HVJ-liposome-mediated transfection of HSVtk gene driven by AFP promoter inhibits hepatic tumor growth of hepatocellular carcinoma in SCID mice.

Suicide gene therapy using ganciclovir (GCV) with transfection of the herpes thymidine kinase (HSVtk) gene has been studied for cancer therapy. The present study demonstrates an efficient method of suicide gene therapy for multiple hepatic tumors, involving repetitive transfection of the HSVtk gene driven by the alpha-fetoprotein (AFP) promoter using hemagglutinating virus of Japan (HVJ)-liposomes. AFP-producing cells (HUH7) and AFP-nonproducing cells (LS180) were injected subcutaneously (s.c.) to establish tumors in nude mice. Two plasmid constructs, bacterial LacZ gene driven by the AFP promoter (AFPLacZ), and HSVtk gene driven by the AFP promoter (AFPTK1) were encapsulated into the HVJ-liposome and used. When AFPLacZ was injected into the s.c. tumors, expression of LacZ gene was confined to HUH7 tumors. Repeated transfection of AFPTK1 followed by GCV treatment markedly suppressed growth of HUH7 tumors, and apoptosis of HUH7 cells was recognized in the tumor. Next, HUH7 cells were injected into the portal vein in severe combined immunodeficiency mice to establish a hepatic tumor model. After inoculation with the tumor, HVJ-liposomes containing the AFPTK1 plasmid vector were injected into the portal vein via the splenic hilum, followed by GCV treatment. This gene therapy significantly inhibited the growth of tumors in the liver and markedly improved survival. Three injections of the AFPTK1 plasmid vector completely inhibited tumor growth. This procedure seems to have great potential for the treatment of multiple hepatic tumors.