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Sánchez-Duffhues G, Hiepen C. Human iPSCs as Model Systems for BMP-Related Rare Diseases. Cells 2023; 12:2200. [PMID: 37681932 PMCID: PMC10487005 DOI: 10.3390/cells12172200] [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: 07/18/2023] [Revised: 08/17/2023] [Accepted: 08/23/2023] [Indexed: 09/09/2023] Open
Abstract
Disturbances in bone morphogenetic protein (BMP) signalling contribute to onset and development of a number of rare genetic diseases, including Fibrodysplasia ossificans progressiva (FOP), Pulmonary arterial hypertension (PAH), and Hereditary haemorrhagic telangiectasia (HHT). After decades of animal research to build a solid foundation in understanding the underlying molecular mechanisms, the progressive implementation of iPSC-based patient-derived models will improve drug development by addressing drug efficacy, specificity, and toxicity in a complex humanized environment. We will review the current state of literature on iPSC-derived model systems in this field, with special emphasis on the access to patient source material and the complications that may come with it. Given the essential role of BMPs during embryonic development and stem cell differentiation, gain- or loss-of-function mutations in the BMP signalling pathway may compromise iPSC generation, maintenance, and differentiation procedures. This review highlights the need for careful optimization of the protocols used. Finally, we will discuss recent developments towards complex in vitro culture models aiming to resemble specific tissue microenvironments with multi-faceted cellular inputs, such as cell mechanics and ECM together with organoids, organ-on-chip, and microfluidic technologies.
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Affiliation(s)
- Gonzalo Sánchez-Duffhues
- Nanomaterials and Nanotechnology Research Center (CINN-CSIC), ISPA-HUCA, Avda. de Roma, s/n, 33011 Oviedo, Spain
- Department of Cell and Chemical Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands
| | - Christian Hiepen
- Department of Engineering and Natural Sciences, Westphalian University of Applied Sciences, August-Schmidt-Ring 10, 45665 Recklinghausen, Germany
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Abstract
Systemic mastocytosis is a clonal disorder of mast cells that may variably present with characteristic skin lesions, episodes of mast cell mediator release, and disturbances of hematopoiesis. No curative therapy presently exists. Conventional management has relied on agents that antagonize mediators released by mast cells, inhibit mediator secretion, or modulate mast cell proliferation. Recent advances in the molecular understanding of the pathophysiology of systemic mastocytosis have provided new therapeutic considerations, including new and novel tyrosine kinase inhibitors.
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Affiliation(s)
- Dean D Metcalfe
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892;
| | - Yoseph A Mekori
- Tel Hai College, Upper Galilee, 1220800 Israel; .,Meir Medical Center, Kfar Saba 44281, Israel.,Sackler School of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
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3
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Lieberman P, Nicklas RA, Randolph C, Oppenheimer J, Bernstein D, Bernstein J, Ellis A, Golden DBK, Greenberger P, Kemp S, Khan D, Ledford D, Lieberman J, Metcalfe D, Nowak-Wegrzyn A, Sicherer S, Wallace D, Blessing-Moore J, Lang D, Portnoy JM, Schuller D, Spector S, Tilles SA. Anaphylaxis--a practice parameter update 2015. Ann Allergy Asthma Immunol 2016; 115:341-84. [PMID: 26505932 DOI: 10.1016/j.anai.2015.07.019] [Citation(s) in RCA: 288] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 07/12/2015] [Indexed: 12/12/2022]
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Abstract
Acute myeloid leukemia (AML) is the most common form of leukemia in adults, and despite some recent progress in understanding the biology of the disease, AML remains the leading cause of leukemia-related deaths in adults and children. AML is a complex and heterogeneous disease, often involving multiple genetic defects that promote leukemic transformation and drug resistance. The cooperativity model suggests that an initial genetic event leads to maturational arrest in a myeloid progenitor cell, and subsequent genetic events induce proliferation and block apoptosis. Together, these genetic abnormalities lead to clonal expansion and frank leukemia. The purpose of this chapter is to review the biology of receptor tyrosine kinases (RTKs) in AML, exploring how RTKs are being used as novel prognostic factors and potential therapeutic targets.
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MESH Headings
- Adult
- Antineoplastic Agents/therapeutic use
- Drug Delivery Systems
- Forecasting
- Gene Duplication
- Humans
- Leukemia, Myeloid, Acute/drug therapy
- Leukemia, Myeloid, Acute/enzymology
- Leukemia, Myeloid, Acute/genetics
- Models, Biological
- Mutation
- Neoplasm Proteins/antagonists & inhibitors
- Neoplasm Proteins/genetics
- Neoplasm Proteins/physiology
- Oncogene Proteins, Fusion/antagonists & inhibitors
- Oncogene Proteins, Fusion/genetics
- Oncogene Proteins, Fusion/physiology
- Protein Kinase Inhibitors/therapeutic use
- Proto-Oncogene Proteins c-kit/antagonists & inhibitors
- Proto-Oncogene Proteins c-kit/genetics
- Proto-Oncogene Proteins c-kit/physiology
- Receptor Protein-Tyrosine Kinases/antagonists & inhibitors
- Receptor Protein-Tyrosine Kinases/genetics
- Receptor Protein-Tyrosine Kinases/physiology
- Signal Transduction/drug effects
- Signal Transduction/physiology
- fms-Like Tyrosine Kinase 3/antagonists & inhibitors
- fms-Like Tyrosine Kinase 3/genetics
- fms-Like Tyrosine Kinase 3/physiology
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Affiliation(s)
- Derek L Stirewalt
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
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5
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Dubreuil P, Letard S, Ciufolini M, Gros L, Humbert M, Castéran N, Borge L, Hajem B, Lermet A, Sippl W, Voisset E, Arock M, Auclair C, Leventhal PS, Mansfield CD, Moussy A, Hermine O. Masitinib (AB1010), a potent and selective tyrosine kinase inhibitor targeting KIT. PLoS One 2009; 4:e7258. [PMID: 19789626 PMCID: PMC2746281 DOI: 10.1371/journal.pone.0007258] [Citation(s) in RCA: 299] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Accepted: 09/07/2009] [Indexed: 12/24/2022] Open
Abstract
Background The stem cell factor receptor, KIT, is a target for the treatment of cancer, mastocytosis, and inflammatory diseases. Here, we characterise the in vitro and in vivo profiles of masitinib (AB1010), a novel phenylaminothiazole-type tyrosine kinase inhibitor that targets KIT. Methodology/Principal Findings In vitro, masitinib had greater activity and selectivity against KIT than imatinib, inhibiting recombinant human wild-type KIT with an half inhibitory concentration (IC50) of 200±40 nM and blocking stem cell factor-induced proliferation and KIT tyrosine phosphorylation with an IC50 of 150±80 nM in Ba/F3 cells expressing human or mouse wild-type KIT. Masitinib also potently inhibited recombinant PDGFR and the intracellular kinase Lyn, and to a lesser extent, fibroblast growth factor receptor 3. In contrast, masitinib demonstrated weak inhibition of ABL and c-Fms and was inactive against a variety of other tyrosine and serine/threonine kinases. This highly selective nature of masitinib suggests that it will exhibit a better safety profile than other tyrosine kinase inhibitors; indeed, masitinib-induced cardiotoxicity or genotoxicity has not been observed in animal studies. Molecular modelling and kinetic analysis suggest a different mode of binding than imatinib, and masitinib more strongly inhibited degranulation, cytokine production, and bone marrow mast cell migration than imatinib. Furthermore, masitinib potently inhibited human and murine KIT with activating mutations in the juxtamembrane domain. In vivo, masitinib blocked tumour growth in mice with subcutaneous grafts of Ba/F3 cells expressing a juxtamembrane KIT mutant. Conclusions Masitinib is a potent and selective tyrosine kinase inhibitor targeting KIT that is active, orally bioavailable in vivo, and has low toxicity.
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Affiliation(s)
- Patrice Dubreuil
- INSERM, U891, Centre de Recherche en Cancérologie de Marseille, Signalisation, Hematopoiesis and Mechanisms of Oncogenesis, Centre de référence des mastocytoses, Marseille, France
- Institut Paoli-Calmettes, Marseille, France
- Univ Méditerranée, Marseille, France
- AB Science SA, Paris, France
- * E-mail: (PD); (OH)
| | - Sébastien Letard
- INSERM, U891, Centre de Recherche en Cancérologie de Marseille, Signalisation, Hematopoiesis and Mechanisms of Oncogenesis, Centre de référence des mastocytoses, Marseille, France
- Institut Paoli-Calmettes, Marseille, France
- Univ Méditerranée, Marseille, France
- AB Science SA, Paris, France
| | - Marco Ciufolini
- AB Science SA, Paris, France
- University of British Columbia, Department of Chemistry, Vancouver, British Columbia, Canada
| | | | | | | | - Laurence Borge
- INSERM, U891, Centre de Recherche en Cancérologie de Marseille, Signalisation, Hematopoiesis and Mechanisms of Oncogenesis, Centre de référence des mastocytoses, Marseille, France
- Institut Paoli-Calmettes, Marseille, France
- Univ Méditerranée, Marseille, France
| | | | | | - Wolfgang Sippl
- Institute of Pharmaceutical Chemistry, Martin-Luther-Universität, Halle, Wittenberg, Germany
| | - Edwige Voisset
- INSERM, U891, Centre de Recherche en Cancérologie de Marseille, Signalisation, Hematopoiesis and Mechanisms of Oncogenesis, Centre de référence des mastocytoses, Marseille, France
- Institut Paoli-Calmettes, Marseille, France
- Univ Méditerranée, Marseille, France
| | - Michel Arock
- Laboratory of Oncology and Molecular Pharmacology, CNRS, UMR 8113, Ecole Normale Supérieure de Cachan, Cachan, France
| | - Christian Auclair
- AB Science SA, Paris, France
- Laboratory of Oncology and Molecular Pharmacology, CNRS, UMR 8113, Ecole Normale Supérieure de Cachan, Cachan, France
| | | | | | | | - Olivier Hermine
- AB Science SA, Paris, France
- Service d'Hematologie, CNRS, UMR 8147, Centre de référence des mastocytoses, Université Paris V René Descartes, Hôpital Necker, Paris, France
- * E-mail: (PD); (OH)
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Letard S, Yang Y, Hanssens K, Palmérini F, Leventhal PS, Guéry S, Moussy A, Kinet JP, Hermine O, Dubreuil P. Gain-of-Function Mutations in the Extracellular Domain of KIT Are Common in Canine Mast Cell Tumors. Mol Cancer Res 2008; 6:1137-45. [DOI: 10.1158/1541-7786.mcr-08-0067] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Henrich CJ, Goncharova EI, Wilson JA, Gardella RS, Johnson TR, McMahon JB, Takada K, Bokesch HR, Gustafson KR. Natural products active in aberrant c-Kit signaling. Chem Biol Drug Des 2007; 69:321-30. [PMID: 17539824 DOI: 10.1111/j.1747-0285.2007.00508.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Development of modulators of constitutively active, kinase domain mutants of c-Kit has proved to be very difficult. Therefore, a high-throughput differential cytotoxicity assay was developed to screen for compounds that preferentially kill cells expressing constitutively active c-Kit. The cells used in the assay, murine IC2 mast cells, express either the D814Y activating mutation (functionally equivalent to human D816Y) or wild type protein. This assay is robust and highly reproducible. When applied to libraries of natural product extracts (followed by assay-guided fractionation), two differentially active compounds were identified. To assess possible mechanisms of action, the active compounds were tested for inhibitory activity against a panel of signaling enzymes (including wild type and mutant c-Kit). Neither of the compounds significantly affected any of the 73 enzymes tested. The effects of commercially available modulators of known signaling components were also assessed using the screening assay. None of these inhibitors reproduced the differential activity seen with the natural products. Finally, both compounds were found to affect mitochondrial potential in cells expressing c-Kit(D814Y). These results suggest that the newly identified natural products may provide new avenues for intervention in aberrant c-Kit signaling pathways.
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Affiliation(s)
- Curtis J Henrich
- Molecular Targets Development Program, NCI-Frederick, Frederick, MD 21702, USA.
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Farini D, La Sala G, Tedesco M, De Felici M. Chemoattractant action and molecular signaling pathways of Kit ligand on mouse primordial germ cells. Dev Biol 2007; 306:572-83. [PMID: 17467686 DOI: 10.1016/j.ydbio.2007.03.031] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 03/22/2007] [Accepted: 03/23/2007] [Indexed: 02/05/2023]
Abstract
Using a Transwell chamber as migration assay for mouse primordial germ cells (PGCs), we show here that these cells posses directional migration in the absence of somatic cell and defined matrix support and in response to a Kit ligand (KL) gradient or medium conditioned by Aorta/Gonad/Mesonephros and gonadal ridges. Other putative PGC chemoattractants such as SDF1 and TGFbeta did not exert any attractive action on PGCs. The chemoattractant activity of KL and conditioned medium was also evidenced by their ability to stimulate actin reorganization in PGCs. In the aim to identify downstream signaling pathways governing KL chemoattraction on PGCs, we demonstrated that in such cells KL rapidly (5 min) increased autophosphorylation of its receptor c-Kit and caused phosphorylation of the serine-threonine kinase AKT through the action of PI3K. 740Y-P peptide, a direct activator of PI3 kinase, stimulated PGC migration at levels similar to those elicited by KL. LY294002 (a specific inhibitor of PI3K) abolished KL-dependent PGC migration or the chemoattractant activity of the conditioned medium and inhibited AKT phosphorylation; Src kinase inhibitors PP2 and SU6656, caused significant reduction of the KL-dependent PGC migration and AKT phosphorylation, while U0126, a selective inhibitor of the MEK/ERK protein kinase cascade, reduced PGC migration and AKT phosphorylation at lesser extent. SU6656 completely abolished the chemoattractant activity of the conditioned medium. Finally, SB202190 (a p38 inhibitor) and rapamycin (mTOR inhibitor) did not affect PGC migration. In addition, to demonstrate that somatic cells are not essential for PGC motility and directional migration, we evidenced a novel role for KL as PGC chemoattractant and for PI3K/AKT and Src kinase, as players involved in the activation of the PGC migratory machinery and likely important for their directional movement towards the gonadal ridges.
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Affiliation(s)
- Donatella Farini
- Department of Public Health and Cell Biology, Section of Histology and Embryology, University of Rome Tor Vergata, Via Montpellier 1, 00173 Rome, Italy
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9
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Heinemann A, Sturm GJ, Ofner M, Sturm EM, Weller C, Peskar BA, Hartnell A. Stem cell factor stimulates the chemotaxis, integrin upregulation, and survival of human basophils. J Allergy Clin Immunol 2005; 116:820-6. [PMID: 16210056 DOI: 10.1016/j.jaci.2005.06.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Revised: 05/31/2005] [Accepted: 06/10/2005] [Indexed: 12/01/2022]
Abstract
BACKGROUND Little is known about the mechanisms that regulate the selective recruitment of basophils to sites of allergic inflammation. OBJECTIVE Here we examine the role of stem cell factor (SCF) in the regulation of basophil function. METHODS Human basophils were isolated from peripheral blood, and their migration was investigated in chemotaxis assays. Apoptosis was detected by means of annexin V and propidium iodide staining. The expression of cell-surface molecules was measured by means of flow cytometry. RESULTS SCF amplified the chemotactic responsiveness of human peripheral blood basophils to the chemoattractants eotaxin, monocyte chemotactic protein 2 and macrophage inflammatory protein 1alpha, and C5a, without being chemotactic or chemokinetic by itself. SCF synergized with chemoattractants in causing basophil upregulation of the integrin CD11b, and this effect was inhibited by a c-kit antibody, the tyrosine kinase inhibitor imatinib mesylate (STI-571), and a phosphatidylinositol 3 kinase inhibitor but not by inhibitors of p38 mitogen-activated protein kinase or mitogen-activated protein kinase/extracellular signal-regulated kinase kinase. Basophils bound fluorescence-labeled SCF and expressed its receptor, c-kit, which was markedly upregulated in culture for 24 to 48 hours in the presence of IL-3. Moreover, SCF prolonged basophil survival in concert with IL-3 by delaying apoptosis. These effects of SCF were selective for basophils because chemotaxis and CD11b upregulation of eosinophils or neutrophils were unchanged. CONCLUSION SCF might be an important selective modulator of basophil function through a phosphatidylinositol 3 kinase-dependent pathway.
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Affiliation(s)
- Akos Heinemann
- Department of Experimental and Clinical Pharmacology, Medical University of Graz, Austria.
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10
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Ishiko J, Mizuki M, Matsumura I, Shibayama H, Sugahara H, Scholz G, Serve H, Kanakura Y. Roles of tyrosine residues 845, 892 and 922 in constitutive activation of murine FLT3 kinase domain mutant. Oncogene 2005; 24:8144-53. [PMID: 16091740 DOI: 10.1038/sj.onc.1208957] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
FLT3 tyrosine kinase domain (TKD) mutations are detected in approximately 7% of acute myeloid leukemia patients, and suggested to correlate with poor prognosis and confer resistance to FLT3 inhibitors. To explore activation mechanism of FLT3 TKD mutation, we analysed critical tyrosine residues for the constitutive activation and downstream signaling of the mutant by generating a series of single Tyr --> Phe substitution mutant of all 22 cytoplasmic tyrosine residues of murine FLT3 TKD-mutant (mFLT3Asp838Val). Tyr845Phe, Tyr892Phe and Tyr922Phe substitutions suppressed the phosphorylation of mFLT3Asp838Val itself, the activation of Erk1/2, STAT3 and STAT5, and the factor-independent cell proliferation and survival. In contrast, these three Tyr --> Phe mutations partially suppressed but maintained the ligand-dependent activation and anti-apoptotic activity of wild-type FLT3, suggesting that these tyrosine residues were more critical for the constitutive activation and signaling of mFLT3Asp838Val. These three Tyr --> Phe mutations also inhibited the constitutive activation of other FLT3 mutants bearing internal tandem duplication, Asp838Tyr or Ile839del. The suppression of mFLT3Asp838Val activation and signaling by these substitutions was partially recovered by shifting the culture temperature from 37 to 33 degrees C, or by the introduction of Cdc37 and Hsp90. Taken together, Tyr845, Tyr892 and Tyr922 are the critical residues in mFLT3Asp838Val activation, possibly through stabilizing the active conformation of mFLT3Asp838Val.
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Affiliation(s)
- Jun Ishiko
- Department of Hematology and Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan
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Abstract
Acute myeloid leukaemia (AML) is an aggressive haematological malignancy that is curable in approximately 40% of cases. Activating mutations of the receptor tyrosine kinase FLT3 (FMS-like tyrosine kinase-3) are the single most common molecular abnormalities in AML and are associated with a distinctly worse prognosis. In an effort to target this mutation and improve outcomes in this subgroup of AML patients, several novel small-molecule FLT3 tyrosine kinase inhibitors are currently in development. Some of these FLT3 inhibitors are useful only as laboratory tools, while others clearly have clinical potential. These compounds are derived from a wide variety of chemical classes and differ significantly both in their potency and selectivity. This review summarises these developments and examines these novel agents with regard to both the assays used to characterise them and their clinical potential.
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Affiliation(s)
- Mark Levis
- Johns Hopkins University School of Medicine, Department of Oncology, Baltimore, MD 21231-1000, USA
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Abstract
Acute myeloid leukaemia (AML) has been proposed to arise from the collaboration between two classes of mutation, a class I, or proliferative, mutation and a class II, or blocking, mutation. A limitation of this so-called 'two-hit' hypothesis has been the lack of identifiable proliferative and blocking mutations in most AML cases. However, it is now known that the CBFbeta-MYH11 fusion gene in AML and inv(16), by disrupting the normal transcription factor activity of core binding factor (CBF), functions as a class II mutation. In addition, nearly 70% of patients with AML and inv(16) are known to possess mutually exclusive mutations of the receptor tyrosine kinases (RTKs), c-KIT and FLT3, as well as RAS genes, that provide a class I, or proliferative, signal. AML and inv(16), therefore, is one of the best understood of the acute leukaemias at the genetic level and so provides a paradigm for the 'two-hit' hypothesis of leukaemogenesis. This paper reviews the recent advances in the molecular pathology of AML and inv(16) and discusses possible therapeutic implications of the current pathogenetic model.
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Affiliation(s)
- John T Reilly
- Molecular Haematology Unit, Division of Molecular and Genetic Medicine, Royal Hallamshire Hospital, Sheffield, UK.
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14
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Abstract
Haematopoiesis is controlled by a number of growth factors and cytokines, a number of which act through binding to high-affinity receptor tyrosine kinases (RTKs). Approximately 20 different RTK classes have been identified, all of which share a similar structure that includes a ligand binding extracellular domain, a single transmembrane domain and an intracellular tyrosine kinase domain. Recent studies have linked an increasing number of mutations in the RTKs to the pathogenesis of both acute and chronic leukaemia. For example, the FLT3 receptor, a RTK class III, is the most commonly mutated gene in acute myeloid leukaemia, while c-kit mutations are strongly linked to the development of mast cell malignancy. This review summarizes the RTK classes that are known to be expressed on normal haematopoietic tissue and highlights the many 'gain-of-function' mutations involved in leukaemogenesis. It is to be hoped that this knowledge will provide important new insights for targeted therapy in leukaemia.
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Mol CD, Dougan DR, Schneider TR, Skene RJ, Kraus ML, Scheibe DN, Snell GP, Zou H, Sang BC, Wilson KP. Structural basis for the autoinhibition and STI-571 inhibition of c-Kit tyrosine kinase. J Biol Chem 2004; 279:31655-63. [PMID: 15123710 DOI: 10.1074/jbc.m403319200] [Citation(s) in RCA: 484] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The activity of the c-Kit receptor protein-tyrosine kinase is tightly regulated in normal cells, whereas deregulated c-Kit kinase activity is implicated in the pathogenesis of human cancers. The c-Kit juxtamembrane region is known to have an autoinhibitory function; however the precise mechanism by which c-Kit is maintained in an autoinhibited state is not known. We report the 1.9-A resolution crystal structure of native c-Kit kinase in an autoinhibited conformation and compare it with active c-Kit kinase. Autoinhibited c-Kit is stabilized by the juxtamembrane domain, which inserts into the kinase-active site and disrupts formation of the activated structure. A 1.6-A crystal structure of c-Kit in complex with STI-571 (Imatinib or Gleevec) demonstrates that inhibitor binding disrupts this natural mechanism for maintaining c-Kit in an autoinhibited state. Together, these results provide a structural basis for understanding c-Kit kinase autoinhibition and will facilitate the structure-guided design of specific inhibitors that target the activated and autoinhibited conformations of c-Kit kinase.
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