For instance, CBX4 functions as a tumor suppressor by inhibiting the c-myc expression and cellular transformation9; CBX4 connects with E2F and Rb to repress the transcription of both cyclin A and cdc2, which consequently reduce cell proliferation, this function is involved in its PRC1 complex10; and CBX4 positively regulates proliferation, angiogenesis, and cancer metastasis in hepatocellular carcinoma (HCC), which is dependent on in its sumoylating E3 activity6,11. This evidence concerns the gene CBX4 and hepatocellular carcinoma.