EFFECTS OF COMPLETE AND INCOMPLETE TUMOR PROMOTERS ON HAIR-GROWTH, ANGIOGENESIS, AND TENASCIN EXPRESSION IN THE SKIN OF NMRI MICE

Although the phorbol esters 12-O-tetradecanoylphorbol-13-acetate (TPA) and 12-O-retinoylphorbol-13-acetate (RPA) are almost equipotent induc ers of an inflammatory and hyperplastic response in NMRI mouse skin, T PA acts as a converting or complete and RPA as a non-converting or inc omplete skin tumor promoter. Bearing in mind the converting effect of skin wounding and TGF beta, we have addressed the question of a relati onship between conversion and stromal events, For this purpose we have compared the effects of TPA acid RPA on dermal angiogenesis, hair reg rowth and the expression of tenascin in NMRI mouse skin in vivo, In th e reticular part of the dermis, shaving alone induced angiogenesis pea king at day 14, concomitant with hair regrowth, While TPA exhibited a stimulatory effect on both parameters, RPA suppressed shaving-induced angiogenesis and delayed the onset of hair regrowth, Whether this diff erence in the phorbol ester effects being consistent with the working hypothesis is critical for conversion, remains to be shown, In the pap illary dermis, however, RPA was more potent than TPA in inducing vascu larization and tenascin expression. The kinetics of both responses cor responded to the time course of hyperproliferation induced by the phor bol esters in the overlaying epidermis, i.e. may be related to promoti on proper, rather than conversion.