Simultaneous silence of bcl-2 and XIAP increases radiosensitivity of UMSCC12 head and neck cancer cells

Abstract

Objective To investigate the radiosensitization effect of the simultaneous silence of bcl-2 and XIAP on human head and neck cancer cell line in vitro.Methods Four groups of UMSCC12 cells were transfected with siRNA-bcl-2,siRNA-XIAP,siRNA-bcl-2 plus siRNA XIAP,and siRNA control,respectively.The silence efficiency was tested by Western blot assay. Apoptosis was evaluated with the activities of caspase-3 and caspase-9,and radiosensitization effect was evaluated with clonogenic assay.Results Bcl-2 and XIAP protein expressions were effectively eliminated in the cells simultaneously transfected with siRNA-bcl-2 and siRNA-XIAP.Transfection of cells with bcl-2 siRNA increased radiationinduced apoptosis ( t =5.32,6.27 ; P ＜ 0.05 ),but transfection with XIAP siRNA did not impact cell apoptosis.Since the simultaneous transfection of the above two siRNAs,the activities of caspase-3 and caspase-9 were increased by 1.36 and 1.34 times ( t =11.47,6.22 ; P ＜ 0.05 ) in nonirradiated cells and increased by 1.72 and 1.98 times ( t =12.02,20.14; P ＜ 0.05 ) in irradiated cells,respectively.The colonic assay showed that the SERs were 1.06,1.15 and 1.41 for the cells transfected with XIAP siRNA,bcl-2 siRNA and both siRNAs,respectively.Conclusions Compared to single silence of XIAP or bcl-2,simultaneous silence of XIAP and bcl-2 offers a potential approach to improving the radiosensitivity of the head and neck cancer cells,and apoptosis might contribute to the enhancement of radiosensitization. Key words: bcl-2; XIAP; UMSCC12; Radiosensitization; Apoptosis