ABSTRACT
Objective To investigate the combined effect of exemestane and low-dose methotrexate on exemestane-resistant MCF-7 human breast cancer cells( MCF-7/EXE). Methods Antiproliferative effects of exemestane and low-dose of methotrexate, alone and in combination on growth of MCF-7/EXE cells were assessed by using the MTT assay. Synergistic interaction between the two drugs was evaluated in vitro by using the combination index ( CI) method. The cell cycle distribution was analyzed by flow cytometry in a half inhibitory concentration of exemestane and low-dose of methotrexate . The changes of apoptosis on MCF-7/EXE cells exposed to two drugs alone or in com-bination were observed by fluorescence microscope. The expression of Bcl-2,AKT,P-AKT and cyclooxygenase-2 was investigated by Western blot. Results MTT assays indicated that the combination treatment apparently decreased the viability of MCF-7/EXE cells compared to single drug treatment (CI<0. 9). In addition, the combination of exemestane and low-dose methotrexate exhibited a synergistic inhibition of cell proliferation, arrested the cell cycle in the S phase significantly and produced a stronger inhibitory effects on P-AKT, Bcl-2 and cyclooxygenase-2 ex-pression than control or individual drug treatment. Conclusion The combination of the two inhibitors significantly increases the response as compared to single agent treatment, suggesting that combination treatment which can re-verse the resistance of exemestane could be a more effective approach to breast cancer.
