SRT1720, a potential sensitizer for radiotherapy and cytotoxicity effects of NVB-BEZ235 in metastatic breast cancer cells

BACKGROUND: Chemo-radio therapy (CRT) resistance is a main barrier in treating the triple negative breast cancer (TNBC). The success of conventional treatment may be ameliorated by elevating the responsiveness of the cancer cells to CRT. NVP-BEZ235 as a PI3K/AKT/mTOR dual inhibitor has been shown promising results in treating breast cancer cells. However, potential radiation-sensitizing effect of NVP-BEZ235 in TNBC remained unclear. In addition, SIRT-1 activation state and environmental cytokine were identified as being responsible for cancer cells responses to CRT. Herein, we investigate the role of interleukin 6 (IL-6) as a tumor environmental cytokine and SIRT1 in the effectiveness of NVP-BEZ235 plus radiotherapy. MATERIAL AND METHODS: TNBC cells were pre-treated with/without IL-6 and were exposed to single and combination of SRT1720 (SIRT1 activator)/EX-527 (SIRT1 inhibitor) and/or NVP-BEZ235 and/or gamma radiation. The effect of our treatments on cellular growth was determined by MTT and the cellular death and CSCs percentage were determined by Flow cytometry. Senescence detection kit was used to assay the effect of our treatments on cellular senescence induction. RESULTS: Activation of SIRT1 via SRT1720 increased the efficacy of CRT in TNBC cells, especially when IL-6 exists in tumor microenvironment. Additionally, IL-6 pre-treatment followed by exposure to SRT1720 and NVP-BEZ235 significantly increased sensitivity of the cancer stem cells to radiation (p < 0.05). CONCLUSION: Our result shows that combination of NVP-BEZ235 and SRT1720 may effectively improve late stage breast cancer cells therapeutics approach. Activation of SIRT1 and STAT3 in resistance breast cancer cells improves the in-vitro therapeutic efficacy of CRT. Copyright © 2018 Elsevier GmbH. All rights reserved.