背景与目的:DNA依赖性蛋白激酶(DNA-dependent protein kinase,DNA-PK)是一种双链断裂修复蛋白,可以修复细胞的DNA双链断裂损伤。本研究通过转染DNA-PKcs反义寡核苷酸入鼻咽癌细胞株,探讨DNA-PKcs反义寡核苷酸对不同p53功能状态的鼻咽癌细胞株的放射敏感性的影响。方法:利用LipofectamineTM2000转染DNA-PKcs反义寡核苷酸入鼻咽癌细胞株CNE-1和CNE-1-wtp53;设0、0.5、1、2、4、6、8Gy7个放射剂量点,用集落形成法分析转染反义寡核苷酸前后细胞的存活情况,并分别用线性二次模型和单击多靶模型拟合出细胞的剂量存活曲线,求出放射生物学参数α、β、α/β、SF2、D0、Dq和N值,评价细胞放射敏感性的变化。结果:转染DNA-PKcs反义寡核苷酸前,CNE-1和CNE-1-wtp53的α值分别为0.03、0.05,SF2值分别为0.73、0.50,D0值分别为2.08Gy、1.13Gy,Dq值分别为2.04Gy、1.36Gy。转染DNA-PKcs反义寡核苷酸后,CNE-1和CNE-1-wtp53的α值分别为0.04、0.26,SF2值分别为0.45、0.21,D0值分别为1.07Gy、0.83Gy,Dq值分别为1.24Gy、0.73Gy。转染DNA-PKcs反义寡核苷酸后,鼻咽癌细胞的α值增大,SF2、D0、Dq值均减小。结论:DNA-PKcs反义寡核苷酸可逆转CNE-1的辐射抗性,该逆转作用不依赖细胞的p53功能状态。
Objective： Radiosensitivity is mainly determined by the number of DNA double-strand breaks （DSBs） induced by ionizing radiation and the extent of its repair. The DNA-PK complex formation is one of the major pathways by which the mammalian cells respond to DSBs repairing. Our previous study suggested that CNE1 is more radioresistant than CNE2. This study was designed to answer whether the radiosensitive difference of Nasopharyngeal Carcinoma cell lines CNE1/CNE2 was related to the expression and localization of Ku70/Ku80/DNA-PKcs. Methods： Immunohistochemistry was performed to detect the subcellular localization of Ku70/Ku80/DNA-PKcs in NPC cells lines CNE1 and CNE2. Western-blot was used to determine the expression of Ku protein in total extract of CNE1 and CNE2 and semi-quantitative assay of protein expression was performed to estimate the optic density （OD） value of each band using automatic image analysis system. Results： Ku70/Ku80/DNA-PKcs primarily located in the nuclei. A part of nucleolus in CNE1 and CNE2 showed positive dyeing of DNA-PKcs. Protein expression of Ku70/Ku80/DNA-PKcs was detected in CNE1 and CNE2, and the integral optical density （IOD） of Ku70 protein was 22.03 ± 7.56 and 19.98 ± 6.04 respectively （t=0.021, P〉0.05）, while the IODs of Ku80 protein in the two cell lines were 33.44 ± 12.87 and 28.98 ± 9.24 respectively （t=0.24, P〉0.05）, and the IODs of DNA-PKcs protein were 45.03 ± 1.77 and 40.87 ± 4.19 （t=1.58, P〉0.05）. The above results suggested that the basic expression of Ku70/Ku80/DNA-PKcs had no statistic difference between the different radiosensitive NPC cell lines CNE1 and CNE2. Conclusion： The variation of radiosensitivity in NPC cell lines CNE1 and CNE2 has no obviously correlation with the subcellular localization and basic expression of DNA-PK protein. So we presumed that the difference of radiosensitivity between CNE1 and CNE2 may be on account of some other factors than subcellular localization and basic expression of DNA-PK.
