For some cancers, promoters that regulate the expression of tumor-specific antigens (TSAs) are optimal candidates for OVTs; for example, the alpha-fetoprotein (AFP) promoter for hepatocellular carcinoma (Figure 5A) and the prostate-specific antigen (PSA) promoter for prostate cancer (Figure 5B) (134, 135). This evidence concerns the gene AFP and hepatocellular carcinoma.