ISG15 and hepatocellular carcinoma: In a recent study by Li et al [136], the expression of ISG15 was found to be associated with tumor grade, metastasis, and survival in HCC patients, and ISG15 was shown to promote tumor cell proliferation and migration by blocking the interaction between X-linked inhibitor of apoptosis (XIAP) and the apoptosis inhibitor, baculoviral IAP repeat containing 5 (BIRC5, formerly survivin).