Synergistic effects of combined treatment with simvastatin and exemestane on MCF-7 human breast cancer cells.

Abstract

Breast cancer is associated with high levels of incidence, morbidity and mortality; therefore, the identification of effective chemopreventive strategies is crucial. It is important for clinicians to be able to identify the populations at risk who would benefit from chemoprevention, and the interventions that are effective and safe. The aim of the present study was to investigate the combined effects of simvastatin and exemestane on MCF-7 human breast cancer cells. The anti-proliferative effects of simvastatin and exemestane, alone and in combination, on the growth of MCF-7 human breast cancer cells were assessed by MTT assay. The synergism between the two drugs was determined in vitro using the combination index (CI) analysis. Cell cycle distribution and apoptosis were analyzed by flow cytometry, and alterations to the signaling pathway in MCF-7 cells were examined by immunoblotting following treatment with various regimens. The results of the MTT assay indicated that the combined treatment of simvastatin and exemestane significantly decreased the viability of MCF-7 estrogen receptor-positive (ER+) human breast cancer cells, as compared with those that were treated with the individual drugs (CI<1). In addition, coadministration of exemestane and simvastatin was shown to result in marked inhibition of tumor cell proliferation, significant cell cycle arrest at G0/G1 phase and induction of apoptosis, as compared with that of the control and individual drug-treated cells. Furthermore, the results of the present study indicated that these synergistic effects may be associated with the B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X protein apoptotic pathway and the mitogen-activated protein kinase/mammalian target of rapamycin/p70S6 kinase growth pathway. The combination of exemestane and simvastatin generated synergistic effects on MCF-7 ER+ breast cancer cells, indicating that the combination of these drugs may be a potential therapeutic strategy for the treatment of hormone-dependent breast cancer. The combination of the two inhibitors markedly increased the efficacy, as compared with the single-agent treatment, suggesting that combination treatment could become a highly effective approach for breast cancer. The results of the present study suggested that this combination of drugs has therapeutic potential, and requires further mechanistic and biomarker investigations in clinical trials.