人剪切修复基因XPD肝癌对人HepG2细胞中Rb和MAD2表达的影响*

 目的：探讨人剪切修复基因着色性干皮病D组基因（xeroderma pigmentosum group D, XPD)转染人肝癌HepG2细胞后视网膜母细胞瘤蛋白(retinoblastoma,Rb)和有丝分裂阻滞缺陷蛋白 2（mitotic arrest deficient 2, MAD2）表达的变化及对细胞增殖的影响。方法：将人工合成的pEGFP-N2-XPD重组质粒通过LipofectamineTM 2000转染HepG2细胞。实验分为4组，分别为无转染HepG2细胞组（空白对照组）、脂质体转染HepG2细胞组（脂质体组）、空载质粒pEGFP-N2转染细胞组（N2 组）和重组质粒pEGFP-N2-XPD转染细胞组（XPD组）。分别用RT-PCR和Western blotting法检测各组细胞中XPD、Rb及MAD2 mRNA和蛋白的表达量，用MTT法检测各组细胞的增殖活力，流式细胞术检测各组的细胞凋亡情况及细胞周期。结果：与其它3组相比，XPD组XPD mRNA及蛋白表达量明显升高（P<0.05），Rb mRNA及蛋白表达量明显升高（P<0.05），而MAD2 mRNA及蛋白表达量显著降低（P<0.05）。XPD组细胞增殖活力显著降低，细胞凋亡率明显升高（P<0.05）。XPD组细胞停滞在G1期，难以进入S期。结论：XPD可以抑制MAD2的表达和肝癌细胞的增殖，促进Rb的表达。

Effects of XPD on expression of Rb and MAD2 in human hepatoma HepG2 cells

AIM：To investigate the effects of xeroderma pigmentosum group D (XPD) protein on the growth of human hepatoma HepG2 cells and the expression of retinoblastoma (Rb) and mitotic arrest deficient 2 (MAD2) proteins. METHODS：The recombinant plasmid pEGFP-N2-XPD and empty plasmid pEGFP-N2 were transfected into  HepG2 cells by LipofectamineTM 2000. The cells were divided into 4 groups including blank control group, liposome group, pEGFP-N2 group (N2 group) and pEGFP-N2-XPD group (XPD group). The expression of XPD, Rb and MAD2 at mRNA and protein levels was detected by RT-PCR and Western blotting. The cell growth was measured by MTT assay. The cell apoptosis and cell cycle were analyzed by flow cytometry. RESULTS：Overexpression of XPD up-regulated the expression of Rb, and down-regulated the expression of MAD2 at mRNA and protein levels. XPD inhibited the proliferation of HepG2 cells and exacerbated the apoptosis. XPD prevented the hepatoma cells from G1 stage to S stage. CONCLUSION：XPD suppresses the growth of hepatoma cells, up-regulates the expression of Rb, and down-regulates the expression of MAD2.