Retinoyl-phorbol-acetate is a complete skin tumor promoter in SENCAR mice

The semi-synthetic phorbol ester 12-O-retinoyl phorbol 13-acetate (RPA) was tested for activity as a complete tumor promoter, as well as for first or second stage promotion activity, in the skin of SENCAR mice. Unlike in NMRI mice where RPA has been reported to act only as a second stage promoter, in SENCAR mice it has moderate complete promoting activity as well as second stage activity. RPA also induces epidermal hyperplasia and an increase in the number of dark basal keratinocytes.