CD8A and neoplasm: The binding of inhibitory immune checkpoints (e.g., PD-1) on CD8+ cells with their ligands (e.g., PD-L1 and PD-L2) on tumor endothelial cells inhibits T cell activation and these ligands can be upregulated by tumor endothelial cells on proinflammatory factors (Georganaki et al., 2018).