中文摘要：

目的比较碳重离子与x射线对肺癌细胞的生物学效应。方法对A549细胞分别进行碳重离子和x射线照射，通过克隆形成实验检测照射后细胞存活情况；流式细胞术检测细胞周期分布；通过Hoechst33258荧光染料对照射后固定的细胞进行染色，计算凋亡率；采用实时荧光定量PCR方法检测照射后48h细胞内DNA依赖性蛋白激酶催化亚单位（DNA—PKcs）和H2AX的mRNA表达水平。结果细胞存活曲线显示，碳重离子造成的细胞存活分数远低于x射线，并将细胞周期阻滞于G，／M期（t=4．77、14．53、14．54，P〈0．05），导致大部分细胞进入凋亡途径。碳重离子与x射线辐照后DNA．PKcs的表达上调（t=10．91、5．05，P〈0．05）。结论碳重离子照射对肺癌细胞造成生物学效应远高于x射线。

英文摘要：

Objective To compare the effects of carbon heavy ion and X-ray irradiation on survival fraction, cell cycle, cell apoptosis and expression of DNA-PKcs of A549 lung cancer cells. Methods A549 cells were irradiated by carbon heavy ion and X-ray. Cell survival fraction, cell cycle and apoptosis were analyzed by clonogenie formation assay, flow cytometry and Hoechst 33258 staining, respectively. Real tirne-PCR was performed to detect the expressions of DNA-PKcs and H2AX mRNA. Results Lower cell survival fraction, more GJM phase arrest and higher apoptosis rate were detected in the A549 cells exposed to carbon heavy ion than X-ray（ t = 4.77,14.53,14.54, P 〈 0.05 ）. Expression of DNA-PKcs was up-regulated after irradiation to carbon heavy ion and X-ray（ t = 10.91,5.05 ,P 〈 0. 05 ）. Conclusions Both heavy ion and X-ray irradiations enhance the expression of DNA-PKcs, induce apoptosis through regulating cell cycle arrest, and hence reduce survival of A549 cells. Heavy ion irradiation shows more stronger biological effects than X-ray irradiation.