CD274 and neoplasm: Many infiltrating cell types contribute to an immunosuppressive TME, including myeloid-derived suppressor cells, CAFs, tumor-associated macrophages, and regulatory T cells, which secrete factors such as TGF-β, IL-10, ARG-1, inducible nitric oxide synthase (iNOS), COX2, PGE2, FAP, and PD-L1 (77, 78).