GSTP1 and hepatocellular carcinoma: The methylation landscape of HCV-positive HCC tissues differs from non-tumor controls and a correlation between HCV infection and aberrant methylation of genes such as CDKN2A (cyclin-dependent kinase inhibitor 2A), CDH1 (cadherin 1), SOCS1 (suppressor of cytokine signaling 1), RASSF1A (Ras associated domain family member 1), APC (adenomatous polyposis coli protein), GSTP1 (glutathione S-transferase Pi 1), STAT1 (Signal transducer and activator of transcription 1), and PRDM2 (PR/SET domain 2) in HCV-positive HCC has been established.