Effects of 10 μM cisplatin on Tca/cisplatin and Tca8113 cell cycle distribution. After exposure to 10 μM cisplatin for 0, 6, 12 and 24 h, cells were harvested and stained with propidium iodide to assess cell cycle distribution by FACS analysis. Representative time course for Tca/cisplatin and Tca8113 cells in different phases of the cell cycle (one time course each) are shown. The results are expressed as mean ± SD of three independent experiments. A predominant S phase block of 74.35% was observed at 24 h in the Tca/cisplatin cells, significantly higher than the 42.91% in the Tca8113 cells.