DNA双链断裂修复蛋白表达水平与肿瘤细胞放射敏感性的关系研究

Correlation of expression of DNA double-strand break repair protein with radiosensitivity of tumor cells

目的:检测肿瘤细胞株中DNA双链断裂修复蛋白(Ku80、DNA-PKcs和ATM)的表达水平和放射敏感性参数,探讨3个蛋白预示肿瘤细胞放射敏感性的价值。方法:培养4株人宫颈癌细胞HeLa、SiHa、C33A和Caski,3株人乳腺癌细胞MCF-7、MDA-MB-231和MDA-MB-453,及1株人肺癌细胞A549,Western blot检测这8株细胞中Ku80、DNA-PKcs和ATM蛋白的表达水平;流式细胞仪检测X线(10 Gy,6 MV)照射48 h后的凋亡率;克隆形成实验检测SF2(surviving fraction at 2 Gy)值和α、β值;Pearson线性相关分析蛋白表达水平与照射后凋亡率、SF2值和α/β比值的相关性。结果:3种蛋白在同一株细胞中的表达及同一蛋白在不同细胞株的表达均存在明显差异;DNA-PKcs的表达水平与SF2之间存在正相关关系(r=0.723,P=0.043);Ku80和ATM的表达与SF2值间无明显相关关系(P>0.05)。3种蛋白与凋亡率和α/β比值均无相关性(均P>0.05)。结论:DNA-PKcs蛋白表达越高,细胞对放射线越抵抗,其表达水平可能成为指示肿瘤细胞放射敏感性的指标。

Objective： To explore the correlation between the expressions of DSB （ DNA double-strand break） repair protein （ including Ku80, DNA-PKcs, and ATM） and radiosensitivity parameters of human tumor cell lines, and to reveal the value of the three proteins for the prognosis of the radiosensitivity of tumor cells. Methods： Eight tumor cell lines were selected including four human cervical carcinoma cell lines （HeLa, SiHa, C33A, and Caski）, three human breast carcinoma cell lines （MCF-7, MDA-MB-231, MDA-MB-453 ）, and one human lung carcinoma cell line （A549）. The expressions of Ku80, DNA-PKcs and ATM protein were measured by Western blotting. The apoptotic ratio of tumor cells was analyzed by flow cytometry after 48 h X-ray irradiation at 10 Gy of 6 MV. SF2 value （survival fraction at 2 Gy） and α and β values were obtained by clone formation assay. The correlation of protein expression with SF2, α/β value or apoptotic ratio was analyzed by Pearson linear correlation analysis. Results：The expression of same protein in different cell lines and the expression of the three proteins in the same cell line had significant difference. There was a positive correlation between the expression of DNA-PKcs and SF2 （r = 0.723, P = 0.043 〈 0.05）. But Ku80 and ATM expression had no correlation with SF2 （ P 〉 0.05 ）. The expression of the three proteins had no correlation with either apoptotic ratio or o./13 value （ P 〉 0.05 ）. Conclusions：Tumor cells with higher expression of DNA-PKcs protein will have higher radioresistance. The expression level of DNA-PKcs protein in tumor cells may be an indicator for predicting the radiosensitivity of tumor cells.