PDCD1 and cancer: In this article, immunotherapy is used exclusively as a term for all cancer therapies based on the specific immune checkpoint inhibitors (ICIs) cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) (Emens et al. 2017).