中文摘要：

目的：探讨新型嘌呤核苷磷酸化酶／6-甲基嘌呤-2＇-脱氧核糖核苷（PNP／MeP-dR）自杀基因系统对肝癌细胞的杀伤作用。方法：构建PNP基因真核表达载体pcDNA3．0／PNP，脂质体介导法将其导入HepG2细胞，利用G418筛选获得稳定转染PNP基因的细胞株HepG2／PNP。采用台盼蓝拒染法测绘细胞生长曲线，MTT法和FCM检测细胞对MeP-dR的敏感性及旁观者效应，HPLC检测PNP酶活性。结果：HepG2／PNP细胞对MeP-dR十分敏感，作用4d后MeP-dR对HepG2／PNP的IC50为4．5μmol／L，而100μmol／L的MeP-dR即可最大限度地杀死HepG2／PNP细胞。100μmol／L MeP-dR作用8d后，混合细胞中HepG2／PNP比例仅占5％即可导致所有细胞死亡。HPLC结果显示，PNP基因产物能够将MeP-dR转化为6-MP。结论：PNP／MeP-dR系统对肝癌细胞的杀瘤效果明显优于传统的自杀基因系统。本研究为该系统应用于肝癌体内治疗打下基础。

英文摘要：

Objective：To investigate the effect of PNP/MePdR suicide gene system on hepatoma cells. Methods：An eukaryotic expression vector pcDNA3.0/PNP was constructed by inserting PNP gene into pcDNA3.0. Then it was transfected into a hepatoma cell line, HepG2,by liposome-mediation. The HepG2/PNP cell line with stable PNP gene expression was established via G418 selection. The cell growth curves were determined by Trypan blue staining. The sensitivity of HepG2/PNP to MePdR and the bystander effect was measured by MTT and FCM assay, respectively. The enzymatic activity of the product of PNP gene was determined with high pressure liquid chromatography （HPLC）. Results： The HepG2/PNP cells were sensitive to MePdR. ICs0 value was 4.5 μmol/L after 4-d treatment with MePdR. MePdR 100 μmol/L killed almost all the HepG2/PNP cells. As for the bystander effect, after 8-d treatment with MePdR 100 μmol/L,5% HepG2/PNP cells in mixed culture could induce all cell death. HPLC analysis showed that PNP gene product could convert MePdR into 6-MP. Conclusion： PNP/MePdR suicide gene system has an advantage over traditional suicide gene systems in hepatoma gene therapy. Our study would lay a substantial basis upon hepatoma therapy in vivo .