Objective: To study the induction of sensitivity to ganciclovir (GCV) or acyclovir (ACV) in human hepatocellular carcinoma (HCC) cell line transferred by an Epstein-Barr virus (EBV)-based replicon expression vector carrying the herpes simplex virus thymidine kinase (HSV-tk) gene, including killing and “bystander” effect, and also the gene delivery procedure and route of gene therapy in vivo for HCC.
Methods: Liposome-entrapped plasmid pDR2/tk was transferred into HCC cells, and then different concentrations of GCV or ACV were added. The transferred cells were mixed with untransferred HCC cells in different proportion and 200 μmol/L GCV was then added into each well. After 72 hours, all samples were measured by MTT colorimetric assay. An EBV-based plasmid eukarotic expression vector carrying IL-2 cDNA was used. Three models of gene direct injection in the local liver, injection through the portal vein, and injection through the embolized hepatic artery were established in closed Wister rats. For each model, two subgroups, injected either naked plasmid DNA or lipofectin-plasmid complex were included. The expression of the IL-2 gene was regularly examined immunohistochemically.
Results: GCV or ACV could apparently kill the transferred HCC cells at a concentration of 0.2 μmol/L. The inhibition rate was changed with different drug concentrations. The “bystander” effect was obviously induced at a transferred to untransferred HCC cells ratio of 1∶5. IL-2 gene expression was observed in liver cells of all animals on day 3, which reached peak within 3-7 days, and declined after day 7. Injection of naked plasmid DNA through the hepatic artery plus embolization obtained a best expression.
Conclusions: EBV-based vector is suitable for carrying suicide gene therapy for hepatocellular carcinoma. Gene direct delivery in vivo combined with interventional surgery can be used to treat hepatocellular carcinoma.