CD274 and neoplasm: They also express inhibitory co-receptors such as programmed cell death protein ligand 1 (PD-L1), secrete soluble immunosuppressive mediators such as indoleamine 2,3-dioxygenase (IDO), and contribute to the release of anti-inflammatory interleukins such as transforming growth factor-β (TGF-β) and interleukin 10 (IL-10) into the tumor microenvironment [12,13,14].