Clonal analysis of NRAS activating mutations in KIT-D816V systemic mastocytosis

Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, 20892-1881, USA.
Haematologica (Impact Factor: 5.81). 12/2010; 96(3):459-63. DOI: 10.3324/haematol.2010.031690
Source: PubMed


Cooperating genetic events are likely to contribute to the phenotypic diversity of KIT-D816V systemic mastocytosis. In this study, 44 patients with KIT-D816V systemic mastocytosis were evaluated for coexisting NRAS, KRAS, HRAS or MRAS mutations. Activating NRAS mutations were identified in 2 of 8 patients with advanced disease. NRAS mutations were not found in patients with indolent systemic mastocytosis. To better understand the clonal evolution of mastocytosis, we evaluated the cell compartments impacted by the NRAS and KIT mutations. Clonal mast cells harbored both mutations. KIT-D816V was not detected in bone marrow CD34(+) progenitors, whereas the NRAS mutation was present. These findings suggest that NRAS mutations may have the potential to precede KIT-D816V in clonal development. Unlike other mature lineages, mast cell survival is dependent on KIT and the presence of these two activating mutations may have a greater impact on the expansion of this cell compartment and in resultant disease severity.

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Available from: Todd M. Wilson, Dec 17, 2013
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    • "Additional cooperating events may contribute to the pathogenesis and/or the phenotype of SM [11], [12], [13]. Mutations in TET2 have been reported in as many as 40% of KIT D816V-positive SM cases [11], [12]. "
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    ABSTRACT: Systemic Mastocytosis (SM) is a clonal disease characterized by abnormal accumulation of mast cells in multiple organs. Clinical presentations of the disease vary widely from indolent to aggressive forms, and to the exceedingly rare mast cell leukemia. Current treatment of aggressive SM and mast cell leukemia is unsatisfactory. An imatinib-resistant activating mutation of the receptor tyrosine kinase KIT (KIT D816V) is most frequently present in transformed mast cells and is associated with all clinical forms of the disease. Thus the etiology of the variable clinical aggressiveness of abnormal mast cells in SM is unclear. TET2 appears to be mutated in primary human samples in aggressive types of SM, suggesting a possible role in disease modification. In this report, we demonstrate the cooperation between KIT D816V and loss of function of TET2 in mast cell transformation and demonstrate a more aggressive phenotype in a murine model of SM when both mutations are present in progenitor cells. We exploit these findings to validate a combination treatment strategy targeting the epigenetic deregulation caused by loss of TET2 and the constitutively active KIT receptor for the treatment of patients with aggressive SM.
    Full-text · Article · May 2014 · PLoS ONE
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    • "All mutations were somatic and led to kit activation. Other oncogenic mutations recently identified in mastocytosis patients include TET2 (TET oncogene family member 2) and N-RAS [21]. These mutation are not specific of mastocytosis and their pathogenetic role and/or prognostic impact is currently uncertain. "
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    ABSTRACT: Mastocytosis is a heterogeneous group of disorders characterized by a clonal proliferation and accumulation of mast cells in one or more organ, primarily in the skin and bone marrow. The clinical spectrum of the disease varies from relatively benign forms with isolated skin lesions to very aggressive variants with extensive systemic involvement and poor prognosis. The growth and proliferation of clonal mast cells is caused by an activating mutation of the tyrosine kinase receptor Kit for Stem Cell Factor, the main growth factor for mast cells. Clinical symptoms are related to mast-cell mediator release, to the tissue mast cell infiltration or both. The degree of infiltration and cell activation determines the highly variable clinical and morphological features. Current treatment of mastocytosis includes symptomatic, antimediator drugs and cytoreductive targeted therapies.
    Full-text · Article · Apr 2014
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    • "Indeed, recent data suggest that a number of additional lesions are detectable in patients with SM-AHNMD, ASM and MCL. These lesions include RAS mutations, TET2 mutations , mutations in IgE receptor genes and other genes [49] [50] [51] [52]. "
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    ABSTRACT: Mastocytosis is a rare disease characterized by abnormal expansion and accumulation of tissue mast cells (MC) in one or multiple organs. In most adult patients, systemic mastocytosis (SM) is diagnosed. Based on histopathological findings and organ damage, SM is divided into indolent SM (ISM), smoldering SM (SSM), SM with an associated hematologic non-MC-lineage disease (SM-AHNMD), aggressive SM (ASM), and MC leukemia (MCL). The clinical course and prognosis vary greatly among these groups of patients. In all variants of SM and most patients, neoplastic cells display the KIT mutation D816V. This suggests that additional KIT-independent molecular defects cause progression. Indeed, additional oncogenic lesions, including RAS- and TET2 mutations, have recently been identified in advanced SM. In patients with SM-AHNMD, such additional lesions are often detectable in the 'AHNMD-component' of the disease. Clinically relevant symptoms of SM result from i) malignant MC infiltration and the subsequent organ damage seen in advanced SM and/or ii) the release of pro-inflammatory and vasoactive mediators from MC, found in all disease-variants. Therapy of SM has to be adjusted to the individual situation in each patient. In ISM, the aim is to control mediator release and mediator effects. In advanced SM, a major goal is to control MC expansion by using conventional drugs or novel targeted drugs directed against mutant forms of KIT and/or other pro-oncogenic kinase-targets. In rapidly progressing ASM, MCL and drug-resistant AHNMD, chemotherapy and subsequent stem cell transplantation has to be considered.
    Preview · Article · Apr 2013 · American Journal of Cancer Research
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