Immune checkpoint blockade with monoclonal antibodies targeted against cytotoxic T-lymphocyte antigen 4 (CTLA-4, otherwise known as CD152), like ipilimumab, and programmed death protein 1 (PD-1) and its ligand PD-L1, like nivolumab and pembrolizumab, have been shown to effectively induce host immune response against the tumor, and several have already been approved for use in metastatic melanoma and are in advanced clinical trials in non-small cell lung cancer and other tumors [38,39,40]. This evidence concerns the gene CTLA4 and metastatic melanoma.