By promoting cell differentiation, miR-100 sensitizes basal-like breast cancer stem cells to hormonal therapy

// Annalisa Petrelli 1,* , Rosachiara Carollo 2,* , Marilisa Cargnelutti 1 , Flora Iovino 2 , Maurizio Callari 3 , Daniela Cimino 4 , Matilde Todaro 2 , Laura Rosa Mangiapane 2 , Alessandro Giammona 2 , Adriana Cordova 2 , Filippo Montemurro 1 , Daniela Taverna 4 , Maria Grazia Daidone 3 , Giorgio Stassi 2,* and Silvia Giordano 1,* 1 University of Torino School of Medicine, Candiolo Cancer Institute-FPO, IRCCS, Str. Provinciale, Candiolo, Torino, Italy 2 Department of Surgical and Oncological Sciences, Cellular and Molecular Pathophysiology Laboratory, University of Palermo, Palermo, Italy 3 Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy 4 Molecular Biotechnology Center (MBC), Department of Oncological Sciences, Center for Molecular Systems Biology, Via Nizza, University of Torino, Torino, Italy * These authors contributed equally to this work Correspondence: Silvia Giordano, email: // Giorgio Stassi, email: // Annalisa Petrelli, email: // Keywords : Breast cancer, basal-like, differentiation, miR-100 Received : September 30, 2014 Accepted : December 10, 2014 Published : December 11, 2014 Abstract Basal-like breast cancer is an aggressive tumor subtype with a poor response to conventional therapies. Tumor formation and relapse are sustained by a cell subset of Breast Cancer Stem Cells (BrCSCs). Here we show that miR-100 inhibits maintenance and expansion of BrCSCs in basal-like cancer through Polo-like kinase1 (Plk1) down-regulation. Moreover, miR-100 favors BrCSC differentiation, converting a basal like phenotype into luminal. It induces the expression of a functional estrogen receptor (ER) and renders basal-like BrCSCs responsive to hormonal therapy. The key role played by miR-100 in breast cancer free-survival is confirmed by the analysis of a cohort of patients’ tumors, which shows that low expression of miR-100 is a negative prognostic factor and is associated with gene signatures of high grade undifferentiated tumors. Our findings indicate a new possible therapeutic strategy, which could make aggressive breast cancers responsive to standard treatments.