MicroRNA-21 links epithelial-to-mesenchymal transition and inflammatory signals to confer resistance to neoadjuvant trastuzumab and chemotherapy in HER2-positive breast cancer patients

// Leticia De Mattos-Arruda 1, * , Giulia Bottai 2, * , Paolo G. Nuciforo 3 , Luca Di Tommaso 4 , Elisa Giovannetti 5, 6 , Vicente Peg 7 , Agnese Losurdo 8 , Jose Perez-Garcia 1 , Giovanna Masci 8 , Fabio Corsi 9 , Javier Cortes 1, 10 , Joan Seoane 1, 11 , George A. Calin 12, 13 , Libero Santarpia 2 1 Vall d’Hebron Institute of Oncology, Vall d’Hebron University Hospital, Universitat Autonoma de Barcelona, Barcelona, Spain 2 Oncology Experimental Therapeutics Unit, IRCCS Humanitas Clinical and Research Institute, Rozzano, Milan, Italy 3 Molecular Oncology Group, Vall d’Hebron Institute of Oncology, Barcelona, Spain 4 Division of Pathology, IRCCS Humanitas Clinical and Research Institute, Rozzano, Milan, Italy, University of Milan, Milan, Italy 5 Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands 6 Cancer Pharmacology Laboratory, AIRC Start-Up Unit, University of Pisa, Pisa, Italy 7 Pathology Department, Vall d’Hebron University Hospital, Universitat Autonoma de Barcelona, Barcelona, Spain 8 Division of Oncology and Hematology, IRCCS Humanitas Clinical and Research Institute, Rozzano, Milan, Italy 9 Deparment of Clinical and Biomedical Sciences “Luigi Sacco”, University of Milan, Milan, Italy 10 Ramon y Cajal University Hospital, Madrid, Spain 11 Institucio Catalana de Recerca i Estudis Avancats (ICREA), Barcelona, Spain 12 Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA 13 Center for RNA Interference and Non-Coding RNAs, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA * These authors have contributed equally to this work Correspondence to: Libero Santarpia, e-mail: libero.santarpia@humanitasresearch.it or e-mail: liberosantarpia@yahoo.it Keywords: HER2-overexpressing breast cancers, microRNA-21, resistance to neoadjuvant trastuzumab-chemotherapy, epithelial-to-mesenchymal transition, tumor-associated immune response Received: June 25, 2015      Accepted: September 25, 2015      Published: October 07, 2015 ABSTRACT Patients with primary HER2-positive breast cancer benefit from HER2-targeted therapies. Nevertheless, a significant proportion of these patients die of disease progression due to mechanisms of drug resistance. MicroRNAs (miRNAs) are emerging as critical core regulators of drug resistance that act by modulating the epithelial-to-mesenchymal transition (EMT) and cancer-related immune responses. In this study, we investigated the association between the expression of a specific subset of 14 miRNAs involved in EMT processes and immune functions and the response to neoadjuvant trastuzumab and chemotherapy in 52 patients with HER2-overexpressing breast tumors. The expression of only a single miRNA, miR-21 , was significantly associated with residual disease ( p = 0.030) and increased after trastuzumab-chemotherapy ( p = 0.012). A target prediction analysis coupled with in vitro and in vivo validations revealed that miR-21 levels inversely correlated with the expression of PTEN (rs = −0.502; p = 0.005) and PDCD4 (rs = −0.426; p = 0.019), which differentially influenced the drug sensitivity of HER2-positive breast cancer cells. However, PTEN expression was only marginally associated with residual disease. We further demonstrated that miR-21 was able to affect the response to both trastuzumab and chemotherapy, triggering an IL-6/STAT3/NF-κB-mediated signaling loop and activating the PI3K pathway. Our findings support the ability of miR-21 signaling to sustain EMT and shape the tumor immune microenvironment in HER2-positive breast cancer. Collectively, these data provide a rationale for using miR-21 expression as a biomarker to select trastuzumab-chemotherapy-resistant HER2-positive breast cancer patients who may benefit from treatments containing PI3K inhibitors or immunomodulatory drugs.