Cisplatin as an initiating agent in two-stage mouse skin carcinogenesis.

Single i.p. injections of cisplatin followed by 12-O-tetradecanoylphorbol-13-acetate TPA promotion led to the formation of skin tumors in mice, as did topical applications of urethane with TPA promotion. This is the first example of the use of cisplatin in a single treatment as an initiating agent in the standard initiation-promotion regime. Treatment of the skin with TPA 24 h before initiation increased tumor yield, both in terms of the percentage of mice with tumors and the average number of tumors per mouse.