Tat—SmacN7对人乳腺癌细胞系的放射增敏作用

The radiosensitization effect of Tat-SmacN7 on breast cancer cell lines

目的观察Tat—SmacN7对人乳腺癌SK—BR-3细胞放射敏感性的影响并探讨其机制。方法取对数生长期乳腺癌SK—BR-3细胞，分为对照组、叮射线照射组、Tat—SmacN7组和Tat—SmacN7联合1射线照射组（联合组）。MTT法检测Tat—SmacN7对SK—BR-3细胞的毒性；克隆形成实验检测Tat—SmacN7的存活分数；单击多靶模型拟合细胞存活曲线并计算放射增敏比（SER）；流式细胞术检测Tat—SmacN7联合1射线照射对细胞凋亡的影响；Westernblot法检测细胞凋亡抑制蛋白XIAP和cIAP-1蛋白表达水平。结果Tat—SmacN7随浓度升高对SK-BR-3细胞的增殖抑制率增大，药物浓度与细胞增殖率呈正相关（r=0．924，P〈0．05），IC50为（62．62±1．19）μmol／L，IC20为（5．66±0．67）μmol／L；5μmol／LTat—SmacN7能增加SK—BR-3细胞的放射敏感性，联合组与照射组放射增敏比为1．48；6Gy．y射线照射后48h，联合组凋亡率显著高于照射组（t=7．01，P〈0．05）；与对照组相比，Tat—SmacN7组XIAP表达水平降低，联合组XIAP和cIAP-1蛋白表达水平均降低。结论Tat—SmacN7通过促进人乳腺癌细胞SK—BR-3细胞的凋亡，增加其辐射敏感性，这一特性与XIAP的表达有关。

Objective To investigate the radiosensitive effect of Tat-SmacN7 on human breast cancer cell line of SK-BR-3 and the underlying mechanism. Methods SK-BR-3 cells in the logarithmic phase were divided into 4 groups： control group, drug group, 137Cs γ-ray radiation group and the case group （γ-ray radiation ＋ Tat-SmacN7 ）. MTT assay was performed to evaluate the cytotoxicity of Tat- SmacN7. Colony formation assay was used to measure cell survival fraction. A single-hit multi-target model was used to fit the survival curve and calculate the sensitive enhancement ratio （SER）. Apoptosis rate was analyzed by using flow cytometry. The expressions of inhibitor of apoptosis proteins（IAP） including XIAP, cIAP-1 proteins were detected by Western blot method. Results Tat-SmacN7 inhibited cell growth in a dose-dependent manner（ r = O. 924, P 〈 0. 05 ） and its 50% inhibition concentration （ IC50 ） was （ 62. 62±1.19）μmol/L,and IC2o was （5.66 ± 0. 67 ） μmol/L. In addition, 5 μmol/L Tat-SmacN7 could enhance cell radiosensitivity with a SER of 1.48. After 6 Gy γ-ray radiation at 48 h, the incidence of apoptosis in the case group was higher than that in the irradiation alone group （t = 7.01 ,P 〈 0.05）. Tat-SmacN7 only inhibited XIAP expression, whereas Tat-SmacN7 combined with radiation inhibited cIAP-1 as well. Conclusions Tat-SmacN7 has a radiosensitization effect on human breast cancer SK-BR-3 cell by promoting apoptosis, which might be related with XIAP expression.