Clin Cancer Res
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It has been proposed that Cyclooxygenase (COX)-2 inhibitors may be able to enhance the effects of chemotherapeutic or radiation treatment; however, currently few studies have been reported that define the radiation-enhancing effect of COX-2 inhibitors. We conducted in vitro radiation survival experiments using rat intestinal epithelial cells which were stably transfected with COX-2 cDNA in the sense (RIE-S) and antisense (RIE-AS) orientations to investigate the potential radiosensitizing effect of the selective COX-2 inhibitor, NS-398. Apoptosis was measured using 7-aminoactinomycin-D with flow cytometry to investigate underlying mechanisms for the effect of NS-398 on radiosensitivity. ⋯ These in vitro and in vivo results suggest that selective COX-2 inhibitors enhance the effect of radiation on tumors that express COX-2 but not on COX-2-lacking tumors. This effect may be attributable to enhancement of radiation-induced apoptosis. Thus, selective COX-2 inhibitors may have potential as radiosensitizers for treatment of human cancers.