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

Abstract

Teieocidin, a new tumor promoter, increased incorporation of radioactive inorganic phosphate ( ³² Pi) into phospholipids in HeLa cells. This effect was detected within 1 h on incubation of the cells in medium containing teieocidin. The half-maximum effective dose of teieocidin was ˜10 ng/ml. The main effect of teieocidin was on the incorporation of ³² Pi into the phosphatidylchotine fraction, with a lesser effect on ³² Pi incorporation into other phospholipid fractions. Increased incorporation of ³² Pi 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 /μg/ml, 4-O-methyl TPA and Ca ²⁺ 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 ³² Pi into phospholipid fractions of HeLa cells.