The initiation of tumours on mouse skin by dihydrodiols derived from 7,12-dimethylbenz(a)anthracene and 3-methylcholanthrene.

The cis-2a,3-diol and the trans-4,5-, trans-7,8-, trans-9,10- and trans-11,12-dihydrodiols of 3-methylcholanthrene and the trans-3,4, trans-5,6-, trans-8,9. and trans-10,11- dihydrodiols of 7,12-dimethylbenz[a]anthrancene have been tested, in comparison with the parent hydrocarbons, for their abilities to initiate skin tumours in female CDI mice. Groups of mice received a single topical application (25 micrograms) of a diol or of a hydrocarbon, and 1 week later repeated topical applications (1 microgram) of 12-0-tetradecanoylphorbol-13-acetate were commenced. The results show that the diol of 3-methylcholanthrene and the 3,4-diol of 7,12-dimethylbenz[a]anthrancene were active as initiating agents but that they were no more active than their parent hydrocarbon. The K-region 5,6-diol of 7,12-dimethylbenz[a]anthrancene, which cannot be converted directly into a vicinal diol-epoxide, was also active as a tumour-initiating agent when applied to mouse skin.