Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P15088 (mast cell)
 14,925 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mast cell tumours are one of the most common tumours of the canine skin and have a reputation for being difficult to manage because of their variable clinical presentation, behaviour and response to treatment. This review of recent literature on canine mast cell tumours suggests that the majority of such tumours may not be as bad as their reputation suggests. Most grade I and grade II tumours can be managed successfully by good surgery. Recent literature also calls into question the utility of clinical staging systems and the value of assessing surgical margins for prognosis and highlights the paucity of well-conducted, case-controlled clinical trials in assessing the efficacy of medical management of high-risk tumours. In terms of more basic research, recent studies have implicated the stem cell factor receptor KIT as having a role in the aetiology of canine mast cell tumours and there appears to be an association between c-kit mutation and higher grade of tumour. This may offer a possible target for new therapeutic approaches.
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PMID:Advances in the diagnosis and management of cutaneous mast cell tumours in dogs. 1755 22

The chimeric BCR-ABL gene, originated by the Philadelphia chromosome, encodes a fusion protein, BCR-ABL, bearing unregulated tyrosine kinase activity, the pivotal pathogenetic step of chronic myeloid leukemia (CML). Imatinib, an inhibitor of the BCR-ABL tyrosine kinase, significantly improves the outcome of patients with CML. Although the majority of CML patients are responsive to imatinib, a subset of patients loses the response and some progress to accelerated- or blast-phase CML. The understanding of mechanisms of imatinib resistance has led to the development of novel BCR-ABL inhibitors; among these, dasatinib emerged as the most promising, being approximately 300-fold more potent than imatinib; it also inhibits SRC family kinases. Preliminary data, after the introduction of dasatinib in clinical trials, in patients with CML, suggest that this drug is safe and well tolerated; furthermore, the majority of patients with imatinib-resistant disease achieved objective responses, although the durability of responses remains to be defined. Recently, dasatinib emerged as a potent inhibitor of imatinib-resistant protein tyrosine kinase (KIT) activation loop mutants and it is able to induce apoptosis in mast cell and leukemic cell lines expressing these mutations. The preclinical data concerning its activity on several human solid tumor lines widen new opportunities for their use outside CML.
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PMID:Dasatinib: a new step in molecular target therapy. 1759 30

The human mast cell line (HMC-1(560, 816)) was used to study the effect of the tyrosine kinase inhibitor STI571 (Glivec) on exocytosis, intracellular Ca(2+) and pH changes, because STI571 inhibits the proliferation of HMC-1(560) and induces its apoptosis. This drug does not have these effects on HMC-1(560, 816). Exocytosis in HMC-1(560, 816) cells can be stimulated by alkalinisation with NH(4)Cl as well as with ionomycin. Surprisingly 24-h pre-incubation with STI571 decreases spontaneous histamine release of HMC-1(560, 816) cells, but increases the histamine response after alkalinisation and not after ionomycin-stimulation. After addition of NH(4)Cl, pH(i) has a higher increase in STI571 pre-incubated cells, without changing intracellular Ca(2+) concentration. Activation of PKC in combination with tyrosine kinase inhibition increases also histamine release in HMC-1(560, 816) cells. Strangely, STI571 pre-incubated cells with PKC inhibited by rottlerin show the same effects. In these cells, cytosolic pH increases more than in control cells. This is the first report of STI571 effect in HMC-1(560, 816) cells. It seems that different pathways modulate signals for proliferation and exocytosis. STI571 does not only inhibit KIT TyrK, but may also influence cytosolic pH after alkalinisation in both cell lines, HMC-1(560) and HMC-1(560, 816), and this ends in induced histamine release. This work is important since HMC-1(560, 816) cells are reported in 80% of aggressive systemic mastocytosis cases and the understanding of some signalling pathways involved in mast cell response could facilitate drug targeting.
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PMID:STI571 (Glivec) affects histamine release and intracellular pH after alkalinisation in HMC-1560, 816. 1761 56

Aggressive mast cell (MC) tumors are hematopoietic neoplasms characterized by uncontrolled growth of MC and resistance to conventional drugs. In most cases, the tyrosine kinase (TK) receptor KIT is involved in malignant cell growth. Therefore, several KIT TK-targeting drugs are currently being tested for their ability to block growth of neoplastic MC. We examined the effects of four TK inhibitors (imatinib, midostaurin, nilotinib, and dasatinib) on C2 canine mastocytoma cells, as well as primary neoplastic canine MC. As assessed by (3)H-thymidine incorporation experiments, all TK inhibitors produced dose-dependent inhibition of proliferation in C2 cells with the following IC(50) values: imatinib: 269 +/- 180 nM, midostaurin: 157 +/- 35 nM, nilotinib: 55 +/- 24 nM, dasatinib: 12 +/- 3 nM. Growth-inhibitory effects of TK inhibitors were also observed in primary neoplastic mast cells, although IC(50) values for each drug varied from patient to patient, with midostaurin being the most potent agent in all samples tested. In consecutive experiments, we were able to show that TK inhibitors cooperate with each other in producing growth inhibition in C2 cells with synergistic effects observed with most drug combinations. In flow cytometry and TUNEL assay experiments, growth-inhibitory effects of TK inhibitors were found to be associated with cell-cycle arrest and apoptosis. Together, these data show that several TK-targeting drugs induce apoptosis and inhibit proliferation in canine mastocytoma cells in vitro, and that synergistic drug interactions can be obtained. Clinical trials are now warranted to explore whether these TK inhibitors also counteract growth of neoplastic cells in vivo in patients with aggressive MC tumors.
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PMID:Synergistic antiproliferative effects of KIT tyrosine kinase inhibitors on neoplastic canine mast cells. 1768 69

Gain-of-function mutations in the proto-oncogene c-kit that induce constitutive kinase activity of its product, KIT protein, are characteristic of human mast cell disease and are believed to play a central role in mast cell leukemia oncogenesis, proliferation and survival. Nuclear overexpression of the Wnt effector beta-catenin and deregulated beta-catenin nuclear signaling can promote malignant transformation in solid tumors and hematologic malignancies. However, a role for beta-catenin in mast cell leukemia has not been described. Nuclear accumulation of beta-catenin is upregulated by its tyrosine phosphorylation, a process that can be exacerbated by deregulated expression of oncogenic tyrosine kinases. Here, we investigated the relationship between activated KIT and beta-catenin signaling in mast cell leukemia. Beta-catenin was tyrosine-phosphorylated in cells with KIT activated by either gain-of-function mutation or incubation with the KIT ligand stem cell factor. Beta-catenin tyrosine phosphorylation depended on KIT activity but not on PI3K-AKT activation. Tyrosine phosphorylation of beta-catenin was associated with its nuclear localization and enhanced transcription of target genes c-myc and cyclin D1. Endogenous KIT and beta-catenin were found to associate in mast cell leukemia cells, and in vitro kinase assay demonstrated that active KIT phosphorylates tyrosine residues of beta-catenin directly. Aberrant beta-catenin-driven transcription caused by deregulated KIT may represent a significant new target for treatment of mast cell leukemia.
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PMID:KIT regulates tyrosine phosphorylation and nuclear localization of beta-catenin in mast cell leukemia. 1794 10

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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PMID:Unique effects of KIT D816V in BaF3 cells: induction of cluster formation, histamine synthesis, and early mast cell differentiation antigens. 1839 Jul 29

Patients with systemic mastocytosis (SM) may acquire an associated hematologic non-mast cell (MC)-lineage disease (AHNMD). In most cases, a myeloid neoplasm is diagnosed, whereas the occurrence of a lymphoproliferative disease is an extremely rare event. We report on a patient with indolent SM associated with small lymphocytic lymphoma (SLL). The patient presented with lymphadenopathy, maculopapular exanthema, and elevated serum tryptase. The bone marrow biopsy showed focal MC aggregates together with SLL. As assessed by immunostaining, neoplastic MC were found to exhibit CD117 and CD25 but did not display CD5 or CD20, whereas SLL cells were found to coexpress CD5 and CD20 but did not express MC antigens. The KIT mutation D816V was detected in sorted CD34(+) cells and unfractionated marrow cells but not in CD5(+) SLL cells, confirming the coexistence of 2 distinct neoplasms.
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PMID:Indolent systemic mastocytosis associated with atypical small lymphocytic lymphoma: a rare form of concomitant lymphoproliferative disease. 1844 46

KIT is a member of the tyrosine kinase family of growth factor receptors which is expressed on a variety of haematopoietic cells including mast cells. Stem cell factor (SCF)-dependent activation of KIT is critical for mast cell homeostasis and function. However, when KIT is inappropriately activated, accumulation of mast cells in tissues results in mastocytosis. Such dysregulated KIT activation is a manifestation of specific activating point mutations within KIT, with the human D816V mutation considered as a hallmark of human systemic mastocytosis. A number of other activating mutations in KIT have recently been identified and these mutations may also contribute to aberrant mast cell growth. In addition to its role in mast cell growth, differentiation and survival, localized concentration gradients of SCF may control the targeting of mast cells to specific tissues and, once resident within these tissues, mast cell activation by antigen may also be amplified by SCF. Thus, KIT inhibitors may have potential application in multiple conditions linked to mast cells including systemic mastocytosis, anaphylaxis, and asthma. In this review, we discuss the role of KIT in the context of mast cells in these disease states and how recent advances in the development of inhibitors of KIT activity and function may offer novel therapies for the treatment of these disorders.
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PMID:Pharmacological targeting of the KIT growth factor receptor: a therapeutic consideration for mast cell disorders. 1850 Mar 55

KIT is a receptor tyrosine kinase that is functionally relevant for hematopoiesis, mast cell development and function, gametogenesis and melanogenesis. Normal KIT signaling requires binding to stem cell factor, and PI3K-Akt is one of the putative effector pathways. In humans, germline loss-of-function KIT mutations have been associated with piebaldism - an autosomal dominant condition characterized by depigmented patches of skin and hair. Gain-of-function KIT mutations are usually acquired and have been associated with myeloid malignancies including core binding factor acute myeloid leukemia and systemic mastocytosis (SM), germ cell tumors, gastrointestinal stromal tumors and sinonasal T cell lymphomas. KITD816V is the most prevalent KIT mutation in mast cell disease and occurs in more than 90% of the cases that fulfill the World Health Organization diagnostic criteria for SM. However, its precise pathogenetic contribution is not well understood. In clinical practice, SM is considered either indolent or aggressive depending on the respective absence or presence of symptomatic target organ dysfunction aside from skin disease. In general, conventional therapy for SM is suboptimal, and efforts are under way to develop and employ small molecule drugs that target mutant KIT.
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PMID:KIT and mastocytosis. 1856 36

Cutaneous mastocytosis (CM) in children is a usually benign skin disorder caused by mast cell proliferation. Progressive disease leading to systemic involvement and fatal outcomes has been described. C-kit receptor mutations have been identified as causative for CM, some of which potentially respond to imatinib treatment as described for patients with systemic mastocytosis. We report successful therapy of progressive CM with imatinib in a 23-month-old boy. KIT gene analysis revealed not only a somatic deletion of codon 419 in exon 8 (c.1255_1257delGAC) which responds to imatinib therapy, but also a novel germ line p. Ser840Asn substitution encoded by exon 18 in the c-kit kinase domain. Family history suggests this exchange does not affect receptor function or cause disease. Imatinib therapy was well tolerated, stopped symptoms and disease progression, and appeared to shorten the course of the disease. Imatinib could possibly represent a novel therapeutic option in patients with progressive CM.
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PMID:Successful treatment of progressive cutaneous mastocytosis with imatinib in a 2-year-old boy carrying a somatic KIT mutation. 1856 37


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