ABSTRACT
<p><b>OBJECTIVE</b>To investigate the radiosensitizing effect of nitric oxide (NO) combined with radiation on esophageal cancer cell line TE-1.</p><p><b>METHODS</b>Methyl thiazolyl tetrazolium (MTT) assay was used to assess the effects of NO and radiation on TE-1 cells regarding inhibition of cell proliferation. Flow cytometry was used to examine the effect of NO and radiation on cell apoptosis and cycle. Reverse transcription polymerase chine reaction and Western blot were used to evaluete the effect of NO on mRNA and protein expression of manganese superoxide dismutase (MnSOD).</p><p><b>RESULTS</b>NO inhibited the proliferation of TE-1 cells while significantly enhancing their radiosensitivity. The application of NO combined with radiation significantly increased the apoptosis rate and G2/M phase proportion of TE-1 cells, with substantial decreases in the MnSOD mRNA and protein expression levels.</p><p><b>CONCLUSIONS</b>NO reduces the MnSOD mRNA and protein expression levels by affecting TE-1 cell cycle, further inhibiting the apoptosis of esophageal cancer cells and enhancing the killing effect of radiation on esophageal cancer cells.</p>