PDCD1 and cancer: ICB, which involves inhibition of programmed cell death protein 1 (PD-1)/ programmed cell death ligand 1 (PDL-1), cytotoxic T lymphocyte-associated protein 4 (CTLA-4), and lymphocyte-activation gene 3 (LAG-3), promotes a robust CD8+ T cell response against cancer cells, the first step toward sustainable tumor regression [4].