For example, treatments with antibodies specific for immune checkpoints (immune checkpoint inhibitors or ICI) expressed on effector T cells (i.e., programmed cell death protein 1 or PD-1) and antigen presenting cells (APC) and, importantly, often on tumor cells (i.e., programmed death ligand 1 or PD-L1) have obtained unprecedented positive results, particularly in metastatic melanoma and non-small cell lung cancer (NSCLC) (10). The gene discussed is PDCD1; the disease is metastatic melanoma.