中文摘要：

目的通过使用哺乳动物雷帕霉素靶蛋白m TOR抑制药依维莫司抑制A549细胞m TOR信号通路,研究依维莫司是否具有放射增敏作用。方法单纯放射治疗（放疗）或联合依维莫司作用于人非小细胞肺癌细胞系A549,采用噻唑蓝（MTT）法测定依维莫司对A549细胞抑制率并计算半数抑制浓度（IC50）。应用药物20%抑制浓度（IC20）作用24 h后X线2,4,6,8 Gy照射。计算细胞克隆存活分数及多靶单击模型拟合生存曲线,并计算平均致死剂量（D0）、准阈剂量（Dq）、照射剂量2 Gy下细胞存活分数（SF2）和放射增敏比（SER）。采用Western blot方法检测γ-H2AX蛋白的表达,并分析相对灰度值。结果依维莫司联合放疗可明显提高A549细胞对射线的敏感性,依维莫司＋照射组D0、Dq及SF2均明显低于单纯照射组,SER为1.36。依维莫司＋照射组X线照射后24 h点γ-H2AX蛋白残余量明显高于单纯照射组。结论依维莫司抑制m TOR信号通路能够提高A549细胞的放射敏感性。

英文摘要：

Objective To explore the effect of mammalian target of rapamycin（ m TOR） inhibitor everolimus on radiosensitivity of human non-small cell lung cancer cell line in vitro by using everolimus to inhibit m TOR signaling pathway of A549. Methods Human non-small cell lung cancer cell line A549 was subjected to radiation alone or in combination with everolimus treatment. The 50% inhibition concentration（ IC50） of everolimus in A549 cells was detected by methylthiazol tetrazolium（ MTT） assay in vitro. Everolimus at the 20% inhibition concentration（ IC20） was used to pretreat A549 cells for 24 h. Cells were then irradiated by X-ray with 2,4,6,8 Gy. The cell survival fraction was computed by clone formation. Cell survival curve was fitted by multitarget one-hit model,and mean lethal dose（ D0）,dose quasithreshold（ Dq）,survival fraction at 2 Gy（ SF2）,and sensitization enhancement ratio（ SER） were calculated. The expression of γ-H2 AX was determined by Western blotting and then the relative gray values were analyzed. Results Everolimus significantly improved the sensitivity of A549 cells to radiation. The D0,Dqand SF2 of everolimus ＋ irradiation group were significantly lower than those of irradiation group. The SER was 1. 36. The residual amount of γ-H2 AX protein in the everolimus ＋ irradiation group was significantly higher than that of the irradiation group.Conclusion Everolimus inhibiting m TOR signaling pathway can increase the radiosensitivity of A549 cells.