UNIPROT:P10721 - FACTA Search

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

Stem cell factor (SCF) stimulates the growth of burst-forming unit-erythroid (BFU-E) and colony-forming unit granulocyte-macrophage (CFU-GM) by binding to a specific cell surface receptor. The receptor for SCF is encoded by the protooncogene c-kit. After immunizing mice with the human erythroleukemia cell line OCIM1, we obtained a monoclonal antibody (MoAb) that recognizes the human c-kit receptor. This MoAb, designated SR-1, blocks binding of 125I-human SCF to the c-kit receptor, and neutralizes the biologic effects of SCF in hematopoietic colony assays. With few exceptions, c-kit expression was identified on all hematopoietic and lymphoid cell lines tested by indirect immunofluorescent analysis using SR-1 and by binding studies with 125I-SCF. SR-1 recognizes a small fraction of normal bone marrow mononuclear cells, and these cells have the morphologic appearance of blasts. Colony assays show that BFU-E and CFU-GM display the c-kit receptor. SR-1 does not cross-react with murine c-kit protein, indicating that the binding epitopes of the human and murine c-kit receptors are antigenically distinct. This MoAb may be useful to characterize the spectrum of cells that display the c-kit receptor and to further define the role of SCF in hematopoiesis.
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PMID:Isolation and characterization of a monoclonal antibody that recognizes the human c-kit receptor. 137 Mar 84

To define the cellular targets for c-kit ligand (KL) and to study their functional properties and composite antigenic profile, we isolated cells expressing c-kit receptor (KR) from bone marrow (BM), peripheral blood, and fetal liver (FL) using immunoadherence to a recently obtained antibody (SR-1) against the human KR. Cells isolated by this approach (designated SR-1Ad) have the morphology of blasts and represent 1% to 4% of the original BM or FL populations. SR-1Ad cells from either source are highly enriched in progenitors (12% to 73%) and respond to KL in distinct patterns. In SR-1Ad cells from BM, the greatest impact of KL stimulation is on burst-forming units-erythroid (BFU-E), whereas in SR1-Ad cells from FL, the most significant KL effect is on a mixed erythroid/nonerythroid progenitor (erythroid/macrophage, colony-forming unit-mix [CFU-Mix]). When antibody SR-1 is continually present in culture, it neutralizes the effects of added KL. Furthermore, in the absence of added KL, it greatly diminishes the erythropoietin- and interleukin-3-dependent BFU-E growth in BM; whereas in FL, a wider spectrum of inhibition is observed, with CFU-Mix most severely curtailed. SR-1Ad cells coexpress other progenitor-associated antigens in a combination reflecting the dominant presence of erythroid progenitors (high expression of CD34, DR, CD38, and Ep-1; low expression of CD33). Several cytoadhesion molecules, ie, alpha L/beta 2 and alpha 4/beta 1 integrins, and intercellular adhesion molecule 1 and homing cell adhesion molecule 1, are also coexpressed. Our data provide new information on the isolation and characterization of KR expressing cells from normal, adult, and fetal hematopoietic tissues. On these biologically relevant target cells, the impact of ligand-induced stimulation or antibody-mediated ablation of KR function has been gauged.
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PMID:Isolation of c-kit receptor-expressing cells from bone marrow, peripheral blood, and fetal liver: functional properties and composite antigenic profile. 171 89

Three monoclonal antibodies (MAbs) to the human c-kit receptor tyrosine kinase (P145c-kit), derived in independent laboratories, have been extensively used in studies of c-kit expression and the role of its ligand, steel factor (SLF), in hemopoiesis and mast cell differentiation and function. In this study, the relationship between the epitopes they identify, and their effects on SLF binding, receptor internalization, and signal transduction are compared. Epitope mapping studies carried out on the high P145c-kit-expressing cell line HEL-DR showed that SR-1 identifies an epitope independent of those bound by YB5.B8 and 17F11, while the latter two antibodies bound to distinct but interacting epitopes. SR-1 potently blocked the binding of SLF to P145c-kit on these cells and also on cells of the factor-dependent line MO7e. In contrast, YB5.B8 and 17F11 had minimal effects on ligand binding. Conversely, SLF partially blocked the binding of SR-1 and YB5.B8 to cells, while binding of 17F11 was actually enhanced by SLf on some target cells. Preincubation of HEL-DR and MO7e cells with MAbs prior to exposure to SLF revealed that 17F11 itself brought about partial down-regulation of P145c-kit and did not inhibit SLF-mediated down-regulation. SR-1 caused minimal down-regulation and inhibited SLF-mediated receptor internalization. YB5.B8 had minimal effects on either cell line in this assay. To determine whether the antibodies had any agonist activity, they were compared with SLF for their ability to bring about receptor phosphorylation in intact MO7e cells. All three antibodies induced detectable tyrosine phosphorylation with 17F11 being the most effective, while YB5.B8 was the least effective. Finally, the ability of the antibodies to influence the proliferation of the MO7e cells was examined. As expected, SR-1 potently inhibited the proliferative response to SLF, while 17F11 weakly inhibited and YB5.B8 had negligible effect. In the absence of SLF both 17F11 and YB5.B8 displayed very weak but reproducible agonist activity.
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PMID:Epitope mapping and functional studies with three monoclonal antibodies to the c-kit receptor tyrosine kinase, YB5.B8, 17F11, and SR-1. 751 Feb 97

Stem cell factor (SCF) is a hematopoietic growth factor produced by fibroblasts and endothelial cells that stimulates the growth of primitive hematopoietic cells. SCF triggers cell growth by binding to the c-kit receptor. Because endothelial cells can respond to certain hematopoietic growth factors, we tested human umbilical vein endothelial cells for display of the c-kit receptor and examined the effect of SCF on endothelial cell proliferation, adhesion molecule expression, and production of tissue factor. Quantitative binding experiments with 125I-SCF showed both high-affinity (Kd = 42 pmol/L) and low-affinity (Kd = 1.7 nmol/L) c-kit receptors. There were approximately 1,100 high-affinity c-kit receptors, and 5,400 low-affinity c-kit receptors per endothelial cell. Enzyme immunoassays showed that endothelial cells released soluble c-kit receptor and SCF. The transmembrane form of SCF was detected by indirect immunofluorescence analysis using monoclonal or polyclonal anti-SCF receptor antibodies. The addition of SCF (100 ng/mL) did not alter endothelial cell proliferation over a 7-day period. Similarly, there was no change in the release of tissue factor or expression of inducible endothelial adhesion molecules (intercellular adhesion molecule-1, endothelial-leukocyte adhesion molecule-1, and vascular cell adhesion molecule-1) measured by enzyme-linked immunosorbant assay at 4 and 24 hours after SCF addition. The neutralizing anti-c-kit receptor monoclonal antibody SR-1 blocked binding of 125I-SCF to the c-kit receptor by 98% but did not alter endothelial cell proliferation or adhesion-molecule expression. c-kit receptors were also detected on adult endothelial cells lining small blood vessels in normal human lymph nodes. These data indicate that normal human endothelial cells produce SCF and show high-affinity c-kit receptors that have the capacity to dimerize. The lack of response to exogenous SCF may be because of intracellular activation of the c-kit receptor via autocrine production of SCF. Alternatively, SCF and c-kit may play a role other than stimulation of proliferation, adhesion-molecule display, or tissue factor production by endothelial cells. The production of soluble c-kit receptors by normal human endothelial cells may serve to regulate the bioactivity of SCF within the bone marrow microenvironment.
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PMID:Human umbilical vein endothelial cells display high-affinity c-kit receptors and produce a soluble form of the c-kit receptor. 751 42

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

We previously demonstrated that highly purified normal human blood burst-forming units-erythroid (BFU-E) need the direct action of recombinant human stem cell factor (rSCF) in the presence of recombinant human erythropoietin (rEP) and recombinant human interleukin-3 (rIL-3) for further development in a serum-free medium. To study the response of polycythaemia vera (PV) BFU-E to rSCF, we performed dose-response experiments in a serum-free medium using highly purified BFU-E from PV patients. A marked increase in the number of PV bursts occurred with increasing concentrations of rSCF, compared to normal burst formation, when the cells were cultured in the presence of rIL-3 at 1 U/ml. The percentage of maximum growth for normal BFU-E was 31 +/- 11% while for PV it was 64 +/- 9% at the highest concentration of rSCF (P < 0.01). Without rIL-3, only 11% of maximum normal BFU-E growth occurred as the rSCF concentration was increased and the size of the colonies was very small, but PV BFU-E still expressed 48% of the maximum number of large erythroid bursts (P < 0.001). This demonstrated an enhanced sensitivity of PV BFU-E to rSCF, compared to normal BFU-E. The pattern of 59Fe incorporation into haem after 8 d of cell culture indicated that PV BFU-E had a time course of maturation and a degree of cellular maturity similar to normal BFU-E. The percentage positivity and intensity of c-kit receptors on PV erythroid cells were examined using immunofluorescence flow cytometry. When BFU-E, CFU-E, or erythroblasts were incubated with phycoerythrin-conjugated SR-1 anti-c-kit receptor monoclonal antibody, 90% of the PV and normal BFU-E displayed c-kit receptor at comparable intensities, as well as 80% of the PV and normal CFU-E. A distinct loss of c-kit expression occurred with erythroid differentiation beyond the CFU-E stage, but at all stages no difference of c-kit receptor expression was evident for PV erythroid precursors compared to normal precursors. These results indicate that the hypersensitivity to rSCF did not appear to be related to the number of c-kit receptors. Since we have previously shown that highly purified PV BFU-E are hypersensitive to rIL-3 and rGM-CSF, as well as rEP, it is now evident that PV BFU-E are hypersensitive to each of the cytokines that have a prominent role in guiding their normal proliferation and differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Polycythaemia vera. III. Burst-forming units-erythroid (BFU-E) response to stem cell factor and c-kit receptor expression. 751 94

During development, mice with mutations of stem cell factor (SCF) or its receptor c-kit exhibit defects in melanogenesis, as well as hematopoiesis and gonadogenesis. Because melanocytes derive from neural crest cells, the role of SCF and c-kit was investigated in the neural crest-derived childhood tumor neuroblastoma. Using reverse transcription-polymerase chain reaction analysis, simultaneous expression of steady-state mRNA for the SCF ligand and its receptor c-kit was found in 14 of 14 (100%) human neuroblastoma cell lines and clones and in 8 of 18 (45%) human neuroblastoma tumor samples. Functional blockade of c-kit receptors in the cell lines SK-N-BE(2) and SH-SY5Y using the mouse monoclonal anti-c-kit antibody SR-1 resulted in a significant decrease in cellular growth rate when measured by either 3H-thymidine incorporation or clonogenicity. In addition, higher levels of c-kit mRNA expression were associated with parental neuroblastoma cell lines and subclones with a neuronal (N) differentiation phenotype, whereas lower levels of c-kit mRNA were associated with neuroblastoma cell line subclones having a schwannian/glial/melanocytic pattern of differentiation. However, the differentiation phenotype of neuroblastoma cell lines was not directly altered when c-kit expression was blocked using the SR-1 antibody. In summary, these data indicate that c-kit receptor expression may play a significant role in the growth regulation of the two neuroblastoma cell lines examined and suggest that c-kit may also play a similar role in neuroblastoma growth regulation in vivo. Simultaneous expression of SCF and c-kit mRNA in both neuroblastoma cell lines and tumors implies that c-kit may act as part of an autocrine growth loop in conjunction with endogenous production of SCF in this disease.
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PMID:Expression of stem cell factor and c-kit in human neuroblastoma. The Children's Cancer Group. 752 40

Hematopoiesis is influenced by the presence of the hematopoietic microenvironment, and Dexter-type liquid culture systems represent an in vitro representation of some aspects of the microenvironment that are optimal for the propagation of myeloid progenitors. Marrow stromal layers, which constitute part of these culture systems, produce growth factors, including stem cell factor (SCF), a ligand for the c-kit proto-oncogene that has been found to increase detection of myeloid, erythroid, and megakaryocytic progenitors in short-term marrow colony assays. In this work, the role of SCF in Dexter-type culture systems was examined to better define its contribution to steady-state myelopoiesis. When cultured in the continued presence of 100 ng/mL SCF, both primary and recharged cultures demonstrated significantly greater CFU-GM output, with quantitative differences noted throughout culture duration (up to 6 weeks). This increase in CFU-GM could be inhibited specifically with the addition of 1:1500 SR-1, a neutralizing anti-c-kit monoclonal antibody (MAb) that neutralizes the biological effects of SCF, and the increase was noted both with recharged light-density marrow cells and purified CD34+ progenitor cells. On the other hand, when primary or recharged marrow cultures were established in the absence of exogenous SCF, but in the continuous presence of SR-1, no inhibition of CFU-GM output was observed. When light-density marrow cells were purged of pre-existing CFU-GM by 4-hydroperoxycyclophosphamide (4-HC) and were seeded over irradiated stromal layers, exogenous SCF resulted in detection of CFU-GM from 4-HC-treated cells as early as 1 week of culture, as compared to the lack of significant emergence of CFU-GMs at 4 weeks in the control cultures. This SCF effect was also inhibited by SR-1. Purified CD34+ progenitor cells did not adhere to SCF immobilized to tissue culture plates, and the adhesion of such progenitors to murine Steel lines transfected with membrane-bound SCF was not greater than to the parent nontransfected Steel line, suggesting that the effect of SCF was not on CD34+ cell adhesion. These studies confirm the action of SCF at a pre-CFU level, and they demonstrate the ability of SCF to stimulate increased production of myeloid progenitors in long-term liquid culture systems.
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PMID:Effect of stem cell factor on myelopoiesis potential in human Dexter-type culture systems. 753 98

Stem cell factor (SCF) acts in synergy with other growth factors such as erythropoietin (Epo), granulocyte-macrophage colony-stimulating factor (GM-CSF), or interleukin-3 (IL-3), to stimulate the growth of primitive hematopoietic cells. Because of the prominent role of CSF in the maintenance of normal erythropoiesis in vivo, we examined the effects of SCF on the Epo-inducible human erythroleukemia cell line MB-02, and characterized the c-kit receptor in these cells. MB-02 cells cultured in serum-containing media do not survive in the absence of exogenous growth factors, but the addition of SCF, Epo, or IL-3 as a single factor enhanced MB-02 survival. Furthermore, in the presence of Epo, SCF (5 to 25 ng/mL) enhanced MB-02 proliferation in a dose-dependent manner, and increased the relative and absolute number of benzidine-positive cells generated. SCF also enhanced cell proliferation in the presence of either IL-3 or low concentrations of GM-CSF. A neutralizing anti-c-kit receptor monoclonal antibody (SR-1) blocked binding of 125I-SCF to MB-02 cells by 98%, and the effect of SCF on MB-02 growth, c-kit receptor-binding parameters were quantitated by equilibrium-binding experiments with 125I-SCF. MB-02 cells display a single class of high-affinity (50 pmol/L) c-kit receptors, with approximately 8,000 receptors per cell. The molecular weight of the c-kit receptor was determined by affinity cross-linking 125I-SCF to MB-02 cells. 125I-SCF-c-kit receptor complexes of approximately 155,000 and approximately 310,000 daltons were found, likely representing the monomeric and dimeric forms of the c-kit receptor. The binding affinity and molecular weight of the c-kit receptor on MB-02 cells are similar to those of normal human marrow cells. These results suggest that SCF synergizes with Epo to influence not only the proliferation but the erythroid differentiation of MB-02 cells. Thus, the MB-02 cell line may be a useful model in which to investigate the molecular mechanisms of SCF action.
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PMID:Stem cell factor influences the proliferation and erythroid differentiation of the MB-02 human erythroleukemia cell line by binding to a high-affinity c-kit receptor. 768 59

Recent data suggest that stem cell factor (SCF or c-kit ligand, KL) is a major regulator of human mast cells (MCs). In the present study, MCs derived from the lung (n = 8), uterus (n = 14) and heart (n = 4) were analyzed for expression of c-kit receptor and for responses to recombinant SCF. MCs of all organs tested were recognized by mAbs to c-kit (YB5.B8, SR-1) as assessed by combined toluidine blue/immunofluorescence staining. Activation by rhSCF (10 ng/ml, 60 min) resulted in histamine release from lung MCs (SCF 12.8 +/- 2.7% histamine release; control 2.8 +/- 0.8%, p < 0.01), uterus MCs (SCF 16.8 +/- 5.8%; control 5.2 +/- 2.5%, p < 0.01) and heart MCs (SCF 18.4 +/- 2.6%; control 1.7 +/- 0.23%, p < 0.01). Short-term pre-incubation with rhSCF (15 min) did not result in histamine secretion (p > 0.05), but in an increase (lung 2.4 +/- 1.0 fold; uterus 2.1 +/- 1.1 fold, and heart 2.0 +/- 0.4 fold) of alpha IgE-induced mediator release (p < 0.05). The effects of SCF were dose-dependent (maximum responses at 10-100 ng/ml) and dependent on extracellular calcium. A monoclonal antibody to SCF was found to inhibit the effects of SCF on MCs. Furthermore, MCs could be desensitized specifically by pre-incubation of MCs with rhSCF in Ca-free medium. Together, these data suggest that SCF triggers mediator secretion from MCs in various organs via binding to the c-kit receptor.
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PMID:Specific activation of human mast cells by the ligand for c-kit: comparison between lung, uterus and heart mast cells. 769

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