Existence of an optimal dose of dihydroteleocidin B for skin tumor promotion.

The tumor-promoting effects of various doses of dihydroteleocidin B, a catalytically hydrogenated derivative of teleocidin B isolated from Streptomyces mediocidicus, were examined in a two-stage carcinogenicity test on mouse skin. Doses of 1.25, 2.5 and 5.0 micrograms of dihydroteleocidin B dissolved in 0.1 ml acetone were applied twice a week to 7,12-dimethylbenz[a]anthracene-initiated mouse skin for 30 weeks. The maximal cumulative tumor incidence, tumor yield, latent period for 50% cumulative tumor incidence (t50) and amount of promoter needed for 50% cumulative tumor incidence (D50) were used to assess tumor-promoting activity. A dose of 2.5 micrograms of dihydroteleocidin B had the maximal tumor-promoting activity. The optimal dose of dihydroteleocidin B for tumor-promoting activity coincided with the optimal dose for ornithine decarboxylase induction.