Inhibition of heat shock protein (Hsp) 27 potentiates the suppressive effect of Hsp90 inhibitors in targeting breast cancer stem-like cells

► Hsp90α overexpressed in ALDH + breast cancer stem-like cells (BCSCs). ► Hsp90 inhibitors induced Hsp27 expression in breast cancer cells. ► HSP inhibitors sensitized ALDH + BCSCs toward the suppression of geldanamycin. ► Knockdown of Hsp27 sensitized ALDH + BCSCs toward the suppression of geldanamycin. ► Combination of Hsp90 and HSP inhibitors is suggested as future breast cancer therapy.