IN-VIVO GENE-THERAPY FOR ALPHA-FETOPROTEIN-PRODUCING HEPATOCELLULAR-CARCINOMA BY ADENOVIRUS-MEDIATED TRANSFER OF CYTOSINE DEAMINASE GENE

The Lu-fetoprotein (AFP) gene is normally expressed in fetal liver and is transcriptionally silent in adult liver but overexpressed in human hepatocellular carcinoma (HCC). Here, we demonstrate that replication defective recombinant adenoviral vectors, containing the human AFP pr omoter/enhancer, can be used to express the Escherichia coil cytosine deaminase (CD) gene (AdAFPCD) and the beta-galactosidase gene (AdAF-Pl acZ) in AFP-producing HCC cell lines, Expression of the CD gene by ade novirus from the AFP promoter/enhancer (AdAFPCD) induced cells sensiti ve to 5-fluorocytosine (5FC) in the AFP-producing cells but not in the AFP-nonproducing cells, Transduction by an adenoviral vector harborin g an ubiquitous strong promoter and CD gene showed enzymatic activity and 5FC killing in all cell lines. When AdAFPlacZ was injected into th e s.c. established hepatoma in vivo, expression of the beta-galactosid ase gene was confined to AFP-producing HCC xenografts, Moreover, HCC x enografts regressed by transduction with AdAFPCD and subsequently with 5FC treatment in vivo, These findings suggest that utilization of the AFP promoter/enhancer in an adenoviral vector can confer selective ex pression of a heterologous suicide gene in hepatocellular carcinoma ce lls in vitro and in vivo.