端粒酶抑制剂联合辐射对人胶质瘤细胞存活的影响

目的 :观察端粒酶抑制剂AZT联合60 Coγ 射线对人脑胶质瘤细胞U2 5 1端粒酶活性及细胞存活的影响 ,探讨AZT的放射增敏作用。方法 :实验分 4组 :A、空白对照组 ;B、放射组 ;C、加药组 ;D、加药放射组。用克隆形成分析法观察AZT对U2 5 1细胞放射敏感性的影响 ,通过拟合生存曲线计算放射增敏比SERD0 、SERDq、SERSF2 。用端粒重复序列扩增 (telomericrepeatamplificationprotocol,TRAP) PCR ELISA方法检测端粒酶活性的动态变化。结果 :照射前经 0 .8mmol·L-1AZT处理 2 4h明显降低了 2Gyγ 射线照射后U2 5 1细胞的存活分数 ,SERD0 、SERDq、SERSFM2 分别为 1.2 94 ,1.2 5和 1.36 5 ;表明AZT具有放射增敏的作用 (P <0 .0 5 )。端粒酶活性分析显示A、B、C、D组细胞的端粒酶活性分别为 1.5 6 3± 0 .0 2 2 ,1.92 3± 0 .188,1.0 5 7± 0 .12 6 ,1.2 0 9± 0 .15 3,各组之间差异均有显著性 (P <0 .0 5 )。结论 :AZT能明显抑制 2Gy照射诱导的U2 5 1细胞端粒酶活性升高 ,并显著增加U2 5 1细胞的放射敏感性 ;AZT的放射增敏作用可能与端粒酶活性受抑制有关。

Effect of Azidothymidine Combined with Irradiation on Cell Survival in Human Glioma Cells

Objective: To investigate the effect of AZT (3’-azido-3’-deoxythymidine) combined with γ -irradiation on cell survival and telomerase activity in human malignant glioma cell line U251. Methods: Exponentially growing U251 cells were divided into four groups: A:control,B:radiation,C:AZT,D:AZT combined with radiation.The radiosensitivity was determined by clonogenic assay. The change in radiosensitivity was quantifited by calculating the sensitization enhance-rate(SER)through survival curves.Telomeric repeat amplification protocol (TRAP-PCR-ELISA) was used to observe telomerase activity of each group at different times. Results: Exposure of U251 cells to 0.8 mmol·L -1 AZT for 24h before irradiation resulted in a decrease in mean SF of U251 cells compared with cells of group B( P< 0.05). SERD_0,SERD_q,SERSF_2 for AZT were 1.294,1.25,1.365 respectively. Telomerase activity of group A,B,C,D were 1.563±0.022, 1.923 ±0.188,1.057±0.126,1.209±0.153 respectively ( P< 0.05 between each two of them). Conclusion: The results indicate that AZT can effectively inhibit telomerase activity of U251 glioma cells treated or untreated with 2 Gy radiation and significantly enhance the radiosensitivity of U251 glioma cells in vitro .The role of radiosensitization of AZT may be related with the inhibition of telomerase activity.