Prevention of 3-methylcholanthrene-induced skin tumors in mice by simultaneous application of 13-cis-retinoic acid and retinyl palmitate (vitamin A palmitate).

Two retinoids (13-cis-retinoic acid and retinyl palmitate ) have been shown to exert a good preventive effect in chemically induced papillomas and carcinomas of the skin in female Swiss mice; this effect was investigated over a period of 23 weeks. The tumors were induced by repeated topical application of 3-methylcholanthrene (0.3% MCA, dissolved in acetone; 14 applications). Retinyl palmitate (RP; 6 mg in 0.1 ml acetone/mouse; 10 applications) and 13-cis-retinoic acid (RA; 3 mg in 0.1 ml acetone/mouse; 10 applications) were also administered topically for the 3rd to 9th week from the start of the experiment. This investigation gave evidence for the fact that both the retinoids did not only inhibit the development of skin papillomas but had also a marked effect on skin carcinomas.