Role of inhibitor of apoptosis protein XIAP in cisplatin-induced apoptosis of Hep-2 laryngeal carcinoma cells

OBJECTIVE To investigate the role of XIAP in cisplatin-induced apoptosis and its possible mechanism. METHODS Hep-2 cells were treated with different concentrations of cisplatin for different times. Using crystal violet assay, RT-PCR and flow cytometry (FCM), we investingated the rate of the cell apoptosis and the expression of XIAP protein and mRNA at different times after treating with different concentrations of cisplatin. RESULTS Hep-2 cells were adherent and in normal survival condition with very low apoptosis rate. After treating with cisplatin, the rate of inhibition, the expression of XIAP protein and the rate of apoptosis were remarkably different between different concentrations and times. The expression of XIAP protein was down regulated accompanied by the augmentation of the rate of Hep-2 cell apoptosis. The products of RT-PCR were analyzed, demonstrating that the XIAP mRNA was down regulated with the increased concentrations of cisplatin overtime. Correlation analysis showed the rate of inhibition and the rate of apoptosis were positively correlated with increased concentrations of cisplatin for different times, however, the expression of XIAP protein was negatively correlated. The expression of XIAP protein and the rate of apoptosis were conversely correlated. CONCLUSION The most important pathway that cisplatin induces cell death is apoptosis. The levels of expression of XIAP proteinand mRNA in Hep2 cells are time-and concentration-dependent after treating with cisplatin. Down-regulation of the XIAP protein expression to augment the rate of apoptosis is one of the mechanisms for the cisplatin tokill the carcinoma cells.