Combined effect of curcumin and 5-FU on apoptosis and COX-2 expression in human colon carcinoma cell line HT-29

Aim:To observe whether curcumin could enhance the anti-proliferation effect of fluorouracil(5-FU) and to investigate the possible link between this combinative effect and cell apoptosis and COX-2 expression.Methods:The inhibitory effects on HT-29 after the treatment with curcumin or 5-FU alone or in combination were investigated using MTT methods.Changes to apoptotic cell content in HT-29 cell were analyzed by the flow cytometry and fluorescence microscope.Inhibition on COX-2 expression after the treatment of curcumin and 5-FU in combination was also evaluated by Western Blot analysis.Results:Proliferation of HT-29 cells was significantly inhibited by curcumin and/or 5-FU in a concentration-dependent manner.The IC_(50) values of curcumin and 5-FU in HT-29 cells were 15.9±1.96 μmol/L and 17.3±1.85 μmol/L,respectively.When HT-29 cells were treated with curcumin and 5-FU in combination,the effect of synergistic inhibition on the growth was quantitatively demonstrated at even higher levels.After the cells were treated with curcumin or curcumin and 5-FU in combination for 24 h and/or 48 h,the apoptotic peak appeared by observation with the analysis of flow cytometry.However,the ratio of apoptotic cell after being treated with the two compounds in combination was lower than that after being treated with curcumin only.The same observation was found by the means of fluorescence microscope.In addition,the level of COX-2 protein expression was reduced nearly 4-fold after the use of the two agents in combination.Conclusion:In the case of colon cancer cell line such as HT-29,combined use of curcumin and 5-FU could synergistically inhibit the cell growth and the expression of COX-2 protein.