PDCD1 and lung adenocarcinoma: Specifically, in renal cell carcinoma, lung adenocarcinoma, and melanoma, antibodies that target immune activation regulators, including programmed cell death protein-1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), and programmed death ligand-1 (PD-L1), have significantly increased survival [18].