Thereinto, programmed cell death 1 (PD-1) inhibitors (e.g., pembrolizumab, nivolumab, and toripalimab) could block the interplay between PD-1 and PD ligand 1/2 (PD-L1/2) and have been shown to provide remarkable improvement in relapse-free survival of eligible melanoma patients and thus have been recommended as a standard treatment instead of IFN [7,8,9]. Here, PDCD1 is linked to melanoma.