Abstract:

Objective: To investigate the effect of celecoxib combined with taxol on the apoptosis of breast cancer MCF-7 cells,and to explore the possible mechanisms of the synergistic effect of Cox-2 inhibitors combined with chemotherapy drugs. Methods: The MCF-7 cells were divided into blank control group(treated with normal medium),celecoxib group(treated with different concentrations of celecoxib),taxol group(treated with different concentrations of taxol),and celecoxib combined with taxol group(combination group,treated with celecoxib combined with taxol).Hoechst 33258 staining was used to observe the morphology of apoptotic cells;MTT assay was adopted to detect the survival rate of MCF-7 cells;flow cytometry with Annexin Ⅴ FITC/PI double staining was used to detect the distribution of cell cycle and the apoptotic rate of MCF-7 cells;Western blotting method was taken to detect the protein expressions of b-cell lymphoma-2(bcl-2),extracellular regulated protein kinase2(ERK2) and phosphorylase-extracellular regulated protein kinase(p-ERK) in the MCF-7 cells. Results: The Hoechst 33258 staining results showed that compared with blank control group,the number of apoptotic cells in both celecoxib group and taxol group were increased,and the number of apoptotic cells in combination group was the highest,and the number of apoptotic cells was increased with the increasing of celecoxib concentration.The MTT assay results showed that the survival rates of MCF-7 cells in celecoxib group and taxol group were decreased with the prolongation of treatment time;during the same period,the MCF-7 cells treated with the combination of 50 mg·L^-1 celecoxib and 30 μg·L^-1 taxol had a much lower survival rate compared with celecoxib or taxol used alone(P<0.05).The flow cytometry results showed that the MCF-7 cells in celecoxib group were arrested at G₀/G₁ phase,and the MCF-7 cells in taxol group were arrested at G₂/M phase;compared with blank control group,the distribution of cell cycle in combination group changed dramatically,such as the ratio of MCF-7 cells arrested at G₀/G₁ phase and G₂/M phase were increased,and the ratio of MCF-7 cells arrested at in S phase was decreased.The Annexin Ⅴ FITC/PI double staining results showed that 6 h after drug treatment,the apoptotic rates of MCF-7 cells in celecoxib group and taxol group were higher than that in blank control group(P<0.05),and the apototic rate of cells in combination group was the highest(P<0.05).The Western blotting results showed that compared with blank control group,the expression levels of bcl-2 and p-ERK proteins in MCF-7 cells in celecoxib group, taxol group and combination group were all decreased,especially in combination group;but there were no significant differences in the ERK2 protein expression levels between various groups(P>0.05). Conclusion: Celecoxib and taxol show a synergistic effect on inducing the apoptosis of MCF-7 cells and its mechanism may be related to the down-regulation of the expressions of bcl-2 and p-ERK proteins.

Key words: celecoxib, taxol, breast carcinoma, MCF-7 cell, b-cell lymphoma-2