Dual blockade of epidermal growth factor receptor (EGFR) and cyclooxygenase 2 (COX 2) may be dependent upon the EGFR mutational status in non-small cell lung cancer (NSCLC) cell lines

Abstract

7170 Background: Recent data has shown that the benefit of EGFR TKIs (tyrosine kinase inhibitors) in NSCLC is in patients with tumors that have EGFR mutations and /or gene amplification. Even among these patients, the median survival with EGFR TKIs is only 22 months. Pre-clinical data has shown that dual blockade of EGFR and COX 2 pathways may be beneficial. A recent clinical trial conducted at our center suggested that this combination primarily impacted NSCLC tumors that have the EGFR biomarkers. We therefore hypothesized that the EGFR biomarker status determines the outcome of dual blockade of these pathways in NSCLC. Methods: Three different cell lines with varying biomarker status and sensitivities to EGFR TKIs were used- H3255 (L858R; gene amplified), H1650 (del E746-A750; gene amplified), H1781 (wild type). Cells were treated with erlotinib, EGFR TKI- 10nM-100nM or celecoxib, COX 2 inhibitor- 5 μM and with the combination of two drugs. Cell survival was determined by a standard MTT assay and apoptosis was measured by ELISA method. Western blot analysis was conducted to assess COX 2, EGFR and pAkt levels. Results: Celecoxib by itself had no effects on any of the cell lines. Erlotinib showed a concentration dependent growth inhibition of both H3255 (IC50–41.72nM; surviving fraction at 50nM was 52%) and H1650 (IC50 > 100nM; Surviving fraction at 50nM was 70%) but had no effect on H1781. Celecoxib added to erlotinib significantly enhanced the growth inhibition of H3255 (p = 0.001) and H1650 (p = 0.014) as well as apoptosis (H3255- p = 0.016; H1650- p = 0.011) at all concentrations of erlotinib but had no effect in H1781 cells. In western Blot analysis the combination significantly reduced levels of COX-2, EGFR and pAkt compared to baseline and either agent alone in H3255 cells. Conclusions: The addition of celecoxib to erlotinib has a differential effect in NSCLC cell lines based on their EGFR biomarker status. This beneficial effect of celecoxib addition may be through improved inhibition of each pathway. [Table: see text]