Demonstration of ras and p53 Gene Mutations in Carcinomas in the Forestomach and Intestine and Soft Tissue Sarcomas Induced by N‐Methyl‐N‐nitrosourea in the Rat

Abstract

The presence of ras family and p53 gene mutations in rat forestomach, intestine and liver tumors and soft tissue sarcomas induced by Nmethyl‐N‐nitrosourea (MNU) was examined using polymerase chain reaction‐single strand conformation polymorphism (PCR‐SSCP) followed by direct sequencing analysis. In the forestomach squamous cell carcinomas (SCC), Ha‐ros and p53 mutations were detected in 2 (40%) and 4 (80%) of 5 cases, respectively. The figures for Ki‐ras and p53 gene mutations in adenocarcinomas of the large and small intestines were 3 (18.8%) and 5 (31.3%) of 16 cases. Soft tissue sarcomas in different sites were found to have mutations of Ki‐ras in 7 (23.3%)and of p53 in 9 (30%) of 30 cases. One forestomach SCC and 2 soft tissue sarcomas had double p53 mutations in different exons. Single cases of forestomach SCC and intestinal adenocarcinoma had mutations in both Ki‐ras and p53 genes. No mutations were found in counterpart benign tumors or hepatocellular adenomas. The p53 mutation spectrum revealed preferential clustering within exon 8 for the forestomach SCCs, and exons 5 and 8 for the intestinal adenocarcinomas, whereas the distribution was evenly spread through exons 5 to 8 in soft tissue sarcomas. All the detected ras or p53 mutations were G:C to A:T transitions. These results indicate firstly that specific Ki‐ras, Ha‐ras and p53 gene mutations in MNU‐induced lesions are related to particular alkylation sites (G:C to A:T transitions) and secondly, although not essential, Ki‐ras, Ha‐ras or p53 gene mutations may be involved in the progression stage of forestomach, intestine and soft tissue neoplasms induced by MNU.

Preferential mammary carcinogenic effects of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) in human c‐Ha‐ras proto‐oncogene transgenic rats

“…For the characterization of mammary tumors, 5 adenocarcinomas from female Hras128 rats, and 2 carcinosarcomas and 3 sarcomas from male Hras128 rats were stained with sheep anti-bovine casein (Biogenesis, Poole, UK), mouse anti-human vimentin (Clone V9, IgG 1 , Sigma, St. Louis, MO), sheep anti-human lysozyme (CALBIOCHEM, San Diego, CA), mouse anti-cytokeratin (Clone K8.13, IgG 2a , Sigma), rabbit T Present addresses: 3 Department of Experimental Pathology and Tumor Biology Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601. 4 To whom correspondence should be addressed.…”

“…2,3) For example, with N-methyl-N-nitrosourea (MNU) in experimental animals, Haras mutations are found primarily in mammary tumors, [4][5][6] while colon tumors generally have Ki-ras mutations. 7) In humans, Ki-ras mutations are preferentially found in colon, 8,9) pancreatic duct 10) and bile duct carcinomas, 11) and N-ras mutations are typically seen in myeloid leukemia.…”

Gene mutations and altered gene expression in azoxymethane‐induced colon carcinogenesis in rodents

“…19,20) This difference can not be explained by species differences, because p53 mutations have been detected in methylnitrosourea (MNU)-induced rat colon tumors and Apc mutations have been found in 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP)-induced tumors. 21,22) Furthermore, K-ras mutation does not appear to be a feature of PhIP-induced colon tumors.…”

p53 Gene Mutation and Loss of Heterozygosity of Chromosome 11 in Methylcholanthrene‐induced Mouse Sarcomas

“…This frequency is one of the highest among chemically induced rodent tumors so far examined. [7][8][9][10][11][12][13][14][15][16][17][18] In addition, our study of MCA-induced sarcomas revealed some similarities in the distribution of p53 gene mutation between human and mouse. Mutations were observed at mouse codons 172 (6 cases), 242 (2 cases), 245 (2 cases), 246 (3 cases), 270 (4 cases) and 279 (1 case), and these corresponded to human p53 gene hot spots 175, 245, 248, 249, 273 and 282.…”

“…5,6) Numerous studies have been conducted on mutation analysis of the p53 gene in rodents with chemically induced tumors. [7][8][9][10][11][12][13][14][15][16][17][18] These analyses revealed that the frequency of p53 alterations in rodent experimental tumors varied greatly depending on the chemical agents and tumor types.…”