CD274 and neoplasm: Examples include (1) the secretion of soluble immunosuppressive factors (TGF-beta, IL-10, VEGF, and indoleamine 2,3 dehydrogenase) [18, 19]; (2) the activation of negative costimulatory signals in the tumour microenvironment such as PD-L1 [20, 21]; (3) tumour-induced impairment of the antigen presentation machinery due to the accumulation of point mutations in the cell surface not recognised by cytotoxic T cells [22]; and finally (4) the downregulation of the major histocompatibility complex (MHC) class I expression which plays a crucial role in tumour antigens presentation to T cells [22].