PTGS2 and neoplasm: In vitro, celecoxib (PTGS2 inhibitor) or exogenous prostaglandin E2 (PGE2, an enzymatic product of PTGS2) failed to affect the growth of Gpx4−/− PDAC cells, indicating that the PTGS2 pathway may not be important for tumor growth associated with GPX4 depletion (Supplementary 3g).