Targeting Triple Negative Breast Cancer Stem Cells by Heat Shock Protein 70 Inhibitors.

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Simple SummaryTriple negative breast cancer (TNBC) has been a leading cause of cancer deaths among women and limited treatment options are currently available. Consequently, developing the promising therapy for TNBC remains an unmet medical need. The aim of this study was to assess the effect of Hsp70 inhibitors on breast cancer stem cells (BCSCs) in TNBC cells. The present study demonstrated the potent in vitro and in vivo anti-BCSCs activity of two Hsp70 inhibitors, compound 1 and 6, in TNBC cells. Our findings suggest that targeting Hsp70 could be an attractive strategy for eliminating BCSCs populations in TNBC.Triple negative breast cancer (TNBC) is considered the most aggressive breast cancer with high relapse rates and poor prognosis. Although great advances in the development of cancer therapy have been witnessed over the past decade, the treatment options for TNBC remain limited. In this study, we investigated the effect and potential underlying mechanism of the Hsp70 inhibitors, compound 1 and compound 6, on breast cancer stem cells (BCSCs) in TNBC cells. Our results showed that compound 1 and 6 exhibited potent tumor suppressive effects on cell viability and proliferation, and effectively inhibited BCSC expansion in TNBC cells. Reminiscent with the effect of Hsp70 inhibitors, Hsp70 knockdown effectively suppressed mammosphere formation and the expressions of BCSCs surface markers. Mechanistically, evidence showed that the Hsp70 inhibitors inhibited BCSCs by down-regulating β-catenin in TNBC cells. Moreover, we used the Hsp70 inhibitors treated TNBC cells and a stable Hsp70 knockdown clone of MDA-MB-231 cells to demonstrate the in vivo efficacy of Hsp70 inhibition in suppressing tumorigenesis and xenograft tumor growth. Together, these findings suggest the potential role of Hsp70 as a target for TNBC therapy and foster new therapeutic strategies to eliminate BCSCs by targeting Hsp70.