PRKG1 and hepatocellular carcinoma: The activity of the AFpg promoter was much lower than the pgk promoter in AFP-negative cells (L-02 and SK-Hep-1), but much higher in AFP-positive HepG2 and Hep3B cells (Figure 2A), This indicated that the AFP enhancer gave the specificity to the pgk promoter and the AFpg promoter may be a valuable AFP-positive-specific promoter for gene therapy targeting HCC.