Relationship between epidermal growth factor receptor (EGFR) mutation and serum cyclooxygenase-2 Level, and the synergistic effect of celecoxib and gefitinib on EGFR expression in non-small cell lung cancer cells.

Epidermal growth factor receptor (EGFR) mutations occur mostly in patients with lung adenocarcinoma; such patients are also more likely to express cyclooxygenase-2 (COX-2), indicating a possible relationship between EGFR mutation and COX-2. The COX-2 and EGFR pathways mutually enhance their procarcinogenic effects in different tumor types. Therefore, simultaneous EGFR and COX-2 inhibition may be a promising therapeutic approach for patients with lung adenocarcinoma. We obtained tissue and serum samples from patients with non-small cell lung cancer (NSCLC) to detect the relationship between EGFR mutation and serum COX-2 level. Subsequently, gefitinib was combined with celecoxib to investigate the efficacy of inhibition in vitro in two NSCLC cell lines: HCC827 (del E746-A750) and A549 (wild-type EGFR). The cells were treated with gefitinib or celecoxib alone or with gefitinib plus celecoxib. Cell proliferation and apoptosis were assessed and correlated with expression of COX-2 and phosphorylated (p)-EGFR. The EGFR mutation rate of the high-COX-2 patients was significantly higher than that in the low-COX-2 patients. Multivariate analysis showed that high COX-2 levels were independently associated with EGFR mutation. Celecoxib and gefitinib inhibited cell growth in both cell lines. At sufficiently high concentrations, celecoxib plus gefitinib significantly mutually enhanced their anti-proliferative and apoptotic effects in both cell lines. At low concentrations, the combination had no additional effects on A549 cells. There was increased down regulation of COX-2 and p-EGFR when both cell lines were treated with high-concentration celecoxib plus gefitinib compared to either agent alone. This study demonstrates that high serum COX-2 levels may indicate EGFR mutations and that the efficacy of combined celecoxib and gefitinib is significantly greater in NSCLC cells with EGFR mutations; at high concentrations, the combination is efficacious in wild-type NSCLC cells.