Teleocidin, isolated from Streptomyces mediocidicus ISP 5021, is an
indole alkaloid. The
teleocidin used was composed of
teleocidin A,
teleocidin B and their isomers. A hydrogenated derivative of
teleocidin B,
dihydroteleocidin B, was recently reported to have
tumor promoting activity in vivo and various
biological activities in vitro, with a specific activity comparable to that of 12-O-tetradecanoylphorbol-13-acetate (TPA). This paper describes the potent
tumor promoting activity of the parent compound of dihydroteleocidins,
teleocidin, on mouse skin in two-stage
carcinogenesis. The
tumor promoting activity was evaluated by measuring the incidence and yield of
tumors, and by histological examination. Groups of mice were given a single application of 100 micrograms of 7,12-dimethylbenz[a]
anthracene (DMBA) and then 2.5 micrograms of
teleocidin twice weekly or the same dose of DMBA plus 2.5 micrograms of TPA twice weekly. Both groups showed 100%
tumor incidence after 24 weeks, and the
tumor yields were 4.0
tumors per mouse in the former group and 9.8 per mouse in the latter group in week 30. We confirmed, through this experiment, that
teleocidin is as potent as TPA in in vivo two-stage
carcinogenesis in mouse skin. These two structurally unrelated classes,
indole alkaloid and
phorbol ester, showed
tumor promoting activity in almost the same range.