Enhanced incorporation of radioactive inorganic phosphate into phospholipids of HeLa cells by tumor promoters.

Teleocidin, a new tumor promoter, increased incorporation of radioactive inorganic phosphate (32Pi) into phospholipids in HeLa cells. This effect was detected within 1 h on incubation of the cells in medium containing teleocidin. The half-maximum effective dose of teleocidin was approximately 10 ng/ml. The main effect of teleocidin was on the incorporation of 32Pi into the phosphatidylcholine fraction, with a lesser effect on 32Pi incorporation into other phospholipid fractions. Increased incorporation of 32Pi into phospholipids was also observed on incubation of the cells with 12-O-tetradecanoylphorbol-13-acetate (TPA), dihydroteleocidin B, or lyngbyatoxin A, which are all complete tumor promoters, and also with mezerein, which is an incomplete and second stage promoter. On the other hand, at concentrations of up to 1 microgram/ml, 4-O-methyl TPA and Ca2+ ionophore A23187, which are incomplete and first stage promoters, and phorbol, which has no promoting activity in skin carcinogenesis, did not cause any increased incorporation of 32Pi into phospholipid fractions of HeLa cells.