Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10721 (c-kit)
 6,575 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutations in the Steel locus, encoding a growth factor (Steel factor or SF) or c-kit, the gene encoding its receptor, result in severe anemia in the mouse. In the present study, we have addressed the mechanism of synergistic growth activation, at the cellular level, by SF and GM-CSF using the blast cells of acute myeloblastic leukemia (AML blasts). Our data indicate that SF drastically alleviates the requirement in cell interaction for blast colony formation in most of the samples tested. Analysis of cultures performed in the presence of SF and GM-CSF at different cell concentrations, ranging from 1,000 to 20,000 cells, suggested a single limiting element, i.e., the blast clonogenic cell, while 2 or more limiting elements were found in cultures stimulated with GM-CSF alone, suggesting interacting cell populations. The presence of membrane-bound SF was detected by immunofluorescence, suggesting the possibility that secreted or membrane-bound SF may, at least in part, contribute to the density-dependent growth of AML blasts. In all samples tested, SF appears to increase the responsiveness of AML blasts to GM-CSF, as demonstrated by a 3-fold decrease of GM-CSF half efficient concentration on addition of SF to the cultures. Exposure of AML blasts to SF did not affect GM-CSF receptor expression, suggesting that this increase in GM-CSF responsiveness is likely to occur at the postreceptor level. Interestingly, 2 of 15 AML samples surveyed did not respond to SF, and were both of the myelomonocytic or monocytic subtype, classified as M4 and M5, respectively.
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PMID:Product of the Steel locus can replace leukemic cell interaction. 138 39

The molecular cloning for most of the hematopoietic growth factor receptors has been achieved over the past few years and revealed that they can by assigned to two discrete receptor families, namely the hematopoietic growth factor superfamily (HRS) and the receptor tyrosine kinase family (RTK). The members of the HRS, including granulocyte-macrophage colony-stimulating factor receptor (GM-CSF-R), interleukin 3 receptor (IL-3-R), granulocyte CSF receptor (G-CSF-R) and erythropoietin receptor (Epo-R), share a common binding domain and the absence of a tyrosine kinase domain in their cytoplasmic portion. In some cases (e.g., GM-CSF-R), the high-affinity receptor structure is obtained through the association of the low-affinity binding chain (alpha chain) with an accessory protein (beta chain). It is conceivable that this protein might also represent the common subunit shared by GM-CSF-R and by IL-3-R when they are co-expressed to form the putative GM-CSF-R/IL-3-R complex. Although tyrosine phosphorylation following ligand receptor activation seems to be a common event in the HRS, its role in the signal transduction mechanisms is unknown. Due to the structural analogies among the members of this family any new insight into one particular receptor member, such as its subunit structure and its signal transduction pathways, will be generalizable to the other family members. The subclass III of the RTK family, including the CSF-1-R and c-kit, is characterized by an additional insert into the kinase domain that recognizes and binds protein substrates. Ligand induced activation of the kinase domain and its signaling potential are mediated by receptor oligomerization which stabilizes interactions between adjacent cytoplasmic domains and leads to activation of kinase function by molecular interaction. Interestingly, the receptors included in this subclass are the products of well known cellular proto-oncogenes. A large variety of structural alteration found in receptor-derived oncogene products may lead to constitutive activation of receptor signals that, consequently, result in the subversion of the mechanisms controlling the cell growth.
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PMID:Hematopoietic growth factor receptors. 189 57

Steel factor (SF), also referred to as Kit ligand, stem cell factor, or mast cell growth factor, is essential for the development of hematopoietic stem cells in vivo. It is shown here that SF is mainly a survival factor for hemopoietic cells with little if any proliferative effect. In contrast, granulocyte macrophage colony-stimulating factor (GM-CSF) acts both as a survival factor and as a potent growth factor. We have probed the pathways activated by SF and GM-CSF in suppression of active cell death (apoptosis) using two classes of inhibitors: Tyrphostins that are specific inhibitors of protein tyrosine kinase, and amiloride derivatives (5-(N,N-ethyl-n-isopropyl)amiloride and 5-(N,N-hexamethylene)amiloride) that have been designed as specific inhibitors of the Na+/H+ antiporter. Both SF-dependent and GM-CSF-dependent pathways are sensitive to inhibition by Tyrphostins with, nonetheless, a quantitative difference. All Tyrphostins tested are more potent inhibitors of c-Kit than of GM-CSF receptor triggered pathways, the most striking being Tyrphostin B42 that is 10 times more potent. In contrast to the discrepancy in Tyrphostin dose-response curves, titration curves for 5-(N-ethyl-n-isopropyl)amiloride and 5-(N,N-hexamethylene)amiloride are comparable in SF- or GM-CSF-stimulated cells. Furthermore, SF induces a rapid and sustained alkalinization of the intracellular pH, as assessed with the pH-sensitive probe 2',7'-bis(2-carboxyethyl)-5-carboxyfluorescein. Taken together, our data indicate that input from two distinct pathways with discrepancy in immediate early events, that of c-Kit and GM-CSF receptor, results in a common output, activation of the Na+/H+ antiporter and suppression of apoptosis by the two ligands.
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PMID:Product of the steel locus suppresses apoptosis in hemopoietic cells. Comparison with pathways activated by granulocyte macrophage colony-stimulating factor. 751 58

In long-term human bone marrow cultures, stromal cells of human origin are usually used on the assumption that human primitive progenitor cells do not respond to cytokines produced by stromal cells from other species. There is accumulating evidence, however, that murine stromal cells also promote maintenance and differentiation of very primitive human stem cells, which suggests the existence of novel stromal activities that cross species barriers. In this study, we show that a murine bone marrow-derived stromal cell line, MS-5, allows the proliferation of the human leukemic cell line UT-7. The long-term growth of UT-7 is usually supported only by human interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or erythropoietin (Epo). None of these three cytokines was involved in the observed effect, since murine GM-CSF and IL-3 do not act on human cells and MS-5 cells do not produce Epo. Soluble stem cell factor (SCF) induced UT-7 cell proliferation. However, S1/S1 mutant fibroblasts also supported UT-7 cell growth and anti-c-kit antibodies only partially abolished UT-7 cell proliferative response to MS-5 cells. These observations excluded a major role of SCF in this system. MS-5-derived growth-promoting activity was diffusible, but attempts to grow UT-7 cells in high levels of known soluble murine stromal-derived cytokines active on human cells showed no or minimal response, suggesting that MS-5's proliferative effect was not mediated by known cytokines. Finally, involvement of an autocrine loop of activation induced by MS-5 was excluded: RT-PCR analysis did not detect increased transcripts for GM-CSF, IL-3, IL-6, SCF, or Epo in UT-7 cells cocultured for 2 to 6 days with MS-5. In addition, UT-7 cell proliferation on MS-5 was not inhibited by neutralizing antibodies against the human GM-CSF receptor or the human IL-6 receptor alpha chain. Whether UT-7 cell proliferation triggered by MS-5 reflects the existence of novel stromal cytokines or results from synergistic interactions on the MS-5 cell surface between extracellular matrix proteins and cytokines will require further investigation.
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PMID:A murine stromal cell line promotes the proliferation of the human factor-dependent leukemic cell line UT-7. 751 51

Leukemic cells from a patient with chronic myelocytic leukemia (CML) basophilic crisis were examined in an in vitro clonogenic assay using recombinant human hematopoietic growth factors to elucidate the proliferative and differentiative behaviors. More than 90% of the leukemic cells showed the morphologic characteristics of basophils and were positive for CD11b and CD13. The phenotype of the leukemic cells was different from that of mast cells. In the clonogenic assay using various recombinant growth factors, the leukemic cells were responsive to interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF), but not to granulocyte-CSF (G-CSF), erythropoietin (Epo), or IL-4. IL-5 showed synergistic effects on colony formations induced by both IL-3 and GM-CSF. Transcripts of the GM-CSF receptor alpha chain gene were detected in the leukemic cells, but transcripts of the IL-4 receptor gene were not. Furthermore, c-kit and IL-7 receptor genes were expressed in the leukemic cells. Our results suggest that the differentiation pathway of basophils is different from that of mast cells, even though the receptor gene for stem cell factor (c-kit) was expressed on the basophilic leukemic cells, as it was on mast cells.
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PMID:Cellular characteristics of chronic myelocytic leukemia basophilic crisis cells: phenotype, responsiveness to and receptor gene expression for various kinds of growth factors and cytokines. 767 84

We have investigated the stimulative effects of mast cell growth factor (MGF) in primary acute myeloid leukemia (AML) in vitro. MGF stimulated DNA synthesis of purified leukemic blasts in eight out of 10 cases and colony formation in four cases in serum-free (SF) culture. MGF synergized with interleukin-3 (IL-3; four out of 10 cases), granulocyte-macrophage colony-stimulating factor (GM-CSF; three out of 10 cases), granulocyte colony-stimulating factor (G-CSF; six out of 10 cases), macrophage colony-stimulating factor (M-CSF; one out of 10 cases) and erythropoietin (EPO; one out of 10 cases) when added to culture in combination. Synergistic effects of MGF in combination with other CSFs were also seen in the colony assay. Antibodies against GM-CSF, M-CSF, G-CSF, and IL-6 did not inhibit the MGF response, suggesting that the stimulative effect of MGF was not mediated through autocrine release of those cytokines. Cell recovery data in liquid cultures that contained MGF, IL-3, or MGF + IL-3, indicated that both MGF and IL-3 augmented the maintenance of clonogenic cells as compared to nonsupplemented cultures, but the effect of the combination of IL-3 + MGF did not show synergy. In contrast, activation of DNA synthesis by MGF was abrogated in the presence of tumor necrosis factor (TNF; four out of 10 cases) and interleukin-4 (IL-4; two out of 10 cases). Fluorescence-activated cell sorting (FACS) analysis with anti c-kit antibodies revealed MGF receptor expression in eight out of nine cases, often in a subpopulation of the cells. Scatchard analysis of MGF receptors in two cases indicated the presence of 1460 and 41,500 (mean) binding sites, respectively, of high affinity (Kd 40-160 pmol/l). The MGF dose-response curve in the presence of IL-3 or GM-CSF resulted in a higher plateau of DNA synthesis, however no shift in the dose response was apparent. The respective reciprocal dose response relations to GM-CSF, IL-3, or G-CSF were similarly elevated when MGF was added. MGF did not alter IL-3 and GM-CSF receptor expression, nor did IL-3, GM-CSF, G-CSF, TNF, or IL-4 influence MGF binding to AML cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effects of mast cell growth factor on acute myeloid leukemia cells in vitro: effects of combinations with other cytokines. 768 Apr 1

In both murine and human systems the c-kit ligand, also known as mast cell growth factor (MGF), acts synergistically with several colony stimulating factors, including the granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin 3 (IL-3), in stimulating the proliferation and differentiation of different types of hematopoietic progenitors. In addition, MGF is also known to enhance the effects of GM-CSF and IL-3 on the in vitro proliferative activity of myeloid leukemic cells. MGF synergizes with a number of other cytokines such as GM-CSF, IL-3, IL-2, IL-4, IL-6 and IL-9 in sustaining the proliferation of growth factor dependent M-07e cells. In order to explore the molecular basis of this synergistic activity and to elucidate the regulatory mechanisms of c-kit expression, we investigated the effects of GM-CSF, IL-3 and MGF on c-kit mRNA and protein levels in M-07e cells. GM-CSF, unlike MGF and IL-3, induced a transient but significant increase of c-kit mRNA levels. Moreover, following MGF and GM-CSF treatment, c-kit protein expression in M-07e cells decreased, whereas all the other cytokines tested are unable to modulate c-kit protein. These data together with the results of protein turnover analysis suggest that MGF and GM-CSF regulate c-kit expression at the post-transcriptional level. In addition, the finding that IL-3 has no detectable effect on c-kit expression raises the possibility that GM-CSF-induced c-kit regulation is not mediated by the common signal transducing element: the beta subunit of the IL-3/GM-CSF receptor complex.
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PMID:Regulation of c-kit expression in human myeloid cells. 769 27

Sorted fractions from mouse bone marrow containing highly purified hemopoietic stem and progenitor cells were studied for the expression of growth factor receptors. With the use of rhodamine 123 WGA+, 15-1.1-, low density cells were separated into quiescent pluripotent stem cells and committed progenitor cells. RNA was extracted and cDNA was prepared by reverse transcription. Using primers specific for growth factor receptors, the cDNA of each sorted fraction was amplified by polymerase chain reaction (PCR). The quiescent rhodamine 123 dull stem cell fraction was found to express the interleukin 3 (IL-3) receptor beta unit and c-kit, but not the granulocyte-macrophage colony stimulating factor (GM-CSF) receptor beta unit nor flk-2. The rhodamine 123 bright fraction with activated stem cells and mostly committed progenitor cells similarly expressed the IL-3-R beta, and c-kit. However, this fraction also expressed flk-2 and GM-CSF-R beta. Since the expression of c-kit in the stem cell fraction does not correspond with the poor response to the kit-ligand stem cell factor (SCF) by these cells, we further analyzed the fractions with respect to their binding of biotinylated SCF. The SCF-binding cells were found to be all rhodamine 123 bright. This indicates that the expression of c-kit is not sufficient to yield a functional receptor for SCF; c-kit probably needs a partner molecule to form a functional high-affinity binding site for SCF. Similar to the beta unit of the GM-CSF receptor, this partner is then not expressed in the stem cell fraction.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The expression of cytokine receptors by purified hemopoietic stem cells. 769 28

Cytokines transduce their signals through specific receptors. Receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-3, and IL-5 share the common signal transducing subunit (beta c), whereas the alpha subunits function as specific ligand binding components. In this study we prepared specific mouse monoclonal antibodies against human GM-CSF receptor-alpha subunit (hGMR alpha) by immunizing mice with Ba/F3 cells transfected with hGMR alpha complementary DNA. Using these anti-hGMR alpha antibodies in combination with antibodies against IL-3 receptor-alpha (IL-3R alpha), beta c subunits, and c-kit, we examined expression patterns and modulation of these receptor subunits on several human hematopoietic cells, including CD34+ cells and leukemic cell lines. GMR alpha and IL-3R alpha were expressed on GM-CSF- and IL-3-responsive cell lines, such as TF-1 and UT-7, whereas the expression levels were much lower on UT-7E, a GM-CSF- and IL-3-unresponsive subline of UT-7. The GMR alpha subunit was expressed only on mature granulocytes and monocytes, and IL-3R alpha was expressed on monocytes but not on mature granulocytes, and none of these subunits were expressed on lymphocytes. For CD34+ cells, GMR alpha was expressed more abundantly on CD34+ CD33high cells than on CD34+ CD33low cells, whereas IL-3R alpha was expressed more abundantly on CD34+ CD33low cells than on CD34+ CD33high and CD34+ CD33neg cells. Slight but significant expression of the beta c subunit was detected on CD34+ cells. Expression of not only GMR alpha and IL-3R alpha subunits but also c-kit was specifically downregulated by 48-hour incubation with their respective ligands. Receptor transmodulation between GM-CSF, IL-3, and stem cell factor (or kit ligand) was not detected on CD34+ cells in 48-hour cultures. We also detected upregulation of these alpha subunits by IL-1 alpha and interferon-gamma on leukemic cell lines. Our study showed expression levels for each receptor subunit--including GMR, IL-3R, and c-kit on human bone marrow and peripheral blood cells and leukemic cell lines--and revealed differential regulation of the expression of the receptor subunits.
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PMID:Differential expression of granulocyte-macrophage colony-stimulating factor and IL-3 receptor subunits on human CD34+ cells and leukemic cell lines. 854 66

Mast cells (MCs) originate from multipotent hematopoietic progenitor cells. However, MCs in various organs are heterogenous in terms of mediator or receptor expression and response to diverse stimuli. We characterized the phenotype and functional properties of human renal mast cells (HRMCs). Tissue was obtained from 17 patients suffering from renal tumors (transitional cell carcinoma, n = 4; renal cell carcinoma, n = 13). HRMCs were isolated by collagenase digestion. Double staining with toluidine blue and immunofluorescence using monoclonal antibodies (mAbs) revealed expression of stem cell factor (SCF)-receptor (c-kit/CD117), CD9, CD29, CD33, CD43, CD44, CD54, and CD63 on HRMCs. In contrast, HRMCs were not recognized by mAbs to CD2, CD3, CD4, CD11b, CD14, CD15, CD16, CDw17, CD19, or CD23. HRMCs were also negative for CD116 (granulocyte-macrophage colony-stimulating factor [GM-CSF] receptor alpha), CD123 (interleukin [IL]-3Ralpha), CD121a (IL-1R type I), CD122 (IL-2Rbeta), and CD127 (IL-7R) and were also found to lack C5aR (CD88). Ligand-induced activation of HRMCs through immunoglobulin (Ig)E-R or SCF-R (c-kit) resulted in histamine secretion (control: <10%; alphaIgE, 1 microg/mL: 50.12 +/-5.18%; rhSCF, 100 ng/mL: 29.24 +/- 22.39), whereas recombinant C5a, erythropoietin (EPO), IL-1 through 10, and GM-CSF exerted no effects. As determined by in situ staining, HRMCs contained tryptase, but only low or undetectable amounts of chymase. Electron microscopy confirmed the presence of MCs in renal tissues and revealed a scroll-rich granule population in HRMCs. Together, HRMCs are tryptase+, C5aR- mast cells exhibiting phenotypic and functional properties similar to those of lung MCs.
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PMID:Phenotypic and functional characterization of mast cells derived from renal tumor tissues. 947 5


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