HOTTIP and hepatocellular carcinoma: The expression of some HOX genes has been reported to be maintained in the malignant state of HCC regardless of the high expression of PRC1 components, including RNF2 and PCGF4 (BMI1), suggesting that the expression of some HOX genes may be regulated by factors other than PRC1, such as lncRNAs (e.g., HOTTIP, described above), regardless of the high RNF2 activity at the malignant stage of HCC.