Radiosensitizing Effect of Nimesulide on Breast Cancer Cells and Corresponding Mechanisms

OBJECTIVE To investigate the effect of nimesulide in enhancing the radiosensitivity of MCF-7 cells and elucidate its mechanisms.METHODS The MCF-7 cells were cultured in vitro with nimesulide.The proliferation inhibition effect of nimesulide on MCF-7 was measured by MTT assay.MCF-7 cells were treated with different radiation doses alone or radiation followed by nimesulide.Colony forming assay was used for survival fraction analysis.Cell cycle was analyzed by flow cytometry.Influence of nimesulide on related protein Bax,Bcl-2 expression levels was investigated by Western blotting.The DNA damage and repair were detected by single cell gel electrophoresis assay.RESULTS The inhibition of Nimesulide on MCF-7 cells was time-dependent and dose-dependent.Nimesulide had not significant cell cycle changes on MCF-7 cells.Western blotting showed that nimesulide had a down-regulation of apoptosis-related bcl-2 but not bax protein.The DNA damage induced by nimesulide was not obvious,but the DNA repair was delayed in MCF-7 cells treated with nimesulide before radiation.CONCLUSION Nimesulide can enhance the radiosensitivity of MCF-7 cells.The possible mechanism of radiosensitization of nimesulide was related to inhibition of DNA repair and down-regulation of bcl-2 expression.