hOGG1核酶介导的肺癌细胞对60Coγ射线放射敏感性的研究

目的 观察 ⁶⁰Co γ 射线对核酶诱导的hOGG1基因低表达的人肺腺癌A549细胞的损伤效应,探讨hOGG1低表达在增加肿瘤细胞放疗敏感性中的作用机制。方法 以A549细胞、转染空质粒的A549-P细胞和转染hOGG1特异性锤头状核酶真核表达载体pcDNA3.1(+)-RZ的A549-R细胞为研究对象,测定射线照射后3种细胞活性氧含量、细胞存活率、细胞染色体损伤及DNA损伤和修复的差异。结果 A549、A549-P和A549-R 3种细胞的存活率随 ⁶⁰Co γ 射线照射剂量的增加而下降,存在较好的剂量-反应关系(r =-0.984、-0.978、-0.975, P＜0.05)。A549-R细胞的IC₅₀(9.37±0.24)显著低于A549细胞(12.98±0.44),差异有统计学意义(t=-12.48, P＜0.05)。 ⁶⁰Co γ 射线照射下细胞活性氧含量、微核形成率及DNA损伤均增加,在相同剂量下,A549-R细胞中活性氧含量和微核形成率均高于A549和A549-P细胞。此外,在相同照射剂量下,hOGG1缺陷的A549-R细胞的DNA损伤较A549和A549-P细胞严重,且损伤后更加不易修复。结论 ⁶⁰Co γ 射线可以诱导A549、A549-P和A549-R 3种试验细胞的活性氧增加,从而导致DNA和染色体损伤,最终使细胞存活率降低,且以hOGG1低表达的 A549-R细胞更为明显,提示hOGG1基因的低表达可能增加肿瘤细胞对射线的敏感性。

Study on the radiosensitivity of lung cancer cells mediated by hOGG1 ribozyme

Objective To study the mechanism of hOGGl down-regulation mediated by hOGGl ribozyme on increasing the radiosensitivity to tumor cells by observing the damage effects induced by ~(60)Co γ-rays on human lung cancer cell line.Methods Human lung adenocarcinoma A549 cells,A549-P cells transfected with empty pcDNA3.1 plasmid and A549-R cells transfected with pcDNA3.1-RZ plasmid in which hOGGl ribozyme was constructed previously were utilized as a model system.The three kinds of cells were exposed to different doses of~(60)Co γ-rays.The level of cellular reactive oxygen species (ROS),the cell viability,the chromosome damage as well as DNA damage and repair were examined respectively. Results The eell viability decreased significantly among A549,A549-P and A549-R cells after exposure to~(60)Co-γ rays with a dose-response relationship(r=-0.984,-0.978,-0.975,P<0.05),and the IC_(50) in A549-R cells (9.37±0.24) was statistically Iower than that in A549 cells (12.98±0.44,t=-l2.48,P<0.05).The ROS level.the rate of micronucleus formation and DNA damage in all three kinds of cells were enhanced after exposure to~(60)Co γ-rays,in which A549-R cells presented the most remarkable effeet compared with A549 and A549-P cells.Similarly.DNA damage in A549-R cells was also more severe and more difficult to be repaired than that in A549 and A549-P cells at the same dose.Conclusions ~(60)Co γ-rays can induce DNA and chromosome damage in A549 cells through the ROS accumulation,leading to the reduction of the eell viability.However,all effects detected were more remarkable in A549-R cells in which hOGGl was down-regulated mediated by ribozyme,suggesting that the deficiency in hOGGl might increase the radiosensivity in tumor cells.