PDCD1 and cancer: Immune checkpoint blockade (ICB) therapy using monoclonal antibodies to block the programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) axis has emerged as a promising approach for clinical treatments of cancers such as bladder cancer and non-small cell lung cancer (Powles et al., 2014; Peters et al., 2017; Rittmeyer et al., 2017).