CD274 and neoplasm: They include: establishment of a metabolically hostile microenvironment [8,9], poor T cell costimulation by tumor cells leading to T cell anergy [10], expression of negative costimulatory ligands such as PD-L1 and Gal-9 within the tumor environment [11,12], production of immune suppressive cytokines and enzymes [13,14], expansion and/or induction of suppressive cell types (regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSC) and macrophages) [15,16].