Deregulated expression of miR-29a-3p, miR-494-3p and miR-660-5p affects sensitivity to tyrosine kinase inhibitors in CML leukemic stem cells

// Simona Salati 1 , Valentina Salvestrini 2 , Chiara Carretta 1 , Elena Genovese 1 , Sebastiano Rontauroli 1 , Roberta Zini 1 , Chiara Rossi 1 , Samantha Ruberti 1 , Elisa Bianchi 1 , Greta Barbieri 1 , Antonio Curti 2 , Fausto Castagnetti 2 , Gabriele Gugliotta 2 , Gianantonio Rosti 2 , Micaela Bergamaschi 3 , Agostino Tafuri 4 , Enrico Tagliafico 5 , Roberto Lemoli 3 and Rossella Manfredini 1 1 Center for Regenerative Medicine, University of Modena and Reggio Emilia, Modena, Italy 2 Department of Experimental, Diagnostic and Specialty Medicine, Institute of Hematology “L. and A. Seragnoli”, University of Bologna, S.Orsola-Malpighi Hospital, Bologna, Italy 3 Department of Internal Medicine (DiMI), Clinic of Hematology, University of Genoa, IRCCS Azienda Ospedaliera Universitaria S. Martino-IST, Genoa, Italy 4 Department of Clinical and Molecular Medicine, Clinic of Hematology, University “La Sapienza”, Rome, Italy 5 Center for Genome Research, University of Modena and Reggio Emilia, Modena, Italy Correspondence to: Rossella Manfredini, email: rossella.manfredini@unimore.it Simona Salati, email: simona.salati@unimore.it Keywords: chronic myeloid leukemia, leukemic stem cells, tyrosine kinase inhibitors, microRNAs, apoptosis Received: January 10, 2017      Accepted: April 24, 2017      Published: May 08, 2017 ABSTRACT The development of Imatinib mesylate (IM), which targets the oncogenic BCR-ABL fusion protein, has greatly improved the outcome of Chronic Myeloid Leukemia (CML) patients. However, BCR-ABL–positive progenitors can be detected in CML patients in complete cytogenetic response. Several evidence suggests that CML stem cells are intrinsically resistant to Tyrosine Kinase Inhibitors (TKI), and therefore they represent the most likely candidate responsible for disease relapse. In this work, we investigated the microRNA (miRNA) expression profile of different subpopulations of CML Leukemic Stem Cells (LSCs): Lin-CD34+CD38- and Lin-CD34-CD38- cells. These cell fractions have been previously shown to be endowed with TKI intrinsic resistance. Our analysis identified 33 common deregulated miRNAs in CML LSCs. Among those, 8 miRNAs were deregulated in CML independently from BCR-ABL kinase activity and therefore are likely to be involved in the BCR-ABL-independent resistance to TKI that characterizes CML LSCs. In particular, the up-regulation of miR-29a-3p and miR-660-5p observed in CML LSCs, led to the down-regulation of their respective targets TET2 and EPAS1 and conferred TKI-resistance to CML LSCs in vitro . On the other hand, miR-494-3p down-regulation in CML LSCs, leading to c-MYC up-regulation, was able to decrease TKI-induced apoptosis. These results demonstrate that aberrant miRNA expression in CML LSCs could contribute to the intrinsic TKI-resistance observed in these cell populations, and support the development of novel therapies aimed at targeting aberrantly regulated miRNAs or their targets in order to effectively eradicate CML LSCs.