Tumor-initiating activity of the 9,10-dihydrodiol- and 9,10-dihydrodiol-7,8-epoxide of 3-methylcholanthrene in SENCAR mice.

Abstract The skin tumor-initiating activities of several bay-region metabolites of 3-methylcholanthrene (3-MCA) were determined in SENCAR mice. 3-MCA- anti -9,10-diol-7,8-epoxide possessed weak tumor-initiating activity when tested at 100 and 200 nmol/mouse doses (0.27 and 0.67 papillomas per mouse after 18 weeks of promotion with 12- O -tetradecanoylphorbol-13-acetate (TPA)). 3-MCA- trans -9,10-diol at initiating doses of 50 and 100 nmol/mouse was as active as 3-MCA. 3-MCA- trans -9,10-diol was also tested for mutagenic activity toward V79 cells in cell-mediated assays and found to be ∼ 2-times more potent than 3-MCA. The data suggest that 3-MCA- trans -9,10-diol is a proximate carcinogen for mouse skin.