The effects of combined treatment with epidermal growth factor receptor-tyrosine kinase inhibitor and selective cyclooxygenase-2 inhibitor on lung cancer cells

Abstract

Introduction: To overcome the acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitors(EGFR-TKIs), various strategies have been explored in preclinical and clinical setting. Cyclooxygenase(COX)-2 inhibitors have been reported to suppress cell growth and to lead to apoptosis of various cancer cells by EGFR down-regulation. In the present study, we assessed whether the combination of celecoxib, a COX-2 inhibitor, and EGFR-TKIs could overcome the acquired resistance in lung cancer cells. Materials and Methods: The EGFR-mutated lung cancer cell lines(HCC827 and PC-9) and drug-resistant cell lines (HCC827/GR, HCC827/ER, PC-9/GR and PC-9/ER) were used. Celecoxib and COX-2 siRNA were used as COX-2 inhibitor. Reversible EGFR-TKIs, gefitinib and erlotinib, and EGFR siRNA were used as EGFR inhibitor. Western blotting was employed to investigate the expression of proteins involved with EGFR signaling. Results: Addition of celecoxib treatment enhances sensitivity to EGFR-TKIs in parental HCC827 and PC-9 cells harboring with EGFR activating mutation. Combined celecoxib and gefitinib treatment overcame gefitinib resistance via the inhibition of the phosphorylation of MET, EGFR and Akt in HCC827/GR cells. In HCC827/ER cells, combination treatment with erlotinib and celecoxib inhibited the expression of AXL, p-Akt and Erk. We evaluated the ability of combination treatment with gefitinib or erlotinib, and celecoxib to inhibit the proliferation of PC-9 cells with an EGFR T790M mutation. These combinations showed an additive growth inhibition in PC-9/GR cells and a synergistic growth inhibition in PC-9/ER cells through the suppression of EGFR and Akt activities. Conclusions: The combination of EGFR-TKIs and celecoxib may be a new strategy to overcome the acquired resistance to EGFR-TKIs in lung cancer.