Skin Carcinogenesis, Mammals Versus Amphibia

Abstract

The successful induction of cancer on the skin by means of topical applications of appropriate chemicals has been known to depend largely on the species employed and on the method of application. Carcinogenesis results in a high percentage of mice when their skins are treated with solutions of polycyclic aromatic hydrocarbons, but much less frequently in rats and rarely in guinea pigs. Only recently have studies been undertaken to try to elucidate the reasons for these profound differences in susceptibility. It was suspected for a long time that the pilosebaceous apparatus was the site of origin of the chemically induced cutaneous cancers. In 1945 Lacassagne and Latarjet (1) found that areas of skin depilated by ultraviolet light irradiation or hairless surgical scars were refractory to carcinogenesis by 3-methylcholanthrene. In 1947 Suntzeff, Carruthers and Cowdry (2) demonstrated that the epidermis of newborn mice, before the appearance of hair follicles, was refractory to a single dose of 3-methylcholanthrene. In 1949 Liang (3) studied the site of origin of cutaneous tumors after application of the same carcinogen by means of an ingenious method of epidermal whole mounting, and localized this site at the junction between the hair follicles and the basal epidermal layer. In 1951 Billingham, Orr and Woodhouse (4) found by epidermal transplantation that interfollicular epithelium treated with carcinogens and transplanted to another site without its hair follicles did not give rise to any tumors, whereas epithelial tumors developed from the area of origin, grafted with untreated epidermis, where the only epithelial structures exposed to the carcinogen were the hair follicles.