中文摘要：

目的探讨西妥昔单抗（C225）对^125I粒子照射下结直肠癌CL187细胞DNA损伤修复和信号传导通路的影响。方法实验分为空白对照组，100nmol／LC225处理组，单独^125I粒子持续低剂量率照射组和C225联合^125I粒子持续低剂量率照射组。在吸收剂量达4Gy后48h，经细胞免疫荧光检测各组细胞中γH2AX聚集点数量以及γH2AX聚集点阳性细胞比例。提取细胞内总蛋白，Westernblot检测DNA修复蛋白的变化。在吸收剂量达4Gy后即刻提取总蛋白，Westernblot分析在照射过程中C225对EGFR下游信号通路中蛋白分子的影响。结果与单独^125I粒子持续低剂量率照射组细胞相比，C225联合^125I持续低剂量率照射组细胞内残余的γH2AX聚集点数量和γH2AX聚集点阳性的细胞比例均高（t=8．0和6．8，P〈0．05），并且细胞中DNA修复蛋白Ku70和DNA．PKes的含量偏低（t=6．6和5．7，P〈0．05）。Westernblot结果显示，在^125I粒子持续低剂量率照射过程中，C225能够降低细胞内EGFR的水平（t=4．9，P〈0．05），抑制Akt的活化（t=5．5，P〈0．05）。结论在^125I放射性粒子持续低剂量率照射下，C225可以降低细胞内Ku70和DNA—PKes的含量，并抑制Akt活化，减弱CL187细胞的DNA损伤修复能力。

英文摘要：

Objective To investigate the effect of C225 on DNA repair and molecular pathways in CL187 coloreetal cancer cells after irradiated by 1251 radioactive seeds. Methods In the experiment involved were four groups： control group, 100 nmol/L C225 treatment group, 125I radioactive seeds continuous low-dose rate irradiation group and C225 combined with 1251 radioactive seeds continuous lowdose rate irradiation group. Cells were collected at 48 h after 4 Gy irradiation, and γH2AX loci/cell and γH2AX loci positive cells were counted with immunofluorescence. At the same time, DNA repair proteins were detected by Western blot. Cells were lyzed immediately after 4 Gy irradiation, and changs in EGFR downstream signaling molecules were detected by Western blot. Results Compared with 12si seeds irradiated cells, cells treated with C225 and 125I seeds irradiation showed more γH2AX loci per cell （t = 8.0, P = 0.05） , and more γH2AX foci positive cells （ t = 6. 8, P 〈 0.05 ） and less expression of Ku70 （t = 6. 6, P 〈 0. 05） and DNA-PKcs （ t = 5.6, P 〈 0. 05 ）. Combined with 125I.CLDR irradiation, C225 reduced cellular EGFR level（t =4.9, P 〈0.05） and inhibited the activation of Akt（t =5.5, P 〈0. 05）. Conclusions In the condition of 1251 seeds irradiation, C225 reduced the expression of Ku70 and DNA- PKcs, inhibited the activation of Akt and attenuated the DNA damage repair capacity in CL187 eoloreetal cancer cells.