12-O-tetradecanoylphorbol-13-acetate-induced rapid loss of persistent 7,12-dimethylbenz[a]anthracene-DNA adducts in mouse epidermis and dermis.

Twice-weekly application to mouse skin of 10 nmol of the potent tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA), beginning at 3 weeks after topical application of 1.2 mumol of 7,12-dimethylbenz[a]anthracene (DMBA), was found to cause a rapid loss of persistent DMBA-DNA adducts from both epidermal and dermal DNA. This effect is thought to reflect TPA-induced proliferation of quiescent initiated skin cells containing persistent adducts and may be causally related to the irreversibility of the initial phase of tumor promotion, which is known to require cell proliferation.