PDCD1 and cancer: In recent years, impressive success of checkpoint inhibitor-based immunotherapy targeting programed cell death 1 (PD1), programed cell death-ligand 1 (PD-L1), cytotoxic T lymphocyte antigen 4 (CTLA4), and lymphocyte activation gene-3 (LAG3) has been observed in the treatment of various types of cancer (Di et al., 2015; Herbst et al., 2016; Xu et al., 2016; Schachter et al., 2017; Sun et al., 2020).