Inhibition of Autophagy Increases Proliferation Inhibition and Apoptosis Induced by the PI3K/mTOR Inhibitor NVP-BEZ235 in Breast Cancer Cells.

ABSTRACT

BACKGROUND: The phosphoinositide 3 kinase (PI3K)/AKT/mammalian target of the rapamycin (mTOR) pathway is a complicated intracellular pathway which leads to cell growth and tumor proliferation and plays a significant role in breast cancer. Multiple compounds targeting this pathway are being evaluated in clinical trials. NVP-BEZ235, a novel and orally available dual PI3K/mTOR inhibitor, showed great antitumor effect and provided a therapy strategy in breast cancer. METHODS: In this study, we detect the effect of NVP-BEZ235 on cell viability, apoptosis, and autophagy in a breast cancer cell line. We also test the effect of NVP-BEZ235 on the expression of PI3K/AKT/mTOR pathway proteins p-AKT, p-mTOR, and p-70S6K. RESULTS: The results showed that the PI3K/AKT/mTOR proteins p-AKT, p-mTOR, and p-70S6K were obviously suppressed by NVP-BEZ235. NVP-BEZ235 inhibited cell proliferation and induced apoptosis and autophagy in breast cancer cells. In combination with autophagy inhibitors or autophagy gene knockdown, enhanced growth inhibition and apoptosis was induced by NVP-BEZ235 in MCF-7 cells. CONCLUSIONS: This study provides a novel treatment strategy that PI3K/AKT/mTOR pathway inhibitors in combination with autophagy inhibitors lead to further apoptosis in breast cancer cells.