DNA-PKcs 表达与鼻咽癌细胞株放射敏感性的关系

 目的 探讨不同放射敏感性鼻咽癌细胞株CNE-1（鼻咽高分化鳞癌细胞株）和CNE-2（鼻咽低分化鳞癌细胞株）中DNA依赖蛋白激酶（DNA-PK）的催化亚基DNA-PKCS基因的表达与鼻咽癌细胞放射敏感性的关系。方法 通过克隆形成实验测定CNE-1、CNE-2不同剂量的存活分数，并用线性二次模型拟合剂量存活曲线求出放射生物学参数α、β,SF2、MID值，以及四氮唑蓝比色分析法（MTT法）检测60Co-γ线4Gy照射后12h细胞的存活率，以评价两株细胞的放射敏感性。逆转录实时荧光定量PCR技术（RTrFQPCR）检测照射前、后不同时间及不同剂量CNE-1、CNE-2细胞mRNA水平DNA-PKCS基因的定量表达。结果CNE-1在各个剂量点的存活分数均比CNE-2高，MID值分别为2．78、1．61，SF2值分别为0．627、0．341；4Gy照射后12h的存活率分别为88．2％、72．3％；RT-FQPCR显示两株细胞中均有DNA-PKCS基因的表达，其相对表达量之比为7．54±2．71（t=4．17，P=0．014），表达差异有统计学意义，DNA-PKCS基因在CNE-2细胞中存在时间、剂量依赖关系。结论实验验证了CNB2比CNE-1对射线更敏感，DNA-PKCS基因的表达与鼻咽癌细胞的放射敏感性有关。

Relationship between the Expression of DNA-PKcs and Radiosensitivity in Nasopharyngeal Carcinoma Cell Lines

Objective 　This study was designed to determine the relationship between expression of DNA-PKcs gene (a catalytic subunit of DNA-PK,which is an important component in NHEJ pathway) and radiosensitivity of nasopharyngeal carcinoma cell lines. Methods 　Radiosensitivity parameters of nasophryngeal carcinoma cell lines were obtained by the colony forming assay and irradiation dose-survival curve were done by linear quadratic model. The two cell lines were exposed to ⁶⁰ Co-γ ray and received 4 Gy , 12 hours later , the survival rate were obtained by MTT assay , and evaluated the different radiosensitivity of two cell lines. After receiving different irradiation dose , the dynamical changes of the expression of DNA-PKcs in mRNA level of CNE-1 and CNE-2 were detected by RT-FQ-PCR. Results 　Survival rate of CNE-1 was higher than those of CNE-2 at each dose point . Mean inactivation dose was higher in CNE-1 (2. 78) than that in the CNE-2 (1. 61) ,and the SF₂ was 0. 627 and 0. 341 respectively. After exposed to irradiation dose of 4 Gy ,survival rate in CNE-1 was also higher than that in the CNE-2. The ratio of relative expression of DNA-PKcs in the two cell lines was 7. 54 ±2. 71 ( t = 4. 17 , P = 0. 014) . The expression of DNA-PKcs in CNE-2 was correlated with the irradiation dose and postirradiation time. Conclusion 　CNE-2 is more radiosensitive than CNE-1. The expression of DNA-PKcs gene is correlated with the radiosensitivity of nasophryngeal carcinoma.