PDCD1 and melanoma: In recent years, the finding of antibodies that target the immune checkpoints has revolutionized the treatment of NSCLC, including programmed cell death protein-1 (PD-1) and programmed cell death protein ligand-1 (PD-L1) [8], and these two therapeutic approaches above have showed promising anti-tumor performance in melanoma and NSCLC [9,10,11].