did not influence the bromodeoxyuridine-labeling indices of the fundic mucosa and the carcinomas. These findings indicate that caerulein enhances gastric carcinogenesis and that the effect may be related to the promoting effect of caerulein on cell proliferation in the antral mucosa.

Topics: Animals; Bromodeoxyuridine; Cell Division; Ceruletide; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The pathologic characteristics of gastric tumors induced by single injections of N-methyl-N'-nitro-N-nitrosoguanidine (15 mg) solution and N-methyl-N-nitrosourea (10 mg) solution in 0.1 ml dimethylformamide were studied in 23 noninbred rats. The chemicals were injected into the antropyloric segment of the stomach. By months 11-15, specific changes in the glandular epithelium had developed at that site in 20 rats: dysplasia--in 6, precancer--7, and adenocarcinoma in 7 animals. Also, there were papillomas (6), squamous cell carcinoma (3), precancer and sarcoma (4) in various segments of the organ.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Methylnitrosourea; Papilloma; Precancerous Conditions; Rats; Sarcoma, Experimental; Stomach Neoplasms

Reflux of duodenal contents into the stomach occurs in patients with pyloric incompetence and after gastric resection when bile-diverting procedures are omitted. In such settings duodenal contents have been considered to favor the development of gastric cancer. We have studied the effect of chronic duodenogastric reflux on gastric tumor promotion in rats treated with N-methyl-N'-nitrosoguanidine (MNNG) in an experimental design that avoids physical trauma to the glandular stomach. Thus the effect of trauma-induced tissue repair on carcinogenesis is eliminated, and duodenogastric reflux is isolated as an experimental parameter. To achieve such reflux the first jejunal loop was anastomosed to the forestomach in rats. Animals were exposed to MNNG in drinking water (83 mg/L) for 12 weeks before induction of reflux. Experimental groups were as follow: I, reflux plus MNNG (n = 32); II, MNNG alone (n = 27); III, reflux alone (n = 28); IV, control (n = 25). The experiment was terminated after 56 weeks. Only animals that had survived for 90 days were included in the effective number of animals, which allowed for equal chances of tumor development. In no animal that died earlier had tumors developed. Animals with reflux plus MNNG treatment had significantly more glandular neoplasms (12/32) than did animals with MNNG treatment alone (4/27; p less than 0.05). Similarly, more animals with squamous cell neoplasms were recorded in group I (9/32) than in group II (2/27; p less than 0.05). In consideration of all tumors of epithelial and mesenchymal origin, more gastric malignant tumors were observed in group I (9/32) than in group II (2/27; p less than 0.05). It is concluded that chronic exposure to duodenal contents promotes the development of gastric neoplasia.

Topics: Adenocarcinoma; Adenoma; Animals; Carcinoma, Squamous Cell; Cocarcinogenesis; Duodenogastric Reflux; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

Primary cultures of mouse epidermal cells are induced to terminally differentiate when extracellular calcium levels are increased to more than 0.1 mM. After carcinogen treatment, cellular foci can be selected that resist this calcium signal to terminally differentiate. Calcium causes these foci to stratify; however, in contrast to normal epidermis, DNA-synthesizing cells in these foci are found in the suprabasal cell layers as well as in basal cells. Cell lines derived from these foci may be considered to be putative initiated cells. Three of these cell lines, designated 308, D, and F, have been characterized for their response to calcium and phorbol ester tumor promoters. The formation of cornified cells and the activity of epidermal transglutaminase were utilized as markers of epidermal differentiation. Neither calcium nor the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) increased transglutaminase activity or cornification of any of the 3 lines. Proliferation was estimated by the [3H]thymidine labeling index, by incorporation of [3H]thymidine into DNA, and by a clonal growth assay. Unlike primary normal cultures, raising the calcium level of the medium did not markedly reduce the rate of proliferation of any of the 3 cell lines. In 2 of the lines, line 308 and line D, proliferation increased in response to TPA exposure. In line F, [3H]thymidine incorporation in confluent cultures was inhibited by TPA, while in cells plated at clonal densities, TPA was cytotoxic at doses of 5 ng/ml or higher. If these calcium-resistant epidermal cell lines correspond to initiated cells, their lack of sensitivity to the induction of terminal differentiation by TPA could account for their growth relative to normal cells. Those lines that also respond to stimulation of proliferation by TPA to a greater extent than normal cells would have a further growth advantage.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Calcium; Carcinogens; Cell Differentiation; Cell Division; Cell Line; Cocarcinogenesis; Colony-Forming Units Assay; Drug Interactions; Epidermal Cells; Epidermis; Methylnitronitrosoguanidine; Mice; Tetradecanoylphorbol Acetate; Transglutaminases

Catechol (CAS: 120-80-9) is present in the environment, being a major industrial chemical as well as a major phenolic component of cigarette smoke. Continuous oral treatment of rats with 0.8% catechol for 51 weeks after a single intragastric dose of 150 mg/kg of N-methyl-N'-nitro-N-nitrosoguanidine strongly enhanced both forestomach and glandular stomach carcinogenesis. In addition, and more importantly, catechol alone induced adenocarcinoma and adenomatous hyperplasia in the pyloric region of the glandular stomach. These results clearly indicate that this environmental contaminant merits classification as an enhancer of forestomach and glandular stomach carcinogenesis with complete carcinogenic potential for the glandular stomach. Its significance for gastric tumor development in man requires elucidation.

Topics: Adenocarcinoma; Adenoma; Animals; Carcinogens, Environmental; Catechols; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms

Chemical carcinogenesis in mouse skin has been divided into the process of initiation, promotion and progression. Recently we have shown that ionizing radiation acts as an initiator in this model system. In this paper we describe a three-stage experiment using ionizing radiation in the third stage of mouse skin carcinogenesis. CD-1 mice were initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) followed by biweekly promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). After 20 weeks of promotion, the animals were treated with either acetone, TPA (twice a week for 2 weeks) or eight fractions of 1 MeV electrons (1 Gy/fraction over a period of 10 days). The conversion of papillomas to squamous cell carcinomas was 80% for animals treated with ionizing radiation compared with 25% for tumor-bearing animals treated with TPA. Ionizing radiation increased the number of cumulative carcinomas per group. The lack of an increase in the number of cumulative papillomas per group due to ionizing radiation suggests that the dose and fractionation protocol used in this study enhanced the progression of pre-existing papillomas.

Topics: Acetone; Animals; Carcinoma; Cocarcinogenesis; Female; Methylnitronitrosoguanidine; Mice; Neoplasms, Radiation-Induced; Papilloma; Skin Neoplasms; Tetradecanoylphorbol Acetate

Five doses of either N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or ethylnitrosourea (ENU) were tested as complete carcinogens, tumor initiators and tumor promoters in the SENCAR skin tumorigenesis model. As tumor initiators, MNNG-induced papillomas at all doses tested, while ENU was active from 10-40 mumol. As complete carcinogens, MNNG from doses of 0.5-5.0 mumol and ENU from doses of 10 mumol-40 mumol were potent inducers of both papillomas and carcinomas indicating that these agents are active as both tumor initiators and tumor promoters.

Topics: Animals; Carcinogens; Carcinoma; Cocarcinogenesis; Ethylnitrosourea; Female; Male; Methylnitronitrosoguanidine; Mice; Mice, Inbred Strains; Neoplasms, Experimental; Papilloma; Skin Neoplasms

An experimental study was performed using an organ culture method to evaluate the effect of a duodenal juice reflux on the development of cancer in the residual stomach. The following results were as follows. An intracellular DNA levels to combine with carcinogenic agents was significantly increased in the mucosa of the residual stomach compared to the parietal mucosa in the whole stomach (control group). In the human gastric mucosa exposed to the bile acid, the intracellular DNA level to combined with carcinogenic agents was increased, and thus the effect of the bile acid as a surfactant on the experimental development of gastric cancer was suggested. An atrophic change was main feature of the residual stomach. Autoradiographic findings revealed that the proliferative zone was extended and a number of immature cells appeared which became to be target cells. Therefore, the residual stomach might provide a situation where the cancer would easily develop.

Topics: Bile Acids and Salts; Bile Reflux; Biliary Tract Diseases; Cocarcinogenesis; DNA; Duodenum; Gastric Mucosa; Humans; Intestinal Secretions; Methylnitronitrosoguanidine; Organ Culture Techniques; Stomach Neoplasms

Ethanol, potassium metabisulfite, formaldehyde and hydrogen peroxide were tested for tumor-promoting activity in a two-stage stomach carcinogenesis experiment. Male outbred Wistar rats were given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water (100 mg/liter) and a diet supplemented with 10% sodium chloride for 8 weeks. Thereafter, they were maintained on drinking water containing either 10% ethanol, 1% potassium metabisulfite, 0.5% formalin (formaldehyde) or 1% hydrogen peroxide for 32 weeks and then sacrificed for necropsy and histological examination. In the pylorus of the glandular stomach, potassium metabisulfite and formaldehyde significantly increased the incidence of adenocarcinoma after initiation with MNNG and sodium chloride. Hydrogen peroxide did not enhance the tumor yield, and ethanol showed a tendency to decrease neoplastic development. In the forestomach the incidence of squamous cell papilloma was significantly increased in the groups given hydrogen peroxide or formaldehyde, irrespective of prior initiation. Duodenal adenocarcinoma was induced by the initiation alone (10%) and the incidence was not affected by the subsequent treatments. The results indicate that potassium metabisulfite and formaldehyde both exert tumor-promoting activity in the rat glandular stomach.

Topics: Adenocarcinoma; Animals; Body Weight; Cocarcinogenesis; Duodenal Neoplasms; Ethanol; Formaldehyde; Gastric Mucosa; Hydrogen Peroxide; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Rats, Inbred Strains; Stomach Neoplasms; Sulfites

The intralaboratory and interlaboratory reproducibility of a DNA virus (SA7) transformation enhancement assay was investigated using nine carcinogenic and noncarcinogenic compounds representing a variety of chemical classes. By the use of standardized procedures designed to limit assay variables, replicate assay data were collected in two independent laboratories and analyzed for concurrence. The carcinogens, 7,12-dimethylbenz(a)anthracene, benzo(a)pyrene, and N-methyl-N'-nitro-N-nitrosoguanidine yielded reproducible dose-dependent cytotoxicity and positive transformation effects (defined as statistically significant [p less than or equal to 0.05] enhancement of virus transformation at two or more consecutive dose levels) in all experiments in both laboratories. The carcinogens lead chromate, diethylnitrosamine, 4-nitroquinoline-N-oxide, and 2-acetylaminofluorene demonstrated enhancement of SA7 transformation at two or more dose levels in 40-50% of the assays. The noncarcinogenic structural analogs anthracene and pyrene consistently did not produce positive assay responses when tested at dose levels up to the limits of solubility. Good interlaboratory concurrence was demonstrated for these model compounds in the Syrian hamster embryo cell-SA7 assay.

Topics: 2-Acetylaminofluorene; 4-Nitroquinoline-1-oxide; 9,10-Dimethyl-1,2-benzanthracene; Adenoviridae; Adenoviruses, Simian; Animals; Benzo(a)pyrene; Carcinogens; Cell Transformation, Neoplastic; Cell Transformation, Viral; Cells, Cultured; Chromates; Cocarcinogenesis; Cricetinae; Diethylnitrosamine; Dose-Response Relationship, Drug; Embryo, Mammalian; Lead; Mesocricetus; Methylnitronitrosoguanidine

The influence of x-radiation and N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7] on intestinal metaplasia and gastric tumorigenesis was examined in 5-week-old male Crj:CD(SD) rats. The animals were treated either with two 10-Gy fractions of x-rays separated by 3 days for a total of 20 Gy to the gastric region and/or with MNNG orally for 4 months. Simultaneous treatment with x-rays and MNNG (group II) and MNNG only (group IV) induced gastric tumors in the majority of the animals. Sequential treatment with x-radiation and MNNG, either x-ray 2 months prior to MNNG (group I) or MNNG 2 months prior to x-ray (group III), resulted in a lower incidence of gastric tumors as compared with the incidence after treatment with MNNG alone. The frequencies of intestinal metaplasia in the x-irradiated groups (groups I and V) were significantly higher than those in group II, III, or IV. The incidence of intestinal metaplasia and of gastric tumor was inversely proportional. These results indicate that intestinal metaplasia does not play a role in the induction of gastric tumors by MNNG.

Topics: Animals; Cocarcinogenesis; Gastric Mucosa; Male; Metaplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Inbred Strains; Regression Analysis; Stomach Neoplasms

Sodium chloride is known to have a modifying effect on MNNG--induced carcinogenesis in rats. Its stimulating effect manifested itself in an increased frequency of MNNG--induced tumors of the stomach and small intestine and shorter latency of gastric tumor. Feeding with highly-salted food was followed by a relatively higher number of multiple lesions in the gastrointestinal tract.

Topics: Animals; Cocarcinogenesis; Gastrointestinal Neoplasms; Male; Methylnitronitrosoguanidine; Neoplasms, Multiple Primary; Rats; Rats, Inbred Strains; Sodium Chloride

The effects of antioxidant administration during the post initiation phase of gastric tumor development were investigated in male Wistar rats treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Animals (20/group) were given MNNG in the drinking water (100 mg/l) for 8 weeks, and for the duration of this treatment were also fed on diet supplemented with 10% sodium chloride. Thereafter, they were divided into 6 groups and were maintained on diet containing either 2% butylated hydroxyanisole (BHA), 1% BHA, 1% butylated hydroxytoluene (BHT), 1% ethoxyquin (EQ) or 1% DL-alpha-tocopherol (alpha-TP) for 32 weeks. A carcinogen control group was fed the basal diet without antioxidant supplementation. The experiment was terminated 40 weeks after the beginning of administration of MNNG and development of gastroduodenal tumors was determined histopathologically. EQ significantly increased the incidence of tumors in the glandular stomach. No modification of tumor development in this region of the organ were observed with 2% BHA, 1% BHA, 1% BHT or 1% alpha-TP, although both 2% BHA and 1% BHA induced and/or promoted tumor development in the forestomach. In addition, nephrocalcinosis was identified only in the kidneys of rats given EQ after MNNG treatment.

Topics: Animals; Antioxidants; Butylated Hydroxyanisole; Butylated Hydroxytoluene; Cocarcinogenesis; Duodenal Neoplasms; Ethoxyquin; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Time Factors; Vitamin E

In study I, 48 ACI and Fisher inbred rats were given MNNG 100 micrograms/ml, with or without 1 per cent or 3 per cent red pepper diet; in study II, 164 Sprague-Dawley rats given MNNG 100 micrograms/ml, with or without 5 per cent or 10 per cent NaCl; in study III, 181 Wistar rats given MNNG 83 micrograms/ml with or without maejoo 10 gm per cent/diet; in study IV, 78 Wistar rats given MNNG 83 micrograms/ml with or without ginseng extract 150 micrograms/ml; in study V, 120 Wistar rats given MNNG 83 micrograms/ml with or without retinyl palmitate 150,000 IU/kg. Except for study II (28 weeks), all rats were fed the diets for 37 weeks and were examined at 38 weeks or 40 weeks. In study I, tumor incidence in rats fed a red pepper diet and MNNG solution were 57 per cent (ACI rats, 1 per cent red pepper) and 63 per cent (Fisher rats, 1 per cent or 3 per cent red pepper) which were higher than control group (44 per cent, 43 per cent); in study II, gastric cancer, 61.9 per cent (10 per cent NaCl-MNNG), 27.3 per cent (control); in study III, gastric cancer, 14.8 per cent (maejoo-MNNG), 24 per cent (control); in study IV, malignant tumor of gastroduodenum, 3.4 per cent (ginseng-MNNG), 32.1 per cent (control); in study V, forestomach papilloma, 10.7 per cent (retinoid-MNNG), 29.4 per cent (control), and cancer in duodenum and small intestine, 50.0 per cent (retinoid-MNNG), 17.6 per cent (control). Thus, gastric carcinogenesis was enhanced by red pepper and a high salt diet, was inhibited by a maejoo and ginseng diet and was not effected by vitamin A.

Topics: Animals; Cocarcinogenesis; Condiments; Diterpenes; Duodenal Neoplasms; Feeding Behavior; Glycine max; Korea; Methylnitronitrosoguanidine; Panax; Plants, Medicinal; Rats; Rats, Inbred ACI; Rats, Inbred F344; Rats, Inbred Strains; Retinyl Esters; Sodium Chloride; Stomach Neoplasms; Vitamin A

The effect of gastrectomy and duodenal reflux on gastric carcinogenesis was studied because gastrectomized patients may be considered at "high risk" for the development of gastric stump cancer. Wistar rats received N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) (83 mg/liter) ad libitum in the drinking water for either four, eight, or twelve weeks. A control group received tap water. After MNNG administration animals were antrectomized. Antrectomy was not performed in a control group. Bowel continuity was restored either with a Billroth II (BIL) or with a ROUX en Y (ROUX) procedure. Duodenogastric reflux is possible after the BIL but not after the ROUX procedure. Eight months after the beginning of the experiment the stomachs of the animals were studied. In both operated and unoperated animals, the number of cancers observed was significantly related to the duration of MNNG administration. Animals receiving MNNG plus the BIL procedure had a significantly higher number of anastomotic cancers than the ROUX animals, indicating that duodenogastric reflux played a promotional role in gastric carcinogenesis. Three BIL gastrectomized rats not receiving the carcinogen had an adenocarcinoma on the anastomotic line further emphasizing the risk attached to the duodeno-gastric reflux.

Topics: Animals; Cocarcinogenesis; Duodenogastric Reflux; Gastrectomy; Male; Methylnitronitrosoguanidine; Pyloric Antrum; Rats; Rats, Inbred Strains; Stomach Neoplasms

Extracts prepared from oil refinery effluents (soxhlet and XAD-2) were tested for carcinogenic potential by means of the rainbow trout (Salmo gairdneri) embryo-injection bioassay. No neoplasms were detected in fish given injections of refinery extracts alone (with and without exogenous rat S-9 activation). Refinery extracts coinjected with aflatoxin B1 induced elevated frequencies of hepatic neoplasms. This cocarcinogenic effect was most pronounced when aflatoxin B1 was preincubated with rat S-9 prior to injection. Effluent extracts coinjected with a direct-acting carcinogen [N-methyl-N'-nitro-N-nitrosoguanidine (CAS: 56-57-5)] did not increase the incidence of hepatic neoplasms (with and without exogenous S-9 activation).

Topics: Aflatoxin B1; Aflatoxins; Animals; Biotransformation; Bone and Bones; Carcinogens, Environmental; Cocarcinogenesis; Fuel Oils; Industrial Waste; Liver Neoplasms; Methylnitronitrosoguanidine; Microinjections; Mutagenicity Tests; Mutagens; Petroleum; Rats; Trout; Water Pollutants; Water Pollutants, Chemical

The effects of prolonged administration of tetragastrin from the beginning of intrarectal instillation of 1 ml of 0.25% N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and after MNNG-treatment on the incidence and histology of colonic tumors were compared in inbred Wistar rats. In week 35 prolonged administration of testragastrin in depot form from the beginning of MNNG-treatment resulted in a significant reduction in the incidence of colonic tumors and a significant increase in the incidence of mucinous adenocarcinoma, unlike the well-differentiated adenocarcinoma produced in controls without gastrin. In contrast, prolonged administration of tetragastrin after MNNG-treatment had little or no influence on the incidence, size or histology of colonic tumors. Thus tetragastrin had no promoting effect on colonic tumors.

Topics: Adenocarcinoma; Animals; Cocarcinogenesis; Colonic Neoplasms; Drug Administration Schedule; Gastrins; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Rats; Rats, Inbred Strains; Tetragastrin

The transformation of C3H/10T1/2 cells can be made to proceed through discrete stages of initiation and promotion. Studies of the effect of cell density upon focus formation in cultures treated with MNNG and TPA suggest that initiation by MNNG is due to a relatively infrequent, irreversible event induced by a single carcinogen treatment. In contrast, promotion appears to be a reversible process requiring multiple treatments with TPA over a protracted period of time. Some evidence suggests that promotion may entail the induction of phenotypic changes which impart a growth advantage to phenotypically unstable "initiated" cell populations. The actual cellular mechanism(s) for most of the phenomena observed in C3H/10T1/2 cultures have eluded precise definition and widely divergent hypotheses have been advanced to explain transformation, initiation, and promotion. Conceivably there are multiple mechanisms responsible for each of these phenomenon. Some agents may transform by a multistage mechanism whereas others may exert their effects in a more direct fashion. Some of the foci produced by promotion may be the result of simple selective processes, others the product of more complex inductive events. Variations would thus be expected between laboratories working with different protocols and agents. As demonstrated by the possible involvement of an MCA residue in transformation, it is also apparent that fundamental technical aspects of this conceptually simple cell transformation system are poorly understood. While it is natural to develop mechanistic models based on quantitative observations of transformation, a limited understanding of the basic cell culture variables which modulate both the induction and expression of transformation dictate that caution be exercised in extrapolating the significance of such models to in vivo carcinogenesis.

Topics: Animals; Cell Communication; Cell Line; Cell Transformation, Neoplastic; Cocarcinogenesis; Embryo, Mammalian; Methylcholanthrene; Methylnitronitrosoguanidine; Mice; Mice, Inbred C3H; Tetradecanoylphorbol Acetate

The modifying effects of 3 antioxidants, sodium L-ascorbate (SA), ascorbic acid (AA) and sodium erythorbate (SE) on two-stage gastric carcinogenesis in F344 rats initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated. Administration of 5% SE in the diet significantly decreased the incidence of dysplasia of the pylorus and, more marginally the incidence of papilloma of the forestomach, whereas administration of 5% and 1% SA and 5% AA in the diet was not associated with effect. These results suggest that SE exerts a weak inhibitory effect on gastric carcinogenesis.

Topics: Animals; Ascorbic Acid; Body Weight; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms; Urinary Bladder Neoplasms

The effect of sodium chloride on the promotion stage of gastric carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in male inbred Wistar rats. Rats in group I were given MNNG at a concentration of 50 micrograms/ml in their drinking water for 12 weeks and then 1 ml of saturated NaCl solution intragastrically once a week until experimental week 65. Rats in group II were given MNNG for 12 weeks and then 1 ml of distilled water intragastrically once a week until week 65. Rats in group III were not treated for the first 12 weeks and were then given 1 ml of saturated NaCl solution intragastrically once a week until week 65. The incidence of adenomatous hyperplasias in the glandular stomach was significantly higher in group I than in group II, but the incidences of gastric adenocarcinomas and adenomas in groups I and II were not significantly different. No neoplastic or preneoplastic changes were observed in the stomach in group III.

Topics: Adenocarcinoma; Adenoma; Animals; Carcinogens; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Sodium Chloride; Stomach Neoplasms

Bile reflux is generally accepted as a causative factor of gastric cancer after partial gastrectomy. The present study was designed to evaluate the promotion, by the per oral administration of taurocholic acid, of methyl-N-nitro-N'-nitrosoguanidine (MNNG)-induced gastric carcinogenesis. MNNG (83 mg/l) was given in the drinking water to half the male Wistar rats during 12 weeks while the other half served as controls. After this treatment half of the MNNG-treated animals and half of the controls were placed under a diet containing 0.2% of taurocholic acid while the other animals received the standard diet. At the 40th week after initiation of MNNG, surviving animals were killed. Their stomachs and their duodenums were observed for macro and microscopic examination. Macroscopically there were 7 animals bearing gastric tumors in the MNNG group and 15 in the MNNG + bile group (P less than 0.05). Microscopically there were 7 animals with severe antral dysplasia in the MNNG group, 7 rats with fundic dysplasia and 18 with severe antral dysplasia in the MNNG + bile group. Both groups developed an identical number of duodenal tumors which were invasive adenocarcinomas or angiosarcomas. In this experiment taurocholic acid significantly promoted gastric carcinogenesis. It is postulated that surgical techniques inducing duodenal reflux in the stomach may produced a 'high risk' group of patients in which a long and careful follow-up is required.

Topics: Adenocarcinoma; Administration, Oral; Animals; Body Weight; Cocarcinogenesis; Duodenal Neoplasms; Gastrointestinal Neoplasms; Hemangiosarcoma; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Taurocholic Acid

A series of experiments was devised to determine possible modifying effects of stress, aspirin, and sodium taurocholate on the activity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the Buffalo rat stomach. MNNG is a well known, direct-reacting carcinogen, and has been a reliable agent for the experimental production of gastric adenocarcinoma. The authors were able to produce adenocarcinomas in rats, but found a great number of gastric leiomyosarcomas. These occurred only in the groups given MNNG in combination with stress, aspirin, or sodium taurocholate, and did not occur in experimental groups given either MNNG, stress, aspirin, or sodium taurocholate alone, and did not occur in the control group.

Topics: Adenocarcinoma; Animals; Aspirin; Cocarcinogenesis; Diet; Disease Models, Animal; Leiomyosarcoma; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred BUF; Stomach Neoplasms; Stress, Physiological; Taurocholic Acid

The promoting effect of partial gastrectomy in the development of cancer in the remnant stomach was examined in rats after oral administration of N-methyl-N'-nitro-N-nitrosoguanidine, using various surgical approaches. The incidence with which cancer developed in the remnant stomach following gastrectomy was lower than the incidence of gastric cancer in the entire glandular stomach. The incidence of cancer in the remnant stomach following Billroth II procedure according to Mayo's method, was higher than the incidence of cancer with other reconstructive methods as well as the corresponding area in the nonresected groups. There was a correlation between the incidence of cancer and the total bile acid concentration in the remnant stomach.

Topics: Administration, Oral; Animals; Bile Acids and Salts; Body Weight; Cocarcinogenesis; Gastrectomy; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms

The tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) was found to increase the incidence of phenotypic alterations induced by the direct-acting carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in human endometrial stromal cells. Following carcinogen treatment, changes in saturation density, gamma-glutamyltranspeptidase expression, morphology, and growth in selective media were enhanced in cell cultures subjected to continuous TPA exposure as compared to cultures receiving ethanol vehicle. This enhancement may have resulted, at least in part, from selection of cells altered by carcinogen, as evidenced by differences in the colony-forming abilities of MNNG-treated and control cultures after prolonged TPA exposure, and by differences in morphologic response to TPA challenge in these two populations.

Topics: Cell Aggregation; Cell Transformation, Neoplastic; Cells, Cultured; Cocarcinogenesis; Culture Media; Female; gamma-Glutamyltransferase; Humans; Methylnitronitrosoguanidine; Phenotype; Phorbols; Tetradecanoylphorbol Acetate; Uterus

Analysis of the etiologic factors and relevant mechanisms involved in carcinogenesis leads to a classification of agents involved in the carcinogenic process as genotoxic or epigenetic. Their mode of action is distinct, especially with regard to dose-response effects and reversibility. The genotoxic carcinogens for colon cancer are unknown, but mutagenic components found in fried beef and fish are under study. Epigenetic agents as promoting factors play a major role in the development of cancer of the colon. Specific nutritional elements associated with colon cancer risk are high fat diets, high cholesterol intake, and low fiber intake. The role of micronutrients as modulators and inhibitors needs to be explored. Through metabolic studies in diverse populations and in reliable animal models, it is now clear that dietary fat and cholesterol control the total flow of bile acids in lumen and a high-fat, high-cholesterol diet increases the total of bile acids in the gut. Bile acids but not neutral sterols have promoting effects and are related to colon cancer risk although bile acids by themselves do not act as complete carcinogens. The effect of dietary fiber such as cereal bran is to increase stool bulk which dilutes the concentration of bile acids. Reducing the concentration of bile acids either by lower dietary fat and cholesterol or by increasing dietary fiber may effectively lower the risk for colon cancer.

Topics: Animals; Bile Acids and Salts; Carcinogens; Cocarcinogenesis; Colonic Neoplasms; Dietary Fats; Dietary Fiber; Humans; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats

Incubation of primary cultures of hamster embryo cells (HEC) or mouse fibroblasts (C3H/10T1/2 cells) in media depleted of thyroid hormones does not alter cell growth or survival but renders the cells resistant to neoplastic transformation by benzo[a]pyrene (B[a]P) or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), carcinogens which yield transformation rates of 10(-4)-10(-2) in media supplemented with triiodothyronine (T3). In C3H/10T1/2 cells, the times of addition or removal of the hormone indicate that T3 exerts maximum effect when added 12 hr prior to treatment with B[a]P and that the progression of transformation from the time of initiation by the carcinogen to full expression and the appearance of transformed foci was independent of the presence or absence of the hormone in the medium. Dependence of transformation on T3 concentration in the medium was observed over the physiological range of 1 pM to 100 nM in C3H/10T1/2 cells treated with B[a]P. These results were similar to our previous findings on the T3 dose-related induction of radiogenic transformation and of Na+,K+-ATPase activity. The latter effect was used as a measure of T3 induction of protein synthesis. A further indication of the potential involvement of protein synthesis in T3 action is the suppression of T3- and B[a]P-dependent transformation by cycloheximide at concentrations that inhibit protein synthesis by approximately equal to 50% in the C3H/10T1/2 cells. We suggest that thyroid hormone induces the synthesis of a host protein that plays a key role in neoplastic transformation by direct-acting chemical carcinogens and by those requiring metabolic activation. In our previous studies, similar T3-dependent mechanisms were implicated in radiogenic transformations.

Topics: Animals; Benzo(a)pyrene; Benzopyrenes; Cell Transformation, Neoplastic; Cells, Cultured; Cocarcinogenesis; Methylnitronitrosoguanidine; Mice; Mice, Inbred C3H; Sodium-Potassium-Exchanging ATPase; Time Factors; Triiodothyronine

The tracheal epithelium of the Fischer 344 rat is histologically very similar to that of the human bronchus. Also, carcinomas of tracheal origin in F-344 rats are similar in morphology to human bronchogenic carcinomas. Tumor promotion in rat tracheal epithelium was studied by using two model systems. The first is a heterotopic transplant system in which rat tracheas are implanted subcutaneously on the backs of isogenic recipents. In the first system, the epithelium was topically exposed to pellets containing 7,12-dimethylbenz(a)anthracene (DMBA), used as the initiating agent, followed by pellets containing the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), the promoting agent. After 98 weeks, a three- to fourfold increase in the percentage of tracheas having malignant tumors was seen in tracheal transplants receiving both DMBA and TPA compared to DMBA alone. Exposure of the tracheal grafts to TPA alone resulted in epithelial hyperplasia and inflammation, but no dysplastic lesions. The second system is an organ culture-cell culture system in which small pieces of trachea are grown in organ culture, then epithelial cells are grown from these pieces as primary cell cultures. The organ cultures were exposed to the direct alkylating agent, N-methyl-N'-nitro-N -nitrosoguanidine (MNNG) used as the initiator, then multiple short exposures to TPA were used to promote. Primary cell cultures and cell lines were then established from these explants. After 52 weeks, a five-fold increase in the percentage of explants producing tumorigenic cell lines was observed when MNNG + TPA-exposed explants were compared to MNNG-exposed explants. Tracheal explants exposed to TPA alone produced many cell lines but none tested were tumorigenic. These two systems provide a means to study tumor promotion in respiratory epithelium. The evidence more importantly suggests that airborne promoting substances may play a key role in the development of bronchogenic carcinoma.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinogens; Cells, Cultured; Cocarcinogenesis; Epithelium; Methylnitronitrosoguanidine; Neoplasms, Experimental; Organ Culture Techniques; Rats; Tetradecanoylphorbol Acetate; Trachea; Tracheal Neoplasms

Albino rats (noninbred) were divided into 4 groups: 1) 56 control rats, 2) 40 rats fed 1 ml aspirin suspension (40 mg/ml) twice a week, 3) 20 rats given N-nitroso-N-methylnitroguanidine (MNNG) solution (250 micrograms/ml) to drink ad libitum, and 4) 40 rats given both aspirin and MNNG. In 18 months, there were no gastrointestinal tumors in groups 1 and 2, 8 cases of gastric tumors in group 3, and 37 cases of gastric tumors in group 4. Adenocarcinomas of the glandular stomach were found in 21 of 40 rats in group 4 but in only 4 of the 20 rats in group 3; the difference in incidence was significant. Histologic and electron microscopic examination of the epidermoid carcinomas and adenocarcinomas in group 4 showed no difference from such tumors induced by MNNG only. Hyperplasia of the forestomach mucosa and hyperplasia of the pyloric gland region of the glandular stomach in group 4 were more severe.

Topics: Adenocarcinoma; Animals; Aspirin; Carcinoma, Squamous Cell; Cocarcinogenesis; Female; Humans; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Papilloma; Probability; Rats; Stomach Neoplasms

C3H/10T 1/2 cells were treated with N-methyl-N'-nitro-N-nitrosoguanidine and then repeatedly exposed to formaldehyde (0.1 to 2.0 micrograms/ml). Exposure of N-methyl-N'-nitro-N-nitrosoguanidine-initiated cultures to formaldehyde concentrations of 0.5 or 1.0 micrograms/ml in a variety of treatment regimens resulted in focus formation in up to 9% of the treated dishes. Transformed foci were observed in 2% or less of the cultures treated with N-methyl-N'-nitro-N-nitrosoguanidine or formaldehyde alone. Formaldehyde thus appears to be only a weak tumor promoter for C3H/10T 1/2 cell transformation.

Topics: Animals; Cell Line; Cell Transformation, Neoplastic; Cocarcinogenesis; Embryo, Mammalian; Formaldehyde; Methylcholanthrene; Methylnitronitrosoguanidine; Mice

Topics: Animals; Benzo(a)pyrene; Benzopyrenes; Cells, Cultured; Cocarcinogenesis; Cricetinae; Cricetulus; Drug Synergism; Female; Fibroblasts; Methylnitronitrosoguanidine; Mutagens; Ovary; Vehicle Emissions

Topics: Animals; Antipain; Caffeine; Carcinogens; Cell Transformation, Neoplastic; Cells, Cultured; Cocarcinogenesis; Cricetinae; DNA Repair; Lymphokines; Methylnitronitrosoguanidine; Mutation; Sister Chromatid Exchange; Tetradecanoylphorbol Acetate; Ultraviolet Rays; X-Rays

In order to define factors which determine susceptibility to chemical carcinogenesis, mice sensitive (SENCAR) and resistant (BALB/c) to epidermal carcinogenesis were studied under several treatment conditions for sensitivity to initiation by 7,12-dimethylbenz(a)anthracene or N-methyl-N'-nitro-N-nitrosoguanidine and promotion by 12-O-tetradecanoylphorbol-13-acetate. In newborns of both strains, topical application of initiator was much less effective than in adults. However, initiation by i.p. injection of 7,12-dimethylbenz(a)anthracene is at least as effective in newborns as in adults, which may indicate that topically applied carcinogen is not delivered effectively to target cells in newborns. Thus, newborn epidermis can respond to 7,12-dimethylbenz(a)anthracene as well as adult epidermis when the initiator is appropriately administered. SENCAR mice are much more sensitive than are BALB/c mice to both initiators, which suggests that enhanced metabolic activation of hydrocarbon carcinogens by SENCAR mice is unlikely to account for their sensitivity. Newborn male SENCAR's developed approximately 50% more papillomas than did females in all groups. BALB/c newborn mice developed so few tumors that a meaningful comparison of sensitivity of males and females could not be made. Thus, the increased sensitivity of SENCAR's was apparent regardless of route of administration of initiator or the age or sex of the mice. SENCAR mice also developed a significant number of papillomas and squamous cell carcinomas with 12-O-tetradecanoylphorbol-13-acetate promotion in the absence of an exogenous initiator. Therefore, the skin of SENCAR mice may contain an initiated population of cells capable of responding to tumor promoters.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Age Factors; Animals; Benz(a)Anthracenes; Carcinoma, Squamous Cell; Cocarcinogenesis; Dose-Response Relationship, Drug; Methylnitronitrosoguanidine; Mice; Mice, Inbred Strains; Papilloma; Skin Neoplasms

Possible promotion of MNNG-induced gastrointestinal carcinogenicity was evaluated in male Wistar rats exposed to unconjugated bile acid given as gavage or as obtained through truncal vagotomy plus pyloroplasty. No significant difference was found compared with the relevant control groups. Even though gastroduodenal erosions were found more frequently in the bile acid gavage and MNNG groups than in MNNG-treated controls, secondary deconjugated bile acids apparently did not reach optimal promoting concentrations. In contrast to partial gastrectomy, vagotomy and pyloroplasty does not increase the tumor yield in the rat.

Topics: Adenocarcinoma; Animals; Bile Acids and Salts; Cocarcinogenesis; Enteral Nutrition; Gastrointestinal Neoplasms; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Pylorus; Rats; Rats, Inbred Strains; Sarcoma; Vagotomy

Methyl linoleate hydroperoxide (MLHP) and native methyl linoleate (ML) were tested for carcinogenicity toward the gastrointestinal (GI) tract in male specific-pathogen-free outbred Wistar rats. N-Methyl-N-nitro-N-nitrosoguanidine (MNNG) was given in the drinking water in a dose of 20 mg/liter when cocarcinogenic properties of the test substances were to be tested. MLHP and ML were fed by stomach tube and had no effect as complete carcinogens. Given concomitantly with MNNG, ML did not enhance carcinogenesis. MLHP in conjunction with MNNG was the only treatment which, as treatment with MNNG in a dose of 83 mg/liter, led to an increase of GI cancers in animals that died before day 354. Cumulative results after a maximum of 612 days showed a distribution of GI cancers in favor of the glandular stomach only after MLHP was given with MNNG.

Topics: Animals; Body Weight; Cocarcinogenesis; Gastrointestinal Neoplasms; Intubation, Gastrointestinal; Linoleic Acids; Lipid Peroxides; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Time Factors

12-O-Tetradecanoylphorbol 13-acetate (TPA), a known tumor promoter, enhances the morphologic transformation of Syrian hamster embryo cells induced by low transforming concentrations of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) (0.025-0.1 microgram/ml) without potentiation of cell lethality or of changes in sister chromatid exchanges (SCEs) or chromosomal aberration frequencies. When MNNG was added to logarithmically growing cultures and TPA was added 2, 24, or 48 hr later, no changes in SCE frequency relative to MNNG alone occurred. Similar results were obtained with TPA in cells that had been exposed to MNNG in stationary growth phase. Whereas no transformation occurred with TPA alone and pretreatment with TPA did not affect MNNG transformation, its addition 2 hr after MNNG reduced transformation frequency but addition 24-72 hr after MNNG increased the transformation frequency up to 6-fold. TPA had a minimal effect on increasing the transformation frequency (2-fold) induced by MNNG at 0.25 micrograms/ml, a high concentration. Of three polycyclic hydrocarbons, perylene, benzo[g,h,i]perylene, and benz[a]anthracene, known as weak or noncarcinogens, only benz[a]anthracene induced a very low transformation frequency; however, after TPA, transformation occurred with all three. Because the number of cells whose transformation was initiated by low doses of carcinogen is much larger than the number of cells giving rise to transformed colonies in the absence of TPA, the frequency of the initial event is greater than can be expected from point mutations. Furthermore, the promotional aspect of transformation is not accompanied by a parallel increase in SCE.

Topics: Animals; Cell Transformation, Neoplastic; Cells, Cultured; Chromosome Aberrations; Cocarcinogenesis; Cricetinae; Mesocricetus; Methylnitronitrosoguanidine; Phorbol Esters; Phorbols; Sister Chromatid Exchange

Topics: Adenocarcinoma; Adenoma; Animals; Cholesterol; Cocarcinogenesis; Colonic Neoplasms; Female; Germ-Free Life; Lithocholic Acid; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred F344

Examinations were made on the carcinogenic effects of a chemical compound, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and a physical carcinogen, whole-body irradiation with fission neutrons, on the gastrointestinal tract of male albino Sprague-Dawley rats. The carcinogens were used singly and together in order to investigate their possible synergistic effects on the induction of adenocarcinomas of the stomach and small intestine. Of the 13 animals treated with the chemical, MNNG, and living more than 9 months, 9 showed gross tumors (5 gastric and 4 duodenal), confirming the high incidence of gastrointestinal carcinomas induced by MNNG in the rat. There were no gastrointestinal tumors found after neutron exposure. When the 2 carcinogens were combined, no additivity or synergism occurred. After neutron irradiation, a dental syndrome with loss of incisor teeth was observed. The effect of neutron irradiation on subgingival pathology of the teeth is being investigated.

Topics: Adenocarcinoma; Animals; Carcinogens; Cocarcinogenesis; Fast Neutrons; Gastrointestinal Neoplasms; Incisor; Intestine, Small; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Neoplasms, Radiation-Induced; Rats; Stomach Neoplasms