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Greenberger S, Landov H, Confino Y, Vaknine H, Avivi C, Baum S, Barzilai A. Immunophenotype of pediatric-onset mastocytosis does not correlate with clinical course. Pediatr Dermatol 2019; 36:477-481. [PMID: 31120154 DOI: 10.1111/pde.13850] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Pediatric mastocytosis differs from adult mastocytosis in its presentation and clinical course. However, the data regarding the immunophenotypic characterization of mast cells in children are limited. Our objective was to evaluate the immunophenotype of mast cells in pediatric mastocytosis and correlate it with the clinical course. METHODS Biopsy specimens of children with cutaneous mastocytosis were retrieved from the institutions of pathology and were stained for CD25, CD2, and CD30. The percentage of mast cells and the staining intensity were correlated with the clinical data. RESULTS Twenty-five biopsy specimens were included in the study. Patients' average age was 15.4 at presentation and 37.5 months at biopsy performance. Clinical presentations included maculopapular cutaneous mastocytosis in 79% and mastocytoma in 21% of cases. CD25, CD2, and CD30 were positive in 60%, 44%, and 84% of the biopsy specimens, respectively. The staining score was significantly higher for CD30 as compared to those for CD25 and CD2 (P = 0.02). No correlation was found between the immunophenotype and the clinical form or course of disease. CONCLUSIONS Our results confirm that CD30 is a sensitive marker for pediatric-onset mastocytosis. Nevertheless, its expression does not correlate with clinical subtype or clinical course. The sensitivity of CD25 is higher than that of CD2 in skin lesions.
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Affiliation(s)
- Shoshana Greenberger
- Department of Dermatology, The Chaim Sheba Medical Center, Ramat Gan, Israel.,Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Hagai Landov
- Department of Dermatology, The Chaim Sheba Medical Center, Ramat Gan, Israel.,Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Yitzhak Confino
- Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel.,Dermatology Unit, Edith Wolfson Medical Center, Holon, Israel
| | - Hananya Vaknine
- Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel.,Institute of Pathology, Edith Wolfson Medical Center, Holon, Israel
| | - Camila Avivi
- Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel.,Institute of Pathology, The Chaim Sheba Medical Center, Ramat Gan, Israel
| | - Sharon Baum
- Department of Dermatology, The Chaim Sheba Medical Center, Ramat Gan, Israel.,Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Aviv Barzilai
- Department of Dermatology, The Chaim Sheba Medical Center, Ramat Gan, Israel.,Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel.,Institute of Pathology, The Chaim Sheba Medical Center, Ramat Gan, Israel
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2
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Arock M, Wedeh G, Hoermann G, Bibi S, Akin C, Peter B, Gleixner KV, Hartmann K, Butterfield JH, Metcalfe DD, Valent P. Preclinical human models and emerging therapeutics for advanced systemic mastocytosis. Haematologica 2018; 103:1760-1771. [PMID: 29976735 PMCID: PMC6278969 DOI: 10.3324/haematol.2018.195867] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 06/27/2018] [Indexed: 12/19/2022] Open
Abstract
Mastocytosis is a term used to denote a group of rare diseases characterized by an abnormal accumulation of neoplastic mast cells in various tissues and organs. In most patients with systemic mastocytosis, the neoplastic cells carry activating mutations in KIT Progress in mastocytosis research has long been hindered by the lack of suitable in vitro models, such as permanent human mast cell lines. In fact, only a few human mast cell lines are available to date: HMC-1, LAD1/2, LUVA, ROSA and MCPV-1. The HMC-1 and LAD1/2 cell lines were derived from patients with mast cell leukemia. By contrast, the more recently established LUVA, ROSA and MCPV-1 cell lines were derived from CD34+ cells of non-mastocytosis donors. While some of these cell lines (LAD1/2, LUVA, ROSAKIT WT and MCPV-1) do not harbor KIT mutations, HMC-1 and ROSAKIT D816V cells exhibit activating KIT mutations found in mastocytosis and have thus been used to study disease pathogenesis. In addition, these cell lines are increasingly employed to validate new therapeutic targets and to screen for effects of new targeted drugs. Recently, the ROSAKIT D816V subclone has been successfully used to generate a unique in vivo model of advanced mastocytosis by injection into immunocompromised mice. Such a model may allow in vivo validation of data obtained in vitro with targeted drugs directed against mastocytosis. In this review, we discuss the major characteristics of all available human mast cell lines, with particular emphasis on the use of HMC-1 and ROSAKIT D816V cells in preclinical therapeutic research in mastocytosis.
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Affiliation(s)
- Michel Arock
- LBPA CNRS UMR8113, Ecole Normale Supérieure Paris-Saclay, Cachan, France .,Laboratory of Hematology, Pitié-Salpêtrière Hospital, Paris, France
| | - Ghaith Wedeh
- LBPA CNRS UMR8113, Ecole Normale Supérieure Paris-Saclay, Cachan, France
| | - Gregor Hoermann
- Department of Laboratory Medicine, Medical University of Vienna, Austria.,Ludwig Boltzmann Cluster Oncology, Medical University of Vienna, Austria
| | - Siham Bibi
- LBPA CNRS UMR8113, Ecole Normale Supérieure Paris-Saclay, Cachan, France
| | - Cem Akin
- Michigan Medicine Allergy Clinic, University of Michigan, Ann Arbor, MI, USA
| | - Barbara Peter
- Ludwig Boltzmann Cluster Oncology, Medical University of Vienna, Austria.,Department of Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Austria
| | - Karoline V Gleixner
- Ludwig Boltzmann Cluster Oncology, Medical University of Vienna, Austria.,Department of Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Austria
| | - Karin Hartmann
- Department of Dermatology, University of Luebeck, Germany
| | | | - Dean D Metcalfe
- Laboratory of Allergic Diseases, NIAID, NIH, Bethesda, MD, USA
| | - Peter Valent
- Ludwig Boltzmann Cluster Oncology, Medical University of Vienna, Austria.,Department of Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Austria
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3
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Golardi N, Sramek JE, Myers JB, Saffer H, George TI, Czuchlewski DR. Two cases of concomitant acquired aplastic anemia and systemic mastocytosis. Hum Pathol 2013; 45:417-20. [PMID: 24182560 DOI: 10.1016/j.humpath.2013.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 06/28/2013] [Accepted: 08/09/2013] [Indexed: 12/01/2022]
Abstract
Reactive bone marrow mast cells reliably lack the morphologic, immunophenotypic, and molecular features of systemic mastocytosis (SM). We report two unusual cases of acquired aplastic anemia (AA) in which multifocal aggregates of bone marrow mast cells fulfilled morphologic and immunophenotypic criteria for SM according to the World Health Organization 2008 classification. In the absence of clinical symptoms attributable to SM, the patients were treated with immunosuppressive therapy directed towards AA. Clinical follow-up and subsequent bone marrow examination revealed no evidence of overt SM in either patient. These cases represent, to our knowledge, the first reported instances in which criteria for SM have been fulfilled in the presence of AA. However, given the clinical courses followed by our patients, the incidental identification of mast cell lesions consistent with indolent SM may be of uncertain significance in the setting of AA.
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Affiliation(s)
- Natalia Golardi
- Department of Pathology, University of New Mexico, Albuquerque, NM 87102, USA
| | - Jacob E Sramek
- Department of Pathology, University of New Mexico, Albuquerque, NM 87102, USA; Penrose - St. Francis Hospital, Department of Pathology, Colorado Springs, CO, USA
| | - Jerome B Myers
- Penrose - St. Francis Hospital, Department of Pathology, Colorado Springs, CO, USA
| | - Helene Saffer
- Analytic Pathology Medical Group, Sharp Grossmont Hospital, La Mesa, CA, USA
| | - Tracy I George
- Department of Pathology, University of New Mexico, Albuquerque, NM 87102, USA
| | - David R Czuchlewski
- Department of Pathology, University of New Mexico, Albuquerque, NM 87102, USA.
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4
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Phospho-ERK(THR202/Tyr214) is overexpressed in hairy cell leukemia and is a useful diagnostic marker in bone marrow trephine sections. Am J Surg Pathol 2013; 37:305-8. [PMID: 23211289 DOI: 10.1097/pas.0b013e3182712481] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BRAF V600E mutations are present in virtually all cases of hairy cell leukemia (HCL). We hypothesized that detection of phospho-ERK (pERK) in tissue sections may be a useful marker for diagnosis of HCL. pERK/CD20 double immunostaining was performed on 90 formalin-fixed bone marrow trephine samples affected with small B-cell lymphoproliferative disorders, including 28 cases of HCL. pERK staining was observed in all 28 cases of HCL and in 1 of 62 cases of non-HCL B-cell lymphoproliferative disorders. By allele-specific polymerase chain reaction, all 11 cases of HCL with available DNA were positive for BRAF V600E, as was the 1 pERK non-HCL case. The remaining 31 non-HCL cases tested were negative for BRAF V600E. The sensitivity and specificity of pERK for diagnosis of HCL was 100% and 98%, respectively. We conclude that the presence of pERK as detected by immunohistochemical staining is a useful surrogate marker for BRAF V600E in the diagnosis of HCL.
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5
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PTEN deficiency in mast cells causes a mastocytosis-like proliferative disease that heightens allergic responses and vascular permeability. Blood 2011; 118:5466-75. [PMID: 21926349 DOI: 10.1182/blood-2010-09-309955] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Kit regulation of mast cell proliferation and differentiation has been intimately linked to the activation of phosphatidylinositol 3-OH kinase (PI3K). The activating D816V mutation of Kit, seen in the majority of mastocytosis patients, causes a robust activation of PI3K signals. However, whether increased PI3K signaling in mast cells is a key element for their in vivo hyperplasia remains unknown. Here we report that dysregulation of PI3K signaling in mice by deletion of the phosphatase and tensin homolog (Pten) gene (which regulates the levels of the PI3K product, phosphatidylinositol 3,4,5-trisphosphate) caused mast cell hyperplasia and increased numbers in various organs. Selective deletion of Pten in the mast cell compartment revealed that the hyperplasia was intrinsic to the mast cell. Enhanced STAT5 phosphorylation and increased expression of survival factors, such as Bcl-XL, were observed in PTEN-deficient mast cells, and these were further enhanced by stem cell factor stimulation. Mice carrying PTEN-deficient mast cells also showed increased hypersensitivity as well as increased vascular permeability. Thus, Pten deletion in the mast cell compartment results in a mast cell proliferative phenotype in mice, demonstrating that dysregulation of PI3K signals is vital to the observed mast cell hyperplasia.
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Abstract
Phosphorylation is one of the most important processes in cell signal transduction. Detection of phosphorylated proteins in cancer tissue is useful for prognosis and diagnosis, and it might be very helpful in monitoring treatment using targeted therapy. For these reasons, the in situ quantitative measurement and subcellular localization of phosphoproteins will likely be important. However, phosphoproteins are extremely labile, a likely explanation for inconsistent or contradictory reports. Thus, the development of new paradigms for tissue handling, immunostaining, and quality control are needed.
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Affiliation(s)
- J Bodo
- Department of Clinical Pathology, Cleveland Clinic, OH 44195, USA
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7
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Hoermann G, Cerny-Reiterer S, Perné A, Klauser M, Hoetzenecker K, Klein K, Müllauer L, Gröger M, Nijman SMB, Klepetko W, Valent P, Mayerhofer M. Identification of oncostatin M as a STAT5-dependent mediator of bone marrow remodeling in KIT D816V-positive systemic mastocytosis. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 178:2344-56. [PMID: 21457934 DOI: 10.1016/j.ajpath.2011.01.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 12/21/2010] [Accepted: 01/07/2011] [Indexed: 01/08/2023]
Abstract
Systemic mastocytosis is a neoplastic disease of mast cells harboring the activating KIT mutation D816V. In most patients, mast cell infiltration in the bone marrow is accompanied by marked microenvironment alterations, including increased angiogenesis, osteosclerosis, and sometimes fibrosis. Little is known about the mast cell-derived molecules contributing to these bone marrow alterations. We show here that neoplastic mast cells in patients with systemic mastocytosis express oncostatin M (OSM), a profibrogenic and angiogenic modulator. To study the regulation of OSM expression, KIT D816V was inducibly expressed in Ba/F3 cells and was found to up-regulate OSM mRNA and protein levels, suggesting that OSM is a KIT D816V-dependent mediator. Correspondingly, KIT D816V(+) HMC-1.2 cells expressed significantly higher amounts of OSM than the KIT D816V(-) HMC-1.1 subclone. RNA interference-induced knockdown of STAT5, a key transcription factor in KIT D816V(+) mast cells, inhibited OSM expression in HMC-1 cells, whereas a constitutively activated STAT5 mutant induced OSM expression. Finally, OSM secreted from KIT D816V(+) mast cells stimulated growth of endothelial cells, fibroblasts, and osteoblasts, suggesting that mast cell-derived OSM may serve as a key modulator of the marrow microenvironment and thus contribute to the pathology of systemic mastocytosis.
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Affiliation(s)
- Gregor Hoermann
- Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
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8
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Current approaches to the diagnosis and treatment of systemic mastocytosis. Ann Allergy Asthma Immunol 2010; 104:1-10; quiz 10-2, 41. [PMID: 20143640 DOI: 10.1016/j.anai.2009.11.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
OBJECTIVE To review the clinical manifestations of mastocytosis and examine the recommended diagnostic procedures and therapeutic options available for the treatment of this condition. DATA SOURCES PubMed searches were performed for articles published regarding presentation and classification of mastocytosis and the diagnostic criteria and treatment options for this condition using the keywords mastocytosis, clinical features, World Health Organization diagnostic criteria, management, pathogenesis, and urticaria pigmentosa. Retrieved articles were surveyed for additional citations. STUDY SELECTION Articles were reviewed for relevance to the study objectives, and more recent articles were preferentially included. Prospective studies were preferentially included when available. RESULTS Mastocytosis is a heterogeneous disorder that results from clonal mast cell proliferation. Symptoms are typically limited to the skin in the pediatric population, requiring only symptomatic treatment with spontaneous resolution by puberty. Disease course in adults ranges from minimally symptomatic in most to highly aggressive but tends to be persistent. Symptoms can be protean and nonspecific. The mainstay of treatment consists of avoidance of triggers of mast cell degranulation and symptom-based therapy. CONCLUSIONS Mastocytosis should be suspected in patients who present with a constellation of symptoms, including flushing, abdominal pain, diarrhea, unexplained syncope, and classic urticaria pigmentosa lesions. Diagnosis should be established by a bone marrow biopsy in all adults. Staging should be performed to assess disease burden and evidence of end-stage organ damage. Patients should be offered symptom-based treatment and cytoreductive therapy only for aggressive systemic mastocytosis or an associated hematologic malignant neoplasm.
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9
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Baumgartner C, Cerny-Reiterer S, Sonneck K, Mayerhofer M, Gleixner KV, Fritz R, Kerenyi M, Boudot C, Gouilleux F, Kornfeld JW, Sillaber C, Moriggl R, Valent P. Expression of activated STAT5 in neoplastic mast cells in systemic mastocytosis: subcellular distribution and role of the transforming oncoprotein KIT D816V. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 175:2416-29. [PMID: 19893034 DOI: 10.2353/ajpath.2009.080953] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent data suggest that the signal transducer and activator of transcription (STAT)5 contributes to differentiation and growth of mast cells. It has also been described that constitutively phosphorylated STAT5 (pSTAT5) plays a pro-oncogenic role in various myeloid neoplasms. We examined the expression of pSTAT5 in neoplastic mast cells in systemic mastocytosis and asked whether the disease-related oncoprotein KIT D816V is involved in STAT5 activation. As assessed by immunohistochemistry using the anti-pSTAT5 antibody AX1, neoplastic mast cells were found to display pSTAT5 in all SM patients examined (n = 40). Expression of pSTAT5 was also demonstrable in the KIT D816V-positive mast cell leukemia cell line HMC-1. Using various staining-protocols, pSTAT5 was found to be located in both the cytoplasmic and nuclear compartment of mast cells. To define the functional role of KIT D816V in STAT5-activation, Ba/F3 cells with doxycycline-inducible expression of KIT D816V were used. In these cells, induction of KIT D816V resulted in an increased expression of pSTAT5 without substantial increase in total STAT5. Moreover, the KIT D816V-targeting kinase-inhibitor PKC412 was found to counteract expression of pSTAT5 in HMC-1 cells as well as doxycycline-induced expression of pSTAT5 in Ba/F3 cells. Finally, a dominant negative STAT5-construct was found to inhibit growth of HMC-1 cells. Together, our data show that neoplastic mast cells express cytoplasmic and nuclear pSTAT5, that KIT D816V promotes STAT5-activation, and that STAT5-activation contributes to growth of neoplastic mast cells.
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10
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Grimwade LF, Happerfield L, Tristram C, McIntosh G, Rees M, Bench AJ, Boyd EM, Hall M, Quinn A, Piggott N, Scorer P, Scott MA, Erber WN. Phospho-STAT5 and phospho-Akt expression in chronic myeloproliferative neoplasms. Br J Haematol 2009; 147:495-506. [DOI: 10.1111/j.1365-2141.2009.07870.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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11
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Bodo J, Durkin L, Hsi ED. Quantitative in situ detection of phosphoproteins in fixed tissues using quantum dot technology. J Histochem Cytochem 2009; 57:701-8. [PMID: 19332430 DOI: 10.1369/jhc.2009.953547] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Detection and quantitation of phosphoproteins (PPs) in fixed tissues will become increasingly important as additional inhibitors of protein kinases enter clinical use and new disease entities are defined by molecular changes affecting PP levels. We characterize fixation conditions suitable for accurate PP quantitation that are achievable in a clinical laboratory and illustrate the utility of in situ quantitation of PPs by quantum dot (QD) nanocrystals in two models: (1) a therapeutic model demonstrating effects of a targeted therapeutic (quantitative reduction of phospho-GSK3beta) in xenografts treated with enzastaurin; and (2) a diagnostic model that identifies elevated levels of nuclear phospho-STAT5 in routine bone marrow biopsies from patients with acute myeloid leukemia based on the presence of the activating FLT3-ITD mutation. Finally, we document production of a well-characterized tissue microarray of widely available cell lines as a multilevel calibrator for validating numerous phosphoprotein assays. QD immunofluorescence is an ideal method for in situ quantitation of PPs in fixed samples, providing valuable cell type-specific and subcellular information about pathway activation in primary tissues.
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Affiliation(s)
- Juraj Bodo
- Department of Clinical Pathology, L-11 Cleveland Clinic, Cleveland, Ohio 44195, USA
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12
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Mayerhofer M, Gleixner KV, Hoelbl A, Florian S, Hoermann G, Aichberger KJ, Bilban M, Esterbauer H, Krauth MT, Sperr WR, Longley JB, Kralovics R, Moriggl R, Zappulla J, Liblau RS, Schwarzinger I, Sexl V, Sillaber C, Valent P. Unique effects of KIT D816V in BaF3 cells: induction of cluster formation, histamine synthesis, and early mast cell differentiation antigens. THE JOURNAL OF IMMUNOLOGY 2008; 180:5466-76. [PMID: 18390729 DOI: 10.4049/jimmunol.180.8.5466] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Oncogenic tyrosine kinases (TK) usually convert growth factor-dependent cells to factor independence with autonomous proliferation. However, TK-driven neoplasms often are indolent and characterized by cell differentiation rather than proliferation. A prototype of an indolent TK-driven neoplasm is indolent systemic mastocytosis. We found that the D816V-mutated variant of KIT, a TK detectable in most patients with systemic mastocytosis, induces cluster formation and expression of several mast cell differentiation and adhesion Ags, including microphthalmia transcription factor, IL-4 receptor, histamine, CD63, and ICAM-1 in IL-3-dependent BaF3 cells. By contrast, wild-type KIT did not induce cluster formation or mast cell differentiation Ags. Additionally, KIT D816V, but not wild-type KIT, induced STAT5 activation in BaF3 cells. However, despite these intriguing effects, KIT D816V did not convert BaF3 cells to factor-independent proliferation. Correspondingly, BaF3 cells with conditional expression of KIT D816V did not form tumors in nude mice. Together, the biologic effects of KIT D816V in BaF3 cells match strikingly with the clinical course of indolent systemic mastocytosis and with our recently established transgenic mouse model, in which KIT D816V induces indolent mast cell accumulations but usually does not induce a malignant mast cell disease. Based on all these results, it is hypothesized that KIT D816V as a single hit may be sufficient to cause indolent systemic mastocytosis, whereas additional defects may be required to induce aggressive mast cell disorders.
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Affiliation(s)
- Matthias Mayerhofer
- Department of Internal Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria
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13
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Oncogenic Kit controls neoplastic mast cell growth through a Stat5/PI3-kinase signaling cascade. Blood 2008; 112:2463-73. [PMID: 18579792 DOI: 10.1182/blood-2007-09-115477] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The D816V-mutated variant of Kit triggers multiple signaling pathways and is considered essential for malignant transformation in mast cell (MC) neoplasms. We here describe that constitutive activation of the Stat5-PI3K-Akt-cascade controls neoplastic MC development. Retrovirally transduced active Stat5 (cS5(F)) was found to trigger PI3K and Akt activation, and to transform murine bone marrow progenitors into tissue-infiltrating MCs. Primary neoplastic Kit D816V(+) MCs in patients with mastocytosis also displayed activated Stat5, which was found to localize to the cytoplasm and to form a signaling complex with PI3K, with consecutive Akt activation. Finally, the knock-down of either Stat5 or Akt activity resulted in growth inhibition of neoplastic Kit D816V(+) MCs. These data suggest that a downstream Stat5-PI3K-Akt signaling cascade is essential for Kit D816V-mediated growth and survival of neoplastic MCs.
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