Specific Expression of Suicide Gene in Liver Cancer Cells Mediated by Adenovirus

Shuttle plasmid containing HSV-tk gene and regulatory sequence of the afp gene was constructed and recombined with the right arm of adenovirus DNA. The recombinant adenovirus vector was named pAdrAFPTK. Meanwhile, an AdCMVTK was constructed as control in which the tk gene was controlled under CMV promoter. PCR and Southern blot analyses were used to identify positive plaques. Virus titer was about 1x10(15) pfu/L determined by plaque forming assay. The AFP-positive cells or AFP-negative cells were infected with AdCMVTK or AdrAFPTK and then treated with GCV, respectively. Cytotoxic effects were assayed with MTT method. The IC(50) of GCV for both HeLa cells or BRL-3A cells (both were AFP-negative cells) and HepG2 cells (AFP-positive cells) were 1.3 &mgr;mol/L, 2&mgr;mol/L and <1&mgr;mol/L, respectively, after infection with AdCMVTK (m.o.i.=100). However, in the cases of infection with AdrAFPTK (m.o.i.=100), IC(50) were 1 000 &mgr;mol/L, >1 000 &mgr;mol/L and <1&mgr;mol/L for HeLa cells, BRL-3A cells and HepG2 cells, respectively. Results showed that this vector possessed advantages of high title, high infectivity coming from adenovirus and the character of cell type-specificity gene expression. The AdrAFPTK/GCV system may become a new, potent and specific approach for the gene therapy of the primary hepatoma.