APEX1 and hepatocellular carcinoma: The present study demonstrated, for the first time, that APE1/Ref-1 mRNA synthesis is increased in HCC, suggesting a transcriptional regulatory mechanism of APE1/Ref-1 expression in HCC, in line with the observation of elevated APE1/Ref-1 transcript levels in other tumors such as prostate cancer [44] and melanoma [45].