Introduction: In this study, the radiation-enhancing effects of combined treatment with nimotuzumab, a humanized EGFR-blocking antibody, and celecoxib, a COX-2 selective inhibitor, in human nasopharyngeal carcinoma (NPC) cells were investigated. 
Materials and methods: 3-(4,5-Dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide and clonogenic survival assays were done to evaluate the combined cytotoxic and radiosensitizing effects of nimotuzumab or celecoxib or the combination on CNE1 and CNE2 cells. Western blot analysis was performed to identify the effect of nimotuzumab and/or celecoxib with or without irradiation on the cytoplasmic and nuclear EGFR signaling pathways in CNE2 cells. 
Results: Our results demonstrated that concurrent administration of nimotuzumab and celecoxib cooperatively enhanced the cytotoxicity and radiosensitivity of CNE2 cells but not CNE1 cells. The combination of both drugs with or without irradiation also cooperatively inhibited cytoplasmic and nuclear EGFR signaling pathways in CNE2 cells. 
Conclusion: Our results suggest a promising approach for the treatment of poorly differentiated NPC.
Keywords: celecoxib, cyclooxygenase-2, epidermal growth factor receptor, nasopharyngeal carcinoma, nimotuzumab, radiosensitivity