PDCD1 and neoplasm: Programmed cell death receptor ligand 1 (PD-L1) interacting with programmed cell death protein 1 (PD-1) can inhibit T cell activation, induce effector T cell apoptosis, finally inhibit tumor immunity , which is important for using immunotherapy to treat tumors (Dong et al., 1999; Ceeraz, Nowak & Noelle, 2013; Zhang, Medeiros & Young, 2018; Wang et al., 2019a; Wang et al., 2019b).