With the rapid development of Immune Checkpoint Inhibitors (ICIs), antibodies against programmed cell death protein 1(PD-1), Programmed cell death-ligand 1(PD-L1)and cytotoxic T-lymphocyte-associated protein 4(CTLA-4) have been approved one after another for the treatment of melanoma (4, 6). Here, PDCD1 is linked to melanoma.