Suppressive role exerted by microRNA-29b-1-5p in triple negative breast cancer through SPIN1 regulation

// Rosa Drago-Ferrante 1 , Francesca Pentimalli 2 , Daniela Carlisi 3 , Anna De Blasio 1 , Christian Saliba 4 , Shawn Baldacchino 5 , James Degaetano 6 , Joseph Debono 7 , Gordon Caruana-Dingli 7 , Godfrey Grech 5 , Christian Scerri 6, 8 , Giovanni Tesoriere 9, 11 , Antonio Giordano 9, 10 , Renza Vento 1, 9, 11 , Riccardo Di Fiore 1, 11 1 Laboratory of Biochemistry, Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo, Polyclinic, Palermo, Italy 2 Oncology Research Center of Mercogliano (CROM), Istituto Nazionale per lo Studio e la Cura dei Tumori “Fondazione Giovanni Pascale”, IRCCS, Naples, Italy 3 Laboratory of Biochemistry, Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Polyclinic, Palermo, Italy 4 Centre of Molecular Medicine and Biobanking, University of Malta, Msida, MSD, Malta 5 Department of Pathology, Faculty of Medicine and Surgery, University of Malta, Msida, MSD, Malta 6 Department of Pathology, Mater Dei Hospital, Msida, MSD, Malta 7 Department of Surgery, Mater Dei Hospital, Msida, MSD, Malta 8 Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, MSD, Malta 9 Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA, USA 10 Department of Medicine, Surgery & Neuroscience, University of Siena, Siena, Italy 11 Associazione Siciliana per la Lotta contro i Tumori (ASLOT), Palermo, Italy Correspondence to: Antonio Giordano, email: giordano@temple.edu Renza Vento, email: renza.vento@unipa.it Riccardo Di Fiore, email: riccardo.difiore@unipa.it Keywords: MiR-29b-1, triple-negative breast cancer, cancer stem cells, SPIN1, Wnt/β-catenin and Akt signaling pathways Received: November 11, 2016     Accepted: February 18, 2017     Published: March 07, 2017 ABSTRACT MiR-29 family dysregulation occurs in various cancers including breast cancers. We investigated miR-29b-1 functional role in human triple negative breast cancer (TNBC) the most aggressive breast cancer subtype. We found that miR-29b-1-5p was downregulated in human TNBC tissues and cell lines. To assess whether miR-29b-1-5p correlated with TNBC regenerative potential, we evaluated cancer stem cell enrichment in our TNBC cell lines, and found that only MDA-MB-231 and BT-20 produced primary, secondary and tertiary mammospheres, which were progressively enriched in OCT4 , NANOG and SOX2 stemness genes. MiR-29b-1-5p expression inversely correlated with mammosphere stemness potential, and miR-29b-1 ectopic overexpression decreased TNBC cell growth, self-renewal, migration, invasiveness and paclitaxel resistance repressing WNT/βcatenin and AKT signaling pathways and stemness regulators. We identified SPINDLIN1 ( SPIN1 ) among predicted miR-29b-1-5p targets. Consistently, SPIN1 was overexpressed in most TNBC tissues and cell lines and negatively correlated with miR-29b-1-5p. Target site inhibition showed that SPIN1 seems to be directly controlled by miR-29b-1-5p. Silencing SPIN1 mirrored the effects triggered by miR-29b-1 overexpression, whereas SPIN1 rescue by SPIN1 miScript protector, determined the reversal of the molecular effects produced by the mimic-miR-29b-1-5p. Overall, we show that miR-29b-1 deregulation impacts on multiple oncogenic features of TNBC cells and their renewal potential, acting, at least partly, through SPIN1, and suggest that both these factors should be evaluated as new possible therapeutic targets against TNBC.