Differential effects of phorbol esters on c-fos and c-myc and ornithine decarboxylase gene expression in mouse skin in vivo

Hyperplasiogenic and tumor-promoting phorbol esters such as12-O-tetradecanoylphorbol-13-acetate or l2-O-retinoylphorbol-13-acetateinduce the sequential transient expression of the proto-oncogenesc-fos and c-myc and the ornithine decarboxylase gene in mouseskin in vivo. This sequence of biochemical events probably dependson an activation of protein kinase C by these agents. The non-irritantskin mitogens 4-O-methyl-12-O-tetradecanoylphorbol-13-acetateand ethyl phenyl propiolate do not increase the expression ofthese genes to a comparable extent. Thus, 12-O-tetradecanoylphorbol-13-acetateand 12-O-retinoylphorbol-13-acetate induce epidermal hyperproliferationby different biochemical mechanisms as do 4-O-methyl-12-O-tetradecanoylphorbol-13-acetateand ethyiphenyipropiolate.