In contrast, COX-2 substrates, including eicosapentaenoic acid and docosahexaenoic acid (two ω-3 fatty acids) and dihomo-γ-linolenic acid (perhaps an exceptional ω-6 fatty acid), have shown some inhibitory effects on cancer cell growth and metastasis, most likely due to their competition with AA for the COX-2 peroxidation to limit PGE2 formation [6–12, 20–23]. Here, PTGS2 is linked to cancer.