GDF6 and hepatocellular carcinoma: The differentially expressed miRNAs, mir-182, mir-340, mir-374a, mir-590 and let-7a, and the differentially methylated genes, AKT1, BMPR1B, CNTFR, DAXX, GDF6, GNA12, HRAS, IL1B, IL1R1, IL7R, JUN, MAP3K2, MYC, NFKB1, NFKB2, PDGFB, RAP1A, STAT3 and TRAF2, regulate cell proliferation, apoptotic process, cell cycle, cell survival and metastasis through TGF-beta, MAPK and JAK-STAT pathways in the switch between stage III HCC and stage IV HCC.