This analysis revealed that treatment of the CRC cells with 2 μg/mL (P = 0.002) or 5 μg/mL (P < 0.001) significantly reduced PACER levels relative to the mock group (Figure 5E), suggesting that, through a negative feedback loop, high PGE2 levels act back to downregulate COX-2 through inhibiting PACER-expression levels. This evidence concerns the gene PTGS2 and colorectal carcinoma.