CTLA4 and liver cancer: CTLA-4 and PDCD-1 are 2 critical proteins associated with tumor immune escape.[70,71] Immune checkpoint inhibitors, such as ipilimumab (CTLA-4 inhibitor) and nivolumab (PDCD-1 inhibitor), significantly improve the overall survival rates of patients with melanoma[72,73] and advanced liver cancer.[74] Therefore, we analyzed the association between SKA1 expression and immunological checkpoint genes, including CTLA-4 and PDCD-1.