Simultaneously Targeting Epidermal Growth Factor Receptor Tyrosine Kinase and Cyclooxygenase-2, an Efficient Approach to Inhibition of Squamous Cell Carcinoma of the Head and Neck

Abstract

Purpose: Epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (Cox-2) contribute to development of squamous cell carcinoma of the head and neck (SCCHN). Simultaneously blocking both EGFR and Cox-2–mediated pathways may be an efficient means of inhibiting cancer cell growth in SCCHN. Experimental Design: A combination of EGFR-selective tyrosine kinase inhibitors (TKIs) AG1478 or ZD1839 (Iressa or gefitinib) with a Cox-2 inhibitor (Cox-2I) celecoxib (Celebrex) was studied for its effects on cell growth, cell cycle progression, and apoptosis in SCCHN cell lines by cell growth assay, clonogenic assay, flow cytometric analysis, and terminal deoxynucleotidyl transferase-mediated nick end labeling assay. A potential effect of EGFR TKIs and Cox-2I on angiogenesis was examined by endothelial capillary tube formation assay. Primary and secondary targets of EGFR TKIs and Cox-2I were also examined using immunoblotting and immunoprecipitation after the combined treatment. Results: The combination of AG1478 or ZD1839 with celecoxib either additively or synergistically inhibited growth of the five SCCHN cell lines examined, significantly induced G₁ arrest and apoptosis, and suppressed capillary formation of endothelium. Furthermore, the combination showed strong reductions of p-EGFR, p-extracellular signal-regulated kinase 1/2, and p-Akt in SCCHN cells as compared with the single agents. Both AG1478 and ZD1839 inhibited expression of Cox-2 protein, whereas celecoxib mainly blocked the production of prostaglandin E₂. Conclusions: These results suggest that cell growth inhibition induced by a combination of EGFR TKIs and Cox-2I is mediated through simultaneously blocking EGFR and Cox-2 pathways. This combination holds a great potential for the treatment and/or prevention of SCCHN.