Analysis of c-Ha-ras gene mutations in skin tumors induced in carcinogenesis-susceptible and carcinogenesis-resistant mice by different two-stage protocols or tumor promoter alone

In the present study we describe the molecular analysis of c-Ha-fas gene mu tations in 47 papillomas and 17 carcinomas developed in two lines of mice, carcinogenesis-susceptible (Car-S) and carcinogenesis-resistant (Car-R), se lectively bred for extreme susceptibility or resistance to chemical skin ca rcinogenesis initiated and promoted with different doses of 7,12-dimethylbe nz[a]anthracene (DMBA) and 12-O-telradecanoylphorbol-13-acetate (TPA). This study also presents the analysis of c-Ha-ras gene mutations in 22 papillom as and 22 carcinomas in Car-S mice initiated with DMBA and promoted with be nzoyl peroxide (BzPo) and in seven papillomas and one carcinoma from a grou p of uniniated Car-S mice that received only BzPo treatment. The data showe d that a A(182) --> T transversion in the c-Ha-ras gene was present in 100% and 81% of the skin tumors developed in Car-S and Car-R mice, respectively , after DMBA initiation and TPA promotion, suggesting that differences in g enetic susceptibility can influence the frequency of c-Ha-ras mutations in the skin tumors produced. The same A(182) --> T mutation with an incidence of 68% was found in papillomas from DMBA-initiated and BzPo-promoted Car-S mice. The difference in the mutation frequency between DMBA/BzPo and DMBA/T PA papillomas suggested that the promotion step contributes to the final mu tation pattern. The tumor induction experiment with BzPo alone showed that this compound can induce tumor development in 26% of Car-S mice, and the mo lecular analysis of the tumors showed a broad mutation spectrum, including mutations in codons 12, 13, and 61 of the c-Ha-ras gene. (C) 2001 Wiley-Lis s.