STAT5 induces miR-21 expression in cutaneous T cell lymphoma

// Lise M. Lindahl 1 , Simon Fredholm 2 , Claudine Joseph 2 , Boye Schnack Nielsen 3 , Lars Jønson 4 , Andreas Willerslev-Olsen 2 , Maria Gluud 2 , Edda Blümel 2 , David L. Petersen 2 , Nina Sibbesen 2 , Tengpeng Hu 2 , Claudia Nastasi 2 , Thorbjørn Krejsgaard 2 , Ditte Jæhger 2 , Jenny L. Persson 5 , Nigel Mongan 6 , Mariusz A. Wasik 7 , Ivan V. Litvinov 8 , Denis Sasseville 9 , Sergei B. Koralov 10 , Charlotte M. Bonefeld 2 , Carsten Geisler 2 , Anders Woetmann 2 , Elisabeth Ralfkiaer 11 , Lars Iversen 1 , Niels Odum 2 1 Department of Dermatology, Aarhus University Hospital, Aarhus, Denmark 2 Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark 3 Bioneer A/S, Hørsholm, Denmark 4 Department of Molecular Medicine, Copenhagen University Hospital, Copenhagen, Denmark 5 Clinical Research Center, Lund University, Malmö, Sweden 6 School of Veterinary Medicine and Science, University of Nottingham, Loughborough, United Kingdom 7 Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA 8 Division of Dermatology, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada 9 Division of Dermatology, McGill University Health Centre, Montréal, Quebec, Canada 10 Department of Pathology, New York University School of Medicine, New York, NY, USA 11 Department of Pathology, Copenhagen University Hospital, Copenhagen, Denmark Correspondence to: Lars Iversen, email: lars.iversen@clin.au.dk Niels Odum, email: ndum@sund.ku.dk Keywords: miR-21, in situ, STAT5, IL-2, cutaneous T-cell lymphoma (CTCL) Received: March 23, 2016      Accepted: June 03, 2016      Published: June 18, 2016 ABSTRACT In cutaneous T cell lymphomas (CTCL), miR-21 is aberrantly expressed in skin and peripheral blood and displays anti-apoptotic properties in malignant T cells. It is, however, unclear exactly which cells express miR-21 and what mechanisms regulate miR-21. Here, we demonstrate miR-21 expression in situ in both malignant and reactive lymphocytes as well as stromal cells. qRT-PCR analysis of 47 patients with mycosis fungoides (MF) and Sezary Syndrome (SS) confirmed an increased miR-21 expression that correlated with progressive disease. In cultured malignant T cells miR-21 expression was inhibited by Tofacitinib (CP-690550), a clinical-grade JAK3 inhibitor. Chromatin immunoprecipitation (ChIP) analysis showed direct binding of STAT5 to the miR-21 promoter. Cytokine starvation ex vivo triggered a decrease in miR-21 expression, whereas IL-2 induced an increased miR-21 expression in primary SS T cells and cultured cytokine-dependent SS cells (SeAx). siRNA-mediated depletion of STAT5 inhibited constitutive- and IL-2-induced miR-21 expression in cytokine-independent and dependent T cell lines, respectively. IL-15 and IL-2 were more potent than IL-21 in inducing miR-21 expression in the cytokine-dependent T cells. In conclusion, we provide first evidence that miR-21 is expressed in situ in CTCL skin lesions, induced by IL-2 and IL-15 cytokines, and is regulated by STAT5 in malignant T cells. Thus, our data provide novel evidence for a pathological role of IL-2Rg cytokines in promoting expression of the oncogenic miR-21 in CTCL.