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Haematologica 2020 Volume 105(1):124-135
Myeloproliferative Neoplasms
Oncogenic D816V-KIT signaling in mast cells causes persistent IL-6 production
Araceli Tobío,1 Geethani Bandara,1 Denise A. Morris,1 Do-Kyun Kim,1 Michael P. O’Connell,2 Hirsh D. Komarow,1 Melody C. Carter,1 Daniel Smrz,1 Dean D. Metcalfe1* and Ana Olivera1*
1Mast Cell Biology Section and 2Genetics and Pathogenesis of Allergy Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
*DDM and AO contributed equally to this work as senior co-authors ABSTRACT
Persistent dysregulation of IL-6 production and signaling have been implicated in the pathology of various cancers. In systemic mastocy- tosis, increased serum levels of IL-6 associate with disease severity and progression, although the mechanisms involved are not well understood. Since systemic mastocytosis often associates with the presence in hematopoietic cells of a somatic gain-of-function variant in KIT, D816V- KIT, we examined its potential role in IL-6 upregulation. Bone marrow mononuclear cultures from patients with greater D816V allelic burden released increased amounts of IL-6 which correlated with the percentage of mast cells in the cultures. Intracellular IL-6 staining by flow cytometry and immunofluorescence was primarily associated with mast cells and suggest- ed a higher percentage of IL-6 positive mast cells in patients with higher D816V allelic burden. Furthermore, mast cell lines expressing D816V-KIT, but not those expressing normal KIT or other KIT variants, produced con- stitutively high IL-6 amounts at the message and protein levels. We further demonstrate that aberrant KIT activity and signaling are critical for the induction of IL-6 and involve STAT5 and PI3K pathways but not STAT3 or STAT4. Activation of STAT5A and STAT5B downstream of D816V-KIT was mediated by JAK2 but also by MEK/ERK1/2, which not only promoted STAT5 phosphorylation but also its long-term transcription. Our study thus supports a role for mast cells and D816V-KIT activity in IL-6 dysregulation in mastocytosis and provides insights into the intracellular mechanisms. The findings contribute to a better understanding of the physiopathology of mastocytosis and suggest the importance of therapeutic targeting of these pathways.
Introduction
Mastocytosis defines a group of heterogeneous disorders characterized by the accumulation of neoplastic/clonal mast cells in the skin, bone marrow (BM) and other organs.1 Mastocytosis is clinically subdivided into systemic (SM) and cuta- neous (CM) mastocytosis, both of which are comprised of several variants defined in accordance with histological and clinical parameters and organ involvement.1 Somatic variants in the receptor for stem cell factor (SCF), KIT, that render it con- stitutively active often associate with SM, particularly p.(D816V), a missense in the tyrosine kinase domain of KIT. D816V-KIT may be accompanied by variants in other genes that further contribute to the oncogenic expansion of mast cells.2-4
Interleukin-6 (IL-6) is a pleiotropic cytokine produced by several cell types includ- ing stromal, hematopoietic and tumor cells. In addition to its involvement in nor- mal inflammatory processes and host immune defense mechanisms, IL-6 may con- tribute to malignancy in a range of cancers including multiple myeloma, B-cell and non-B-cell leukemias and lymphomas,5,6 by modulating cellular development, growth, apoptosis, metastasis and/or cellular resistance to chemotherapy.6 As ele- vated IL-6 levels in the serum of patients with such malignancies have been associ-
Correspondence:
ANA OLIVERA
ana.olivera@nih.gov
Received: November 16, 2018. Accepted: April 2, 2019. Pre-published: April 4, 2019.
doi:10.3324/haematol.2018.212126
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/105/1/124
©2017 NIH (National Institutes of Health)
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