PTGS2 and neoplasm: Furthermore, the COX-2/PGE2 signaling plays a main role in immunosuppressive TME through exacerbating the immunosuppressive activities of myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs), polarizing them towards an M2-like, pro-tumoral phenotype, directly inhibiting cytotoxic cell function and aggravating tumor immune evasion [[25], [26], [27]].