Indole alkaloids: dihydroteleocidin B, teleocidin, and lyngbyatoxin A as members of a new class of tumor promoters.

Dihydroteleocidin B, which is a derivative of teleocidin from Streptomyces, showed potent tumor-promoting activity in vivo when painted on mouse skin. Although the chemical structure of dihydroteleocidin B is entirely different from those of phorbol esters, the tumor-promoting activity of dihydroteleocidin B was found to be comparable to that of 12-O-tetradecanoylphorbol 13-acetate (TPA) in vivo. Teleocidin from Streptomyces and lyngbyatoxin A and debromoaplysiatoxin from the marine blue-green alga Lyngbya majuscula induced ornithine decarboxylase activity when painted on mouse skin, their effects being similar to those of dihyroteleocidin B and TPA. 13-cis-Retinoic acid inhibited this ornithine decarboxylase induction when painted on the skin 1 hr before these natural products. These three compounds produced adhesion of human promyelocytic leukemia cells (HL-60) to the flasks and inhibited differentiation of Friend erythroleukemia cells induced by dimethyl sulfoxide. The in vitro biological potencies of teleocidin and lyngbyatoxin A were almost as great as those of dihydroteleocidin B and TPA, but that of debromoaplysiatoxin was much weaker.