PDCD1 and cancer: Antibodies specifically against programmed death-1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T lymphocyte antigen 4 (CTLA-4) (e.g., ipilimumab, tremelimumab) are regarded as recent breakthroughs in cancer immunotherapy (Quezada and Peggs, 2013; Herbst et al., 2014; Turajlic et al., 2018; Rahimi Kalateh Shah Mohammad et al., 2020).