CD274 and neoplasm: Tumor cells can evade the immune responses by two ligands, programmed death ligand 1 (PD-L1) and programmed death ligand 2 (PD-L2), both of which engage the PD-1 receptor and inhibit T-cell activation, known as tumor immune evasion (Freeman et al., 2000; Latchman et al., 2001; Juneja et al., 2017; Dong et al., 2018; Zhao and Huang, 2020).