PDCD1 and melanoma: Among the ICIs, programmed cell death protein 1(PD-1)/programmed cell death-ligand 1(PD-L1) and cytotoxic T-lymphocyte-associated protein 4(CTLA-4) inhibitors showed promising therapeutic outcomes, and some have been approved for numerous cancer therapy, such as melanoma, renal cell carcinoma (RCC), and non-small cell lung cancer (NSCLC) (4, 5).