电离辐射对缺氧条件下肝癌细胞HIF-1α及VEGF表达的影响

Effect of ionization on the expression of hypoxia-inducible factor-1α and VEGF in hepatocellular carcinoma HepG2 cells under anoxic condition

目的探讨缺氧条件下电离辐射对肝癌细胞HepG2中缺氧诱导因子(HIF)-1α及血管生成因子(VEGF)表达的影响,从理论上寻找一种提高放射治疗肿瘤有效性的方法。方法将HepG2肝癌细胞分为对照组、缺氧组、单纯照射组和缺氧加照射组。缺氧组:氯化钴处理细胞模拟缺氧条件;单纯照射组:按照照射率4Gy/min,共8Gy的剂量利用X射线照射细胞;缺氧加照射组:氯化钴处理细胞一定时间后,按照与单纯照射组相同的剂量照射细胞。利用荧光显微镜观察各组肝癌细胞的凋亡情况,MTT法分析细胞存活分数,RT-PCR技术检验各组肝癌细胞中的HIF-1α和VEGF表达情况。结果(1)细胞凋亡情况:对照组未观察到细胞凋亡,缺氧组中少部分肝癌细胞出现凋亡,单纯照射组中大量肝癌细胞出现凋亡,但缺氧加照射组肝癌细胞凋亡情况较单纯照射组明显减少(P<0.05)。(2)MTT检测结果:细胞存活分数排列顺序为:对照组>缺氧组>缺氧加照射组>单纯照射组。(3)HIF-1α表达情况:缺氧加照射组>缺氧组>正常组(P<0.05),单纯照射组与正常组无明显差异;VEGF表达变化情况:缺氧加照射组>缺氧组>单纯照射组>正常组(P<0.05)。结论提示HIF-1α可能通过VEGF发挥重要的保护作用,从而降低实体瘤中内部癌细胞对辐射的敏感性。

Objective To investigate the effect of ionization on the expression ofhypoxia-inducible factor-1α （HIF-1α） and vascular endothelial growth factor （VEGF） in human hepatocellular carcinoma HepG2 cells under anoxic condition, and search for an effective method for improving the radiosensitivity of the tumor cells. Methods HepG2 cells were divided into 4 groups, namely the control group, hypoxia group, ionization radiation group, and hypoxia and radiation group, with corresponding treatments. The cell apoptosis was detected by fluorescence microscope, and the cell viability analyzed by MTT assay. The expressions of HIF-1α and VEGF mRNAs were detected by RT-PCR. Results A few apoptotic cells were found in hypoxia group, but significant apoptosis occurred in the radiation group; fewer apoptotic cells were observed in the hypoxia and radiation group than in the hypoxia group. The viable cell fraction increased in the order of the control group〉hypoxia group〉 hypoxia plus radiation group〉 radiation group （P〈0.05）, and the expression of HIF-1α mRNA increased in the order of hypoxia plus radiation group〉hypoxia group〉radiation group （P〈0.05）, and no significant difference was found in the radiation group and control group. The expression of VEGF mRNA increased in the order of hypoxia plus radiation group〉 hypoxia group〉radiation group〉control group （P〈0.05）. Conclusion The expression of HIF-1α may protect the hepatocellular carcinoma cells from damages by radiation in hypoxic condition, and HIF-1α decreases the radiosensitivity of the cells possibly by inducing VEGF expression.