Mutagenic specificities of four stereoisomeric benzo[c]phenanthrene dihydrodiol epoxides.

The pS189 shuttle vector carrying a supF target gene was used to compare the mutagenic specificities of the four configurational isomers of benzo[c]phenanthrene 3,4-dihydrodiol 1,2-epoxide. One of these isomers is the most tumorigenic dihydrodiol epoxide tested to date and another is essentially inactive as a tumorigen. Overall mutagenicities were not correlated with tumorigenicities, but each configurational isomer induced a unique spectrum of mutational hot spots in the supF target gene, which monitors primarily point mutations. It is suggested that the demonstrated isomer-specific selectivity for mutation targets within the supF gene may be indicative of a similar selectivity for one gene versus another and that such selectivity may be one determinant of relative tumorigenicity.