渥曼青霉素对胶质瘤细胞U251的辐射增敏作用

Wortmannin enhances radiation sensitivity of malignant glioma cells

目的利用渥曼青霉素（wortmannin,WM）抑制人恶性胶质瘤细胞U251磷脂酰肌醇-3-激酶（PI3K）通路的活性,探讨对U251细胞辐射敏感性的影响及可能的作用机制.方法 采用10μmol/L WM预处理U251 2 h,并接受10 Gy X射线照射,检测PI3K/Akt信号通路的活性、集落形成率和凋亡的变化;通过Western blot方法检测凋亡相关蛋白活化型Caspase-3、Bax、Bcl-2及XIAP表达的变化.结果 10 μmol/L WM预处理2h,明显抑制了U251细胞phospho-Akt的表达（t=0.000 1,P＜0.01）.WM预处理联合X射线照射后,U251细胞的凋亡率由对照组和单纯照射组的（2.14±1.32）％和（11.5±2.9）％增加到（22.6±3.8）％,差异具有统计学意义（t=0.009 3、0.002 7,P＜0.01）;集落形成率由对照组和单纯照射组的（88.54±4.76）％和（56.31±4.05）％降低到（12.25±9.59）％（t=0.000 03、0.000 2,P＜0.01）;同时伴随着凋亡相关蛋白活化型Caspase-3表达显著增加,Bax/Bcl-2的比值明显增高以及XIAP的显著降低.结论 WM通过抑制PI3 K/Akt信号通路活性,增加凋亡蛋白Caspase-3的活化和Bax/Bcl-2比值,下调凋亡抑制蛋白XIAP来增强恶性胶质瘤细胞的辐射敏感性.

Objective To explore the effect of wortmannin （WM）,an inhibitor of PI3K signalingpathway,on the radiation sensitivity of human malignant glioma cells （U251） and the underlyingmechanism.Methods U251 cells were pretreated with 10 μmol/L WM for 2 h and irradiated with 10 GyX-rays,then the activity of PI3K/Akt signaling pathway,the colony-forming ability and apoptosis weredetected to evaluate the effect of WM on radiosensitivity.The protein expressions of cleaved Caspase-3,Bax,Bcl-2 and XIAP were detected with Western blot assay.Results The expression of phospho-Akt wassignificantly inhibited by the pretreatment of cells with 10 μ mol/L WM （t =0.000 1,P ＜0.01）.The ratioof apoptotic cells in the WM ＋ IR group was significantly increased from （2.14 ± 1.32）％ of control groupand （11.5 ±2.9）％ of IR group to （22.6 ±3.8）％ （t =0.009 3,0.002 7,P＜0.01）.The colony-forming rate of WM ＋ IR group was decreased from （88.54 ± 4.76） ％ of control group and （56.31 ±4.05）％ of IR group to （12.25 ±9.59）％ significantly （t=0.000 03,0.000 2,P＜0.01） accompaniedwith the increases of Caspase-3 and Bax/Bcl-2 but decrease of XIAP.Conclusions WM significantlyincreased the radiation sensitivity of human malignant glioma cells by inhibiting the activity of PI3Ksignaling pathway and the expressions of Bcl-2 and XIAP and activating Caspase-3 and Bax.