Recently, the most effective treatment for patients with advanced malignant melanoma is reported to be immune checkpoint therapy using the anti-PD-1 (programmed cell death 1) antibodies nivolumab and pembrolizumab, and/or the anti-CTLA-4 (cytotoxic T-lymphocyte-associated antigen 4) antibody ipilimumab, as the response rate of a combination of these antibodies has been reported to be 40-50% [4]. The gene discussed is PDCD1; the disease is melanoma.