Gene Therapy for α–Fetoprotein–Producing Human Hepatoma Cells by Adenovirus–Mediated Transfer of the Herpes Simplex Virus Thymidine Kinase Gene

Abstract

We have developed a recombinant replication–defective adenovirus containing human α–fetoprotein (AFP) promoter/enhancer to direct cell type–specific expression of the herpes simplex virus thymidine kinase (HSV tk ) gene to AFP–producing hepatocellular carcinoma (HCC) cells. After an in vitro infection by a recombinant adenovirus carrying the lacZ gene under the control of human AFP promoter/enhancer (AdAFP lacZ ), an expression of the lacZ gene was demonstrated efficiently in AFP–producing HuH–7 and HepG2 cell lines, but not in AFP–nonproducing HLE and HLF cell lines, although lacZ gene expression was demonstrated in all these cell lines when infected with adenovirus vector carrying lacZ gene driven by the β–actin–based promoter. Expression of the HSV tk gene by adenovirus, from AFP promoter/enhancer (AdAFP tk ) induced the cells sensitive to ganciclovir (GCV) in the AFP–producing cell line efficiently, but not in AFP–nonproducing HLF hepatoma cells. An in vitro bystander effect was observed when only 10% of the cells were infected with AdAFP tk . These findings suggest that the AFP promoter/enhancer sequence can provide the tumor–specific activity for the therapeutic gene expression, and that the AdAFP tk vector induces the selective growth inhibition by GCV in the adenovirus–infected human hepatoma cells in vitro . Recombinant adenovirus transfer of the HSV tk gene under the control of tumor–specific promoter followed by GCV may have promise as a targeted in situ treatment for solid neoplasms.