CD274 and neoplasm: Tumor cells, including CSCs, can escape immune surveillance and immune-mediated cell killing by downregulating tumor-associated antigens (TAAs), increasing the expression of immune checkpoints such as programmed death-ligand 1 (PD-L1) and, therefore, inhibiting CD8+ cytotoxic T cells, and reducing the expression levels of major histocompatibility complex class I (MHC-I) and the transporter associated with antigen processing (TAP) molecules, which play vital roles in antigen processing and presentation processes [61,62,63,64,65,66,67,68,69,70,71,72,73].