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Query: UNIPROT:P10721 (c-kit)
 6,575 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The gene product of the murine Steel (Sl) locus encodes an early-acting hematopoietic growth factor that is a ligand for the c-kit protooncogene. Several cDNAs for the Sl gene product, known as mast cell growth factor (MGF), stem cell factor (SCF), or kit ligand (KL), have recently been isolated, and both soluble and membrane-associated versions have been shown to be biologically active. The potential for therapeutic usage of recombinant MGF (rMGF) indicated a need for determining the biodistribution and elimination parameters of this cytokine. Pharmacokinetic studies demonstrated that radiolabeled rMGF had a distribution half-life of 2 min and an elimination half-life of 2.1 h in wild-type mice following iv injection, during which a striking localization of labeled rMGF in the lungs was noted. When administered by subcutaneous injection the elimination half-life was prolonged to 8.4 h. The primary sites of rMGF elimination appeared to be the kidneys and the liver. Pharmacokinetic analysis of labeled rMGF in mutant Sl/Sld mice, which are mast cell deficient, demonstrated similar distribution and elimination half-lives compared to wild-type mice (1.4 min and 1.8 h, respectively). In addition, the biodistribution pattern of the labeled rMGF in Sl/Sld mice was similar to that observed in wild-type mice, including the striking localization to the lungs. Binding of radiolabeled rMGF to lungs in vivo subsequent to iv injection was completely inhibited by excess unlabeled rMGF. Interestingly, mice that received an iv injection of the higher doses of rMGF (15 micrograms) demonstrated profound respiratory distress and hypotension within minutes of administration. Histologic analysis of lungs from such mice revealed extensive mast cell degranulation, which was associated with vasodilatation and pronounced hyperemia of virtually all pulmonary vessels. The respiratory distress in normal mice was probably a consequence of mast cell degranulation induced by rMGF since similar findings were not observed in Sl/Sld mice injected with identical concentrations of rMGF.
Lymphokine Cytokine Res 1992 Oct
PMID:Pharmacokinetic parameters of recombinant mast cell growth factor (rMGF). 128 75

Cytokine regulation of prethymic T-lymphoid progenitor-cell proliferation and/or differentiation has not been well-defined, although much is known of cytokine regulation of hemopoietic stem- and progenitor-cell development. Here we use a recently identified hemopoietic growth factor, stem-cell factor (SCF) (a form of the c-kit ligand), and a transplant model of thymocyte regeneration to assess the effect of SCF on the in vivo generation of prethymic, thymocyte progenitor-cell activity. We show that recombinant rat SCF (rrSCF164) administered to weanling rats selectively induces an increase in thymocyte progenitor activity in the spleens of treated rats as compared to rats treated with vehicle, polyethylene glycol (PEG)-conjugated rat albumin, or recombinant human granulocyte colony-stimulating factor (rhG-CSF). These data demonstrate that administration of SCF in vivo affects extrathymic-origin thymocyte regenerating cells and may influence, directly or indirectly, early prethymic stages of T-cell lymphopoiesis in addition to its known effect on early stages of myelopoiesis and erythropoiesis.
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PMID:Rat stem-cell factor induces splenocytes capable of regenerating the thymus. 128 80

By employing a monoclonal antibody against the stem cell factor receptor (SCF-R), c-kit oncogene product, we analysed in flow cytometric technique the density of SCF-R on GM/SO cells which were incubated under various culture conditions. These experiments revealed that there is an inverse correlation between the SCF-R density on the cells and the doses of granulocyte-macrophage colony-stimulating factor (GM-CSF) in culture medium; the lower the dose, the higher the density of SCF-R on the cells. More detailed analyses showed that, in contrast to SCF which rapidly downregulates its own receptor, GM-CSF does not alter the measurable level of SCF-R in an exposition period of 60 minutes, which suggests that the internalization or shedding of the receptor is not the mechanism of action. Since the most striking difference regarding density of SCF-R between GM-CSF-treated and untreated cells was observed on day 2, the modulation of c-kit oncogene protein by GM-CSF likely occur prior to expression of protein onto the cell surface. In order to exclude the possibility that altered cell viability due to insufficient GM-CSF content in culture medium might be responsible for the increased SCF-R densities on GM-CSF-dependent cells, we subsequently generated a GM-CSF-independent subclone which still responded to GM-CSF as well as the dependent did. The experiments carried out with this subclone confirmed the results presented above. Thus our data suggest that GM-CSF is directly involved in the regulation of SCF receptor density on GM/SO cells.
Eur Cytokine Netw
PMID:Granulocyte-macrophage colony-stimulating factor (GM-CSF) reduces the density of stem cell factor receptors (c-kit oncogene product) on a GM-CSF-dependent human myeloid cell line. 750 37

Activation of phosphatidylinositol (PI) 3-kinase is a common sequel to tyrosine kinase activation and appears to be essential for tyrosine kinases to induce proliferation. Since multiple hemopoietic growth factors activate tyrosine kinases, we investigated whether these growth factors activate PI 3-kinase. We show that interleukin-3 (IL-3), interleukin-4 (IL-4), interleukin-5 (IL-5), granulocyte-macrophage colony stimulating factor (GM-CSF), and steel factor (SLF) all activate PI 3-kinase. These cytokines increased the amount of PI 3-kinase activity that could be immunoprecipitated with anti-phosphotyrosine antibodies from the MC-9 mast cell line or from the hemopoietic progenitor cell line FDC-P1. Increases in this assay frequently correlate with PI 3-kinase activation in vivo. To determine directly whether these factors activate PI 3-kinase in vivo, we measured the levels of 3-phosphorylated inositol phospholipids in intact 32P-labeled MC-9 cells. IL-3, IL-4, IL-5, GM-CSF, and SLF all caused increased synthesis of the PI 3-kinase products phosphatidylinositol 3,4-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate with a relative potency of SLF >> IL-3 > IL-5, GM-CSF > IL-4. In contrast, IL-4 caused the largest increase in the in vitro anti-phosphotyrosine immune complex PI 3-kinase assay. Thus, the in vitro assay does not accurately reflect in vivo activation of PI 3-kinase. Cytokine treatment did not stimulate tyrosine phosphorylation of either the 85-kDa regulatory subunit or the 110-kDa catalytic subunit of PI 3-kinase and is therefore not required for activation of PI 3-kinase by these factors. Cytokine treatment did induce PI 3-kinase to associate with other tyrosine-phosphorylated proteins in a cytokine-specific manner. PI 3-kinase associated with c-kit after SLF stimulation, a 170-kDa protein after IL-4 stimulation, and a 70-kDa protein after treatment with IL-3 or GM-CSF. Thus, multiple hemopoietic growth factors that act through different types of receptors activate PI 3-kinase in vivo and induce factor-specific interactions of PI 3-kinase with other tyrosine-phosphorylated proteins.
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PMID:Multiple cytokines activate phosphatidylinositol 3-kinase in hemopoietic cells. Association of the enzyme with various tyrosine-phosphorylated proteins. 750 38

In vitro growth of primitive hematopoietic progenitors is severely impaired in the myelodysplastic syndromes (MDS). To determine if the c-kit ligand mast cell growth factor (MGF) can improve progenitor growth in MDS, we evaluated in vitro responsiveness of bone marrow progenitors from 25 patients to MGF and/or GM-CSF, interleukin-3 (IL-3) and PIXY 321, and examined the relationship between progenitor response and cellular expression of the c-kit receptor. MGF and erythropoietin gave rise to macroscopic colonies and dose-dependently increased CFU-GEMM and BFU-E up to 27-fold in 15 (60%) and 20 (80%) patients, respectively. Among 17 patients with absent growth in lymphocyte-conditioned media, MGF stimulated CFU-GEMM recovery in 59%, compared to 23% with PIXY 321, 12% with IL-3 and 8% with GM-CSF. Cytokine combinations did not augment recovery of erythropoietin-dependent progenitors above that achieved with MGF alone. MGF and/or IL-3 were comparatively weak stimulants of CFU-GM formation, whereas GM-CSF and PIXY in combination with MGF increased colony number 2- to 15-fold in 60 and 70% of patients, respectively, while preserving maturation competence as evidenced by colony composition and increased colony/cluster ratio. The stimulatory effects of MGF were observed in all morphologic categories of MDS except chronic myelomonocytic leukemia. A mononuclear cell population expressing the c-kit receptor was identified by flow cytometry in 57% of cases. Neither SR-1 reactivity nor cytogenetic pattern predicted progenitor response to MGF. These data indicate that MGF improves the colony-forming capacity of hematopoietic progenitors in MDS and is a potent co-stimulant of multipotent and committed progenitor recovery. The heterogeneity in MGF responsiveness implies an intrinsic defect in growth regulation not explained by cellular loss of c-kit display.
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PMID:Mast cell growth factor (c-kit ligand) restores growth of multipotent progenitors in myelodysplastic syndrome. 751 48

The GM/SO cell line bears a high level of stem cell factor receptors (SCF-R) i.e. c-kit protein, and therefore constitutes a potential model for studying the regulation of this crucial receptor on myeloid cells. In this study we evaluated the effect of tumor necrosis factor alpha (TNF-alpha) on the expression of SCF-R by flow cytometry. In contrast to 1 hour of preincubation, the experiments carried out after 24 hours preincubation revealed that TNF-alpha, if added alone, reduced the density of SCF-R on GM/SO cells in a dose-dependent manner. However, if combined with GM-CSF, which per se downregulates the SCF-R on these cells as well, TNF-alpha antagonized the effect of GM-CSF and slightly increased the density of SCF-R. Yet the cells incubated for 24 hours in medium without cytokines invariably expressed a higher level of SCF-R than the cells incubated in the presence of TNF-alpha and GM-CSF, either alone or in combination. In contrast to these cytokines, stem cell factor (SCF), which was also tested simultaneously in all experiments, downregulated its own natural receptor on these cells also after a preincubation of 1 hour. Furthermore, prolonged exposure of GM/SO cells to TNF-alpha for 5-7 days yielded a monocyte-macrophage-like morphology of some cells as these cells displayed an apparent glass and plastic adherence. In contrast, no such morphological changes could be observed in the presence of GM-CSF or SCF.
Eur Cytokine Netw
PMID:Regulation of the density of the stem cell factor receptor (c-kit) by tumor necrosis factor alpha on a human myeloid cell line. 751 54

Kit ligand, or stem cell factor, is a recently identified growth factor, which binds to and activates the c-kit proto-oncogene, and which has been shown to act synergistically with other haematopoietic growth factors in the bone marrow. We have previously shown that several isoforms of kit ligand, which arise due to alternative splicing, are expressed in human placenta. In order to elucidate the role of c-kit and its ligand during human placental development we have investigated the expression of c-kit and kit ligand in human first trimester and term placenta as well as in pregnant and non-pregnant endometrium, by immunocytochemistry and flow cytometric analysis. In non-pregnant endometrium no expression of kit ligand was seen. By contrast, in first trimester decidua, kit ligand was strongly expressed by the arterial media of maternal blood vessels. Kit ligand was also expressed throughout pregnancy by invasive fetal extravillous trophoblast, and by fetal fibroblasts within the placental villi. c-kit was found to be expressed on Hofbauer cells within the chorionic villi, and by decidual macrophages at all stages in pregnancy. c-kit was also detected on the small CD56dim subset of uterine large granular lymphocytes which form the major leukocyte population in human first trimester decidua. Our results suggest that kit ligand may be involved in the regulation of fetal macrophages, and in particular in signalling between invading extravillous trophoblast which expresses kit ligand, and maternal leukocytes bearing the c-kit receptor.
Cytokine 1994 Mar
PMID:Expression of c-kit and kit ligand at the human maternofetal interface. 751 62

Although IL-12 has been reported to synergize with c-kit ligand (KL) in promoting hematopoietic stem cell proliferation in vitro, administration of recombinant mouse IL-12 (rIL-12) to normal mice caused a dose- and time-dependent anemia, leukopenia, and thrombocytopenia in vivo. Decreased numbers of bone marrow cells were recovered from the tibiae of IL-12-treated mice, and histologic examination of the marrow revealed a loss of mature neutrophils and red blood cell precursors. However, simultaneously with the suppression of hematopoiesis in the bone marrow, the IL-12-treated mice developed splenomegaly, which was largely caused by a marked enhancement of splenic extramedullary hematopoiesis of the erythroid, myeloid, and megakaryocytic lineages. These histologic observations were confirmed by colony-forming cell assays in which administration of IL-12 was shown to cause a time-dependent decrease in bone marrow CFU-GM, CFU-E, and BFU-E hematopoietic colony-forming cells while causing an increase in splenic CFU-GM and BFU-E colony-forming cells. All these effects were reversible upon cessation of IL-12 treatment. The observation that in IL-12-treated mice hematopoiesis was suppressed in the marrow but enhanced in the spleen suggests that myelosuppression was not caused by a direct effect of IL-12 on hematopoietic progenitors. It seems likely that myelosuppression was caused instead by an IL-12-induced alteration in the local environment of the marrow.
J Interferon Cytokine Res 1995 Apr
PMID:Administration of recombinant interleukin-12 to mice suppresses hematopoiesis in the bone marrow but enhances hematopoiesis in the spleen. 762 13

We investigated the effects of stem cell factor (SCF) on the growth of blast clonogenic cells from 27 patients with acute myeloblastic leukemia (AML) and 3 patients with chronic myelocytic leukemia in myeloid crisis. SCF alone showed a significant stimulatory activity in 15 of 30 patients (50%). A marked reduction in the number of blast cell colonies supported by SCF alone was noted by the addition of neutralizing antibody (Ab) against granulocyte-macrophage colony-stimulating factor (GM-CSF). Ab against interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) also moderately reduced the number of colonies, whereas Ab against granulocyte CSF (G-CSF) failed to do so. All four Ab together completely abolished the growth in 5 of 6 patients tested. c-kit antisense oligonucleotides reduced the colony formation supported by IL-3 or G-CSF or, in the absence of growth factor, in only 2 of 10 patients tested. SCF caused stimulation by acting synergistically with G-CSF, GM-CSF, IL-3, IL-6, IL-9, IL-11, and IL-12 in 20 of 27 (74%), 17 of 27 (63%), 14 of 28 (50%), 9 of 28 (32%), 1 of 15 (7%), 3 of 28 (11%), and 2 of 15 (13%) patients, respectively. Thus, SCF alone or in combination with some other factor stimulated the growth in 27 of 30 (90%) patients. Of 3 nonresponders, 2 were AML, M3 at presentation. G-CSF at the optimal concentration increased the sensitivity of blasts to SCF. Taken together, SCF acting in combination with other factors, but not alone, stimulates the growth of blast clonogenic cells. GM-CSF, IL-6, and TNF-alpha may be produced endogenously, whereas G-CSF and SCF may be supplied exogenously. Autocrine regulation of the growth of blasts seems to increase the responsiveness of the cells to any of these factors, allowing them to achieve a highly active growth state.
J Interferon Cytokine Res 1995 Oct
PMID:Roles of stem cell factor in the in vitro growth of blast clonogenic cells from patients with acute myeloblastic leukemia. 856 3

Mast cells play a critical role in allergic airway responses via IgE-specific activation and release of potent inflammatory mediators. In the present study, we have isolated and characterized primary mast cell lines derived from the upper airways of normal mice. The primary mast cell lines were grown and maintained by incubation with interleukin-3 (IL-3) and stem cell factor (SCF) and shown to be c-kit (SCF receptor) positive by flow cytometry. Subsequently, we examined the proliferation of both airway and bone marrow derived mast cell lines in response to inflammatory and hematopoietic cytokines, including SCF, IL-1, IL-3, interferon-gamma, IL-4, and IL-10. The results from the pulmonary mast cell lines were compared with those from bone marrow derived mast cells. Pulmonary mast cell lines were capable of proliferating in response to IL-3, IL-4, IL-10, and SCF, whereas the combination of SCF with the other cytokines did not increase the response over SCF alone. In contrast, the bone marrow-derived mast cells proliferated strongest to SCF or IL-3, but only modestly to IL-4 and IL-10. Furthermore, the combination of SCF with IL-3, but not the other cytokines, exhibited an increase in bone marrow-derived mast cell proliferation. Cytokine-specific stimulation of histamine release in the airway-derived and bone marrow-derived mast cells showed parallel results. SCF was the only cytokine shown to induce substantial histamine release. However, when certain nonhistamine releasing cytokines were combined with SCF, a synergistic increase in histamine release was induced in upper airway, but not bone marrow-derived mast cells. The results of these studies suggest that cytokines differentially modulate induction of proliferation and degranulation of bone marrow and upper airway-derived mast cells and may further indicate a cytokine activational cascade in tissue mast cells.
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PMID:The role of stem cell factor (c-kit ligand) and inflammatory cytokines in pulmonary mast cell activation. 863 Mar 86


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