PTGS2 and neoplasm: For example, tumor-derived exosomes could transfer prostaglandin E2 (PGE2) and TGF-β to induce the accumulation of myeloid-derived suppressor cells (MDSCs) expressing cyclooxygenase-2 (COX-2), interleukin 6 (IL-6), vascular endothelial growth factor (VEGF) and arginase-1.