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Kaur A, Venkatesan A, Kandarpa M, Talpaz M, Raghavan M. Lysosomal degradation targets mutant calreticulin and the thrombopoietin receptor in myeloproliferative neoplasms. Blood Adv 2024; 8:3372-3387. [PMID: 38640435 PMCID: PMC11255115 DOI: 10.1182/bloodadvances.2023011432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 03/24/2024] [Accepted: 04/15/2024] [Indexed: 04/21/2024] Open
Abstract
ABSTRACT Somatic mutants of calreticulin (CRT) drive myeloproliferative neoplasms (MPNs) via binding to the thrombopoietin receptor (MPL) and aberrant activation of the JAK/STAT pathway. Compared with healthy donors, platelets from mutant CRT-expressing patients with MPN display low cell surface MPL. Additionally, coexpression of MPL with an MPN-linked CRT mutant (CRTDel52) reduces cell surface MPL, suggesting that CRTDel52 may induce MPL degradation. We show that lysosomal degradation is relevant to the turnover of CRTDel52 and MPL. Furthermore, CRTDel52 increases the lysosomal localization and degradation of MPL. Mammalian target of rapamycin (mTOR) inhibitors reduce cellular CRTDel52 and MPL, secreted CRTDel52 levels, and impair CRTDel52-mediated cell proliferation. mTOR inhibition also reduces colony formation and differentiation of CD34+ cells from patients with MPN but not from healthy donors. Together, these findings indicate that low-surface MPL is a biomarker of mutant CRT-mediated MPN and that induced degradation of CRTDel52 and MPL is an avenue for therapeutic intervention.
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Affiliation(s)
- Amanpreet Kaur
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI
| | - Arunkumar Venkatesan
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI
| | - Malathi Kandarpa
- Division of Hematology/Oncology, Department of Internal Medicine, University of Michigan Rogel Cancer Center, Ann Arbor, MI
| | - Moshe Talpaz
- Division of Hematology/Oncology, Department of Internal Medicine, University of Michigan Rogel Cancer Center, Ann Arbor, MI
| | - Malini Raghavan
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI
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2
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Papadopoulos N, Pristavec A, Nédélec A, Levy G, Staerk J, Constantinescu SN. Modulation of human thrombopoietin receptor conformations uncouples JAK2 V617F-driven activation from cytokine-induced stimulation. Blood 2023; 142:1818-1830. [PMID: 37616564 DOI: 10.1182/blood.2022019580] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 07/25/2023] [Accepted: 07/27/2023] [Indexed: 08/26/2023] Open
Abstract
The thrombopoietin receptor (TpoR) plays a central role in myeloproliferative neoplasms (MPNs). Mutations in JAK2, calreticulin, or TpoR itself drive the constitutive activation of TpoR and uncontrolled proliferation and differentiation of hematopoietic stem cells and progenitors. The JAK2 V617F mutation is responsible for most MPNs, and all driver mutants induce pathologic TpoR activation. Existing therapeutic strategies have focused on JAK2 kinase inhibitors that are unable to differentiate between the mutated MPN clone and healthy cells. Surprisingly, the targeting of TpoR itself has remained poorly explored despite its central role in pathology. Here, we performed a comprehensive characterization of human TpoR activation under physiological and pathological conditions, focusing on the JAK2 V617F mutant. Using a system of controlled dimerization of the transmembrane and cytosolic domains of TpoR, we discovered that human TpoR (hTpoR) adopts different dimeric conformations upon Tpo-induced vs JAK2 V617F-mediated activation. We identified the amino acids and specific dimeric conformation of hTpoR responsible for activation in complex with JAK2 V617F and confirmed our findings in the full-length receptor context in hematopoietic cell lines and primary bone marrow cells. Remarkably, we found that the modulation of hTpoR conformations by point mutations allowed for specific inhibition of JAK2 V617F-driven activation without affecting Tpo-induced signaling. Our results demonstrate that modulation of the hTpoR conformation is a viable therapeutic strategy for JAK2 V617F-positive MPNs and set the path for novel drug development by identifying precise residues of hTpoR involved in JAK2 V617F-specific activation.
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Affiliation(s)
- Nicolas Papadopoulos
- de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
- Ludwig Institute for Cancer Research, Brussels, Belgium
- Walloon Excellence in Life Sciences and Biotechnology Department, Walloon Excellence Research Institute, Wavre, Belgium
| | - Ajda Pristavec
- de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Audrey Nédélec
- de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
- Ludwig Institute for Cancer Research, Brussels, Belgium
- Walloon Excellence in Life Sciences and Biotechnology Department, Walloon Excellence Research Institute, Wavre, Belgium
| | - Gabriel Levy
- de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
- Ludwig Institute for Cancer Research, Brussels, Belgium
- Walloon Excellence in Life Sciences and Biotechnology Department, Walloon Excellence Research Institute, Wavre, Belgium
| | - Judith Staerk
- de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
- Ludwig Institute for Cancer Research, Brussels, Belgium
- Centre for Molecular Medicine Norway, Nordic European Molecular Biology Laboratory Partnership, University of Oslo, Oslo, Norway
| | - Stefan N Constantinescu
- de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
- Ludwig Institute for Cancer Research, Brussels, Belgium
- Walloon Excellence in Life Sciences and Biotechnology Department, Walloon Excellence Research Institute, Wavre, Belgium
- Nuffield Department of Medicine, Ludwig Institute for Cancer Research, Oxford University, Oxford, United Kingdom
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3
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Yang V, Kragstrup TW, McMaster C, Reid P, Singh N, Haysen SR, Robinson PC, Liew DFL. Managing Cardiovascular and Cancer Risk Associated with JAK Inhibitors. Drug Saf 2023; 46:1049-1071. [PMID: 37490213 PMCID: PMC10632271 DOI: 10.1007/s40264-023-01333-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2023] [Indexed: 07/26/2023]
Abstract
Janus kinase inhibitors (JAKi) have enormous appeal as immune-modulating therapies across many chronic inflammatory diseases, but recently this promise has been overshadowed by questions regarding associated cardiovascular and cancer risk emerging from the ORAL Surveillance phase 3b/4 post-marketing requirement randomized controlled trial. In that study of patients with rheumatoid arthritis with existing cardiovascular risk, tofacitinib, the first JAKi registered for chronic inflammatory disease, failed to meet non-inferiority thresholds when compared with tumor necrosis factor inhibitors for both incident major adverse cardiovascular events and incident cancer. While this result was unexpected by many, subsequently published observational data have also supported this finding. Notably, however, such a risk has largely not yet been demonstrated in patients outside the specific clinical situation examined in the trial, even in the face of many studies examining this. Nevertheless, this signal has practically re-aligned approaches to both tofacitinib and other JAKi to varying extents, in other patient populations and contexts: within rheumatoid arthritis, but also in psoriatic arthritis, axial spondyloarthritis, inflammatory bowel disease, atopic dermatitis, and beyond. Application to individual patients can be more challenging but remains important to harness the substantive potential of JAKi to the maximum extent safely possible. This review not only explores the evolution of the regulatory response to the signal, its informing data, biological plausibility, and its impact on guidelines, but also the many factors that clinicians must consider in navigating cardiovascular and cancer risk for their patients considering JAKi as immune-modulating therapy.
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Affiliation(s)
- Victor Yang
- Department of Rheumatology, Level 1, North Wing, Heidelberg Repatriation Hospital, Austin Health, 300 Waterdale Road, PO Box 5444, Heidelberg West, VIC, 3081, Australia
| | - Tue W Kragstrup
- Department of Rheumatology, Aarhus University Hospital, Aarhus, Denmark
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Sector for Rheumatology, Diagnostic Center, Silkeborg Regional Hospital, Silkeborg, Denmark
| | - Christopher McMaster
- Department of Rheumatology, Level 1, North Wing, Heidelberg Repatriation Hospital, Austin Health, 300 Waterdale Road, PO Box 5444, Heidelberg West, VIC, 3081, Australia
- Department of Clinical Pharmacology and Therapeutics, Austin Health, Melbourne, VIC, Australia
- Centre for Digital Transformation of Health, University of Melbourne, Melbourne, VIC, Australia
| | - Pankti Reid
- Division of Rheumatology and Committee on Clinical Pharmacology and Pharmacogenomics, Department of Medicine, University of Chicago Biological Sciences Division, Chicago, IL, USA
| | - Namrata Singh
- Division of Rheumatology, Department of Medicine, University of Washington, Seattle, WA, USA
| | - Stine R Haysen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Philip C Robinson
- Faculty of Medicine, University of Queensland, Brisbane, QLD, Australia
- Royal Brisbane and Women's Hospital, Metro North Hospital and Health Service, Herston, QLD, Australia
| | - David F L Liew
- Department of Rheumatology, Level 1, North Wing, Heidelberg Repatriation Hospital, Austin Health, 300 Waterdale Road, PO Box 5444, Heidelberg West, VIC, 3081, Australia.
- Department of Clinical Pharmacology and Therapeutics, Austin Health, Melbourne, VIC, Australia.
- Department of Medicine, University of Melbourne, Melbourne, VIC, Australia.
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4
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Willekens C, Laplane L, Dagher T, Benlabiod C, Papadopoulos N, Lacout C, Rameau P, Catelain C, Alfaro A, Edmond V, Signolle N, Marchand V, Droin N, Hoogenboezem R, Schneider RK, Penson A, Abdel-Wahab O, Giraudier S, Pasquier F, Marty C, Plo I, Villeval JL, Constantinescu SN, Porteu F, Vainchenker W, Solary E. SRSF2-P95H decreases JAK/STAT signaling in hematopoietic cells and delays myelofibrosis development in mice. Leukemia 2023:10.1038/s41375-023-01878-0. [PMID: 37100881 DOI: 10.1038/s41375-023-01878-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 03/10/2023] [Accepted: 03/15/2023] [Indexed: 04/28/2023]
Abstract
Heterozygous mutation targeting proline 95 in Serine/Arginine-rich Splicing Factor 2 (SRSF2) is associated with V617F mutation in Janus Activated Kinase 2 (JAK2) in some myeloproliferative neoplasms (MPNs), most commonly primary myelofibrosis. To explore the interaction of Srsf2P95H with Jak2V617F, we generated Cre-inducible knock-in mice expressing these mutants under control of the stem cell leukemia (Scl) gene promoter. In transplantation experiments, Srsf2P95H unexpectedly delayed myelofibrosis induced by Jak2V617F and decreased TGFβ1 serum level. Srsf2P95H reduced the competitiveness of transplanted Jak2V617F hematopoietic stem cells while preventing their exhaustion. RNA sequencing of sorted megakaryocytes identified an increased number of splicing events when the two mutations were combined. Focusing on JAK/STAT pathway, Jak2 exon 14 skipping was promoted by Srsf2P95H, an event detected in patients with JAK2V617F and SRSF2P95 co-mutation. The skipping event generates a truncated inactive JAK2 protein. Accordingly, Srsf2P95H delays myelofibrosis induced by the thrombopoietin receptor agonist Romiplostim in Jak2 wild-type animals. These results unveil JAK2 exon 14 skipping promotion as a strategy to reduce JAK/STAT signaling in pathological conditions.
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Affiliation(s)
- Christophe Willekens
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
- Département d'hématologie, Gustave Roussy Cancer Campus, Villejuif, France
| | - Lucie Laplane
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Institut d'Histoire et Philosophie des Sciences et des Techniques, Université Paris I Panthéon-Sorbonne, Paris, France
| | - Tracy Dagher
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
| | - Camelia Benlabiod
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
- Institut d'Histoire et Philosophie des Sciences et des Techniques, Université Paris I Panthéon-Sorbonne, Paris, France
| | - Nicolas Papadopoulos
- Ludwig Institute for Cancer Research Brussels, Brussels, Belgium
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
| | | | | | | | | | - Valérie Edmond
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
| | | | - Valentine Marchand
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
| | - Nathalie Droin
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
- Gustave Roussy Cancer Campus, Villejuif, France
| | - Remco Hoogenboezem
- Department of Hematology, Erasmus University, Rotterdam, The Netherlands
| | - Rebekka K Schneider
- Department of Hematology, Erasmus University, Rotterdam, The Netherlands
- Department of Hematology, Oncology, Hemostaseology, and Stem Cell Transplantation, RWTH Aachen University, Aachen, Germany
| | - Alex Penson
- Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Omar Abdel-Wahab
- Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | | | - Florence Pasquier
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Département d'hématologie, Gustave Roussy Cancer Campus, Villejuif, France
| | - Caroline Marty
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
| | - Isabelle Plo
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
| | - Jean-Luc Villeval
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
| | - Stefan N Constantinescu
- Ludwig Institute for Cancer Research Brussels, Brussels, Belgium
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
- WELBIO department, WEL Research Institute, Wavre, Belgium
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, Oxford University, Oxford, UK
| | - Françoise Porteu
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
| | - William Vainchenker
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France
| | - Eric Solary
- INSERM U1287, Gustave Roussy Cancer Campus, Villejuif, France.
- Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France.
- Département d'hématologie, Gustave Roussy Cancer Campus, Villejuif, France.
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5
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Eaton N, Boyd EK, Biswas R, Lee-Sundlov MM, Dlugi TA, Ramsey HE, Zheng S, Burns RT, Sola-Visner MC, Hoffmeister KM, Falet H. Endocytosis of the thrombopoietin receptor Mpl regulates megakaryocyte and erythroid maturation in mice. Front Oncol 2022; 12:959806. [PMID: 36110936 PMCID: PMC9468709 DOI: 10.3389/fonc.2022.959806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 07/29/2022] [Indexed: 12/13/2022] Open
Abstract
Dnm2fl/fl Pf4-Cre (Dnm2Plt-/- ) mice lacking the endocytic GTPase dynamin 2 (DNM2) in platelets and megakaryocytes (MKs) develop hallmarks of myelofibrosis. At the cellular level, the tyrosine kinase JAK2 is constitutively active but decreased in expression in Dnm2Plt-/- platelets. Additionally, Dnm2Plt-/- platelets cannot endocytose the thrombopoietin (TPO) receptor Mpl, leading to elevated circulating TPO levels. Here, we assessed whether the hyperproliferative phenotype of Dnm2Plt-/- mice was due to JAK2 constitutive activation or to elevated circulating TPO levels. In unstimulated Dnm2Plt-/- platelets, STAT3 and, to a lower extent, STAT5 were phosphorylated, but their phosphorylation was slowed and diminished upon TPO stimulation. We further crossed Dnm2Plt-/- mice in the Mpl-/- background to generate Mpl-/-Dnm2Plt-/- mice lacking Mpl ubiquitously and DNM2 in platelets and MKs. Mpl-/- Dnm2Plt-/- platelets had severely reduced JAK2 and STAT3 but normal STAT5 expression. Mpl-/- Dnm2Plt-/- mice had severely reduced bone marrow MK and hematopoietic stem and progenitor cell numbers. Additionally, Mpl-/- Dnm2Plt-/- mice had severe erythroblast (EB) maturation defects, decreased expression of hemoglobin and heme homeostasis genes and increased expression of ribosome biogenesis and protein translation genes in spleen EBs, and developed anemia with grossly elevated plasma erythropoietin (EPO) levels, leading to early fatality by postnatal day 25. Mpl-/- Dnm2Plt+/+ mice had impaired EB development at three weeks of age, which normalized with adulthood. Together, the data shows that DNM2-dependent Mpl-mediated endocytosis in platelets and MKs is required for steady-state hematopoiesis and provides novel insights into a developmentally controlled role for Mpl in normal erythropoiesis, regulating hemoglobin and heme production.
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Affiliation(s)
- Nathan Eaton
- Translational Glycomics Center, Versiti Blood Research Institute, Milwaukee, WI, United States
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Emily K. Boyd
- Translational Glycomics Center, Versiti Blood Research Institute, Milwaukee, WI, United States
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Ratnashree Biswas
- Translational Glycomics Center, Versiti Blood Research Institute, Milwaukee, WI, United States
| | - Melissa M. Lee-Sundlov
- Translational Glycomics Center, Versiti Blood Research Institute, Milwaukee, WI, United States
| | - Theresa A. Dlugi
- Translational Glycomics Center, Versiti Blood Research Institute, Milwaukee, WI, United States
| | - Haley E. Ramsey
- Division of Newborn Medicine, Boston Children’s Hospital, Boston, MA, United States
- Department of Pediatrics, Harvard Medical School, Boston, MA, United States
| | - Shikan Zheng
- Translational Glycomics Center, Versiti Blood Research Institute, Milwaukee, WI, United States
| | - Robert T. Burns
- Translational Glycomics Center, Versiti Blood Research Institute, Milwaukee, WI, United States
| | - Martha C. Sola-Visner
- Division of Newborn Medicine, Boston Children’s Hospital, Boston, MA, United States
- Department of Pediatrics, Harvard Medical School, Boston, MA, United States
| | - Karin M. Hoffmeister
- Translational Glycomics Center, Versiti Blood Research Institute, Milwaukee, WI, United States
- Departments of Medicine and Biochemistry, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Hervé Falet
- Translational Glycomics Center, Versiti Blood Research Institute, Milwaukee, WI, United States
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
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6
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Spivak JL. Advances in polycythemia vera and lessons for acute leukemia. Best Pract Res Clin Haematol 2021; 34:101330. [PMID: 34865702 DOI: 10.1016/j.beha.2021.101330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The myeloproliferative neoplasms (MPN), polycythemia vera (PV), essential thrombocytosis and primary myelofibrosis, are an unusual group of myeloid neoplasms, which arise in a pluripotent hematopoietic stem cell (HSC) due to gain of function driver mutations in the JAK2, CALR and MPL genes that constitutively activate JAK2, the cognate tyrosine kinase of the type 1 hematopoietic growth factor (HGF) receptors. PV is the ultimate phenotypic expression of constitutive JAK2 activation since it alone of the three MPN is characterized by overproduction of normal red cells, white cells and platelets. Paradoxically, however, although PV is a panmyelopathy involving myeloid, erythroid and megakaryocytic progenitor cells, pluripotent HSC only express a single type of HGF receptor, the thrombopoietin receptor, MPL. In this review, the basis for how a pluripotent HSC with one type of HGF can give rise to three separate types of myeloid cells will be explained and it will be demonstrated that PV is actually a hormone-sensitive disorder, characterized by elevated thrombopoietin levels. Finally, it will be shown that the most common form of acute leukemia in PV is due to the inappropriate use of chemotherapy, including hydroxyurea, which facilitates expansion of DNA-damaged, mutated HSC at the expense of their normal counterparts.
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Affiliation(s)
- Jerry L Spivak
- Division of Hematology, Johns Hopkins University School of Medicine, Traylor 924, 720 Rutland Avenue, Baltimore, MD, 20037, USA.
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Levy G, Mambet C, Pecquet C, Bailly S, Havelange V, Diaconu CC, Constantinescu SN. Targets in MPNs and potential therapeutics. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 366:41-81. [PMID: 35153006 DOI: 10.1016/bs.ircmb.2021.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Philadelphia-negative classical Myeloproliferative Neoplasms (MPNs), including Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF), are clonal hemopathies that emerge in the hematopoietic stem cell (HSC) compartment. MPN driver mutations are restricted to specific exons (14 and 12) of Janus kinase 2 (JAK2), thrombopoietin receptor (MPL/TPOR) and calreticulin (CALR) genes, are involved directly in clonal myeloproliferation and generate the MPN phenotype. As a result, an increased number of fully functional erythrocytes, platelets and leukocytes is observed in the peripheral blood. Nevertheless, the complexity and heterogeneity of MPN clinical phenotypes cannot be solely explained by the type of driver mutation. Other factors, such as additional somatic mutations affecting epigenetic regulators or spliceosomes components, mutant allele burdens and modifiers of signaling by driver mutants, clonal architecture and the order of mutation acquisition, signaling events that occur downstream of a driver mutation, the presence of specific germ-line variants, the interaction of the neoplastic clone with bone marrow microenvironment and chronic inflammation, all can modulate the disease phenotype, influence the MPN clinical course and therefore, might be useful therapeutic targets.
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Affiliation(s)
- Gabriel Levy
- Ludwig Institute for Cancer Research, Brussels, Belgium; SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; Department of Pediatric Hematology and Oncology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Cristina Mambet
- Department of Cellular and Molecular Pathology, Stefan S. Nicolau Institute of Virology, Bucharest, Romania; Department of Hematology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
| | - Christian Pecquet
- Ludwig Institute for Cancer Research, Brussels, Belgium; SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; WELBIO (Walloon Excellence in Life Sciences and Biotechnology), Brussels, Belgium
| | - Sarah Bailly
- Ludwig Institute for Cancer Research, Brussels, Belgium; SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; Department of Hematology, Cliniques Universitaires Saint Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Violaine Havelange
- SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; Department of Hematology, Cliniques Universitaires Saint Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Carmen C Diaconu
- Department of Cellular and Molecular Pathology, Stefan S. Nicolau Institute of Virology, Bucharest, Romania
| | - Stefan N Constantinescu
- Ludwig Institute for Cancer Research, Brussels, Belgium; SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; WELBIO (Walloon Excellence in Life Sciences and Biotechnology), Brussels, Belgium; Ludwig Institute for Cancer Research, Nuffield Department of Medicine, Oxford University, Oxford, United Kingdom.
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8
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Roy A, Shrivastva S, Naseer S. In and out: Traffic and dynamics of thrombopoietin receptor. J Cell Mol Med 2021; 25:9073-9083. [PMID: 34448528 PMCID: PMC8500957 DOI: 10.1111/jcmm.16878] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 07/27/2021] [Accepted: 08/04/2021] [Indexed: 12/17/2022] Open
Abstract
Thrombopoiesis had long been a challenging area of study due to the rarity of megakaryocyte precursors in the bone marrow and the incomplete understanding of its regulatory cytokines. A breakthrough was achieved in the early 1990s with the discovery of the thrombopoietin receptor (TpoR) and its ligand thrombopoietin (TPO). This accelerated research in thrombopoiesis, including the uncovering of the molecular basis of myeloproliferative neoplasms (MPN) and the advent of drugs to treat thrombocytopenic purpura. TpoR mutations affecting its membrane dynamics or transport were increasingly associated with pathologies such as MPN and thrombocytosis. It also became apparent that TpoR affected hematopoietic stem cell (HSC) quiescence while priming hematopoietic stem cells (HSCs) towards the megakaryocyte lineage. Thorough knowledge of TpoR surface localization, dimerization, dynamics and stability is therefore crucial to understanding thrombopoiesis and related pathologies. In this review, we will discuss the mechanisms of TpoR traffic. We will focus on the recent progress in TpoR membrane dynamics and highlight the areas that remain unexplored.
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Affiliation(s)
- Anita Roy
- Kusuma School of Biological Sciences, Indian Institute of Technology, New Delhi, India
| | - Saurabh Shrivastva
- Kusuma School of Biological Sciences, Indian Institute of Technology, New Delhi, India
| | - Saadia Naseer
- Kusuma School of Biological Sciences, Indian Institute of Technology, New Delhi, India
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9
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Bleeding diathesis in mice lacking JAK2 in platelets. Blood Adv 2021; 5:2969-2981. [PMID: 34342643 DOI: 10.1182/bloodadvances.2020003032] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 04/14/2021] [Indexed: 12/18/2022] Open
Abstract
The tyrosine kinase JAK2 is a critical component of intracellular JAK/STAT cytokine signaling cascades that is prevalent in hematopoietic cells, such as hematopoietic stem cells and megakaryocytes (MKs). Individuals expressing the somatic JAK2 V617F mutation commonly develop myeloproliferative neoplasms (MPNs) associated with venous and arterial thrombosis, a leading cause of mortality. The role of JAK2 in hemostasis remains unclear. We investigated the role of JAK2 in platelet hemostatic function using Jak2fl/fl Pf4-Cre (Jak2Plt-/-) mice lacking JAK2 in platelets and MKs. Jak2Plt-/- mice developed MK hyperplasia and splenomegaly associated with severe thrombocytosis and bleeding. This notion was supported by failure to occlude in a ferric chloride carotid artery injury model and by a cremaster muscle laser-induced injury assay, in which Jak2Plt-/- platelets failed to form stable thrombi. Jak2Plt-/- platelets formed thrombi poorly after adhesion to type 1 collagen under arterial shear rates. Jak2Plt-/- platelets spread poorly on collagen under static conditions or on fibrinogen in response to the collagen receptor GPVI-specific agonist, collagen-related peptide (CRP). After activation with collagen, CRP, or the CLEC-2 agonist rhodocytin, Jak2Plt-/- platelets displayed decreased α-granule secretion and integrin αIIbβ3 activation or aggregation, but showed normal responses to thrombin. Jak2Plt-/- platelets had impaired intracellular signaling when activated via GPVI, as assessed by tyrosine phosphorylation. Together, the results show that JAK2 deletion impairs platelet immunoreceptor tyrosine-based activation motif signaling and hemostatic function in mice and suggest that aberrant JAK2 signaling in patients with MPNs affects GPVI signaling, leading to hemostatic platelet function.
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Functional Consequences of Mutations in Myeloproliferative Neoplasms. Hemasphere 2021; 5:e578. [PMID: 34095761 PMCID: PMC8171364 DOI: 10.1097/hs9.0000000000000578] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 04/13/2021] [Indexed: 01/14/2023] Open
Abstract
Driver mutations occur in Janus kinase 2 (JAK2), thrombopoietin receptor (MPL), and calreticulin (CALR) in BCR-ABL1 negative myeloproliferative neoplasms (MPNs). From mutations leading to one amino acid substitution in JAK2 or MPL, to frameshift mutations in CALR resulting in a protein with a different C-terminus, all the mutated proteins lead to pathologic and persistent JAK2-STAT5 activation. The most prevalent mutation, JAK2 V617F, is associated with the 3 entities polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF), while CALR and MPL mutations are associated only with ET and MF. Triple negative ET and MF patients may harbor noncanonical mutations in JAK2 or MPL. One major fundamental question is whether the conformations of JAK2 V617F, MPL W515K/L/A, or CALR mutants differ from those of their wild type counterparts so that a specific treatment could target the clone carrying the mutated driver and spare physiological hematopoiesis. Of great interest, a set of epigenetic mutations can co-exist with the phenotypic driver mutations in 35%–40% of MPNs. These epigenetic mutations, such as TET2, EZH2, ASXL1, or DNMT3A mutations, promote clonal hematopoiesis and increased fitness of aged hematopoietic stem cells in both clonal hematopoiesis of indeterminate potential (CHIP) and MPNs. Importantly, the main MPN driver mutation JAK2 V617F is also associated with CHIP. Accumulation of several epigenetic and splicing mutations favors progression of MPNs to secondary acute myeloid leukemia. Another major fundamental question is how epigenetic rewiring due to these mutations interacts with persistent JAK2-STAT5 signaling. Answers to these questions are required for better therapeutic interventions aimed at preventing progression of ET and PV to MF, and transformation of these MPNs in secondary acute myeloid leukemia.
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Spivak JL, Moliterno AR. The Thrombopoietin Receptor, MPL, Is a Therapeutic Target of Opportunity in the MPN. Front Oncol 2021; 11:641613. [PMID: 33777803 PMCID: PMC7987816 DOI: 10.3389/fonc.2021.641613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 01/28/2021] [Indexed: 12/12/2022] Open
Abstract
The myeloproliferative neoplasms, polycythemia vera, essential thrombocytosis and primary myelofibrosis share driver mutations that either activate the thrombopoietin receptor, MPL, or indirectly activate it through mutations in the gene for JAK2, its cognate tyrosine kinase. Paradoxically, although the myeloproliferative neoplasms are classified as neoplasms because they are clonal hematopoietic stem cell disorders, the mutations affecting MPL or JAK2 are gain-of-function, resulting in increased production of normal erythrocytes, myeloid cells and platelets. Constitutive JAK2 activation provides the basis for the shared clinical features of the myeloproliferative neoplasms. A second molecular abnormality, impaired posttranslational processing of MPL is also shared by these disorders but has not received the recognition it deserves. This abnormality is important because MPL is the only hematopoietic growth factor receptor expressed in hematopoietic stem cells; because MPL is a proto-oncogene; because impaired MPL processing results in chronic elevation of plasma thrombopoietin, and since these diseases involve normal hematopoietic stem cells, they have proven resistant to therapies used in other myeloid neoplasms. We hypothesize that MPL offers a selective therapeutic target in the myeloproliferative neoplasms since impaired MPL processing is unique to the involved stem cells, while MPL is required for hematopoietic stem cell survival and quiescent in their bone marrow niches. In this review, we will discuss myeloproliferative neoplasm hematopoietic stem cell pathophysiology in the context of the behavior of MPL and its ligand thrombopoietin and the ability of thrombopoietin gene deletion to abrogate the disease phenotype in vivo in a JAK2 V617 transgenic mouse model of PV.
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Affiliation(s)
- Jerry L Spivak
- Hematology Division, Department of Medicine, Johns Hopkins University School of Medicine Baltimore, Baltimore, MD, United States
| | - Alison R Moliterno
- Hematology Division, Department of Medicine, Johns Hopkins University School of Medicine Baltimore, Baltimore, MD, United States
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12
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Abstract
Megakaryocytes give rise to platelets, which have a wide variety of functions in coagulation, immune response, inflammation, and tissue repair. Dysregulation of megakaryocytes is a key feature of in the myeloproliferative neoplasms, especially myelofibrosis. Megakaryocytes are among the main drivers of myelofibrosis by promoting myeloproliferation and bone marrow fibrosis. In vivo targeting of megakaryocytes by genetic and pharmacologic approaches ameliorates the disease, underscoring the important role of megakaryocytes in myeloproliferative neoplasms. Here we review the current knowledge of the function of megakaryocytes in the JAK2, CALR, and MPL-mutant myeloproliferative neoplasms.
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13
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MPN: The Molecular Drivers of Disease Initiation, Progression and Transformation and their Effect on Treatment. Cells 2020; 9:cells9081901. [PMID: 32823933 PMCID: PMC7465511 DOI: 10.3390/cells9081901] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 08/07/2020] [Accepted: 08/11/2020] [Indexed: 02/07/2023] Open
Abstract
Myeloproliferative neoplasms (MPNs) constitute a group of disorders identified by an overproduction of cells derived from myeloid lineage. The majority of MPNs have an identifiable driver mutation responsible for cytokine-independent proliferative signalling. The acquisition of coexisting mutations in chromatin modifiers, spliceosome complex components, DNA methylation modifiers, tumour suppressors and transcriptional regulators have been identified as major pathways for disease progression and leukemic transformation. They also confer different sensitivities to therapeutic options. This review will explore the molecular basis of MPN pathogenesis and specifically examine the impact of coexisting mutations on disease biology and therapeutic options.
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14
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Spivak JL, Merchant A, Williams DM, Rogers O, Zhao W, Duffield A, Resar LS, Moliterno AR, Zhao ZJ. Thrombopoietin is required for full phenotype expression in a JAK2V617F transgenic mouse model of polycythemia vera. PLoS One 2020; 15:e0232801. [PMID: 32479500 PMCID: PMC7263591 DOI: 10.1371/journal.pone.0232801] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 04/21/2020] [Indexed: 12/30/2022] Open
Abstract
The myeloproliferative neoplasms, polycythemia vera, essential thrombocytosis and primary myelofibrosis are hematopoietic stem cell disorders and share driver mutations that either directly activate the thrombopoietin receptor, MPL, or activate it indirectly through gain-of-function mutations in the gene for JAK2, its cognate tyrosine kinase. Paradoxically, MPL surface expression in hematopoietic stem cells is also reduced in the myeloproliferative neoplasms due to abnormal post-translational glycosylation and premature destruction of JAK2, suggesting that the myeloproliferative neoplasms are disorders of MPL processing since MPL is the only hematopoietic growth factor receptor in hematopoietic stem cells. To examine this possibility, we genetically manipulated MPL expression and maturation in a JAK2V617F transgenic mouse model of polycythemia vera. Elimination of MPL expression completely abrogated the polycythemia vera phenotype in this JAK2V617F transgenic mouse model, which could only be partially restored by expression of one MPL allele. Most importantly, elimination of thrombopoietin gene expression abrogated the polycythemia vera phenotype in this JAK2V617F transgenic mouse model, which could be completely restored by expression of a single thrombopoietin allele. These data indicate that polycythemia vera is in part a thrombopoietin-dependent disorder and that targeting the MPL-thrombopoietin axis could be an effective, nonmyelotoxic therapeutic strategy in this disorder.
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Affiliation(s)
- Jerry L. Spivak
- Hematology Division, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
| | - Akil Merchant
- Samuel Oschin Comprehensive Cancer Institute, Blood and Marrow Transplant Program, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Donna M. Williams
- Hematology Division, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Ophelia Rogers
- Hematology Division, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Wanke Zhao
- Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Amy Duffield
- Department of Pathology, Hematologic Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Linda S. Resar
- Hematology Division, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Alison R. Moliterno
- Hematology Division, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Zhizhuang J. Zhao
- Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
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15
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16
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Vainchenker W, Plo I, Marty C, Varghese LN, Constantinescu SN. The role of the thrombopoietin receptor MPL in myeloproliferative neoplasms: recent findings and potential therapeutic applications. Expert Rev Hematol 2019; 12:437-448. [PMID: 31092065 DOI: 10.1080/17474086.2019.1617129] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Introduction: Classical Myeloproliferative Neoplasms (MPNs) include three disorders: Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF). MPNs are associated with constitutive activation of JAK2 leading to persistent cell signaling downstream of the dimeric myeloid cytokine receptors due to mutations in three genes encoding JAK2, calreticulin (CALR) and the thrombopoietin (TPO) receptor (MPL or TPOR). CALR and MPL mutants induce JAK2 activation that depends on MPL expression, thus explaining why they induce megakaryocyte pathologies including ET and PMF, but not PV. In contrast, JAK2 V617F drives all three diseases as it induces persistent signaling via EPOR, G-CSFR (CSF3R) and MPL. Areas Covered: Here, we review how different pathogenic mutations of MPL are translated into active receptors by inducing stable dimerization. We focus on the unique role of MPL on the hematopoietic stem cell (HSC), explaining why MPL is indispensable for the development of all MPNs. Last but not least, we describe how CALR mutants are pathogenic via binding and activation of MPL. Expert Opinion: Altogether, we believe that MPL is an important, but challenging, therapeutic target in MPNs that requires novel strategies to interrupt the specific conformational changes induced by each mutation or pathologic interaction without compromising the key functions of wild type MPL.
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Affiliation(s)
- William Vainchenker
- a UMR1170 , INSERM , Villejuif , France.,b Université Paris-Saclay , Villejuif , France
| | - Isabelle Plo
- a UMR1170 , INSERM , Villejuif , France.,b Université Paris-Saclay , Villejuif , France
| | - Caroline Marty
- a UMR1170 , INSERM , Villejuif , France.,b Université Paris-Saclay , Villejuif , France
| | - Leila N Varghese
- c Ludwig Institute for Cancer Research Brussels , Brussels , Belgium.,d de Duve Institute, Université catholique de Louvain , Brussels , Belgium
| | - Stefan N Constantinescu
- c Ludwig Institute for Cancer Research Brussels , Brussels , Belgium.,d de Duve Institute, Université catholique de Louvain , Brussels , Belgium.,e WELBIO (Walloon Excellence in Life Sciences and Biotechnology) , Brussels , Belgium
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17
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Stolyar MA, Gorbenko AS, Olkhovskiy IA. Platelet miR-28 expression level and thrombocytosis in MPN patients. Int J Lab Hematol 2018; 41:e43-e45. [PMID: 30480878 DOI: 10.1111/ijlh.12951] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Marina A Stolyar
- Department of Health, Krasnoyarsk Branch of the "National Research Center for Hematology", Krasnoyarsk, Russian Federation.,Federal Research Center Krasnoyarsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences, Krasnoyarsk, Russian Federation
| | - Aleksey S Gorbenko
- Department of Health, Krasnoyarsk Branch of the "National Research Center for Hematology", Krasnoyarsk, Russian Federation
| | - Igor A Olkhovskiy
- Department of Health, Krasnoyarsk Branch of the "National Research Center for Hematology", Krasnoyarsk, Russian Federation.,Federal Research Center Krasnoyarsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences, Krasnoyarsk, Russian Federation
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18
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Giudice V, Biancotto A, Wu Z, Cheung F, Candia J, Fantoni G, Kajigaya S, Rios O, Townsley D, Feng X, Young NS. Aptamer-based proteomics of serum and plasma in acquired aplastic anemia. Exp Hematol 2018; 68:38-50. [PMID: 30312735 DOI: 10.1016/j.exphem.2018.09.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 09/18/2018] [Accepted: 09/29/2018] [Indexed: 11/25/2022]
Abstract
Single-stranded oligonucleotides containing deoxyuridine are aptamers (SOMAmers) that can bind proteins with high specificity and affinity and slow dissociation rates. SOMAscan, an aptamer-based proteomic technology, allows measurement of more than 1,300 proteins simultaneously for the identification of new disease biomarkers. The aim of the present study was to identify new serum and plasma protein markers for diagnosis of acquired aplastic anemia (AA) and response to immunosuppressive therapies (IST). SOMAscan was used to screen 1,141 serum proteins in 28 AA patients before and after therapy and 1,317 plasma proteins in seven SAA patients treated with standard IST and a thrombopoietin receptor agonist. From our analysis, 19 serum and 28 plasma proteins were identified as possible candidate diagnostic and prognostic markers. A custom immunobead-based multiplex assay with five selected serum proteins (BMP-10, CCL17, DKK1, HGF, and SELL) was used for validation in a verification set (n = 65) of samples obtained before and after IST and in a blinded validation cohort at baseline (n = 16). After technical validation, four biomarkers were employed to predict diagnosis (accuracy, 88%) and long-term response to IST (accuracy, 79%). In conclusion, SOMAscan is a powerful tool for the identification of new biomarkers. We propose further larger studies to validate new candidate serum and plasma diagnostic and prognostic markers of AA.
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Affiliation(s)
- Valentina Giudice
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health (NIH), Bethesda, MD, USA.
| | - Angélique Biancotto
- Trans-NIH Center for Human Immunology, Autoimmunity, and Inflammation, National Institutes of Health, Bethesda, MD, USA
| | - Zhijie Wu
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health (NIH), Bethesda, MD, USA
| | - Foo Cheung
- Trans-NIH Center for Human Immunology, Autoimmunity, and Inflammation, National Institutes of Health, Bethesda, MD, USA
| | - Julián Candia
- Trans-NIH Center for Human Immunology, Autoimmunity, and Inflammation, National Institutes of Health, Bethesda, MD, USA
| | - Giovanna Fantoni
- Trans-NIH Center for Human Immunology, Autoimmunity, and Inflammation, National Institutes of Health, Bethesda, MD, USA
| | - Sachiko Kajigaya
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health (NIH), Bethesda, MD, USA
| | - Olga Rios
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health (NIH), Bethesda, MD, USA
| | - Danielle Townsley
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health (NIH), Bethesda, MD, USA
| | - Xingmin Feng
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health (NIH), Bethesda, MD, USA
| | - Neal S Young
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health (NIH), Bethesda, MD, USA
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19
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Platelet clearance by the hepatic Ashwell-Morrell receptor: mechanisms and biological significance. Thromb Res 2017; 141 Suppl 2:S68-72. [PMID: 27207430 DOI: 10.1016/s0049-3848(16)30370-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The daily production of billions of platelets must be regulated to avoid spontaneous bleeding or arterial occlusion and organ damage. Complex mechanisms control platelet production and clearance in physiological and pathological conditions. This review will focus on the mechanisms of platelet senescence with specific emphasis on the role of post-translational modifications in platelet life-span and thrombopoietin production downstream of the hepatic Ashwell-Morrell receptor.
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20
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Varghese LN, Defour JP, Pecquet C, Constantinescu SN. The Thrombopoietin Receptor: Structural Basis of Traffic and Activation by Ligand, Mutations, Agonists, and Mutated Calreticulin. Front Endocrinol (Lausanne) 2017; 8:59. [PMID: 28408900 PMCID: PMC5374145 DOI: 10.3389/fendo.2017.00059] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 03/17/2017] [Indexed: 12/13/2022] Open
Abstract
A well-functioning hematopoietic system requires a certain robustness and flexibility to maintain appropriate quantities of functional mature blood cells, such as red blood cells and platelets. This review focuses on the cytokine receptor that plays a significant role in thrombopoiesis: the receptor for thrombopoietin (TPO-R; also known as MPL). Here, we survey the work to date to understand how this receptor functions at a molecular level throughout its lifecycle, from traffic to the cell surface, dimerization and binding cognate cytokine via its extracellular domain, through to its subsequent activation of associated Janus kinases and initiation of downstream signaling pathways, as well as the regulation of these processes. Atomic level resolution structures of TPO-R have remained elusive. The identification of disease-causing mutations in the receptor has, however, offered some insight into structure and function relationships, as has artificial means of receptor activation, through TPO mimetics, transmembrane-targeting receptor agonists, and engineering in dimerization domains. More recently, a novel activation mechanism was identified whereby mutated forms of calreticulin form complexes with TPO-R via its extracellular N-glycosylated domain. Such complexes traffic pathologically in the cell and persistently activate JAK2, downstream signal transducers and activators of transcription (STATs), and other pathways. This pathologic TPO-R activation is associated with a large fraction of human myeloproliferative neoplasms.
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Affiliation(s)
- Leila N. Varghese
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- SIGN Pole, de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Jean-Philippe Defour
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- SIGN Pole, de Duve Institute, Université catholique de Louvain, Brussels, Belgium
- Department of Clinical Biology, Cliniques universitaires St Luc, Université catholique de Louvain, Brussels, Belgium
| | - Christian Pecquet
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- SIGN Pole, de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Stefan N. Constantinescu
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- SIGN Pole, de Duve Institute, Université catholique de Louvain, Brussels, Belgium
- *Correspondence: Stefan N. Constantinescu,
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21
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An incomplete trafficking defect to the cell-surface leads to paradoxical thrombocytosis for human and murine MPL P106L. Blood 2016; 128:3146-3158. [PMID: 28034873 DOI: 10.1182/blood-2016-06-722058] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 11/03/2016] [Indexed: 12/30/2022] Open
Abstract
The mechanisms behind the hereditary thrombocytosis induced by the thrombopoietin (THPO) receptor MPL P106L mutant remain unknown. A complete trafficking defect to the cell surface has been reported, suggesting either weak constitutive activity or nonconventional THPO-dependent mechanisms. Here, we report that the thrombocytosis phenotype induced by MPL P106L belongs to the paradoxical group, where low MPL levels on platelets and mature megakaryocytes (MKs) lead to high serum THPO levels, whereas weak but not absent MPL cell-surface localization in earlier MK progenitors allows response to THPO by signaling and amplification of the platelet lineage. MK progenitors from patients showed no spontaneous growth and responded to THPO, and MKs expressed MPL on their cell surface at low levels, whereas their platelets did not respond to THPO. Transduction of MPL P106L in CD34+ cells showed that this receptor was more efficiently localized at the cell surface on immature than on mature MKs, explaining a proliferative response to THPO of immature cells and a defect in THPO clearance in mature cells. In a retroviral mouse model performed in Mpl-/- mice, MPL P106L could induce a thrombocytosis phenotype with high circulating THPO levels. Furthermore, we could select THPO-dependent cell lines with more cell-surface MPL P106L localization that was detected by flow cytometry and [125I]-THPO binding. Altogether, these results demonstrate that MPL P106L is a receptor with an incomplete defect in trafficking, which induces a low but not absent localization of the receptor on cell surface and a response to THPO in immature MK cells.
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22
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A thrombopoietin receptor antagonist is capable of depleting myelofibrosis hematopoietic stem and progenitor cells. Blood 2016; 127:3398-409. [PMID: 27114459 DOI: 10.1182/blood-2015-10-674465] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 04/21/2016] [Indexed: 01/12/2023] Open
Abstract
Recently, interactions between thrombopoietin (TPO) and its receptor, the myeloproliferative leukemia (MPL) virus oncogene, have been shown to play a role in the development and progression of myeloproliferative neoplasms including myelofibrosis (MF). These observations have led to the development of strategies to disrupt the association of TPO with its receptor as a means of targeting MF hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs). In this report, we show that although both splenic and peripheral blood MF CD34(+) cells expressed lower levels of MPL than normal CD34(+) cells, TPO promoted the proliferation of MF CD34(+) cells and HPCs in a dose-dependent fashion. Furthermore, the treatment of MF but not normal CD34(+) cells with a synthesized MPL antagonist, LCP4, decreased the number of CD34(+)Lin(-) cells and all classes of assayable HPCs (colony-forming unit-megakaryocyte [CFU-MK], CFU-granulocyte/macrophage, burst-forming unit-erythroid/CFU-erythroid, and CFU-granulocyte/erythroid/macrophage/MK) irrespective of their mutational status. In addition, LCP4 treatment resulted in the depletion of the number of MF HPCs that were JAK2V617F(+) Moreover, the degree of human cell chimerism and the proportion of malignant donor cells were significantly reduced in immunodeficient mice transplanted with MF CD34(+) cell grafts treated with LCP4. These effects of LCP4 on MF HSCs/HPCs were associated with inhibition of JAK-STAT activity, leading to the induction of apoptosis. These findings demonstrate that such specific anti-cytokine receptor antagonists represent a new class of drugs that are capable of targeting MF HSCs.
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Inflammation as a Driver of Clonal Evolution in Myeloproliferative Neoplasm. Mediators Inflamm 2015; 2015:606819. [PMID: 26538830 PMCID: PMC4619974 DOI: 10.1155/2015/606819] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 08/02/2015] [Indexed: 12/19/2022] Open
Abstract
Our understanding of inflammation's role in the pathogenesis of myeloproliferative neoplasm (MPN) is evolving. The impact of chronic inflammation, a characteristic feature of MPN, likely goes far beyond its role as a driver of constitutional symptoms. An inflammatory response to the neoplastic clone may be responsible for some pathologic aspects of MPN. Moreover, JAK2V617F mutated hematopoietic stem and progenitor cells are resistant to inflammation, and this gives the neoplastic clone a selective advantage allowing for its clonal expansion. Because inflammation plays a central role in MPN inflammation is a logical therapeutic target in MPN.
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24
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Regulating billions of blood platelets: glycans and beyond. Blood 2015; 126:1877-84. [PMID: 26330242 DOI: 10.1182/blood-2015-01-569129] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 08/25/2015] [Indexed: 01/01/2023] Open
Abstract
The human body produces and removes 10(11) platelets daily to maintain a normal steady state platelet count. Platelet production must be regulated to avoid spontaneous bleeding or arterial occlusion and organ damage. Multifaceted and complex mechanisms control platelet production and removal in physiological and pathological conditions. This review will focus on different mechanisms of platelet senescence and clearance with specific emphasis on the role of posttranslational modifications. It will also briefly address platelet transfusion and the role of glycans in the clearance of stored platelets.
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25
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Debeurme F, Lacout C, Moratal C, Bagley RG, Vainchenker W, Adrian F, Villeval JL. JAK2 inhibition has different therapeutic effects according to myeloproliferative neoplasm development in mice. J Cell Mol Med 2015; 19:2564-74. [PMID: 26176817 PMCID: PMC4627562 DOI: 10.1111/jcmm.12608] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 04/03/2015] [Indexed: 11/28/2022] Open
Abstract
JAK2 inhibition therapy is used to treat patients suffering from myeloproliferative neoplasms (MPN). Conflicting data on this therapy are reported possibly linked to the types of inhibitors or disease type. Therefore, we decided to compare in mice the effect of a JAK2 inhibitor, Fedratinib, in MPN models of increasing severity: polycythemia vera (PV), post-PV myelofibrosis (PPMF) and rapid post-essential thrombocythemia MF (PTMF). The models were generated through JAK2 activation by the JAK2(V617F) mutation or MPL constant stimulation. JAK2 inhibition induced a correction of splenomegaly, leucocytosis and microcytosis in all three MPN models. However, the effects on fibrosis, osteosclerosis, granulocytosis, erythropoiesis or platelet counts varied according to the disease severity stage. Strikingly, complete blockade of fibrosis and osteosclerosis was observed in the PPMF model, linked to correction of MK hyper/dysplasia, but not in the PTMF model, suggesting that MF development may also become JAK2-independent. Interestingly, we originally found a decreased in the JAK2(V617F) allele burden in progenitor cells from the spleen but not in other cell types. Overall, this study shows that JAK2 inhibition has different effects according to disease phenotypes and can (i) normalize platelet counts, (ii) prevent the development of marrow fibrosis/osteosclerosis at an early stage and (iii) reduce splenomegaly through blockage of stem cell mobilization in the spleen.
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Affiliation(s)
- Franck Debeurme
- Inserm, U.1009, Institut Gustave Roussy (IGR), Université Paris XI, Villejuif, France
| | - Catherine Lacout
- Inserm, U.1009, Institut Gustave Roussy (IGR), Université Paris XI, Villejuif, France
| | - Claudine Moratal
- iBV, CNRS UMR7277, INSERM U1091, Université Nice-Sophia Antipolis, Nice, France
| | | | - William Vainchenker
- Inserm, U.1009, Institut Gustave Roussy (IGR), Université Paris XI, Villejuif, France
| | | | - Jean-Luc Villeval
- Inserm, U.1009, Institut Gustave Roussy (IGR), Université Paris XI, Villejuif, France
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Lipocalin produced by myelofibrosis cells affects the fate of both hematopoietic and marrow microenvironmental cells. Blood 2015; 126:972-82. [PMID: 26022238 DOI: 10.1182/blood-2014-12-618595] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 05/18/2015] [Indexed: 12/20/2022] Open
Abstract
Myelofibrosis (MF) is characterized by cytopenias, constitutional symptoms, splenomegaly, and marrow histopathological abnormalities (fibrosis, increased microvessel density, and osteosclerosis). The microenvironmental abnormalities are likely a consequence of the elaboration of a variety of inflammatory cytokines generated by malignant megakaryocytes and monocytes. We observed that levels of a specific inflammatory cytokine, lipocalin-2 (LCN2), were elevated in the plasmas of patients with myeloproliferative neoplasms (MF > polycythemia vera or essential thrombocythemia) and that LCN2 was elaborated by MF myeloid cells. LCN2 generates increased reactive oxygen species, leading to increased DNA strand breaks and apoptosis of normal, but not MF, CD34(+) cells. Furthermore, incubation of marrow adherent cells or mesenchymal stem cells with LCN2 increased the generation of osteoblasts and fibroblasts, but not adipocytes. LCN2 priming of mesenchymal stem cells resulted in the upregulation of RUNX2 gene as well as other genes that are capable of further affecting osteoblastogenesis, angiogenesis, and the deposition of matrix proteins. These data indicate that LCN2 is an additional MF inflammatory cytokine that likely contributes to the creation of a cascade of events that results in not only a predominance of the MF clone but also a dysfunctional microenvironment.
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Abstract
Dynamins are highly conserved large GTPases (enzymes that hydrolyze guanosine triphosphate) involved in endocytosis and vesicle transport, and mutations in the ubiquitous and housekeeping dynamin 2 (DNM2) have been associated with thrombocytopenia in humans. To determine the role of DNM2 in thrombopoiesis, we generated Dnm2(fl/fl) Pf4-Cre mice specifically lacking DNM2 in the megakaryocyte (MK) lineage. Dnm2(fl/fl) Pf4-Cre mice had severe macrothrombocytopenia with moderately accelerated platelet clearance. Dnm2-null bone marrow MKs had altered demarcation membrane system formation in vivo due to defective endocytic pathway, and fetal liver-derived Dnm2-null MKs formed proplatelets poorly in vitro, showing that DNM2-dependent endocytosis plays a major role in MK membrane formation and thrombopoiesis. Endocytosis of the thrombopoietin receptor Mpl was impaired in Dnm2-null platelets, causing constitutive phosphorylation of the tyrosine kinase JAK2 and elevated circulating thrombopoietin levels. MK-specific DNM2 deletion severely disrupted bone marrow homeostasis, as reflected by marked expansion of hematopoietic stem and progenitor cells, MK hyperplasia, myelofibrosis, and consequent extramedullary hematopoiesis and splenomegaly. Taken together, our data demonstrate that unrestrained MK growth and proliferation results in rapid myelofibrosis and establishes a previously unrecognized role for DNM2-dependent endocytosis in megakaryopoiesis, thrombopoiesis, and bone marrow homeostasis.
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The thrombopoietin receptor, MPL, is critical for development of a JAK2V617F-induced myeloproliferative neoplasm. Blood 2014; 124:3956-63. [PMID: 25339357 DOI: 10.1182/blood-2014-07-587238] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The most frequent contributing factor in Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) is the acquisition of a V617F mutation in Janus kinase 2 (JAK2) in hematopoietic stem cells (HSCs). Recent evidence has demonstrated that to drive MPN transformation, JAK2V617F needs to directly associate with a functional homodimeric type I cytokine receptor, suggesting that, although acquiring JAK2V617F may promote disease, there are additional cellular components necessary for MPN development. Here we show that loss of the thrombopoietin (TPO) receptor (MPL) significantly ameliorates MPN development in JAK2V617F(+) transgenic mice, whereas loss of TPO only mildly affects the disease phenotype. Specifically, compared with JAK2V617F(+) mice, JAK2V617F(+)Mpl(-/-) mice exhibited reduced thrombocythemia, neutrophilia, splenomegaly, and neoplastic stem cell pool. The importance of MPL is highlighted as JAK2V617FMpl(+/-) mice displayed a significantly reduced MPN phenotype, indicating that Mpl level may have a substantial effect on MPN development and severity. Splenomegaly and the increased neoplastic stem cell pool were retained in JAK2V617F(+)Tpo(-/-) mice, although thrombocytosis was reduced compared with JAK2V617F(+) mice. These results demonstrate that Mpl expression, but not Tpo, is fundamental in the development of JAK2V617F(+) MPNs, highlighting an entirely novel target for therapeutic intervention.
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Carbone CJ, Fuchs SY. Eliminative signaling by Janus kinases: role in the downregulation of associated receptors. J Cell Biochem 2014; 115:8-16. [PMID: 23959845 DOI: 10.1002/jcb.24647] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 07/31/2013] [Indexed: 12/11/2022]
Abstract
Activation of cytokine receptor-associated Janus kinases (JAKs) mediates most, if not all, of the cellular responses to peptide hormones and cytokines. Consequently, JAKs play a paramount role in homeostasis and immunity. Members of this family of tyrosine kinases control the cytokine/hormone-induced alterations in cell gene expression program. This function is largely mediated through an ability to signal toward activation of the signal transducer and activator of transcription proteins (STAT), as well as toward some other pathways. Importantly, JAKs are also instrumental in tightly controlling the expression of associated cytokine and hormone receptors, and, accordingly, in regulating the cell sensitivity to these cytokines and hormones. This review highlights the enzymatic and non-enzymatic mechanisms of this regulation and discusses the importance of the ambidextrous nature of JAK as a key signaling node that integrates the combining functions of forward signaling and eliminative signaling. Attention to the latter aspect of JAK function may contribute to emancipating our approaches to the pharmacological modulation of JAKs.
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Affiliation(s)
- Christopher J Carbone
- Department of Animal Biology and Mari Lowe Center for Comparative Oncology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, 19104
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Cleyrat C, Darehshouri A, Steinkamp MP, Vilaine M, Boassa D, Ellisman MH, Hermouet S, Wilson BS. Mpl traffics to the cell surface through conventional and unconventional routes. Traffic 2014; 15:961-82. [PMID: 24931576 PMCID: PMC4141020 DOI: 10.1111/tra.12185] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 06/10/2014] [Accepted: 06/11/2014] [Indexed: 12/20/2022]
Abstract
Myeloproliferative neoplasms (MPNs) are often characterized by JAK2 or calreticulin (CALR) mutations, indicating aberrant trafficking in pathogenesis. This study focuses on Mpl trafficking and Jak2 association using two model systems: human erythroleukemia cells (HEL; JAK2V617F) and K562 myeloid leukemia cells (JAK2WT). Consistent with a putative chaperone role for Jak2, Mpl and Jak2 associate on both intracellular and plasma membranes (shown by proximity ligation assay) and siRNA-mediated knockdown of Jak2 led to Mpl trapping in the endoplasmic reticulum (ER). Even in Jak2 sufficient cells, Mpl accumulates in punctate structures that partially colocalize with ER-tracker, the ER exit site marker (ERES) Sec31a, the autophagy marker LC3 and LAMP1. Mpl was fused to miniSOG, a genetically encoded tag for correlated light and electron microscopy. Results suggest that a fraction of Mpl is taken up into autophagic structures from the ER and routed to autolyososomes. Surface biotinylation shows that both immature and mature Mpl reach the cell surface; in K562 cells Mpl is also released in exosomes. Both forms rapidly internalize upon ligand addition, while recovery is primarily attributed to immature Mpl. Mpl appears to reach the plasma membrane via both conventional ER-Golgi and autolysosome secretory pathways, as well as recycling.
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Affiliation(s)
- Cédric Cleyrat
- Department of Pathology & Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM, 87131 USA
- INSERM UMR892/CNRS UMR6299, Centre de Recherche en Cancérologie Nantes-Angers (CRCNA), Institut de Recherche Thérapeutique-Université de Nantes, Nantes, France
| | - Anza Darehshouri
- Department of Pathology & Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM, 87131 USA
| | - Mara P. Steinkamp
- Department of Pathology & Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM, 87131 USA
| | - Mathias Vilaine
- INSERM UMR892/CNRS UMR6299, Centre de Recherche en Cancérologie Nantes-Angers (CRCNA), Institut de Recherche Thérapeutique-Université de Nantes, Nantes, France
| | - Daniela Boassa
- National Center for Microscopy and Imaging Research, University of California at San Diego, San Diego CA 92093 USA
| | - Mark H. Ellisman
- National Center for Microscopy and Imaging Research, University of California at San Diego, San Diego CA 92093 USA
| | - Sylvie Hermouet
- INSERM UMR892/CNRS UMR6299, Centre de Recherche en Cancérologie Nantes-Angers (CRCNA), Institut de Recherche Thérapeutique-Université de Nantes, Nantes, France
| | - Bridget S. Wilson
- Department of Pathology & Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM, 87131 USA
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JAK2 and MPL protein levels determine TPO-induced megakaryocyte proliferation vs differentiation. Blood 2014; 124:2104-15. [PMID: 25143485 DOI: 10.1182/blood-2014-03-559815] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Megakaryopoiesis is a 2-step differentiation process, regulated by thrombopoietin (TPO), on binding to its cognate receptor myeloproliferative leukemia (MPL). This receptor associates with intracytoplasmic tyrosine kinases, essentially janus kinase 2 (JAK2), which regulates MPL stability and cell-surface expression, and mediates TPO-induced signal transduction. We demonstrate that JAK2 and MPL mediate TPO-induced proliferation arrest and megakaryocytic differentiation of the human megakaryoblastic leukemia cell line UT7-MPL. A decrease in JAK2 or MPL protein expression, and JAK2 chemical inhibition, suppress this antiproliferative action of TPO. The expression of JAK2 and MPL, which progressively increases along normal human megakaryopoiesis, is decreased in platelets of patients diagnosed with JAK2- or MPL-mutated essential thrombocytemia and primary myelofibrosis, 2 myeloproliferative neoplasms in which megakaryocytes (MKs) proliferate excessively. Finally, low doses of JAK2 chemical inhibitors are shown to induce a paradoxical increase in MK production, both in vitro and in vivo. We propose that JAK2 and MPL expression levels regulate megakaryocytic proliferation vs differentiation in both normal and pathological conditions, and that JAK2 chemical inhibitors could promote a paradoxical thrombocytosis when used at suboptimal doses.
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Iida R, Welner RS, Zhao W, Alberola-lla J, Medina KL, Zhao ZJ, Kincade PW. Stem and progenitor cell subsets are affected by JAK2 signaling and can be monitored by flow cytometry. PLoS One 2014; 9:e93643. [PMID: 24699465 PMCID: PMC3974768 DOI: 10.1371/journal.pone.0093643] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 03/05/2014] [Indexed: 12/31/2022] Open
Abstract
Although extremely rare, hematopoietic stem cells (HSCs) are divisible into subsets that differ with respect to differentiation potential and cell surface marker expression. For example, we recently found that CD86(-) CD150(+) CD48(-) HSCs have limited potential for lymphocyte production. This could be an important new tool for studying hematological abnormalities. Here, we analyzed HSC subsets with a series of stem cell markers in JAK2V617F transgenic (Tg) mice, where the mutation is sufficient to cause myeloproliferative neoplasia with lymphocyte deficiency. Total numbers of HSC were elevated 3 to 20 fold in bone marrow of JAK2V617F mice. Careful analysis suggested the accumulation involved multiple HSC subsets, but particularly those characterized as CD150(HI) CD86(-) CD18(L)°CD41(+) and excluding Hoechst dye. Real-Time PCR analysis of their HSC revealed that the erythropoiesis associated gene transcripts Gata1, Klf1 and Epor were particularly high. Flow cytometry analyses based on two differentiation schemes for multipotent progenitors (MPP) also suggested alteration by JAK2 signals. The low CD86 on HSC and multipotent progenitors paralleled the large reductions we found in lymphoid progenitors, but the few that were produced functioned normally when sorted and placed in culture. Either of two HSC subsets conferred disease when transplanted. Thus, flow cytometry can be used to observe the influence of abnormal JAK2 signaling on stem and progenitor subsets. Markers that similarly distinguish categories of human HSCs might be very valuable for monitoring such conditions. They could also serve as indicators of HSC fitness and suitability for transplantation.
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Affiliation(s)
- Ryuji Iida
- Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States of America
| | - Robert S. Welner
- Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
| | - Wanke Zhao
- Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - José Alberola-lla
- Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States of America
| | - Kay L. Medina
- Department of Immunology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Zhizhuang Joe Zhao
- Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Paul W. Kincade
- Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States of America
- * E-mail:
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Persistent STAT5 activation in myeloid neoplasms recruits p53 into gene regulation. Oncogene 2014; 34:1323-32. [PMID: 24681953 DOI: 10.1038/onc.2014.60] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 01/24/2014] [Accepted: 01/28/2014] [Indexed: 01/10/2023]
Abstract
STAT (Signal Transducer and Activator of Transcription) transcription factors are constitutively activated in most hematopoietic cancers. We previously identified a target gene, LPP/miR-28 (LIM domain containing preferred translocation partner in lipoma), induced by constitutive activation of STAT5, but not by transient cytokine-activated STAT5. miR-28 exerts negative effects on thrombopoietin receptor signaling and platelet formation. Here, we demonstrate that, in transformed hematopoietic cells, STAT5 and p53 must be synergistically bound to chromatin for induction of LPP/miR-28 transcription. Genome-wide association studies show that both STAT5 and p53 are co-localized on the chromatin at 463 genomic positions in proximal promoters. Chromatin binding of p53 is dependent on persistent STAT5 activation at these proximal promoters. The transcriptional activity of selected promoters bound by STAT5 and p53 was significantly changed upon STAT5 or p53 inhibition. Abnormal expression of several STAT5-p53 target genes (LEP, ATP5J, GTF2A2, VEGFC, NPY1R and NPY5R) is frequently detected in platelets of myeloproliferative neoplasm (MPN) patients, but not in platelets from healthy controls. In conclusion, persistently active STAT5 can recruit normal p53, like in the case of MPN cells, but also p53 mutants, such as p53 M133K in human erythroleukemia cells, leading to pathologic gene expression that differs from canonical STAT5 or p53 transcriptional programs.
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Germ-line JAK2 mutations in the kinase domain are responsible for hereditary thrombocytosis and are resistant to JAK2 and HSP90 inhibitors. Blood 2014; 123:1372-83. [PMID: 24398328 DOI: 10.1182/blood-2013-05-504555] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The main molecular basis of essential thrombocythemia and hereditary thrombocytosis is acquired, and germ-line-activating mutations affect the thrombopoietin signaling axis. We have identified 2 families with hereditary thrombocytosis presenting novel heterozygous germ-line mutations of JAK2. One family carries the JAK2 R867Q mutation located in the kinase domain, whereas the other presents 2 JAK2 mutations, S755R/R938Q, located in cis in both the pseudokinase and kinase domains. Expression of Janus kinase 2 (JAK2) R867Q and S755R/R938Q induced spontaneous growth of Ba/F3-thrombopoietin receptor (MPL) but not of Ba/F3-human receptor of erythropoietin cells. Interestingly, both Ba/F3-MPL cells expressing the mutants and platelets from patients displayed thrombopoietin-independent phosphorylation of signal transducer and activator of transcription 1. The JAK2 R867Q and S755R/R938Q proteins had significantly longer half-lives compared with JAK2 V617F. The longer half-lives correlated with increased binding to the heat shock protein 90 (HSP90) chaperone and with higher MPL cell-surface expression. Moreover, these mutants were less sensitive to JAK2 and HSP90 inhibitors than JAK2 V617F. Our results suggest that the mutations in the kinase domain of JAK2 may confer a weak activation of signaling specifically dependent on MPL while inducing a decreased sensitivity to clinically available JAK2 inhibitors.
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Choong ML, Pecquet C, Pendharkar V, Diaconu CC, Yong JWY, Tai SJ, Wang SF, Defour JP, Sangthongpitag K, Villeval JL, Vainchenker W, Constantinescu SN, Lee MA. Combination treatment for myeloproliferative neoplasms using JAK and pan-class I PI3K inhibitors. J Cell Mol Med 2013; 17:1397-409. [PMID: 24251790 PMCID: PMC4117552 DOI: 10.1111/jcmm.12156] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 09/09/2013] [Indexed: 12/17/2022] Open
Abstract
Current JAK2 inhibitors used for myeloproliferative neoplasms (MPN) treatment are not specific enough to selectively suppress aberrant JAK2 signalling and preserve physiological JAK2 signalling. We tested whether combining a JAK2 inhibitor with a series of serine threonine kinase inhibitors, targeting nine signalling pathways and already used in clinical trials, synergized in inhibiting growth of haematopoietic cells expressing mutant and wild-type forms of JAK2 (V617F) or thrombopoietin receptor (W515L). Out of 15 kinase inhibitors, the ZSTK474 phosphatydylinositol-3′-kinase (PI3K) inhibitor molecule showed strong synergic inhibition by Chou and Talalay analysis with JAK2 and JAK2/JAK1 inhibitors. Other pan-class I, but not gamma or delta specific PI3K inhibitors, also synergized with JAK2 inhibitors. Synergy was not observed in Bcr-Abl transformed cells. The best JAK2/JAK1 and PI3K inhibitor combination pair (ruxolitinib and GDC0941) reduces spleen weight in nude mice inoculated with Ba/F3 cells expressing TpoR and JAK2 V617F. It also exerted strong inhibitory effects on erythropoietin-independent erythroid colonies from MPN patients and JAK2 V617F knock-in mice, where at certain doses, a preferential inhibition of JAK2 V617F mutated progenitors was detected. Our data support the use of a combination of JAK2 and pan-class I PI3K inhibitors in the treatment of MPNs.
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Affiliation(s)
- Meng Ling Choong
- Experimental Therapeutics Centre, Agency for Science Technology and Research, Singapore
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Gäbler K, Behrmann I, Haan C. JAK2 mutants (e.g., JAK2V617F) and their importance as drug targets in myeloproliferative neoplasms. JAKSTAT 2013; 2:e25025. [PMID: 24069563 PMCID: PMC3772115 DOI: 10.4161/jkst.25025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 05/13/2013] [Accepted: 05/13/2013] [Indexed: 12/25/2022] Open
Abstract
The Janus kinase 2 (JAK2) mutant V617F and other JAK mutants are found in patients with myeloproliferative neoplasms and leukemias. Due to their involvement in neoplasia and inflammatory disorders, Janus kinases are promising targets for kinase inhibitor therapy. Several small-molecule compounds are evaluated in clinical trials for myelofibrosis, and ruxolitinib (INCB018424, Jakafi®) was the first Janus kinase inhibitor to receive clinical approval. In this review we provide an overview of JAK2V617F signaling and its inhibition by small-molecule kinase inhibitors. In addition, myeloproliferative neoplasms are discussed regarding the role of JAK2V617F and other mutant proteins of possible relevance. We further give an overview about treatment options with special emphasis on possible combination therapies.
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Affiliation(s)
- Karoline Gäbler
- Signal Transduction Laboratory; Life Sciences Research Unit; University of Luxembourg; Luxembourg
| | - Iris Behrmann
- Signal Transduction Laboratory; Life Sciences Research Unit; University of Luxembourg; Luxembourg
| | - Claude Haan
- Signal Transduction Laboratory; Life Sciences Research Unit; University of Luxembourg; Luxembourg
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Abstract
Abstract
The discovery of the JAK2V617F mutation triggered an unexpected flowering of basic and clinical studies in the field of myeloproliferative neoplasms (MPNs), resulting after just a few years in an exceptional amount of new information. One important consequence of those new findings was the modification of the World Health Organization classification and diagnostic algorithms for these diseases, which is still based on the original concept developed by William Dameshek in 1951 and keeps distinct entities under the umbrella of classical Philadelphia-negative MPNs. These MPNs are essential thrombocythemia, polycythemia vera, and primary myelofibrosis. Could a new molecular classification be a better tool to manage MPN patients? Several studies have shown that essential thrombocythemia and primary myelofibrosis can be divided into distinct subtypes based on the presence of the JAK2V617F mutation. Can we now define JAK2-positive diseases to depict a distinct entity from JAK2-negative MPNs? This chapter reviews the significance of JAK2 mutation positivity in the diagnosis, prognosis, and therapy of MPNs.
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Abstract
Abstract
The ATP-binding pocket of the kinase domain of JAK2 is the major target of the present treatment of myeloproliferative neoplasms. Several inhibitors of JAK2 that are ATP competitive have been developed, but they do not discriminate between wild-type and mutant JAK2. These inhibitors have been used in myelofibrosis and, for the first time, treatment induced a reduction in spleen size and in constitutional symptoms. However, no dramatic effects on BM fibrosis, allele burden, or peripheral blast numbers were observed. These data indicate that other avenues should be explored that would either target mutant molecules (JAKs or receptors) more specifically and spare wild-type JAK2 or that would address other pathways that contribute to the malignant proliferation. Future success in treating myeloproliferative neoplasms will depend on advances of the understanding of JAK-STAT signaling and also on a better understanding of the disease pathogenesis, especially the role that mutants in spliceosome factors and epigenetic regulators play in the phenotype of the disease and the precise mechanism of fibrosis development.
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Abstract
Abstract
Thrombosis is a leading cause of morbidity and mortality in patients with Philadelphia chromosome–negative myeloproliferative neoplasms (MPNs), particularly polycythemia vera and essential thrombocythemia. Mechanisms involved in the pathogenesis of the acquired thrombophilic state associated with these diseases include abnormalities of MPN clone–derived blood cells, which display prothrombotic features, and abnormalities of normal vascular cells, which become procoagulant in response to inflammatory stimuli. Ultimately, the release into the blood of elevated levels of procoagulant microparticles by platelets and vascular cells and the increase in the global thrombin generation due to an acquired activated protein C resistance result in a highly prothrombotic scenario in patients with polycythemia vera and essential thrombocythemia. The acquired point mutation in the pseudokinase domain of JAK2 (JAK2V617F) in these disorders is variably associated with thrombosis and, more consistently, with elevations in WBC counts and alterations in biomarkers of blood-clotting abnormalities. The predictive value of these biomarkers for thrombosis remains to be established to identify subsets of patients at elevated risk who may benefit from prophylaxis with antithrombotic drugs.
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Abstract
Decreased expression of the thrombopoietin receptor (TPOR or MPL) on the cell surface of platelets and megakaryocytes is an established feature of and myelofibrosis; however, the exact mechanism responsible for this phenomenon has gone largely unexplained. In this issue of Blood, Pecquet and colleagues publish an excellent study revealing that MPL expression is downregulated in the context of the mutant protein, JAK2V617F.
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