Molecular mechanism of A375 cell apoptosis induced by paclitaxel

OBJECTIVE:To investigate the apoptotic inducing effect of paclitaxel on A375 cells. METHODS: A375 cells were cultured with paclitaxel for different concentrations and different time. The proliferation activities of them were measured by MTT assay. The cell cycle progression and apoptotic inducing effect of paclitaxel on A375 cells were determined by flow cytometry and morphology observation. The expressions of bcl-2, Bax and Caspase-3 proteins were determined by Western blot. RESULTS: Paclitaxel (0.001-1.000 μmol/L) inhibited the growth of A375 cells and induced apoptosis in both a time-dependent and dose-dependent manner. The early apoptosis rate of A375 cells was increased from (0.5±0.1)% to (32.4±1.1)% exposure to 0.000-1.000 μmol/L paclitaxel at 24 h,P0.05. After exposure to 0.100 μmol/L paclitaxel for 24 h or 48 h, it was also increased from (20.9±0.9)% to (52.6±1.0)%, t=28.89, P=0.001. It is by different mechanisms for high or low concentrations of paclitaxel to induce apoptosis in A375 cells. 0.001 μmol/L Paclitaxel did not change cell cycle progression before A375 cell apoptosis. 0.010 μmol/L Paclitaxel acted mainly on G0/G1 phases in A375 cells (24-48 h). A375 cells were arrested mainly in G2/M phases by paclitaxel over the concentration of 0.100 μmol/L. With paclitaxel, the protein level of bcl-2 decreased, while Bax expression was upregulated. The activity of caspase-3 in A375 cells was increased by paclitaxel. CONCLUSIOS: Paclitaxel can induce apoptosis of human melanoma A375 cells. The upregulation of Bax, downregulation of bcl-2 and increase of the activity of caspase-3 may play an important role. However, it accelerates the apoptosis in vitro by disrupting normal microtubular network and G2/M phases arrest for high dose and by the other ways and G0/G1 phases arrest for low dose.