Comparison of 12-O-tetradecanoylphorbol-13-acetate and teleocidin for induction of epidermal hyperplasia, activation of epidermal PKC isozymes and skin tumor promotion in SENCAR and C57BL/6 mice.

The present study compared the ability of 12-O-tetradecanoylphorbol-13-acetate (TPA) and teleocidin to induce sustained epidermal hyperplasia, activate partially purified epidermal protein kinase C (PKC) isozymes and promote skin tumors in SENCAR and C57BL/6 mice. Teleocidin was less effective than TPA on a molar basis for inducing sustained epidermal hyperplasia, promoting skin tumors and activating partially purified epidermal PKC isozymes in vitro when examined using SENCAR mice. In contrast, teleocidin was more effective than TPA on a molar basis for inducing sustained epidermal hyperplasia, approximately equi-effective for promoting skin tumors and significantly less effective for activating PKC isozymes in vitro when examined using C57BL/6 mice. Despite the differences in response of C57BL/6 mice to TPA and teleocidin, this mouse strain was still highly resistant to skin tumor promotion by both types of promoters when compared with SENCAR mice. The current results, when considered in light of our recent studies (Cancer Res., 51, 1398-1405, 1991), indicate that C57BL/6 are generally resistant to a variety of classes of skin tumor promoters, including the teleocidins. In addition, except for the phorbol esters, the induction of sustained epidermal hyperplasia does not appear to be as good a marker for overall promotion responsiveness between SENCAR and C57BL/6 mice with other classes of tumor promoters; although the induction of a significant sustained hyperplasia in the latter mouse strain did yield a weak tumor response. Taken together, the current data suggest that factors in addition to the induction of sustained epidermal hyperplasia, control responsiveness of C57BL/6 mice to skin tumor promotion by diverse promoting stimuli.