While ω-3 PUFAs produce PGE3 after binding to COX-1, PGE3 can inhibit the production of PGE2 and can inhibit phospholipase A2 (PLA2), phosphatidylinositol-specific phospholipase C (PI-PLC), nuclear factor-κB, and COX-2 activities, which in turn reduce the proliferation and invasion of tumor cells and play a role in inhibiting the growth and metastasis of malignant tumors (8, 12, 19–21). Here, PTGS2 is linked to cancer.