BACKGROUNDHerpes simplex virus thymidine kinase phosphorylates ganciclovir to ganciclovir monophosphate, which is then converted to ganciclovir triphosphate by endogenous cellular nucleoside kinases. The ganciclovir triphosphate acts as a DNA chain terminator due to the lack of a functional 3'-OH group and terminates the process of DNA replication, hence leading to cell apoptosis. At present, HSVtk gene usually acts as suicide gene to kill tumor cells. The aim of this study was to investigate the selective cytotoxicity of the herpes simplex virus thymidine kinase/ganciclovir (HSVtK/GCV) suicide gene system controlled by the a-fetoprotein (AFP) promoter on hepatocellular carcinoma (HCC) cells in vitro.

METHODSpAFP-HSVtk-IRES2-EGFP recombinant plasmid vectors driven by the AFP promoter were constructed. HL-7702 liver cells, HUH-7 HCC, and HepG2 HCC were transfected with the recombinant plasmids. HSVtK gene expression was detected using Western blotting analysis. HepG2 cells line stably expressing HSVtk gene was selected by G418 reagent. The cytotoxicity of HSVtK/GCV suicide gene system on hepatoma cells was measured by CCK-8 reagents when different doses of ganciclovir were added.

RESULTSPlasmid pAFP-TK-IRES2-EGFP-expressed HSVtk gene was constructed successfully. HSVtk gene expression level was significantly higher in AFP-positive hepatoma cells than in AFP-negative liver cells. After G418 selection, a HepG2 cells line stably expressing HSVtk gene was acquired. With the increase of the dose of ganciclovir the optical density at 450 nm of HepG2 cells stably expressing HSVtk gene gradually decreased (P < 0.05).

CONCLUSIONThe HSVtK gene-specific expression in hepatoma cells as well as the cytotoxicity of the suicide gene system in HepG2 cells provided the basis for the targeted gene therapy of HCC.