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Moulis G, Garabet L. Markers of refractory primary immune thrombocytopenia. Br J Haematol 2023; 203:112-118. [PMID: 38019080 DOI: 10.1111/bjh.19076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 07/31/2023] [Indexed: 11/30/2023]
Abstract
Refractory immune thrombocytopenia (ITP) is a challenging disease that can be defined by refractoriness to second-line treatments. In this review, we list and comment available evidence about clinical and biological factors associated with refractoriness to splenectomy, thrombopoietin receptor agonists (TPO-RAs), rituximab and fostamatinib, as well as those associated with multirefractory ITP (active disease with failure of rituximab, TPO-RAs and splenectomy).
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Affiliation(s)
- Guillaume Moulis
- Department of Internal Medicine, Referral Center for Autoimmune Cytopenia, Toulouse University Hospital, Toulouse, France
- Clinical Investigation Center 1436, Team PEPSS, Toulouse University Hospital, Toulouse, France
| | - Lamya Garabet
- Center for Laboratory Medicine, Østfold Hospital Trust, Grålum, Norway
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2
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Mei H, Zhou H, Hou M, Sun J, Zhang L, Luo J, Jiang Z, Ye X, Xu Y, Lu J, Wang H, Hui A, Zhou Y, Hu Y. Avatrombopag for adult chronic primary immune thrombocytopenia: a randomized phase 3 trial in China. Res Pract Thromb Haemost 2023; 7:102158. [PMID: 37700877 PMCID: PMC10493258 DOI: 10.1016/j.rpth.2023.102158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 06/13/2023] [Accepted: 06/14/2023] [Indexed: 09/14/2023] Open
Abstract
Background Immune thrombocytopenia (ITP) is an autoimmune disorder with decreased platelet counts and increased bleeding risk. Objectives To evaluate the efficacy and safety of avatrombopag, a second-generation oral thrombopoietin receptor agonist, for the treatment of Chinese patients with chronic primary ITP. Methods This multicenter, randomized, double-blind, placebo-controlled phase 3 study (CTR20210431) consisted of a 6-week double-blind core treatment phase followed by a 20-week, open-label extension phase. Chinese adults with chronic primary ITP for at least 12 months and a platelet count <30 × 109/L were randomized (2:1) to receive avatrombopag (initial dose of 20 mg/day) or matched placebo. The primary endpoint was the proportion of subjects with a platelet count ≥50 × 109/L at week 6 of the core treatment phase in absence of rescue therapy. Results In total, 74 patients were randomized (avatrombopag: N = 48; placebo: N = 26) between March 5, 2021, and August 6, 2021; all of whom entered the extension phase (72 received avatrombopag up to 26 weeks). At week 6 of the core study, the platelet response (≥50 x 109/L) rate was significantly higher in the avatrombopag group (77.1%; 95% CI, 62.7, 88.0) vs placebo (7.7%; 95% CI, 1.0, 25.1); the treatment difference was 69.4% (95% CI, 56.2, 86.3; P < .0001). During the 6-week core study, treatment-emergent adverse events were reported in 41 (85.4%) and 20 (76.9%) patients in the avatrombopag and placebo groups, respectively. The most common avatrombopag-related treatment-emergent adverse events were upper respiratory tract infection (14/48 [29.2%]), increased platelet count (13/48 [27.1%]) and headache (7/48 [14.6%]). Conclusion Avatrombopag was efficacious and generally well tolerated in Chinese patients with chronic primary ITP, with comparable efficacy and safety to previous reports in Western patients.
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Affiliation(s)
- Heng Mei
- Institute of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hu Zhou
- Department of Hematology, The Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, Zhengzhou, China
| | - Ming Hou
- Department of Hematology, Qilu Hospital of Shandong University, Shandong University, Jinan, China
| | - Jing Sun
- Department of Hematology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Lei Zhang
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Haihe Laboratory of Cell Ecosystem, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin Key Laboratory of Gene Therapy for Blood Diseases, CAMS Key Laboratory of Gene Therapy for Blood Diseases, Tianjin, China
- Tianjin Institute of Health Science, Tianjin, China
| | - Jianmin Luo
- Department of Hematology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Zhongxing Jiang
- Department of Hematology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Xu Ye
- Department of Hematology, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Yajing Xu
- Department of Hematology, Xiangya Hospital, Central South University; Hunan Hematology Oncology Clinical Medical Research Center, Changsha, China
| | - Jun Lu
- R&D Center, Fosun Pharma, Shanghai, China
| | - Hui Wang
- R&D Center, Fosun Pharma, Shanghai, China
| | - Aimin Hui
- R&D Center, Fosun Pharma, Shanghai, China
| | | | - Yu Hu
- Institute of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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3
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Zhou H, Zhou J, Wu D, Ma L, Du X, Niu T, Yang R, Liu J, Zhang F, Shi Q, Wang X, Jing H, Li J, Wang X, Cui Z, Zhou Z, Hou M, Shao Z, Jin J, Li W, Ren H, Hu J, Shen J, Liu L, Zeng Y, Zhou J, Liu X, Shen Y, Ding K, Taira T, Cai H, Zhao Y. Romiplostim in primary immune thrombocytopenia that is persistent or chronic: phase III multicenter, randomized, placebo-controlled clinical trial in China. Res Pract Thromb Haemost 2023; 7:100192. [PMID: 37601010 PMCID: PMC10439391 DOI: 10.1016/j.rpth.2023.100192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 04/02/2023] [Accepted: 04/15/2023] [Indexed: 08/22/2023] Open
Abstract
Background Multiple trials have confirmed that romiplostim could increase platelet count in individuals with primary immune thrombocytopenia (ITP), but no related study has assessed Chinese patients. Objectives To assess the effectiveness of romiplostim as a second-line treatment of persistent or chronic ITP in Chinese adults. Methods This phase III multicenter, randomized, placebo-controlled, double-blind, then open-label clinical trial (NCT02868099, CTR20150395) was conducted at 28 investigational sites in China. The patients were randomly assigned (3:1) to romiplostim (starting and maximum doses of 1 and 10 μg/kg, respectively) or placebo for 9 weeks (double-blind period), followed by the open-label period (both groups administered romiplostim) to week 22. The primary endpoint was the time (in weeks) during which platelet counts were ≥50 × 109/L in the double-blind period. Results In this study, 202 patients (romiplostim, n = 151; placebo, n = 51) started the treatment. The median (range) numbers of weeks with platelet response after 6 weeks of treatment were 2 (0-6) and 0 (0-2) in patients administered romiplostim and placebo, respectively (P < .001). During the double-blind period, the proportions of patients with treatment-emergent adverse events were comparable between the romiplostim and placebo groups (82.8% vs 82.4%). The treatment-emergent adverse event with ≥10% difference in incidence between these 2 groups was injection site bleeding (1.3% vs 11.8%). Conclusion Romiplostim significantly increased the time with maintained platelet response in patients with persistent or chronic ITP in comparison with placebo. No new safety signal was observed. Trial registration ClinicalTrials.gov, NCT02868099. www.chinadrugtrials.org.cn/clinicaltrials.searchlist.dhtml, CTR20150395.
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Affiliation(s)
- Hu Zhou
- Henan Cancer Hospital/The Affiliated Cancer Hospital of Zhengzhou University, Zhenzhou, China
| | - Jianfeng Zhou
- Tongji Hospital affiliated to Tongji Medical College of Huazhong University of Science & Technology, Wuhan, China
| | - Depei Wu
- The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Liping Ma
- Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Xin Du
- Shenzhen Second People’s Hospital, Shenzhen, China
| | - Ting Niu
- West China Hospital, Sichuan University, Chengdu, China
| | - Renchi Yang
- Institute of Hematology & Blood Disease Hospital, Chinese Academy of Medical Science & Peking Union Medical College, Tianjin, China
| | - Jing Liu
- The Third Xiangya Hospital of Central South University, Changsha, China
| | - Feng Zhang
- The First Affiliated Hospital of Bengbu Medical College, Bengbu, China
| | - Qingzhi Shi
- The Second affiliated Hospital of Nanchang University, Nanchang, China
| | - Xiuli Wang
- The Second Hospital of Jilin University, Jilin, China
| | - Hongmei Jing
- Peking University Third Hospital, Beijing, China
| | - Junmin Li
- Rui Jin Hospital Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xin Wang
- Shandong Provincial Hospital, Jinan, China
| | - Zhongguang Cui
- The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Zeping Zhou
- Second Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Ming Hou
- Qilu Hospital of Shandong University, Jinan, China
| | - Zonghong Shao
- Tianjin Medical University General Hospital, Tianjin, China
| | - Jie Jin
- The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Wenqian Li
- Qinghai Provincial People`s Hospital, Xining, China
| | - Hanyun Ren
- Peking University First Hospital, Beijing, China
| | - Jianda Hu
- Fujian Medical University Union Hospital, Fuzhou, China
| | | | - Li Liu
- Tangdu Hospital, Xi’an, China
| | - Yun Zeng
- First Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Jin Zhou
- The First Affiliated Hospital of Haerbin Medical University, Haerbin, China
| | - Xin Liu
- Anhui Provincial Hospital, Hefei, China
| | | | - Kai Ding
- Kyowa Kirin China Pharmaceutical Co, Ltd, Beijing, China
| | | | - Huacong Cai
- Chinese Academy of Medical Sciences & Peking Union Medical College Hospital, Beijing, China
| | - Yongqiang Zhao
- Chinese Academy of Medical Sciences & Peking Union Medical College Hospital, Beijing, China
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Pogozheva ID, Cherepanov S, Park SJ, Raghavan M, Im W, Lomize AL. Structural modeling of cytokine-receptor-JAK2 signaling complexes using AlphaFold Multimer. bioRxiv 2023:2023.06.14.544971. [PMID: 37398331 PMCID: PMC10312770 DOI: 10.1101/2023.06.14.544971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Homodimeric class 1 cytokine receptors include the erythropoietin (EPOR), thrombopoietin (TPOR), granulocyte colony-stimulating factor 3 (CSF3R), growth hormone (GHR), and prolactin receptors (PRLR). They are cell-surface single-pass transmembrane (TM) glycoproteins that regulate cell growth, proliferation, and differentiation and induce oncogenesis. An active TM signaling complex consists of a receptor homodimer, one or two ligands bound to the receptor extracellular domains and two molecules of Janus Kinase 2 (JAK2) constitutively associated with the receptor intracellular domains. Although crystal structures of soluble extracellular domains with ligands have been obtained for all the receptors except TPOR, little is known about the structure and dynamics of the complete TM complexes that activate the downstream JAK-STAT signaling pathway. Three-dimensional models of five human receptor complexes with cytokines and JAK2 were generated using AlphaFold Multimer. Given the large size of the complexes (from 3220 to 4074 residues), the modeling required a stepwise assembly from smaller parts with selection and validation of the models through comparisons with published experimental data. The modeling of active and inactive complexes supports a general activation mechanism that involves ligand binding to a monomeric receptor followed by receptor dimerization and rotational movement of the receptor TM α-helices causing proximity, dimerization, and activation of associated JAK2 subunits. The binding mode of two eltrombopag molecules to TM α-helices of the active TPOR dimer was proposed. The models also help elucidating the molecular basis of oncogenic mutations that may involve non-canonical activation route. Models equilibrated in explicit lipids of the plasma membrane are publicly available.
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Affiliation(s)
- Irina D. Pogozheva
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109, United States
| | | | - Sang-Jun Park
- Departments of Biological Sciences and Chemistry, Lehigh University, Bethlehem, PA 18015, United States
| | - Malini Raghavan
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, United States
| | - Wonpil Im
- Departments of Biological Sciences and Chemistry, Lehigh University, Bethlehem, PA 18015, United States
| | - Andrei L. Lomize
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109, United States
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Ringelstein-Harlev S, Fanadka M, Horowitz NA, Bettman NP, Katz T. In chronic lymphocytic leukemia, activation of the thrombopoietin receptor promotes T-cell inhibitory properties, contributing to immunosuppression. Eur J Haematol 2023; 110:371-378. [PMID: 36478591 DOI: 10.1111/ejh.13912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 11/29/2022] [Accepted: 12/01/2022] [Indexed: 12/12/2022]
Abstract
In chronic lymphocytic leukemia (CLL), the immune system is skewed towards a suppressive milieu. Levels of thrombopoietin (TPO), promoting cellular immune regulatory activity in immune thrombocytopenic purpura, were shown to be elevated in CLL patients. This study explored TPO as a potential immunomodulator, supporting CLL progression. We evaluated CLL cell-induced expression of TPO receptor (TPO-R) on T-cells and effects of its activation on T-cell responses. CLL cell involvement in TPO generation was also assessed. Baseline TPO-R expression on CD4 + T-cells was found to be higher in CLL patients than in healthy controls (HC). Exposure of HC-T-cells to B-cells, especially to CLL-B-cells stimulated with B-cell activating molecules, resulted in enhanced TPO-R expression on T-cells. CLL-T-cell stimulation with TPO reduced their proliferation and expanded the regulatory T-cell (Treg) population. At baseline, phosphorylation of STAT5, known to impact the Treg phenotype, was elevated in CLL-T-cells relative to those of HC. Exposure to TPO further enhanced STAT5 phosphorylation in CLL-T-cells, possibly driving the observed Treg expansion. The CLL immune milieu is involved in promotion of inhibitory features in T-cells through increased TPO-R levels and TPO-induced intracellular signaling. TPO and its signaling pathway could potentially support immunosuppression in CLL, and may emerge as novel therapeutic targets.
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Affiliation(s)
- Shimrit Ringelstein-Harlev
- Department of Hematology and Bone Marrow Transplantation, Rambam Health Care Campus, Haifa, Israel.,The Ruth and Bruce Rappaport Faculty of Medicine, Technion, Israel Institute of Technology, Haifa, Israel
| | - Mona Fanadka
- The Ruth and Bruce Rappaport Faculty of Medicine, Technion, Israel Institute of Technology, Haifa, Israel
| | - Netanel A Horowitz
- Department of Hematology and Bone Marrow Transplantation, Rambam Health Care Campus, Haifa, Israel.,The Ruth and Bruce Rappaport Faculty of Medicine, Technion, Israel Institute of Technology, Haifa, Israel
| | - Noam P Bettman
- Department of Hematology and Bone Marrow Transplantation, Rambam Health Care Campus, Haifa, Israel
| | - Tami Katz
- Department of Hematology and Bone Marrow Transplantation, Rambam Health Care Campus, Haifa, Israel.,The Ruth and Bruce Rappaport Faculty of Medicine, Technion, Israel Institute of Technology, Haifa, Israel
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Desikan H, Kaur A, Pogozheva ID, Raghavan M. Effects of calreticulin mutations on cell transformation and immunity. J Cell Mol Med 2023; 27:1032-1044. [PMID: 36916035 PMCID: PMC10098294 DOI: 10.1111/jcmm.17713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 02/22/2023] [Accepted: 02/24/2023] [Indexed: 03/16/2023] Open
Abstract
Myeloproliferative neoplasms (MPNs) are cancers involving dysregulated production and function of myeloid lineage hematopoietic cells. Among MPNs, Essential thrombocythemia (ET), Polycythemia Vera (PV) and Myelofibrosis (MF), are driven by mutations that activate the JAK-STAT signalling pathway. Somatic mutations of calreticulin (CRT), an endoplasmic reticulum (ER)-localized lectin chaperone, are driver mutations in approximately 25% of ET and 35% of MF patients. The MPN-linked mutant CRT proteins have novel frameshifted carboxy-domain sequences and lack an ER retention motif, resulting in their secretion. Wild type CRT is a regulator of ER calcium homeostasis and plays a key role in the assembly of major histocompatibility complex (MHC) class I molecules, which are the ligands for antigen receptors of CD8+ T cells. Mutant CRT-linked oncogenesis results from the dysregulation of calcium signalling in cells and the formation of stable complexes of mutant CRT with myeloproliferative leukemia (MPL) protein, followed by downstream activation of the JAK-STAT signalling pathway. The intricate participation of CRT in ER protein folding, calcium homeostasis and immunity suggests the involvement of multiple mechanisms of mutant CRT-linked oncogenesis. In this review, we highlight recent findings related to the role of MPN-linked CRT mutations in the dysregulation of calcium homeostasis, MPL activation and immunity.
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Affiliation(s)
- Harini Desikan
- Department of Microbiology and ImmunologyUniversity of Michigan Medical SchoolAnn ArborMichiganUSA
| | - Amanpreet Kaur
- Department of Microbiology and ImmunologyUniversity of Michigan Medical SchoolAnn ArborMichiganUSA
| | - Irina D. Pogozheva
- Department of Medicinal ChemistryCollege of Pharmacy, University of MichiganAnn ArborMichiganUSA
| | - Malini Raghavan
- Department of Microbiology and ImmunologyUniversity of Michigan Medical SchoolAnn ArborMichiganUSA
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Lu J, Jamieson BD, Hui AM. Avatrombopag ethnic sensitivity analysis in chronic liver disease and thrombocytopenia patients: individual-level pooled analysis. Therap Adv Gastroenterol 2022; 15:17562848221105976. [PMID: 35795378 PMCID: PMC9252017 DOI: 10.1177/17562848221105976] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 05/19/2022] [Indexed: 02/04/2023] Open
Abstract
INTRODUCTION Few data have been published on the ethnic sensitivity of effectiveness, pharmacokinetics (PK), and pharmacodynamics (PD) of avatrombopag for the management of thrombocytopenia in patients with chronic liver disease (CLD). METHODS An ethnic sensitivity analysis was performed based on the results from two phase III studies (ADAPT-1 and ADAPT-2), with a primary endpoint of the proportion of patients without the requirement of platelet transfusion or rescue treatment for bleeding after randomization to 7 days following a scheduled procedure, and three phase I studies in healthy subjects. Cochran-Mantel-Haenszel and Fisher's exact tests were used to compare the differences in effectiveness in different ethnicities and overall population. RESULTS In total, 435 patients (placebo, n = 158; avatrombopag, n = 277) were stratified into various ethnic groups: 121 East Asians, including the subgroup of 27 Chinese, and 259 Caucasians. The proportion of patients who did not receive a platelet transfusion and those with a platelet count ⩾50 × 109/L in the avatrombopag 40 and 60 mg groups were higher than that of placebo for all ethnicities and in the overall population. Statistical significance was obtained in the overall population and for all ethnicities other than Chinese patients, a group with a very small sample size. No significant difference was observed in the proportion of responders in each ethnic group compared to overall population (p > 0.05). The incidence of adverse events in East Asians was similar to that in both Caucasians and the overall population. CONCLUSION Avatrombopag was effective and safe in the management of thrombocytopenia in Chinese patients with CLD. Ethnicity does not appear to influence the efficacy, safety, PK, or PD of avatrombopag.
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Affiliation(s)
- Jun Lu
- Clinical Research Department, Shanghai Fosun Pharmaceutical Development, Co., Ltd, Shanghai, China
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Hitchcock IS, Hafer M, Sangkhae V, Tucker JA. The thrombopoietin receptor: revisiting the master regulator of platelet production. Platelets 2021; 32:770-778. [PMID: 34097561 PMCID: PMC8292222 DOI: 10.1080/09537104.2021.1925102] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 04/27/2021] [Accepted: 04/28/2021] [Indexed: 12/25/2022]
Abstract
Thrombopoietin (TPO) and its receptor, MPL, are the primary regulators of platelet production and critical for hematopoietic stem cell (HSC) maintenance. Since TPO was first cloned in 1994, the physiological and pathological roles of TPO and MPL have been well characterized, culminating in the first MPL agonists being approved for the treatment of chronic immune thrombocytopenia in 2008. Dysregulation of the TPO-MPL signaling axis contributes to the pathogenesis of hematological disorders: decreased expression or function results in severe thrombocytopenia progressing to bone marrow failure, while hyperactivation of MPL signaling, either by mutations in the receptor or associated Janus kinase 2 (JAK2), results in pathological myeloproliferation. Despite its importance, it was only recently that the long-running debate over the mechanism by which TPO binding activates MPL has been resolved. This review will cover key aspects of TPO and MPL structure and function and their importance in receptor activation, discuss how these are altered in hematological disorders and consider how a greater understanding could lead to the development of better-targeted and more efficacious therapies.
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Affiliation(s)
- Ian S. Hitchcock
- York Biomedical Research Institute, Department of Biology, University of York, York, UK
| | - Maximillian Hafer
- Department of Biology and Center of Cellular Nanoanalytics, University of Osnabrück, Osnabrück, Germany
| | - Veena Sangkhae
- Center for Iron Disorders, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Julie A. Tucker
- York Biomedical Research Institute, Department of Biology, University of York, York, UK
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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11
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Edahiro Y, Araki M, Komatsu N. Mechanism underlying the development of myeloproliferative neoplasms through mutant calreticulin. Cancer Sci 2020; 111:2682-2688. [PMID: 32462673 PMCID: PMC7419020 DOI: 10.1111/cas.14503] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 05/12/2020] [Accepted: 05/22/2020] [Indexed: 01/14/2023] Open
Abstract
Deregulation of cytokine signaling is frequently associated with various pathological conditions, including malignancies. In patients with myeloproliferative neoplasms (MPNs), recurrent somatic mutations in the calreticulin (CALR) gene, which encodes a molecular chaperone that resides in the endoplasmic reticulum, have been reported. Studies have defined mutant CALR as an oncogene promoting the development of MPN, and deciphered a novel molecular mechanism by which mutant CALR constitutively activates thrombopoietin receptor MPL and its downstream molecules to induce cellular transformation. The mechanism of interaction and activation of MPL by mutant CALR is unique, not only due to the latter forming a homomultimeric complex through a novel mutant‐specific sequence generated by frameshift mutation, but also for its ability to interact with immature asparagine‐linked glycan for eventual engagement with immature MPL in the endoplasmic reticulum. The complex formed between mutant CALR and MPL is then transported to the cell surface, where it induces constitutive activation of downstream kinase JAK2 bound to MPL. Refined structural and cell biological studies can provide an in‐depth understanding of this unusual mechanism of receptor activation by a mutant molecular chaperone. Mutant CALR is also involved in modulation of the immune response, transcription, and intracellular homeostasis, which could contribute to the development of MPN. In the present article, we comprehensively review the current understanding of the underlying molecular mechanisms for mutant molecular chaperone‐induced cellular transformation.
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Affiliation(s)
- Yoko Edahiro
- Department of Hematology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Marito Araki
- Department of Transfusion Medicine and Stem Cell Regulation, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Norio Komatsu
- Department of Hematology, Juntendo University Graduate School of Medicine, Tokyo, Japan
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12
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Hasan MJ, Rabbani R, Huq SMR. The Use of High Dose Eltrombopag in the Management of Sepsis-Associated Thrombocytopenia in Critically Ill Patients. ACTA ACUST UNITED AC 2019; 5:123-9. [PMID: 31915717 DOI: 10.2478/jccm-2019-0019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 08/05/2019] [Indexed: 12/19/2022]
Abstract
Introduction Sepsis is a life-threatening condition, and sepsis-associated thrombocytopenia (SAT) is a common consequence of the disease where platelet count falls drastically within a very short time. Multiple key factors may cause platelet over-activation, destruction and reduction in platelet production during the sepsis. Eltrombopag is a thrombopoietin receptor agonist and is the second-line drug of choice in the treatment of chronic immune thrombocytopenia (ITP). Aim of the study The objective of this study was to observe the therapeutic outcome of high dose eltrombopag in SAT management in critically ill patients. Material and Methods This 6-month-long single group, observational study was conducted on seventeen ICU patients with SAT. Eltrombopag 100 mg/day in two divided doses was given to each patient. Platelet counts were monitored. A low platelet blood count returning to 150 K/μL or above, is taken as indicative of a successful reversal of a thrombocytopenia event. Results The mean Apache II score of patients (n= 17) was 18.71 (p-value: >0.05). No eltrombopag-induced adverse event was observed among the patients during the study period. Thrombocytopenia events were reversed successfully in 64.71% of patients (11; n= 17) within eight days of eltrombopag therapy. Conclusions The therapeutic potentiality of high dose eltrombopag regime in the management of sepsis-associated thrombocytopenia was found clinically significant in over two-thirds of critically ill adult patients enrolled in the study. These data may point to a new strategy in the management of acute type of thrombocytopenia in septic patients.
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13
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Xie C, Zhao H, Bao X, Fu H, Lou L. Pharmacological characterization of hetrombopag, a novel orally active human thrombopoietin receptor agonist. J Cell Mol Med 2018; 22:5367-5377. [PMID: 30156363 PMCID: PMC6201220 DOI: 10.1111/jcmm.13809] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 06/29/2018] [Indexed: 01/07/2023] Open
Abstract
Nonpeptide thrombopoietin receptor (TPOR/MPL) agonists, such as eltrombopag, have been used to treat thrombocytopenia of various aetiologies. Here, we investigated the pharmacological properties of hetrombopag, a new orally active small‐molecule TPOR agonist, in preclinical models. Hetrombopag specifically stimulated proliferation and/or differentiation of human TPOR‐expressing cells, including 32D‐MPL and human hematopoietic stem cells, with low nanomolar EC50 values through stimulation of STAT, PI3K and ERK signalling pathways. Notably, hetrombopag effectively up‐regulated G1‐phase–related proteins, including p‐RB, Cyclin D1 and CDK4/6, normalized progression of the cell cycle, and prevented apoptosis by modulating BCL‐XL/BAK expression in 32D‐MPL cells. Moreover, hetrombopag and TPO acted additively in stimulating TPOR‐dependent signalling, promoting cell viability, and preventing apoptosis. Orally administered hetrombopag specifically promoted the viability and growth of 32D‐MPL cells in hollow fibres implanted into nude mice with much higher potency than that of the well‐known TPOR agonist, eltrombopag, in association with activation of TPOR‐dependent signal transduction in vivo. Taken together, our findings indicate that, given its favourable pharmacological characteristics, hetrombopag may represent a new, orally active, small‐molecule TPOR agonist for patients with thrombocytopenia.
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Affiliation(s)
- Chengying Xie
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Huajun Zhao
- College of Pharmaceutical Sciences, Zhejiang Chinese Medical University, Hangzhou, Zhejiang, China
| | - Xubin Bao
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Haoyu Fu
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Liguang Lou
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
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14
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Vibor M, Rogulj IM, Ostojic SK. Is there any Role for Splenectomy in Adulthood Onset Chronic Immun e Thrombocytopenia in the Era of TPO Receptors Agonists? A Critic al Overview. Cardiovasc Hematol Disord Drug Targets 2018; 17:38-51. [PMID: 28034281 DOI: 10.2174/1871529x16666161229155608] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 12/09/2016] [Accepted: 12/21/2016] [Indexed: 11/22/2022]
Abstract
BACKGROUND Immune thrombocytopenia (ITP) in adulthood is characterized by chronic relapsing course. Despite the efficacious first line treatment (corticosteroid, intravenous immunoglobulin), majority of patients will enter the chronic phase warranting another treatment approach. Until recently, splenectomy performed in ITP chronic phase represented the standard of care with longterm remissions in more than 70% of patients, but it has never been tested in clinical trials. However, with the advances of our understanding of ITP pathophysiology and the shifting focus on megakaryocyte impairment, novel drugs were introduced in the treatment paradigm, mainly trombopoietin receptor agonists (TPO-RAs); romiplostim and eltrombopag. METHODS These TPO-RAs were tested in randomized controlled trials resulting in adequate platelet response with few side effects and less need for additional therapy leading to approval of corresponding regulatory agencies and wide acceptance by hematological community, but however TPO-RAs must be taken continuously to maintain the response. With their onset, the rate of splenectomy in chronic ITP has diminished in modern era. CONCLUSION The main aim behind conducting this review is to evaluate the pros and cons of splenectomy compared to TPO-RAs treatment in order to provide the critical overview which may help the practicing clinician in managing often challenging cases of chronic ITP.
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Affiliation(s)
- Milunovic Vibor
- Lombardi Comprehensive Cancer Centre, Georgetown University, 3970 Reservoir Road NW E501, 20007 Washington D.C., United States
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15
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Araki M, Komatsu N. Novel molecular mechanism of cellular transformation by a mutant molecular chaperone in myeloproliferative neoplasms. Cancer Sci 2017; 108:1907-1912. [PMID: 28741795 PMCID: PMC5623763 DOI: 10.1111/cas.13327] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 07/19/2017] [Indexed: 12/03/2022] Open
Abstract
Deregulation of the cytokine‐receptor signaling pathway plays a significant role in tumorigenesis. Such deregulation is frequently caused by alterations in the genes involved in the signaling pathway. At the end of 2013, recurrent somatic mutations in the calreticulin (CALR) gene that encodes a molecular chaperone were identified in a subset of patients with Philadelphia‐chromosome negative myeloproliferative neoplasms (MPN). The present review focuses on the role of CALR mutations in the oncogenic transformations observed in MPN. All the CALR mutations were found to generate a + 1 frameshift in the reading frame on exon 9, which encodes the carboxy (C)‐terminus end of CALR, and thus conferred a common mutant‐specific sequence in all the CALR mutants. The mutant CALR (but not the wild‐type) constitutively activates the thrombopoietin (TPO) receptor, myeloproliferative leukemia protein (MPL), even in the absence of TPO to induce cellular transformation. Preferential interaction between the mutant CALR and MPL is achieved by a presumptive conformational change induced by the mutant‐specific C‐terminus domain, which allows N‐domain binding to MPL. Even though mutant CALR is expressed on the cell surface and is secreted out of cells, it only presents autocrine capacity for MPL activation. These findings define a novel molecular mechanism by which the mutant molecular chaperone constitutively activates the cytokine receptor to induce cellular transformation.
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Affiliation(s)
- Marito Araki
- Department of Transfusion Medicine and Stem Cell Regulation, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Norio Komatsu
- Department of Hematology, Juntendo University Graduate School of Medicine, Tokyo, Japan
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16
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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: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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17
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Ngo A, Koay AZ, Pecquet C, Diaconu CC, Ould-Amer Y, Huang Q, Kang C, Poulsen A, Lee MA, Jenkins D, Shiau A, Constantinescu SN, Choong ML. A Phenotypic Screen for Small-Molecule Inhibitors of Constitutively Active Mutant Thrombopoietin Receptor Implicated in Myeloproliferative Neoplasms. Comb Chem High Throughput Screen 2016; 19:824-833. [PMID: 27748177 DOI: 10.2174/1386207319666161010163825] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/20/2016] [Accepted: 09/29/2016] [Indexed: 11/22/2022]
Abstract
BACKGROUND Rather than a Janus Kinase 2 inhibitor (ruxolitinib), a specific thrombopoietin receptor (TpoR) inhibitor would be more specific for the treatment of myeloproliferative neoplasms due to TpoR mutations. OBJECTIVE A cell-based phenotypic approach to identify specific TpoR inhibitors was implemented and a library of 505,483 small molecules was screened for inhibitory effects on cells transformed by TpoR mutants. RESULTS Among the identified hits are two analogs of 3-(4-piperidinyl) indole. The analogs showed about five-fold preferential inhibition of cell viability towards Ba/F3 cells expressing the TpoR W515L mutation compared to the parental cells. There was no significant difference in inhibition of cell viability between the TpoR wild type and the TpoR W515L mutant cells. Preferential inhibition of viability was observed in Ba/F3 cells expressing erythropoietin receptor (EpoR) when stimulated with Epo compared to stimulation with interleukin-3 (IL3). The indole analog inhibited ex vivo colony formations of primary bone marrow cells from heterozygous JAK2 V617F knock-in mice. Drug combination treatment study was performed using ruxolitinib and the indole analog. Drug synergistic effects were observed when cells were stimulated to proliferate through both the IL3 and TpoR pathways. Our compound specifically targets monoamine receptors in the rhodopsin-like receptor family of G protein-coupled receptor. CONCLUSION This screen has identified a monoamine receptor inhibitor that can inhibit viability of cells with active TpoR or EpoR signalings. Drug synergism with ruxolitib is demonstrated.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | - Meng Ling Choong
- Experimental Therapeutics Centre, 31 Biopolis Way, #03-01 Nanos, Singapore 138669, Singapore.. Singapore
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18
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Singh VK, Kumar N, Kalsan M, Saini A, Chandra R. A Novel Peptide Thrombopoietin Mimetic Designing and Optimization Using Computational Approach. Front Bioeng Biotechnol 2016; 4:69. [PMID: 27630985 PMCID: PMC5006622 DOI: 10.3389/fbioe.2016.00069] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 08/10/2016] [Indexed: 01/22/2023] Open
Abstract
Thrombopoietin receptor (TPOR) is a cytokine receptor protein present on the cell surface. The activation of TPOR by thrombopoietin (TPO) (a glycoprotein hormone) triggers an intracellular cascade of megakaryocytopoiesis for the formation of platelets. Recent studies on ex vivo megakaryocytopoiesis have evolved the possibilities of therapeutics uses. These findings have paved the way for the development of various TPO alternatives (recombinant TPO, peptide, and non-peptide TPO mimetics), which are useful in regenerative medicine. However, these alternatives possess various limitations such as induction of autoimmune effects, high production cost, low specificity, and hence activity. In the present study, a novel peptidic TPO mimetic was designed through computational studies by studying the binding sites of TPO and TMP to TPOR and analogs of known mimetics. Screening of combinatorial library was done through molecular docking using ClusPro. These studies indicated mimetic-9 as a significant molecule since it was found to have better binding score of −938.8 kcal/mol with seven hydrogen bonds and a high number of hydrophobic interactions, than known mimetic TMP with docking score of −798.4 kcal/mol and TMP dimer with docking score of −811.9 kcal/mol for TPOR. Mimetic9-TPOR complex was further assessed by the molecular dynamics simulation, and their complex was found to be stable with an RMSD value of 0.091 Å. While studying the parameters, mimetic-9 was found to have overall good physiochemical properties with positive grand average hydropathy (GRAVY) score and high instability index score and was found to be localized in the extracellular region. The designed mimetic-9 might prove to be a useful lead molecule for mimicking the role of TPO for in vitro platelet production with higher efficiency.
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Affiliation(s)
- Vimal Kishor Singh
- Founder and O/I Stem Cell Research Laboratory, Department of Biotechnology, INSPIRE Faculty, Delhi Technological University , Delhi , India
| | - Neeraj Kumar
- Department of Chemistry, University of Delhi , Delhi , India
| | - Manisha Kalsan
- Department of Chemistry, University of Delhi , Delhi , India
| | - Abhishek Saini
- Stem Cell Research Laboratory, Department of Biotechnology, Delhi Technological University , Delhi , India
| | - Ramesh Chandra
- Department of Chemistry, University of Delhi , Delhi , India
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Leroy E, Defour JP, Sato T, Dass S, Gryshkova V, Shwe MM, Staerk J, Constantinescu SN, Smith SO. His499 Regulates Dimerization and Prevents Oncogenic Activation by Asparagine Mutations of the Human Thrombopoietin Receptor. J Biol Chem 2015; 291:2974-87. [PMID: 26627830 DOI: 10.1074/jbc.m115.696534] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2015] [Indexed: 01/18/2023] Open
Abstract
Ligand binding to the extracellular domain of the thrombopoietin receptor (TpoR) imparts a specific orientation on the transmembrane (TM) and intracellular domains of the receptors that is required for physiologic activation via receptor dimerization. To map the inactive and active dimeric orientations of the TM helices, we performed asparagine (Asn)-scanning mutagenesis of the TM domains of the murine and human TpoR. Substitution of Asn at only one position (S505N) activated the human receptor, whereas Asn substitutions at several positions activated the murine receptor. Second site mutational studies indicate that His(499) near the N terminus of the TM domain is responsible for protecting the human receptor from activation by Asn mutations. Structural studies reveal that the sequence preceding His(499) is helical in the murine receptor but non-helical in peptides corresponding to the TM domain of the inactive human receptor. The activating S505N mutation and the small molecule agonist eltrombopag both induce helix in this region of the TM domain and are associated with dimerization and activation of the human receptor. Thus, His(499) regulates the activation of human TpoR and provides additional protection against activating mutations, such as oncogenic Asn mutations in the TM domain.
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Affiliation(s)
- Emilie Leroy
- From the Ludwig Institute for Cancer Research, 1200 Brussels, Belgium de Duve Institute, Université catholique de Louvain, 1200 Brussels, Belgium
| | - Jean-Philippe Defour
- From the Ludwig Institute for Cancer Research, 1200 Brussels, Belgium de Duve Institute, Université catholique de Louvain, 1200 Brussels, Belgium
| | - Takeshi Sato
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Sharmila Dass
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11794-5215, and
| | - Vitalina Gryshkova
- From the Ludwig Institute for Cancer Research, 1200 Brussels, Belgium de Duve Institute, Université catholique de Louvain, 1200 Brussels, Belgium
| | - Myat M Shwe
- From the Ludwig Institute for Cancer Research, 1200 Brussels, Belgium de Duve Institute, Université catholique de Louvain, 1200 Brussels, Belgium
| | - Judith Staerk
- Stem Cell Group, Nordic European Molecular Biology Laboratory Partnership and Center for Molecular Medicine, 0318 Oslo, Norway
| | - Stefan N Constantinescu
- From the Ludwig Institute for Cancer Research, 1200 Brussels, Belgium de Duve Institute, Université catholique de Louvain, 1200 Brussels, Belgium,
| | - Steven O Smith
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11794-5215, and
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Vianello F, Vettore S, Tezza F, Toni LD, Scandellari R, Sambado L, Treleani M, Fabris F. Serum Thrombopoietin and cMpl Expression in Thrombocytopenia of Different Etiologies. Hematol Rep 2014; 6:4996. [PMID: 24711916 PMCID: PMC3977153 DOI: 10.4081/hr.2014.4996] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Revised: 01/21/2014] [Accepted: 02/10/2014] [Indexed: 12/20/2022] Open
Abstract
The relationship between thrombopoietin (TPO) and its receptor cMpl in thrombocytopenic conditions has not been entirely clarified. To elucidate this interplay may expand the spectrum of indications of TPO mimetics. In this study we have explored the relationship between TPO and cMpl in platelets and megakaryocytes of 43 patients with thrombocytopenia due to idiopathic thrombocytopenic purpura (ITP), bone marrow hypoplasia, myelodysplastic syndromes (MDS), and familial thrombocytopenia. Data were compared to cMpl and TPO in patients with a normal platelet count and in patients with thrombocytosis due to essential thrombocythemia (ET). All but familial patients showed higher TPO compared to controls. All thrombocytopenic states were invariably associated with increased expression of platelet cMPL compared to healthy controls. ET patients showed normal TPO and a trend toward a reduced cMpl expression. Immunofluorescence of bone marrow sections from patients with ITP and MDS failed to show a peculiar pattern compared to controls. Multiple mechanisms regulate TPO and cMpl in thrombocytopenic conditions.
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Affiliation(s)
- Fabrizio Vianello
- Internal Medicine Unit, Department of Medicine DIMED, University of Padova Medical School , Padova, Italy
| | - Silvia Vettore
- Internal Medicine Unit, Department of Medicine DIMED, University of Padova Medical School , Padova, Italy
| | - Fabiana Tezza
- Internal Medicine Unit, Department of Medicine DIMED, University of Padova Medical School , Padova, Italy
| | - Luca De Toni
- Centre for Human Reproduction Pathology, Department of Medicine DIMED, University of Padova Medical School , Padova, Italy
| | - Raffaella Scandellari
- Internal Medicine Unit, Department of Medicine DIMED, University of Padova Medical School , Padova, Italy
| | - Luisa Sambado
- Internal Medicine Unit, Department of Medicine DIMED, University of Padova Medical School , Padova, Italy
| | - Martina Treleani
- Internal Medicine Unit, Department of Medicine DIMED, University of Padova Medical School , Padova, Italy
| | - Fabrizio Fabris
- Internal Medicine Unit, Department of Medicine DIMED, University of Padova Medical School , Padova, Italy
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Kawaguchi T, Nakano M, Satani M, Sumie S, Yamada S, Amano K, Kuromatsu R, Sata M. Usefulness of short-term eltrombopag treatment as a supportive treatment in hepatocellular carcinoma patients with cirrhosis and severe thrombocytopenia: A report of two cases. Oncol Lett 2014; 7:2130-2134. [PMID: 24932302 PMCID: PMC4049767 DOI: 10.3892/ol.2014.1976] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Accepted: 02/11/2014] [Indexed: 12/21/2022] Open
Abstract
Eltrombopag is an oral thrombopoietin (TPO) receptor agonist that increases platelet counts in patients with idiopathic thrombocytopenic purpura and in patients with liver cirrhosis. When cirrhotic patients with thrombocytopenia undergo elective invasive procedures, eltrombopag treatment reduces the requirement for platelet transfusions. However, TPO is known to have proliferative effects on hepatic progenitor cells and hepatic sinusoidal endothelial cells, which indicates that eltrombopag may accelerate tumor progression. Thus, the effect of eltrombopag on hepatocellular carcinoma (HCC) progression is an important issue. The current study describes two cases of HCC with cirrhosis-related thrombocytopenia. A two-week administration of eltrombopag increased platelet counts from 4.8 to 11.3×104 /μl in case 1 and 4.5 to 23.2×104 /μl in case 2. However, no changes were identified in the serum levels of tumor markers or HCC size following eltrombopag administration in the two cases. These HCCs were curatively treated by radiofrequency ablation without platelet transfusions or serious bleeding. Thus, short-term eltrombopag administration may not accelerate HCC proliferation and may be beneficial for invasive HCC treatment in cirrhotic patients with thrombocytopenia.
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Affiliation(s)
- Takumi Kawaguchi
- Division of Gastroenterology, Department of Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan ; Department of Digestive Disease Information and Research, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Masahito Nakano
- Division of Gastroenterology, Department of Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Manabu Satani
- Division of Gastroenterology, Department of Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Shuji Sumie
- Division of Gastroenterology, Department of Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Shingo Yamada
- Division of Gastroenterology, Department of Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Keisuke Amano
- Division of Gastroenterology, Department of Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Ryoko Kuromatsu
- Division of Gastroenterology, Department of Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Michio Sata
- Division of Gastroenterology, Department of Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan ; Department of Digestive Disease Information and Research, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
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22
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Zhao AB, Yu B, Wu XL, Cao KJ, Li EQ, Li QM, Chen XY. Protective effects on myelosuppression mice treated by three different classic Chinese medicine formulae. Pharmacogn Mag 2011; 7:133-40. [PMID: 21716623 PMCID: PMC3113352 DOI: 10.4103/0973-1296.80671] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 10/03/2010] [Accepted: 05/09/2011] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND In order to observe the protective therapeutic action and mechanism of Liuwei Dihuang Decoction, Buzhong Yiqi Decoction, and Compound Danshen Decoction on Myelosuppression induced by cyclophosphamide. MATERIALS AND METHODS The mice model was established by intraperitoneal injected with 100 mg/kg cyclophosphamide by human and mice dose conversion on the 9(th), 11(th), 13(th) days during the experiment. Flow cytometry (FCM) was used for detecting the number of cells and investigating bone marrow cell cycles. Spleen was taken out and the mRNA expression level of thrombopoietin (TPO) and c-Mpl were detected by Q-PCR, and c-Mpl in spleen in order to discuss the mechanism of myelosuppression and the protective effects of traditional Chinese medicine. RESULTS Both Liuwei Dihuang Decoction Group and Buzhong Yiqi Decoction Group can accelerate bone marrow hematopoietic stem progenitor cells (HSPCs) in marrow-suppressed mice and enhance cell proliferation by promoting cell cycles from G0/G1 phase to access into S, G2/M phase. And at the same time these Chinese decoctions can increase the mRNA expression level of TPO and c-Mpl in spleen. CONCLUSION Researched showed that Chinese formula take effect by affecting these genes on myelosuppressed mice.
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Affiliation(s)
- An-Bin Zhao
- The first two authors contributed equally to this work
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Metjian A, Abrams CS. New advances in the treatment of adult chronic immune thrombocytopenic purpura: role of thrombopoietin receptor-stimulating agents. Biologics 2009; 3:499-513. [PMID: 20054440 PMCID: PMC2802075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Decades of basic science and clinical research have led to an increased understanding of the pathophysiology of immune thrombocytopenic purpura (ITP), the processes underlying thrombopoiesis, and the treatment of chronic ITP. Now, new agents are available to treat ITP in a nonimmunosuppressive fashion. Lessons learned from the clinical trials of recombinant human thrombopoietin (TPO) have led to the development of a novel class of compounds: nonimmunogenic agonists of the thrombopoietin receptor. Representing the first nonimmunosuppressive agents to treat chronic refractory ITP in decades, medications such as romiplostim and eltrombopag were recently approved by the US Food and Drug Administration. These new agents offer physicians a new tool for treating difficult cases of ITP in their medical armamentarium. Additional TPO mimetics are also being developed that show promise in vitro, and await future development.
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Affiliation(s)
- Ara Metjian
- Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Charles S Abrams
- Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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