Immune checkpoint inhibitors (ICIS) such as ipilimumab (CTLA-4 inhibitor) and nivolumab (PDCD-1 inhibitor) significantly improve the overall survival rates of patients with melanoma (Hodi et al., 2010; Long et al., 2017) and advanced liver cancer (Waidmann, 2018). This evidence concerns the gene PDCD1 and liver cancer.