Radiosensitization of cyclooxygenase-2 selective inhibitor NS-398 in esophageal carcinoma cell and its mechanism

Objective Objective To study the influence of NS-398,a selective cyclooxygenase-2 inhibitor on the radiosensitivity of human esophageal carcinoma cell line EC9706 cell. Methods EC9706 cell, highly expressing COX-2, had been incubated with NS-398 at 10、20、50 and 100?μmol/L for 24?h or 48?h before irradiation ranging from 0 to 10?Gy. Cell survival was measured by a standard clonogenic assay after 8 days of incubation. Apoptotic percentage was measured by FCM and DNA fragmentation by agarose electrophronesis. Results The senstization enhancement ratios (ratio of D_q) in EC9706 cell were 1.11, 1.24, 1.40, 1.54 at 10, 20, 50, 100?μmol/L of NS-398 for 24?h pre-incubation and 1.11, 1.27, 1.58, 1.67 for 48?h pre-incubation, which showed a dose-dependant and time-dependant manner. FCM analysis revealed a higher sub-G_1 cell peak in NS-398 group after irradiation. Agarose electrophronesis showed a marked ladder. Radiation-induced apoptosis was enhanced by NS-398 (P0.05 or P0.001). Conclusions NS-398, a COX-2 inhibitor, can enhance the radiosensitivity of esophageal carcinoma cell. The mechanism may be associated with induced apoptosis of EC9706 cells.