Inhibition of COX-2 with NS-398 decreases colon cancer cell motility through blocking epidermal growth factor receptor transactivation: possibilities for combination therapy

ABSTRACT

Abstract. The use of non-steroidal anti-inflammatory drugs has proved of great interest in the prevention and treatment of colorectal cancer, although their precise mechanisms of action remain unclear. Overexpression of cyclooxygenase-2 (COX-2) and subsequent prostaglandin production promote metastasis and have been shown to increase cell motility in vitro. Objective: We have aimed to elucidate whether specific inhibition of COX-2 with NS-398 (NS-398 is a selective inhibitor of COX-2) would be able to inhibit motility of colorectal cancer cells and whether this was modulated through epidermal growth factor receptor (EGFR) transactivation. Materials and Methods: A transwell filter assay was used to study cell motility. Expression of COX-2, EGFR phosphorylation and prostaglandin E₂ (PGE₂) receptors were assessed by Western blot analysis and reverse transcriptase-polymerase chain reaction. PGE₂ concentrations after NS-398 treatment were estimated by enzyme immunoassay. Results: Treatment with NS-398 significantly reduced PGE₂ levels and reduced cell migration in the HT29 and HCA7 colorectal carcinoma cell lines and this effect was rescued by addition of PGE₂. Furthermore, specific inhibition of COX-2 with NS-398 reduced EGFR phosphorylation in colorectal cancer cells. Direct inhibition of EGFR activity with AG1478 reduced PGE₂-stimulated motility, clearly demonstrating that PGE₂ acts via the EGFR-signalling pathway. The novel combination of NS-398 and AG1478 dramatically reduced migration of colorectal cancer cells. Conclusion: The data presented indicate that the use of NS-398 in chemoprevention and adjuvant therapy for colorectal cancer may work in part, through the inhibition of cell motility. Furthermore, our data suggest that the combined use of non-steroidal anti-inflammatory drugs with EGFR antagonists could be explored further for future use in the clinic.