Tumor-initiating activity of the dihydrodiols of 8-methylbenz[a]anthracene and 8-hydroxymethylbenz[a]anthracene.

The tumor-initiating activity of the 3,4-dihydrodiols (diols) as well as other metabolites of 8-methylbenz[a]anthracene (8-MBA) and 8-hydroxymethylbenz[a]anthracene (8-OHMBA) were examined in the classical 2-stage initiation-promotion model on mouse skin. The 3,4-diol of 8-MBA caused 2.2 times as many papillomas/mouse as did 8-MBA. The 3,4-diol of 8-OHMBA was not more tumorigenic than either 8-MBA or 8-OHMBA. None of the other diols tested, including the 5,6- and 8,9-diol of 8-MBA and the 5,6 and 10,11-diol of 8-OHMBA were remarkably tumorigenic. These data indicate that the 3,4-diol of 8-MBA is a good candidate as a proximate carcinogen of 8-MBA and further suggest that the bay region 3,4-diol-1,2-epoxide is a likely ultimate carcinogen of this compound on mouse skin.