methylnitronitrosoguanidine and Papilloma

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

This paper describes specific genetic changes involving chromosome 7 in mouse skin tumors, the most important consequence of which appears to be an alteration in the allelic balance of normal and mutant H-ras genes. The use of restriction-fragment-length polymorphisms in F1 hybrid mice demonstrates that trisomy of chromosome 7 is an early event preceding papilloma formation, and further events, such as mitotic recombination, seem to occur during progression to malignant carcinomas. There is some evidence of a tumor-suppressor locus situated on chromosome 7.

Topics: Alleles; Animals; Carcinoma; Chromosomes; DNA Damage; Gene Expression Regulation, Neoplastic; Genes, ras; Genes, Tumor Suppressor; Hybridization, Genetic; Methylnitronitrosoguanidine; Mice; Papilloma; Polymorphism, Restriction Fragment Length; Proto-Oncogene Proteins p21(ras); Recombination, Genetic; Skin Neoplasms; Trisomy

The SENCAR mouse stock was selectively bred for eight generations for sensitivity to skin tumor induction by the two-stage tumorigenesis protocol using 7,12-dimethylbenz(a)anthracene (DMBA) as the initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as the promoter. The SENCAR mouse was derived by crossing Charles River CD-1 mice with skin-tumor-sensitive mice (STS). The SENCAR mice are much more sensitive to both DMBA tumor initiation and TPA tumor promotion than CD-1, BALB/c, and DBA/2 mice. An even greater difference in the sensitivity to two-stage skin tumorigenesis is apparent between SENCAR and C57BL/6 mice when using DMBA-TPA treatment. However, the SENCAR and C57BL/6 mice have a similar tumor response to DMBA-benzoyl peroxide treatment, suggesting that TPA is not an effective promoter in C57BL/6 mice. The DBA/2 mice respond in a similar manner to the SENCAR mice when using N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-TPA treatment. The SENCAR mouse model provides a good dose-response relationship for many carcinogens used as tumor initiators and for many compounds used as tumor promoter. When compared to other stocks and strains of mice, the SENCAR mouse has one of the largest data bases for carcinogens and promoters.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinogens; Carcinoma; Disease Models, Animal; Drug Evaluation, Preclinical; Methylnitronitrosoguanidine; Mice; Mice, Inbred Strains; Papilloma; Skin Neoplasms; Species Specificity; Tetradecanoylphorbol Acetate

Hyperinsulinemia and hyperglycemia in prediabetic and diabetic patients are thought to increase the risk of developing neoplasms because insulin is a growth factor with pre-eminent metabolic but also mitogenic effects. To determine the effect of hypoinsulinemic diabetic conditions on carcinogenesis, we examined N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced forestomach carcinogenesis in hypoinsulinemic diabetic WBN/Kob rats aged about 45 weeks (DM) compared with non-diabetic younger WBN/Kob rats (C1), non-diabetic Wistar rats age-matched to DM (C2), and non-diabetic Wistar rats age-matched to C1 (C3). All rats were treated with MNNG by gavage and were killed at 40 weeks after dosing. Various-sized tumors were disseminated throughout the forestomach of all rats, and the ratio of the area of tumors to the whole forestomach area was 23.3% in the DM group and was higher than in the C1-3 (4.2-14.3%) groups. The incidence of carcinoma was much higher in the DM group (36.8%) than in the C1-3 (7.1-16.7%) groups, and the incidence of papilloma was also significantly higher in the DM group (84.2%) than in the C1-3 (28.5-50.0%) groups. The average thickness of the squamous epithelium in the non-neoplastic mucosa was significantly greater in the DM group (50.8 mum) than in the C1-3 (29.6-37.9 microm) groups. Immunohistochemically, the Ki-67-positive index in the non-tumorous mucosa of the DM group (42.0%) was significantly higher than that of the C1-3 groups (18.8-33.3%). These results suggest that prolonged hyperglycemic conditions without hyperinsulinemia enhance tumorigenesis of MNNG-induced tumors by enhanced proliferative activity of the squamous epithelium in the rat forestomach.

Topics: Adipose Tissue; Animals; Carcinogens; Carcinoma; Diabetes Mellitus, Experimental; Epithelial Cells; Gastric Mucosa; Insulin; Ki-67 Antigen; Male; Methylnitronitrosoguanidine; Pancreatitis; Papilloma; Rats; Rats, Inbred Strains; Rats, Wistar; Stomach; Stomach Neoplasms

Hypermethylation of CpG sites within the promoter region of the O6-methylguanine-DNA methyltransferase (MGMT) gene occurs frequently in human cancer, preventing both MGMT expression and repair of alkylation damage. To assess the role of MGMT in the development of mouse skin tumors induced by initiation-promotion protocols, methylation of the MGMT promoter was examined in tumor DNA using methylation-specific PCR. To determine whether MGMT promoter methylation was affected by the tumor induction protocol, tumors were initiated by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or 7,12-dimethylbenz[a]anthracene (DMBA) and promoted by 12-O-tetradecanoylphorbol-13-acetate (TPA) or mezerein. Although the MGMT promoter was not methylated in normal skin, promoter methylation was found in 56 of 136 papillomas (41.2%) and in 19 of 37 squamous cell carcinomas (51.4%). When methylation of the MGMT promoter was compared in the 4 treatment groups, hypermethylation was found more frequently in tumors initiated by DMBA and promoted by mezerein, a protocol associated with a high frequency of malignant conversion. Methylation was found in some tumors as early as 5 weeks after initiation, but the methylation frequency increased with time. MGMT promoter methylation reduced MGMT expression as determined by immunohistochemistry. Although MGMT promoter methylation was not generally correlated with ras mutations, the frequency of MGMT methylation was higher in MNNG-initiated, mezerein-promoted papillomas with mutations in Ha-ras compared to papillomas with Ki-ras. Methylation of the MGMT promoter, associated with reduced MGMT expression, is found in nearly half of mouse skin tumors, but varies with both the tumor initiator and tumor promoter, and may be a key step in the progression from papillomas to carcinomas.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinogens; Carcinoma, Squamous Cell; Diterpenes; DNA Methylation; Gene Expression Regulation, Neoplastic; Genes, ras; Humans; Methylnitronitrosoguanidine; Mice; Mutation; O(6)-Methylguanine-DNA Methyltransferase; Papilloma; Promoter Regions, Genetic; Skin; Skin Neoplasms; Tetradecanoylphorbol Acetate

The effects of sodium nitrite (NaNO2), in combination with one of three antioxidants, tert-butylhydroquinone (TBHQ), alpha-tocopherol (alpha-Toc) and propyl gallate (PG), on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) stomach carcinogenesis were investigated in F344 rats. Groups of 15 male rats were treated with an intragastric dose of 150 mg/kg body weight of MNNG, and starting 1 week later, were treated with 0.5% TBHQ, 1% alpha-Toc, 1% PG or basal diet with or without 0.2% NaNO2 in their drinking water until they were killed at the end of week 36. Macroscopically, in MNNG-treated animals, combined administration of alpha-Toc or PG with NaNO2 significantly increased the areas and numbers of forestomach nodules as compared with the respective antioxidant alone values. Microscopically, in MNNG-treated animals, treatment with TBHQ significantly increased the incidence and multiplicity of forestomach papillomas as compared with basal diet alone value. Combined administration of alpha-Toc with NaNO2 significantly raised the multiplicity of forestomach papillomas, with a tendency to elevation in the incidence as compared with the group given alpha-Toc alone. Incidences of forestomach moderate and/or severe hyperplasias were significantly higher in the TBHQ or PG plus NaNO2 groups than in the single compound groups. In rats without MNNG treatment, combined treatment of antioxidants with NaNO2 significantly increased the incidences of mild or moderate hyperplasia. In the glandular stomach, although the incidence of atypical hyperplasia showed a non-significant tendency for decrease with TBHQ treatment, additional administration of NaNO2 caused significant increase. These results indicate that co-administration of NaNO2 with alpha-Toc, TBHQ or PG and particularly the first, promotes forestomach carcinogenesis. Concurrent alpha-Toc, TBHQ or PG treatment with NaNO2 is likely to induce forestomach tumors in the long term.

Topics: alpha-Tocopherol; Animals; Antioxidants; Body Weight; Carcinoma, Squamous Cell; Drug Combinations; Drug Interactions; Food Preservatives; Hydroquinones; Hyperplasia; Male; Methylnitronitrosoguanidine; Papilloma; Propyl Gallate; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach Neoplasms

The skin tumor initiators N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 7,12-dimethylbenz[a]anthracene (DMBA) differ in effectiveness when tumor formation is promoted by 12-O-tetradecanoylphorbol-13-acetate (TPA). Even at high doses, MNNG is less effective, producing fewer benign and malignant tumors with a longer latent period. In DMBA-initiated skin, 10 wk of TPA promotion produced a maximal tumor response. With MNNG, 20 wk of TPA promotion was required, producing nearly four times as many papillomas as 10 wk of promotion. Promotion of MNNG-initiated skin with mezerein induced the appearance of very rapidly-growing papillomas within 5 wk, 3 wk earlier than the first TPA-promoted papillomas. Thus, MNNG may induce a novel mutation resulting in a population of initiated cells that respond especially well to mezerein. Since ras mutations are common in experimental tumors in many tissues, we determined the frequency of activating mutations in the Ha-ras, Ki-ras, and N-ras oncogenes. Activating Ha-ras mutations were present in essentially all DMBA-initiated tumors and about 70% of MNNG-initiated tumors. No N-ras mutations were found in tumors lacking other ras mutations. Surprisingly, 41% of the papillomas arising in the first 11 wk in MNNG-initiated, mezerein-promoted mice bore mutations in codon 12 of the Ki-ras oncogene. Activating Ki-ras mutations were also found in more than 60% of squamous cell carcinomas and 40% of keratoacanthomas. Although mutations in Ha-ras are frequently detected in mouse skin tumors, mutations in Ki-ras are rare. This is the first report of mutated Ki-ras in skin tumors from mice initiated by MNNG.

Topics: Animals; Base Sequence; Carcinogens; Codon; Diterpenes; DNA Primers; Female; Genes, ras; Methylnitronitrosoguanidine; Mice; Mutagens; Mutation; Papilloma; Skin Neoplasms; Terpenes

The modifying effect of diethyl maleate (DEM) on gastric tumor development was studied in rats initially given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and hypertonic sodium chloride (H-NaCl 10% or 5%). Groups of animals were maintained with or without a 0.2% DEM dietary supplement after treatment with MNNG and H-NaCl and sacrificed at week 20. Forestomachs and livers cytosolic NAD(P)H:quinone-acceptor oxidoreductase (QR) activity was also analyzed. The incidences of forestomach severe hyperplasias in the MNNG + H-NaCl --> DEM groups were also significantly higher than in the MNNG + H-NaCl alone group (P < 0.01 and P < 0.05 for 5% and 10% groups, respectively). Similarly, in the glandular stomach, the numbers of preneoplastic pepsinogen 1 altered pyloric glands (PAPGs) in the MNNG + H-NaCl --> DEM groups were significantly increased (P < 0.01 for both concentrations). The QR activities in the groups treated with DEM showed 2- to 3-fold increases as compared with the control level. The results indicate that treatment with 0.2% DEM after MNNG initiation exerts enhancing effects on both forestomach and glandular stomach carcinogenesis. Induction of QR, a Phase II enzyme, activity in the rat stomach by DEM may be associated with promotion of stomach carcinogenesis rather than inhibition.

Topics: Animals; Body Weight; Carcinogenicity Tests; Carcinogens; Carcinoma, Squamous Cell; Gastric Mucosa; Male; Maleates; Methylnitronitrosoguanidine; NAD(P)H Dehydrogenase (Quinone); Papilloma; Pepsinogen A; Rats; Rats, Wistar; Saline Solution, Hypertonic; Stomach; Stomach Neoplasms

Secreted phosphoprotein 1 (spp1), the gene encoding osteopontin (OPN), is expressed in many human carcinomas, although its in vivo functions remain unclear. To delineate the role of OPN during tumor progression, we have subjected OPN null mutant mice to repeated applications of a mutagen/carcinogen to induce cutaneous squamous cell carcinoma. OPN null animals exhibited accelerated tumor growth and progression and had a greater number of metastases per animal compared with wild-type animals. However, metastases in the OPN null animals were significantly smaller than in controls. When injected into nude mice, the growth of OPN null tumor lines and the same lines engineered to reexpress spp1 recapitulated the growth differences observed in the progression study. These differences in tumor growth inversely correlated with the degree of macrophage infiltration. Slower-growing, OPN-producing tumors contained significantly more macrophages, although a higher proportion were mannose receptor positive, a characteristic of differentiated resting macrophages. In vitro, OPN null cell lines displayed decreased survival at clonal density compared with OPN-producing lines, an observation consistent with the smaller metastases of the OPN null mice. Overall, we provide evidence for a model where host-derived OPN acts as a macrophage chemoattractant, whereas tumor-derived OPN is able to inhibit macrophage function and enhances the growth or survival of metastases.

Topics: Animals; Carcinogens; Carcinoma; Carcinoma, Squamous Cell; Cell Count; Cell Division; Disease Progression; Female; Male; Methylnitronitrosoguanidine; Mice; Neoplasm Proteins; Osteopontin; Papilloma; Phenotype; Sialoglycoproteins; Skin Neoplasms

To investigate the relationship between p53 gene mutations and mouse skin tumors induced by three-step carcinogenesis.. The exons 5-8 of p53 gene were examined in 37 DMBA-TPA-MNNG induced mouse skin tumors [including 6 mice with papillomas, 15 mice having well differentiated squamous cell carcinomas (SCCI) and 16 mice with intermediately differentiated squamous cell carcinomas (SCC II)].. No p53 gene mutation was detected in the papilloma group, whereas 25.8% (8/31) of the SCC group had p53 gene mutations (4/15 of the SCC I mice and 4/16 of the SCC II mice). A total of 9 mutations were found in 8 mice with SCC, of which 7 were located in exon 8 and 7 were G-->A transitions.. The p53 gene mutations occurred during the process of malignant transformation from papilloma to SCC induced by three step carcinogenesis.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinoma, Squamous Cell; Cell Transformation, Neoplastic; Exons; Genes, p53; Methylnitronitrosoguanidine; Mice; Mice, Inbred SENCAR; Papilloma; Point Mutation; Skin Neoplasms; Tetradecanoylphorbol Acetate

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

Skin papillomas and squamous cell carcinomas (SCCs) are induced in mice by tumor initiation with a carcinogen followed by tumor promotion with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). These usually arise from preneoplastic lesions characterized by epidermal proliferation and hyperplasia, dermal edema, and inflammation. To evaluate the role of polypeptide growth factors in chemically induced skin carcinogenesis, we used transgenic mice carrying the cDNA for a TGF-beta related molecule, bone morphogenetic protein-4 (BMP-4), under the control of the regulatory elements of the cytokeratin IV* gene in a skin carcinogenesis protocol. Control non-transgenic littermates and BMP-4 transgenic mice were treated with a single dose of a carcinogen, N-methyl-N'-nitrosoguanidine (MNNG), and biweekly with the tumor promoter TPA for 9 months. In control littermates TPA induced epidermal hyperproliferation, atypia with "dark" cells, and dermal inflammation, resulting in papillomas and SCCs in 13 of 26 animals tested. In BMP-4 transgenic mice, TPA treatment induced the expression of the BMP-4 transgene in interfollicular epidermis but only minimal epidermal thickening, hyperproliferation, and inflammation were noted after the initial dose of TPA. Furthermore, the mitotic indices in transgenic epidermis after 9 months of TPA treatment were significantly lower than the corresponding indices from untreated transgenic epidermis. Consequently, none of the 22 transgenic animals tested developed papillomas or SCCs. In conclusion, we have shown that the TPA induced expression of the BMP-4 transgene blocks proliferation and inflammation in skin, steps that are critical to the subsequent formation of papillomas and SCCs and we characterized an inducible promotersystem which expresses polypeptides in interfollicular epidermis after exogenous stimulation.

Topics: Animals; Bone Morphogenetic Proteins; Bromodeoxyuridine; Carcinoma, Squamous Cell; Cell Division; Epidermis; Methylnitronitrosoguanidine; Mice; Mice, Transgenic; Papilloma; Proteins; Skin; Skin Neoplasms; Tetradecanoylphorbol Acetate; Transforming Growth Factor beta

Recently, an epidemiological study showed a lower risk of gastric cancer among people who consume a large amount of green tea. (-)-Epigallocatechin gallate (EGCG), one of the main constituents of green tea, inhibited tumor promotion by teleocidin in a two-stage carcinogenesis experiment with the use of mouse skin. The inhibitory effect of EGCG on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced carcinogenesis of the glandular stomach in rats was examined. The percentage of tumor-bearing rats in the group treated with MNNG plus EGCG was 31%, compared to 62% in the MNNG group. The difference was statistically significant (P < 0.05). To assess the effect of p.o. administration of EGCG, the gastric mucosal cellular kinetics was examined with the use of the bromodeoxyuridine labeling index, ornithine decarboxylase activity, and tissue polyamine levels. The labeling index of the EGCG treatment group decreased significantly (P < 0.05) compared to the EGCG plus MNNG treatment group. The ornithine decarboxylase activity and tissue spermidine levels were also decreased. On the other hand, the tissue putrescine and spermine levels were partly increased. These findings suggest that EGCG inhibits the cellular kinetics of the gastric mucosa during the promotion stage of MNNG-induced gastric carcinogenesis. EGCG may be useful in preventing gastric carcinogenesis. Moreover, EGCG may be applied clinically without any harmful effects and at a low cost.

Topics: Adenocarcinoma; Adenoma; Animals; Antineoplastic Agents; Carcinoma, Papillary; Catechin; Drug Screening Assays, Antitumor; Male; Methylnitronitrosoguanidine; Ornithine Decarboxylase; Papilloma; Rats; Rats, Wistar; Stomach Neoplasms

The histological changes occurring in the esophageal mucosa of shrews (Suncus murinus) after N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment were investigated sequentially. Six-week-old female shrews were given a 50 micrograms/ml MNNG solution as drinking water for 30 weeks, and 5 selected at random were killed at 10 and 20 weeks of age, and thereafter at 5-week intervals until 45 weeks of age. Controls were killed at 45 weeks of age. The MNNG-induced esophageal lesion in shrews began from basal cell hyperplasia at 20 weeks of age, followed by dysplasia occurring at 25 weeks of age, then progressed toward intraepithelial carcinoma to invasive squamous cell carcinoma at 35 weeks of age. Apparent sequential dysplasia-carcinoma transition was seen. Papillomas were seen from 25 weeks of age but there was no evidence of papilloma-carcinoma sequence. Five MNNG-untreated shrews killed at the end of the experiment were free of esophageal tumors.

Topics: Animals; Carcinoma in Situ; Carcinoma, Squamous Cell; Cell Transformation, Neoplastic; Disease Models, Animal; Esophageal Neoplasms; Female; Immunoenzyme Techniques; Methylnitronitrosoguanidine; Papilloma; Shrews

In experiment I, short-term effects of combined treatment with anti-oxidants, sodium ascorbate (NaAsA) and sodium nitrite (NaNO2) on forestomach cell proliferation were examined in F344 male rats. Groups of 5 animals aged 6 weeks were treated for 4 weeks with 0.8% catechol, 0.8% hydroquinone, 1% tert-butyl-hydroquinone (TBHQ), 2% gallic acid or 2% pyrogallor alone or in combination with 0.3% NaNO2 in the drinking water and/or 1% NaAsA in the diet. The thicknesses of forestomach mucosa in rats treated with anti-oxidants and NaNO2 in combination were greater than those with antioxidant alone and additional NaAsA treatment further enhanced the thickening of mucosa. It was noteworthy that values for mucosae of animals treated with NaNO2 and NaAsA without anti-oxidant were similar to those for anti-oxidants. In experiment 2, effects of combined treatment with NaAsA or ascorbic acid (AsA) and NaNO2 on carcinogenesis were examined in F344 male rats with or without N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) pre-treatment. Groups of 20 or 15 rats, respectively, aged 6 weeks, were given a single intra-gastric administration of 150 mg/kg body weight of MNNG in DMSO:water = 1:1 or the vehicle alone by stomach tube. Starting 1 week later, they received supplements of 1% NaAsA or 1% AsA in the diet and 0.3% NaNO2 in drinking water in combination, each of the individual chemicals alone, or basal diet until the end of week 52. In MNNG-treated animals, incidences of forestomach papillomas and carcinomas were significantly enhanced in the NaNO2 alone group (84 and 47%, respectively) as compared with the basal diet group (30 and 10%), with further significant increase in carcinomas occurring with additional NaAsA (79%, p < 0.05) or AsA (85%, p < 0.05) treatment. In animals without MNNG, all animals in the NaNO2 group demonstrated mild hyperplasia, additional administration of NaAsA or AsA remarkably enhancing the grade of hyperplasia, and resulting in 53% and 20% incidences, respectively, of papillomas. Thus NaNO2 was demonstrated to exert promoter action for forestomach carcinogenesis, with NaAsA and AsA acting as co-promoters. The results strongly indicate that combined treatment with NaAsA or AsA and NaNO2 may induce forestomach carcinomas in the long term.

Topics: Animals; Ascorbic Acid; Body Weight; Carcinoma, Squamous Cell; Drug Interactions; Kidney; Liver; Male; Methylnitronitrosoguanidine; Organ Size; Papilloma; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach Neoplasms

A 1-ml dose of 4.5 M NaCl was given intragastrically to male Wistar rats at 10 min, 1 h, 4 h, 12 h, 24 h or 48 h before a single intragastric dose of 250 mg/kg N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). After 52 weeks the incidence of forestomach squamous cell carcinoma was 21% in control animals receiving MNNG alone. The cancer incidence in the forestomach varied with the time elapsed between application of NaCl and MNNG, and was significantly increased in animals pretreated with NaCl 4 h (43%), 12 h (54%) and 24 h (41%) before MNNG. These results show that salt has a cocarcinogenic effect on initiation of forestomach carcinogenesis in rats, and that this effect depends on the time interval between pretreatment with NaCl and application of MNNG. Gastric adenocarcinomas occurred more frequently in the antrum (78%) than in the corpus (22%). The incidence of gastric adenocarcinoma in animals pretreated with salt before application of MNNG (11%-22%) was not significantly influenced by the time elapsed between pretreatment with salt and application of MNNG, and did not differ from animals receiving MNNG alone (18%). The lack of a cocarcinogenic effect of NaCl on glandular gastric carcinogenesis might be due to the use of dimethyl/sulfoxide as solvent for MNNG.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Drug Administration Schedule; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Rats, Wistar; Saline Solution, Hypertonic; Stomach; Stomach Neoplasms

Topics: Animals; Anticarcinogenic Agents; Antioxidants; Benzodioxoles; Butylated Hydroxyanisole; Caffeic Acids; Carcinogens; Carcinoma; Catechols; Cell Division; Hydroquinones; Kidney Neoplasms; Male; Maleates; Methylnitronitrosoguanidine; Organ Specificity; Papilloma; Phenols; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

Female 6-week-old shrews were given a solution of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at a concentration of 50 micrograms/ml or 100 micrograms/ml in the drinking water. All 11 shrews receiving 100 micrograms/ml MNNG died 8-13 days after the beginning of carcinogen administration and 6 of the 20 shrews receiving 50 micrograms/ml MNNG died after 10-54 days. When animals were between 43 and 54 weeks of age, multiple esophageal lesions were evoked in all 14 that had received 50 micrograms/ml MNNG for 30 weeks. All shrews developed a protruding, ulcerative, or superficial type of squamous-cell carcinoma of the esophagus, accompanied by papillomas. Local invasion was seen in squamous-cell carcinoma but no distant metastasis was noted. None of the 5 control shrews developed any esophageal abnormality. No gastric adenocarcinoma, intestinal sarcoma, or other tumors were induced with MNNG. It can be concluded that MNNG has a carcinogenic effect on shrew esophageal epithelium.

Topics: Animals; Carcinoma, Squamous Cell; Disease Models, Animal; Esophageal Neoplasms; Female; Methylnitronitrosoguanidine; Papilloma; Shrews

Initiation and promotion in mouse skin carcinogenesis produce multiple benign tumors, squamous papillomas, but only a few squamous cell carcinomas. The spontaneous conversion from the benign to the malignant phenotype occurs over many months and in stages, but induced malignant conversion can be accomplished more rapidly by exposure of papilloma-bearing mice to mutagens or by transfection of papilloma cell lines with specific oncogenes. The analysis of genetic targets responsible for carcinogen-induced neoplastic progression would be facilitated by the development of in vitro models where the process is rapid, focal, and quantitative. To this end, primary newborn mouse keratinocytes were initiated in vitro by the introduction of the v-rasHa oncogene via a defective retrovirus. Recipient cells produce squamous papillomas and have a high proliferation rate in culture medium with 0.05 mM Ca2+, but fail to grow in medium with 0.5 mM Ca2+ which is permissive for growth of malignant keratinocytes. When v-rasHa-keratinocytes were exposed to mutagens in vitro, proliferative foci emerged after culture in 0.5 mM Ca2+ for 4 weeks. These foci stained intensely red with rhodamine stain, could be easily quantitated, and readily incorporated bromodeoxyuridine. Dose-response studies with several mutagens indicated that the number of foci increased with concentration to the point where excessive cytotoxicity developed. Mutagens varied in potency for producing foci in the following order: cis-diamminedichloroplatinum greater than or equal to benzo(a)pyrene diolexpoxide I greater than N-methyl-N'-nitro-N-nitrosoguanidine greater than or equal to 4-nitroquinoline-N-oxide greater than N-acetoxy-acetyl- aminofluorene. The tumor promoter 12-O-tetradecanoylphorbol-13-acetate was inactive in the assay. A subset of cell lines derived from foci produced malignant tumors in vivo, while others were not tumorigenic. Analysis of DNA from cell lines and tumors revealed that most tumorigenic cell lines maintained the v-rasHa genome, whereas the viral sequences were deleted in nontumorigenic cell lines. Immunohistochemical analysis indicated that proliferative foci and quiescent v-rasHa keratinocytes expressed keratin 8, a marker of v-rasHa expression in cultured keratinocytes. Cells in foci, but not v-rasHa control cells, expressed keratin 13, a marker which is strongly associated with the malignant progression of skin tumors in vivo. This in vitro assay provides a quantitative model to

Topics: Animals; Animals, Newborn; Base Sequence; Carcinogens; Carcinoma, Squamous Cell; Cell Transformation, Neoplastic; Cells, Cultured; Epidermal Cells; Epidermis; Genes, ras; Keratinocytes; Keratins; Methylnitronitrosoguanidine; Mice; Mice, Inbred BALB C; Molecular Sequence Data; Oligodeoxyribonucleotides; Papilloma; Polymerase Chain Reaction; Skin Neoplasms; Tetradecanoylphorbol Acetate; Transfection

The sensitivity of outbred SENCAR mice and inbred SENCAR (SSIN) mice to multistage carcinogenesis was studied. Tumors were induced using either 7,12-dimethylbenz[a]anthracene or N-methyl-N'-nitro-N-nitrosoguanidine as initiators and 12-O-tetradecanoylphorbol-13-acetate or benzoyl peroxide as promoting agents. Although the number of papillomas per mouse was higher in SSIN than in outbred SENCAR mice, the number of carcinomas observed in the SSIN strain was significantly lower regardless of the initiator or promoter used. It was also observed that the expression of markers of premalignant progression (i.e., dysplasia, expression of keratin K13, and loss of keratin K1 expression) was markedly suppressed in SSIN papillomas. After 50 wk of promotion with 12-O-tetradecanoylphorbol-13-acetate, the pattern of expression of K13 and K1 in SSIN mice was comparable to the pattern observed in outbred SENCAR mice after 10 to 20 wk of promotion with 12-O-tetradecanoylphorbol-13-acetate. It was also observed that 67% of the tumors induced in SSIN mice by initiation with 7,12-dimethylbenz[a]anthracene exhibited a mutation in codon 61 of the Ha-ras-1 gene. This latter finding suggests that the differences observed in tumor progression between the inbred strain and the outbred stock are not related to a genetic alteration in the Ha-ras-1 gene but rather to an independent event that we have postulated to involve a putative suppressor gene. The data reported here suggest that the putative gene(s) that confers susceptibility to tumor promotion was segregated from the gene(s) involved in tumor progression during selection and inbreeding of the SENCAR mouse stock.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Benzoyl Peroxide; Carcinoma, Squamous Cell; Female; Genes, ras; Keratins; Methylnitronitrosoguanidine; Mice; Mutation; Papilloma; Skin Neoplasms; Species Specificity; Tetradecanoylphorbol Acetate

Promotion effects of the o-dihydroxybenzene derivatives, protocatechuic acid (PCA), dopamine hydrochloride (DAH), dl-dopa and caffeic acid on forestomach and glandular stomach carcinogenesis were investigated in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Groups of 20 male F344 rats were given a single intragastric administration of 150 mg/kg body wt MNNG and starting 1 week later than received diet containing 1.5% PCA, 1.5% DAH, 1.5% dl-dopa or 1% caffeic acid or basal diet alone for 51 weeks and then killed. Other groups of 10-15 rats were given PCA, DAH, dl-dopa or basal diet alone without the MNNG pretreatment. On histological assessment, the incidences of forestomach papillomas and squamous cell carcinomas were significantly enhanced in the group treated with caffeic acid (95 and 100%) as compared with the control values (35 and 10%). Although the incidence was not different, the number of papillomas per rat in the group given DAH (0.79 +/- 0.79) was also significantly increased (0.35 +/- 0.49). PCA and dl-dopa treatments did not modify the development of neoplastic lesions in the forestomach epithelium to any significant extent. None of the four chemicals enhanced glandular stomach carcinogenesis. The results thus demonstrated that whereas caffeic acid and DAH respectively, exert strong and weak promotion activity for rat forestomach carcinogenesis this promotion potential is not shared by all dihydroxybenzene derivatives. An influence of substituents in the para position in addition to the o-dihydroxy moiety is indicated.

Topics: Adenocarcinoma; Animals; Body Weight; Caffeic Acids; Carcinogens; Carcinoma, Squamous Cell; Dihydroxyphenylalanine; Dopamine; Drug Synergism; Epithelium; Hydroxybenzoates; Hyperplasia; Leiomyosarcoma; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

The effects of butylated hydroxyanisole (BHA) pretreatment on subsequent low dose N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or N,N-dibutylnitrosamine (DBN) treatment on forestomach or esophageal carcinogenesis were investigated in male F344 rats. Groups of animals were pretreated with 2% BHA or basal diet alone for 24 weeks and then were given 20 mg/kg body wt MNNG once every 2 weeks, 0.025% DBN in drinking water continuously or basal diet alone for the subsequent 24 weeks. Further groups of rats were similarly treated with BHA or basal diet alone for 24 weeks, placed on basal diet for the next 24 weeks and then treated with MNNG, DBN or basal diet alone for the subsequent 24 weeks. Animals were killed 48 or 72 weeks after the beginning of the experiment. Histopathological examination showed that the incidence of forestomach tumors was not significantly affected by the BHA pretreatment in the MNNG-treated groups. On the other hand, the incidence of esophageal squamous cell carcinomas was lower in the group pretreated with BHA followed by DBN than in that treated with basal diet followed by DBN (48 week experiment). There was no significant difference in esophageal tumor incidence in the 72 week experiment. The results thus indicate that continuous treatment with 2% BHA for 24 weeks does not exert initiating activity on forestomach and esophageal epithelia.

Topics: Animals; Body Weight; Butylated Hydroxyanisole; Carcinogens; Carcinoma, Squamous Cell; Esophageal Neoplasms; Esophagus; Hyperplasia; Male; Methylnitronitrosoguanidine; Nitrosamines; Organ Size; Papilloma; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

Topics: Adenoma; Animals; Antioxidants; Butylated Hydroxyanisole; Carcinoma; Cell Division; Epithelium; Female; Hyperplasia; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

A single topical treatment of mouse skin with the potent tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) results in transient inductions of a variety of genes. Based on the time courses of their inductions, these genes can be classified into two main groups: "early" response genes whose mRNA expression reaches a maximum 0.5-2 h after TPA treatment and "secondary" response genes whose mRNA expression is maximal 4 h or more after treatment. The nuclear oncogenes c-fos, c-myc, and c-jun belong to the early response group, whereas the metallothionein, osteopontin, and urokinase genes belong to the secondary response group. The steady-state expressions of these early and secondary response genes are all very low in normal skin, except that of c-jun, which is relatively high. Steady-state levels of expression and inducibility of these genes by TPA were not altered in initiated skin or in apparently normal skin during tumor promotion. We examined the expressions of these genes in papillomas and carcinomas produced by two-stage (initiator-promoter) and three-stage (initiator-promoter-initiator) protocols in mouse skin. Steady-state expression of the early responding nuclear oncogenes in papillomas and carcinomas was found to remain at the same low level as in normal skin. However, all the secondary responding genes were found to be expressed constitutively at high levels in these tumors. Elevated expressions of the genes for transforming growth factor alpha and beta were also observed in papillomas and to varying extents in carcinomas. These observations suggest that the regulatory machinery for transcription by the protein kinase C-mediated pathway through nuclear oncogenes is altered during the processes of tumor promotion and progression. The genes whose expression is elevated may be associated directly or indirectly with tumor promotion and progression.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Blotting, Northern; Carcinogens; Carcinoma; Female; Gene Expression; Metallothionein; Methylnitronitrosoguanidine; Mice; Mice, Inbred Strains; Osteopontin; Papilloma; Proto-Oncogene Proteins; RNA, Messenger; Sialoglycoproteins; Skin; Skin Neoplasms; Skin Physiological Phenomena; Tetradecanoylphorbol Acetate; Transforming Growth Factors; Tubulin; Urokinase-Type Plasminogen Activator

The modifying effects of para-methoxyphenol (PMP) second stage treatment on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-initiated rat forestomach carcinogenesis were investigated. Groups of 15 6 week old male F344 rats were given a single intragastric administration of 150 mg/kg body wt MNNG and starting 1 week later were administered powdered diet containing 2.0, 1.0, 0.5, 0.25 or 0% PMP until they were killed at week 52. PMP caused epithelial damage and hyperplasia in a dose-dependent manner in the forestomach epithelium, but nevertheless was not associated with any increase in the incidence of either papillomas or squamous cell carcinomas. The results thus clearly indicated that stimulation of cell proliferation does not necessarily correlate with promotion in the second stage of two-stage forestomach carcinogenesis.

Topics: Animals; Anisoles; Carcinogenicity Tests; Carcinoma; Cell Division; Hyperplasia; Male; Methylnitronitrosoguanidine; Muscle, Smooth; Organ Size; Papilloma; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

We have shown previously that the risk of tumor initiation, promotion, and progression in animals initiated with alkylating agents can be drastically altered by hyperthermia treatments. We show here that ionizing radiation can also alter the risk of tumor initiation by alkylating agents. Using a two-step skin tumorigenesis protocol in female SENCAR mice (initiation by MNNG, promotion with TPA), we exposed the dorsal skin of the mice to various doses of 90Sr/90Y beta radiation near the time of initiation. The radiation produced a dose-dependent reduction in the number of papillomas which appeared after TPA promotion, with about a 20% reduction in animals receiving 0.5 Gy surface dose just before initiation, about 50% reduction after 2.5 Gy, and greater than 80% at doses above 5 Gy. A dose of 2.5 Gy in animals initiated with DMBA produced no significant reduction. One skin hyperthermia treatment (44 degrees C, 30 min) along with radiation in MNNG-initiated animals partially blocked the protective effect of radiation and increased the papilloma frequency. Radiation (2.5 Gy) given either 6 days before or after MNNG initiation was less effective but still reduced papilloma frequency about 20%. In sharp contrast to the marked reduction in papilloma formation, these same animals showed no change in carcinoma frequency with any of the doses or schedules of beta radiation. MNNG initiation alone produced three types of initiated cells. One type, produced in low yield, was promotion-independent with a high probability of progression to a carcinoma and appeared unaffected by the radiation. A second type, produced in intermediate yield, was promotion-dependent and also had a high progression probability, but was likewise unaffected by the radiation. The third and most abundant type was promotion-dependent with a very low progression probability. Radiation exposure resulted in a decrease in the risk of an MNNG initiation event which led only to the third type of cell. The data therefore indicate that the risk of some, but not all, tumor-initiating events caused by alkylating agents can be reduced by an exposure to ionizing radiation.

Topics: Animals; Beta Particles; Carcinoma; Female; Methylnitronitrosoguanidine; Mice; Papilloma; Skin Neoplasms; Strontium Radioisotopes

Peculiarities of carcinogenic effect of N-methyl-N'-nitro-N-nitrosoguanidine administered through a stomach tube on rats were studied in 30 rats given 1-2 ml MNNG dissolved in distilled water (5 mg/ml) through a gastric tube for 2-3 days. The procedure is repeated every 4-10 days. This intermittent carcinogen administration continued until week 20; the animals were killed on week 25. All effective 26 (100%) rats had multiple papillomas and squamous cell carcinomas of the forestomach, 5 (19.2%) had adenomatous hyperplasias and adenocarcinomas of the glandular stomach, 7 (26.9%) had adenocarcinomas and sarcomas of the small intestine.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Intestinal Neoplasms; Intestine, Small; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Papilloma; Rats; Sarcoma, Experimental; Stomach Neoplasms; Time Factors

Topics: Amino Acid Sequence; Base Sequence; Biomarkers, Tumor; Blotting, Northern; Blotting, Southern; Carcinogens; Carcinoma, Squamous Cell; DNA; Fibroblasts; Gene Expression Regulation; Genes, Dominant; Genes, ras; Methylnitronitrosoguanidine; Molecular Sequence Data; Neoplasms, Radiation-Induced; Papilloma; Plasmids; Proto-Oncogenes; RNA; Skin Neoplasms; Suppression, Genetic; Transfection

Carcinogen treatment of normal mouse epidermal cells causes some cells, if cultured under the appropriate conditions, to continue to proliferate instead of terminally differentiate, forming foci at 37 degrees C in medium with a calcium level above 0.1 mM. We have examined these Calcium (Ca)-resistant cells formed in the skin of SENCAR mice after treatment with the carcinogen initiator 7,12-dimethylbenz[a]anthracene (DMBA) followed by tumor promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). Although in our previous studies TPA promotion initially increased the size but reduced the number of foci caused by the carcinogen initiator N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), TPA promotion of DMBA-treated mice increased the size but had no effect on the number of foci. Papillomas resulting from DMBA plus TPA treatment contained many rapidly growing Ca-resistant cells, corroborating our earlier results with MNNG. Permanent cell lines prepared from papilloma-derived foci formed squamous cell carcinomas in nude mice after relatively short periods in culture. These data provide further evidence that Ca-resistant cells may be papilloma (and perhaps carcinoma) precursors in vivo. In addition, since TPA tends to reduce the number of early Ca-resistant cells caused by MNNG but not by DMBA, this may at least partially explain why treatment with DMBA plus TPA is much more effective in producing papillomas in SENCAR mice than is treatment with MNNG plus TPA.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Cell Differentiation; Epidermal Cells; Female; Methylnitronitrosoguanidine; Mice; Papilloma; Skin Neoplasms; Tetradecanoylphorbol Acetate

In order to establish an effective method to induce selectively experimental dog esophageal carcinoma, we compared the restricted oral administration of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) with projecting spout with the ad libitum oral administration of it. Five dogs were given a solution of ENNG at a concentration of 50mg/l with restricted oral administration with projecting spout for 52 weeks. In all of them, elevated type of esophageal lesions were endoscopically observed soon after the cessation of the ENNG administration. Histological examination revealed that besides the multiple squamous cell carcinomas of the esophagus, various degrees of dysplasias were seen. Two dogs had metastasizes to the regional lymph nodes and one dog had metastatic lesions in the lung. Gastric carcinomas were also seen in four dogs. Another five dogs were given ad libitum the same concentration of ENNG solution. Gastric carcinomas were induced in four dogs, but esophageal carcinomas were seen in small lesions in two dogs. The restricted oral administration of ENNG with projecting spout is a reliable method for the selective induction of esophageal carcinoma in dog.

Topics: Administration, Oral; Animals; Carcinogens; Carcinoma, Squamous Cell; Dogs; Esophageal Neoplasms; Female; Male; Methylnitronitrosoguanidine; Papilloma; Stomach Neoplasms

A single hyperthermia treatment given near the time of initiation with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or 7,12-dimethylbenz[a]anthracene (DMBA) increased the number of initiated cells in the skin of SENCAR mice subjected to a two-stage tumorigenesis protocol. In animals subsequently promoted with 12-O-tetradecanoylphorbol-13-acetate (TPA), a 44 degrees C, 30-min hyperthermia treatment given just before, just after or 24 h before MNNG initiation increased the average papilloma frequency by 40-50%. In the groups of animals that received a hyperthermia treatment just before MNNG initiation, tumor latency was reduced by 40-60%. Treatment with MNNG in the absence of hyperthermia produced two classes of initiated cells. One type, formed in low yield, was independent of TPA promotion and formed tumors with a high probability of progression to malignancy. The other type was promotion dependent, and formed in relatively high yield but produced tumors with a probability of progression to carcinomas approximately 10-fold less than promotion-independent initiated cells. A single hyperthermia treatment given just before or just after MNNG initiation increased the yield of both promotion-dependent and promotion-independent initiated cells, and consequently increased the yield of carcinomas. In animals given a single hyperthermia treatment 24 h prior to initiation (to induce thermotolerant skin cells), MNNG exposure resulted in an increased yield of promotion-dependent initiated cells but no change in the yield of promotion-independent initiated cells. Hyperthermia treatment of DMBA-initiated skin increased the yield of initiated cells (promotion-dependent) only when given just after exposure to the initiator. The extra initiated cells produced by hyperthermia treatment of MNNG or DMBA exposed skin had the same probability of progression to carcinomas as initiated cells produced by the same initiation in the absence of hyperthermia. As noted previously for DMBA-initiated mice, hyperthermia given at the time of each application of TPA promoter also suppressed the formation of papillomas initiated by MNNG. Only the promotion and progression of promotion-dependent initiated cells, and not of promotion-independent cells, was suppressed. The results show that a single hyperthermia treatment near the time of exposure to an alkylating agent increased the number of both promotion-dependent and promotion-independent initiated cells and, as a consequence, increased th

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinoma; DNA Repair; Female; Glutathione; Hyperthermia, Induced; Methylnitronitrosoguanidine; Mice; Papilloma; Skin Neoplasms; Tetradecanoylphorbol Acetate

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

Alkaline elution was used to examine DNA single-strand breaks in cultured normal and carcinogen-altered mouse keratinocytes exposed to 12-O-tetradecanoyl phorbol-13-acetate and benzoyl peroxide. Seven cell lines derived from carcinogen-induced mouse skin papillomas and three cell lines derived from N-methyl-N'-nitro-N-nitrosoguanidine-treated non-tumor bearing mouse skin were resistant to phorbol ester-mediated DNA strand breaks after 6 or 24 h. Normal keratinocytes sustained strand breaks after 24 h but not after 6 h. Benzoyl peroxide induced extensive strand breaks in normal keratinocytes at both 6 and 24 h, and this was associated with marked cytotoxicity. In contrast, 9 of 10 cell lines showed complete or partial resistance to strand breaks following benzoyl peroxide exposure. It is proposed that differential resistance to DNA strand breaks and cytotoxicity among normal and carcinogen-altered keratinocytes provides the biological basis for the promoting action of benzoyl peroxide. Furthermore, sublethal DNA damage in preneoplastic or neoplastic keratinocytes may account for the potency of benzoyl peroxide in causing malignant conversion.

Topics: Animals; Benzoyl Peroxide; DNA Damage; Keratins; Methylnitronitrosoguanidine; Mice; Mice, Inbred BALB C; Papilloma; Peroxides; Skin; Skin Neoplasms

The effect of exogenous synthetic prostaglandins and the inhibition of endogenous prostaglandin synthesis on gastrointestinal tumorigenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7] was studied in female Wistar rats (100 g). Animals were divided into 6 groups: Group I was treated with MNNG alone (No. = 43); group II was treated with MNNG after application of the cyclo-oxygenase inhibitor flurbiprofen (No. = 44); group III was treated with MNNG after oral administration of 16,16-dimethyl-prostaglandin E2 (16,16-dm-PGE2; No. = 43); group IV received flurbiprofen alone (No. = 15); group V was treated with 16,16-dm-PGE2 alone (No. = 11). Animals in group VI served as controls (No. = 15). All drugs were administered orally. Hyperkeratosis and hyperplasia of the forestomach developed by 10 days after the first treatment with the carcinogen. Later, benign papillomas and dysplastic lesions were noted. Progressive ingrowth of squamous epithelium from the forestomach ridge into the glandular stomach started as early as day 13 and was more frequent in animals treated with a combination of MNNG plus flurbiprofen (P less than .001). The first squamous cell carcinomas of the forestomach were detected on day 51. Their incidence was 38, 60, and 42% in groups I, II, and III, respectively. This difference was not statistically significant. The incidence of mesenchymal tumors (leiomyosarcoma) in the stomach and duodenum was higher following treatment with MNNG plus flurbiprofen as compared to the incidence following treatment with MNNG alone or in combination with 16,16-dm-PGE2 (P less than .005). No malignant tumors developed in the gastrointestinal tracts of animals treated with flurbiprofen or 16,16-dm-PGE2 alone or in controls. The higher incidence of gastric and duodenal leiomyosarcomas after treatment with flurbiprofen suggests that reduction of prostaglandin synthesis favored the development of MNNG-induced cancer in mesenchymal tissues of the upper gastrointestinal tract.

Topics: Animals; Body Weight; Carcinoma, Squamous Cell; Female; Flurbiprofen; Gastric Acid; Gastrointestinal Neoplasms; Leiomyosarcoma; Methylnitronitrosoguanidine; Papilloma; Propionates; Prostaglandins E, Synthetic; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: Animals; Carcinoma, Squamous Cell; Intubation, Gastrointestinal; Methylnitronitrosoguanidine; Mice; Papilloma; 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

Mouse skin tumors were induced by a single topical application of 7,12-dimethylbenzanthracene (DMBA), followed by biweekly promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). After 20 weeks of promotion, mice were treated twice weekly for 2 weeks with either ethylnitrosourea (ENU), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or TPA. Thereafter all groups were treated biweekly with TPA. The ENU-treated group had a higher percentage of animals with carcinomas and developed 217% more cumulative carcinomas per group than TPA-treated controls. The percentage of mice with carcinomas and the cumulative number of carcinomas per group in MNNG-treated mice was higher than TPA-treated controls but was less than ENU-treated mice. The ratio of cumulative carcinomas to cumulative papillomas in ENU treated, MNNG-treated and TPA-treated mice was 16%, 9% and 6%, respectively. Histological examination of tumors remaining at the termination of the experiment revealed the presence of keratoacanthomas, some of which stained positive for gamma-glutamyltransferase (GGT), in the ENU-treated and MNNG-treated, but not the TPA-treated groups. The fact that no new papillomas developed during the progression stage indicated that enhanced carcinogenesis resulted from the progression of pre-existing tumors. Enhanced progression of benign skin tumors in mice by only a few treatments of an agent may serve as a potential model for studies into the mechanisms and the inhibition of malignant progression. The model also allows for a comparison of the potency of agents in enhancing malignant progression.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Ethylnitrosourea; Female; gamma-Glutamyltransferase; Methylnitronitrosoguanidine; Mice; Papilloma; Skin Neoplasms; Tetradecanoylphorbol Acetate

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

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Duodenal Neoplasms; Female; Intubation, Gastrointestinal; Jejunal Neoplasms; Male; Methylnitronitrosoguanidine; Mice; Papilloma; Stomach Neoplasms

Of 158 channel catfish (Ictalurus punctatus) exposed to N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS:70-25-7] in water for 28 days, 2 developed disseminated lymphosarcoma. One fish was necropsied at 12 months and another at 18 months following exposure. Both fish had a massive neoplastic infiltration of the bilateral pairs of head and trunk kidneys from which the neoplastic cells appeared to originate. The neoplastic infiltration was also observed in the following: thymus, gills, oral mucosa, liver, skin, skeletal muscle of head-neck region, and to a lesser extent spleen and bone marrow. This is probably the first report of lymphosarcoma in channel catfish. Although the occurrence of lymphosarcoma in these 2 catfish appeared to be related to exposure to MNNG, the exact role MNNG played in the tumor formation was not determined.

Topics: Animals; Carcinoma; Carcinoma, Squamous Cell; Fish Diseases; Fishes; Kidney Neoplasms; Lipoma; Lymphoma, Non-Hodgkin; Methylnitronitrosoguanidine; Mouth Mucosa; Mouth Neoplasms; Papilloma; Water Pollutants, Chemical

Tumor initiation in CD-1 mice by benzo[a]pyrene (BaP) or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was unaffected by topical pretreatment with 13-cis-retinoic acid (13-cis-RA). Likewise, anthralin-induced tumor promotion in SENCAR mice was unaffected by pretreatment with 13-cis-RA. These results suggest that the action of retinoids in preventing either tumor initiation or promotion is very carcinogen or cocarcinogen specific.

Topics: Animals; Anthralin; Benzo(a)pyrene; Benzopyrenes; Female; Isotretinoin; Methylnitronitrosoguanidine; Mice; Papilloma; Skin Neoplasms; Time Factors; Tretinoin

Solution of N-methyl-N-nitrosourea (MNU), diazoacetic ester (DAAE), N-methyl-N-nitro-N-nitrosoguanidine (MNNG), N-methyl-N,N'-dinitroguanidine, 4-dimethylaminoazobenzene (DAB), o-aminoazotoluene or 7,12-dimethylbenz(a)anthracene (DMBA) were applied to rat skin. Neoplasms (skin tumors) were found only in the experiments with MNU, DAAE, MNNG, DAB and DMBA, MNU, MNNG, DAB and DMBA induced tumours in the sites of skin painting. In experiments with DAAE distant skin neoplasms developed as well. Possible mechanisms of action of these compounds are discussed.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinoma, Squamous Cell; Diazonium Compounds; Female; Keratoacanthoma; Male; Methylnitronitrosoguanidine; Methylnitrosourea; o-Aminoazotoluene; p-Dimethylaminoazobenzene; Papilloma; Rats; Skin 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

After 12 oral applications of 80 mg/kg MNNG as a suspension in 30% aqueous ethanol at weekly intervals, 98 Sprague-Dawley rats died with multiple tumors of the forestomach after a medium latency period of 226 days. Histological examination showed generalized papillomatosis developing into keratinizing squamous cell carcinomas with infiltrative growth in 88/98 (89%) animals. Tumorigenic lesions in the glandular stomach ware only observed in 3/98 rats. In two of these animals, mucosal adenocarcinomas were found and in the third a leiomyosarcoma. In about 30% of the animals treated with MNNG, degenerative liver changes were found, especially single cell and focal necroses, cystic alterations, and bile-duct proliferations.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Leiomyosarcoma; Liver; Methylnitronitrosoguanidine; Neoplasms, Experimental; Papilloma; Rats; Rats, Inbred Strains; Stomach Neoplasms

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

The effect of ulcers on the development of gastric tumors by N-methyl-N'-nitro-N-nitrosoguanidine in (MNNG) was studied in male Wistar rats. Ulcers were produced by the application of a steel rod, 5 mm in diameter and frozen at -78 degrees C, to the serosal surface of the forestomach, fundus, pylorus, or proximal duodenum. The existence of the ulcers at these areas was confirmed 1 week later in a preliminary experiment. Experimental groups were given MNNG in their drinking water at a concentration of 100 micrograms/ml for 16 weeks beginning 7 days after the ulcers developed. Administration of MNNG after ulceration resulted in a relative increase in the tumor incidences at each ulcer site, especially the proximal duodenum, which suggested that regenerating cells in the duodenum were the most susceptible cells among the cells of the four sites. The increase in tumor incidence following ulceration may be due to exposure of MNNG to a greater number of regenerating cells during the renewal process that seem to be more responsive to carcinogenic influences that normal cells.

Topics: Adenocarcinoma; Animals; Duodenal Neoplasms; Duodenal Ulcer; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Stomach Neoplasms; Stomach Ulcer

Laboratory-bred European hamsters received intragastric administrations of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) once weekly for 20 weeks. The animals showed mainly squamous cell papillomas and carcinomas of the fore-stomach. The tumour incidence was higher in males (80%) than in females (30%). The average tumour latency was comparatively short (25 weeks).

Topics: Animals; Carcinogens; Carcinoma, Squamous Cell; Cricetinae; Female; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Papilloma; Species Specificity; Stomach Neoplasms

Topics: Animals; Croton Oil; DNA; DNA Repair; DNA Replication; Drug Synergism; Female; Methylnitronitrosoguanidine; Mice; Neoplasms, Experimental; Papilloma; Skin; Skin Neoplasms; Time Factors

The effect of vitamin A deficiency on the sensitivity of the colon to the carcinogenic effect of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a direct-acting carcinogen, given intrarectally was studied in female Fischer rats. Animals maintained on Purina laboratory chow, semipurified vitamin A-free diet, or semipurified vitamine A-supplemented diet were given intrarectally 1.25, 0.63, or 0.31 mg MNNG 3 times weekly for 30 weeks and autopsied at the 45th week. The number of large bowel tumors per tumor-bearing rat was higher in animals receiving 1.25 mg MNNG compared to those given 0.63 or 0.31 mg. Vitamin A deficiency in rats given 1.25 mg MNNG significantly suppressed the large bowel tumor induction compared to rats fed adequate vitamin A. A high incidence of squamous cell papillomatosis of the urinary bladder was observed in rats fed vitamin A-free diet and given 1.25 mg MNNG. The present experiment suggests that the large intestine has a susceptibility that is different from that of the respiratory and urinary tracts to tumorigenic stimulation in vitamin A-deficient status.

Topics: Animals; Colonic Neoplasms; Female; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitrosoguanidines; Papilloma; Rats; Urinary Bladder Neoplasms; Vitamin A Deficiency

Topics: Animals; Dog Diseases; Dogs; Eye Neoplasms; Eyelid Neoplasms; Male; Methylnitronitrosoguanidine; Mouth Neoplasms; Papilloma; Papillomaviridae

Topics: Adenocarcinoma; Animals; Carcinoid Tumor; Carcinoma, Hepatocellular; Carcinoma, Squamous Cell; Duodenal Neoplasms; Female; Hyperplasia; Liver Neoplasms; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitrosoguanidines; Papilloma; Rats; Rodent Diseases; Stomach Neoplasms

The effects were studied of NaCl on the production of gastric carcinomas by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and by 4-nitroquinoline-1-oxide (NQO) in male Wistar rats. Nine groups of rats were treated as follows: Group 1 was given 50 mg MNNG/liter and 6 g NaCl solution/liter to drink and was fed a stock diet supplemented with 10% NaCl. Group 2 received 1 ml saturated NaCl once a week and 50 mg MNNG/liter to drink. Group 3 was treated with MNNG alone. Group 4 was given a solution of 1 mg NQO once a week and fed a stock diet supplemented with 10% NaCl. Group 5 received a solution of 1 mg NQO saturated with NaCl. Group 6 was given NQO alone. Groups 7 and 8 were given NaCl alone. Group 9 was untreated. Adenocarcinomas developed in the glandular stomach in group 2 at a significantly higher incidence than in group 3. Poorly differentiated adenocarcinomas of the glandular stomach were detected in only groups 1 and 2. One poorly differentiated adenocarcinoma metastasized to the lymph nodes. A high incidence of squamous cell carcinomas of the forestomach was found in groups 4 and 5. No malignant tumors were seen in groups 6-9. NaCl given alone had no apparent carcinogenicity in rats but, when administered with MNNG or NQO, it enhanced the carcinogenic effects of MNNG and NQO in the stomach.

Topics: 4-Nitroquinoline-1-oxide; Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Drug Synergism; Gastric Mucosa; Intestinal Neoplasms; Intestine, Small; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitroquinolines; Nitrosoguanidines; Papilloma; Rats; Sarcoma; Sodium Chloride; Stomach; Stomach Neoplasms