Moreover, immunotherapy (for example, programmed cell death protein 1 [PD1] and cytotoxic T-lymphocyte-associated antigen 4 [CTLA-4] immune checkpoint inhibitors) has resulted in significantly improved long-term survival in patients with metastatic melanoma, renal cancer, non-small cell lung cancer, and squamous cell carcinoma [87, 88]. This evidence concerns the gene PDCD1 and metastatic melanoma.