12-O-tetradecanoylphorbol-13-acetate (TPA) induces sister-chromatid exchanges and delays in cell progression in Chinese hamster ovary and human cell lines.

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) induced a 20-45% increase in sister-chromatid exchange (SCE) frequency in Chinese hamster ovary cells (CHO) and in 2 SV40-transformed human fibroblast cell lines (GM637 and XP12RO) at concentrations up to 1 microgram/ml. The increase was independent of the time at which the cells were fixed after treatment and was not due to an impurity in the TPA preparation or to increased incorporation of bromodeoxyuridine into the DNA. There was no synergistic effect on SCE induction when CHO cells were simultaneously exposed to TPA and the carcinogens mitomycin C or ultraviolet light, but there was when TPA and benzo[a]pyrene were used. In addition to its weak SCE-inducing effects in CHO cells, TPA caused slight delays in cell cycle progression and greatly enhanced the cell cycle delay induced by benzo[a]pyrene.