Reduced COX-1 and COX-2 expression (Fig. 2d) and activity (Fig. 2e) in COXlow-CT26 cells resulted in increased sensitivity to EPA (IC50 148.9 ± 1.2 μM) compared with CT26 cells (IC50 241.8 ± 1.1 μM; p = 0.03, 2-way ANOVA; Fig. 2f), thereby supporting the hypothesis that COX-1 and COX-2 mediate CRC cell resistance to EPA in vitro. Here, PTGS1 is linked to colorectal carcinoma.