Effect of triptolide on cytokinetics of HeLa cells

The cytostatic effects of triptolide on HeLa cells in different proliferation stages and cell cycle phases were studied by colony-forming units assay. An exposure of exponential-phase cells to triptolide 0.02-4.00 micrograms/ml for 0.5 h resulted in a biphasic-exponential dose-survival curve (n = 1, D0 = 0.3 micrograms/ml in the most sensitive population; D0 = 2.8 micrograms/ml in the more resistant population). The plateau-phase cells in the same conditions seemed to have lower sensitivity to the drug. The synchronized cells caused by excess TdR double block and the selective detachment of mitotic cells from monolayer were exposed to triptolide 0.06 micrograms/ml for 0.5 h. The sensitivity of cell cycle phases to the drug ranked as follows: S greater than G2, M greater than G1. The result showed that triptolide is one of the cell cycle phase non-specific agents, but more sensitive to S phase cells.