Highly expressed DNMT3a reduces the expression of suppressor of cytokine signaling 3 (SOCS3) by promoting the over-methylation of CpG islands in the SOCS3 promoter, thereby activating the Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway to drive the tumorigenesis of HCC. The gene discussed is SOCS3; the disease is hepatocellular carcinoma.