P4HA1 and hepatocellular carcinoma: In human hepatic stellate cells, during the self-renewal of embryonic stem cells, and during hepatocellular carcinoma proliferation, miR-122 can regulate the expression of target genes (encoding the prolyl 4-hydroxylase subunit alpha-1 precursor and pyruvate kinase isozymes) to participate in the corresponding biological processes (Jung et al., 2011; Li et al., 2013).