PDCD1 and melanoma: PD-1 or PD-L1 inhibitors such as nivolumab and pembrolizumab can prevent the binding of PD-1 to PD-L1, thus restoring T cell activity and killing melanoma, non-small lung cancer (NSCLC) and other tumors (Larkin et al., 2015; Ribas et al., 2015; Weber et al., 2015).