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)

Ineffective erythropoiesis due to an impaired response to erythropoietin (EPO) is a prominent abnormality in myelodysplastic syndromes (MDS). The growth factor kit ligand (KL) may restore the in vitro erythroid colony-forming response to EPO in a subset of patients. The inability of MDS erythroid progenitors to react properly to EPO and/or KL has not been resolved. We have investigated erythropoietin receptor (EPO-R) and KL receptor (c-kit) expression in 15 cases of MDS by FACS analysis. The percentage of bone marrow cells expressing the EPO-R from patients with MDS were comparable to normal marrow. No apparent correlation was found between the number of MDS cells coexpressing the EPO-R and CD34 and impaired erythroid response. C-kit was expressed in most MDS patients, including those not responding to KL in EPO-induced cultures. In nine MDS cases the different splice variants of the EPO-R were analyzed. MDS cells, like normal marrow, expressed the full length EPO-R. These results show that impaired erythroid response in MDS cannot be explained by a quantitative lack of receptors for EPO or KL and that most likely suppression of erythroid response is caused by defective receptor signalling following ligand binding, representing a functional defect within the receptor itself or at a level downstream of the receptor.
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PMID:Erythropoiesis in myelodysplastic syndrome: expression of receptors for erythropoietin and kit ligand. 864 63

A human cytoplasmic signaling protein has been cloned that possesses the same structural arrangement of SH3-SH2-SH3 domains as Grb2. This protein is designated Grap for Grb2-related adaptor protein. The single 2.3-kilobase (kb) grap transcript was expressed predominantly in thymus and spleen, while the ubiquitously expressed grb2 gene produced two mRNA species of 3.8 and 1.5 kb. Grap and Grb2 consist of 217 amino acids and share 59% amino acid sequence identity, with highest homology in the N-terminal SH3 domain. The GrapSH2 domain interacts with ligand-activated receptors for stem cell factor (c-kit) and erythropoietin (EpoR). Grap also forms a stable complex with the Bcr-Abl oncoprotein via its SH2 domain in K562 cells. Furthermore, Grap is associated with a Ras guanine nucleotide exchange factor mSos1, primarily through its N-terminal SH3 domain. These results show that a family of Grb2-like proteins exist and couple signals from receptor and cytoplasmic tyrosine kinases to the Ras signaling pathway.
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PMID:Grap is a novel SH3-SH2-SH3 adaptor protein that couples tyrosine kinases to the Ras pathway. 864 2

Recombinant human interferon-inducible protein-10 (rIP-10) has been recently identified, purified and shown to suppress the multiplication of normal marrow early hemopoietic progenitors. In the present study we investigated the effect of rIP-10 on different normal and acute myelogenous leukemia (AML) progenitor populations. We first studied hematologically normal bone marrow using the delta culture assay, in which marrow low-density cells were incubated in liquid culture with recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) for 1 week, to allow the differentiation of mature progenitors, and thereafter cultured in methylcellulose in the presence of rGM-CSF and recombinant erythropoietin (rEPO). In this assay rIP-10 significantly inhibited the proliferation of normal marrow hemopoietic progenitors in a dose-dependent fashion. However, when fresh normal marrow cells were cultured in methylcellulose without preincubation in liquid culture, rIP-10 did not affect the growth of colony-forming cells. In contrast, when recombinant c-kit ligand (rKL) was added to rGM-CSF and rEPO, an increment in colony numbers was observed that was eliminated by rIP-10. Similar experiments performed with low-density, non-adherent, T cell-depleted AML marrow cells, obtained from 12 untreated adult AML patients, revealed qualitatively similar results: rIP-10 inhibited the proliferation of AML progenitors in the AML delta assay but did not affect the growth of rGM-CSF-responsive AML colony-forming cells when plated in semisolid media in the presence of rGM-CSF. When rKL was added to rGM-CSF during plating in an effort to recruit additional AML progenitor populations, there was an increment in leukemic blast colony numbers that was eliminated by rIP-10. As observed with normal progenitors, the effect of rIP-10 on these AML progenitors was concentration-dependent, statistically significant and reversible with a rIP-10-neutralizing antiserum. To delineate the mechanism of action of rIP-10 we used the thymidine suicide assay and found that rIP-10 significantly reduced the fraction of leukemic progenitors synthesizing DNA. Our data suggest the rIP-10 inhibits the proliferation of (probably immature) AML progenitor populations by reducing the fraction of cells undergoing DNA synthesis. Additional studies are needed to further elucidate the mechanism of this inhibition and to determine the potential clinical benefits of rIP-10 in future therapies for AML.
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PMID:Human recombinant interferon-inducible protein-10 inhibits the proliferation of normal and acute myelogenous leukemia progenitors. 865 68

A mouse spleen stromal cell line, MSS62, can create an in vitro erythropoietic microenvironment in which development of erythropoietin-responsive progentor cells is stimulated by cell-cell contact via stem cell factor (SCF)/c-Kit and vascular cell adhesion molecule-1 (VCAM-1)/very late activation antigen-4 (VLA-4) interactions between stromal and erythroid cells. To find out the effect of src on the erythropoietic microenvironment, MSS62 cells were transfected with v-src oncogene, and its effect on erythropoietic stimulatory activity was measured. Transfectants with high v-Src activity showed reduction in erythropoietic stimulatory activity. A decrease in cell-surface VCAM-1 and SCF mRNA was accompanied by high v-Src activity. These results suggest that v-Src interferes with the erythropoietic stimulatory activity of the stromal cells through repression of VCAM-1 and SCF.
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PMID:v-src interferes with the in vitro erythropoietic stimulatory ability of spleen stromal cells through repression of vascular cell adhesion molecule-1 and stem cell factor. 869 46

Miniature swine are being used as a large animal model in which cultured and retrovirus-transduced hematopoietic stem cells (HSC) can be tested in a reproducible manner for their long-term in vivo repopulating ability. As part of these studies, long-term bone marrow culture (LTBMC) and progenitor colony assay systems were developed and used to characterize the in vitro growth potential and in vivo frequency of hematopoietic progenitors in this species. We found that LTBMCs initiated with a single marrow inoculum produced myeloid colony progenitors continuously for at least 7 weeks. The sites of myelopoietic activity in these cultures were uniquely restricted to isolated, morphologically diverse germinal centers rather than more disperse cobblestone patches. We also used the progenitor assay to screen several human and murine recombinant cytokines for cross-reactivity to swine bone marrow cells, including interleukin-3 (IL-3), IL-6, Il-11, granulocyte and granulocyte-macrophage colony-stimulating factors (G-CSF and GM-CSF), c-kit ligand (also called mast cell growth factor [MGF]), and erythropoietin (Epo). With the exception of human and murine IL-3, each of the cytokines tested induced swine progenitor colony formation to varying degrees, with some combinations leading to the formation of primitive multilineage and high proliferative potential colonies. Finally, in an attempt to characterize alternative sources of HSC from swine, we compared the progenitor content of adult and juvenile swine bone marrow and fetal liver. The fetal liver samples were found to be highly enriched for both primitive and mature progenitors, while analysis of postnatal marrow samples revealed an approximately two-fold decline in overall progenitor frequency between the ages of 10 and 20 weeks. Taken together, these studies demonstrate the development and use of in vitro culture methods for characterizing hematopoietic elements from miniature swine and suggest a hierarchy of progenitor cell content in various hematopoietic tissues from the large animal model.
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PMID:Culture and characterization of hematopoietic progenitor cells from miniature swine. 869 52

The phenotypes of mice that harbor a defect in the genes encoding either stem cell factor (SCF) or its receptor, c-kit, indicate that this ligand/receptor pair is necessary for maintenance of normal hematopoiesis in the adult. Our objective was to determine whether SCF, like erythropoietin, is necessary for acute erythroid expansion during recovery from hemolytic anemia. Monoclonal antibody ACK2, which recognizes the murine c-kit receptor, was used to selectively block the hematopoietic growth-promoting effects of SCF. Mice were treated with phenylhydrazine on day 0 and day 1 to induce hemolytic anemia and also received no antibody, control IgG, or ACK2 on day 0. The mice were killed on day 3 and the hematocrit (Hct), reticulocyte count, and numbers of erythroid and myeloid hematopoietic progenitor cells (colony-forming unit-erythroid [CFU-E], burst-forming unit [BFU]-E, and CFU-granulocyte-macrophage [GM]) were quantitated in the femoral marrow and spleen using hematopoietic colony-forming assays. Induction of hemolytic anemia with phenylhydrazine resulted in a drop in the Hct from approximately 50% to 30%, and an approximate 8- to 10-fold increase in the reticulocyte count. The numbers of CFU-E increased modestly in the femur, and approximately 25- to 50-fold in the spleen, in comparison with normal mice. BFU-E and CFU-GM values did not increase in the femur but expanded 6- to 10-fold in the spleen, in comparison with normal mice. This confirms that much of the erythroid expansion in response to hemolytic anemia occurs in the murine spleen. Neutralizing quantities of the ACK2 antibody reduced femoral CFU-E, BFU-E, and CFU-GM content to less than half that found in phenylhydrazine-treated control mice and nearly totally ablated splenic hematopoiesis. These results suggest that c-kit receptor function may be required for optimal response to acute erythropoietic demand and that erythropoiesis in the splenic microenvironment is more dependent on SCF/c-kit receptor interaction than is erythropoiesis in the marrow microenvironment. Because expansion of late erythropoiesis in the spleen was preferentially blocked, we tested the hypothesis that homing of more primitive hematopoietic cells to the spleen was dependent on c-kit receptor function. Lethally irradiated mice were injected with marrow cells obtained from mice that had received phenylhydrazine plus control IgG or with marrow cells obtained from mice that had received phenylhydrazine plus ACK2. In parallel experiments, normal murine marrow cells were treated in vitro with control IgG or with ACK2 and were injected into lethally irradiated mice. The fraction of BFU-E and CFU-GM retrieved from the marrow and spleen of the recipient mice 4 hours later was reduced by approximately 75% when progenitor cells had been exposed to ACK2, in comparison with control IgG. These data suggest that interaction of SCF with the c-kit receptor affects the homing behavior of hematopoietic progenitor cells in the adult animal.
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PMID:Interaction of stem cell factor and its receptor c-kit mediates lodgment and acute expansion of hematopoietic cells in the murine spleen. 870 4

The lymphohematopoietic progenitors represent < 0.01% of nucleated marrow cells. We have shown that murine lymphohematopoietic progenitors can be immortalized by a recombinant retroviral vector harboring a dominant-negative retinoic acid (RA) receptor. The immortalized progenitors proliferate as a stem-cell factor-dependent clonal line designated EML C1. The EML C1 cell line spontaneously generates prepro-B-lymphocytes and erythroid and myeloid progenitors. Upon stimulation with interleukin 7 and marrow stromal cells, the prepro-B-lymphocytes express recombination-activating gene 1 (RAG-1) and undergo D-J rearrangements of the immunoglobulin heavy-chain genes. With erythropoietin, the erythroid progenitors proliferate and differentiate into red cells. Generation of the common progenitors for neutrophils and macrophages [colony-forming units-granulocyte-macrophage (CFU-GM)] is suppressed in EML C1 cells but is inducible by high concentrations of RA. An additional block in neutrophil differentiation occurs at the promyelocyte stage, but this can also be overcome by high concentrations of RA. Although c-fms is homologous to c-kit, which encodes the receptor for stem-cell factor (SCF), EML C1 cells neither express c-fms nor respond to macrophage colony-stimulating factor (M-CSF), the ligand for c-fms. Transduction and expression of c-fms cDNA in EML C1 cells confers responsiveness to M-CSF. This finding indicates that c-kit and c-fms share substantially overlapping signal-transduction pathways. However, c-fms-transduced EML C1 cells (EML C1/c-fms cells) exhibit different development patterns when stimulated by SCF alone or by M-CSF alone. When stimulated by SCF alone, EML C1/c-fms cells show mostly erythroid and B-lymphoid development. When stimulated by M-CSF alone, development switches to mostly myeloid (neutrophil and macrophage) development. This observation suggests that c-kit and c-fms must have unique signal-transduction pathways in addition to the common ones.
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PMID:Differential effects of c-fms and c-kit ligands on the lineage development of the lymphohematopoietic cell line EML C1. 876 19

Glycoprotein (gp) 130, a receptor component for interleukin 6 (IL-6), can associate with a soluble IL-6 receptor (sIL-6R)-IL-6 complex. To examine the role of gp130 signaling in human hematopoietic progenitor-cell proliferation and differentiation, we studied the effects of the sIL-6R-IL-6 complex in combination with other cytokines on human CD34+ cells in clonal and suspension cultures. The sIL-6R-IL-6 complex, but not sIL-6R or IL-6 alone, in the presence of stem-cell factor (SCF) produced dramatic increases in the populations of various cell lineages, including erythroid cells and various hematopoietic progenitors, in suspension culture. Significant numbers of colonies of (particularly) multilineage and blast cells were generated in methylcellulose culture supplemented with a combination of sIL-6R-IL-6 complex and SCF. Addition of anti-gp130 monoclonal antibodies (MAbs) and anti-IL-6R MAbs to the above-mentioned cultures dose-dependently inhibited the generation of cells of various lineages and of progenitor cells in suspension culture and completely blocked multilineage colony production in methylcellulose culture; an anti-erythropoietin antibody did not cause inhibition. These findings demonstrate that both proliferation and differentiation of hematopoietic progenitor cells can be induced through gp130 and c-Kit signaling, indicating that progenitor cells are responsive to the sIL-6R-IL-6 complex, even though they do not express IL-6R. Together with previous studies showing that detectable levels of sIL-6R, IL-6, and SCF are present in human serum, these results suggest that gp130 signaling may play an important role in human hematopoiesis in vivo.
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PMID:Role of glycoprotein 130 and c-Kit signaling in proliferation and differentiation of human hematopoietic progenitor cells. 876 20

The megakaryoblastic cell line, UT-7, is dependent for its growth upon interleukin-3 (IL-3), erythropoietin, or granulocyte-macrophage colony stimulating factor (GM-CSF). A subculture of this line can be maintained in recombinant human c-kit ligand [stem cell factor (SCF)] at 100 ng/ml without requirement for other growth factors. Removal of this subculture from SCF results in rapid loss of viability and decreased proliferation. Cells grown in SCF also can be maintained in GM-CSF but not vice versa. In this work, we have characterized the SCF dependence of this UT-7 subculture. Stem cell factor removal results in apoptosis and a decline in viability which can be restored partially by re-addition of SCF, GM-CSF, or co-culture with adherent marrow stromal cells. Apoptosis in the factor-starved UT-7 population has been documented by light microscopy, electron microscopy and DNA analysis, showing the typical 180 base pair laddering characteristic of apoptosis. To quantitate the degree of apoptosis in the cell populations, and to assess whether apoptosis decreased with re-exposure of starved cells to growth factors or stroma, we utilized flow cytometry. This confirmed that exposure of previously factor-starved cells to stroma decreased the percentage of cells undergoing apoptosis. Co-culture with an SCF-deficient murine stromal cell line was also able to prevent apoptosis, suggesting contribution of other stromal cell factors. Experiments performed using trans-well inserts which do not allow cell passage, showed greatest viability of cells in contact with stroma, but viability was also improved in cells cultured in the presence of, but not in contact with, stromal cells compared to those cultured above plastic, suggesting a role for soluble stroma-produced substances. These data demonstrate that SCF alone can prevent apoptosis in cells dependent upon its presence for proliferation. Also, marrow stromal cells can serve as a partial substitute for growth factor in the prevention of apoptosis in these cells, probably due to constitutive presentation of SCF and other hematopoietic growth factors in both soluble and surface-bound forms.
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PMID:Stem cell factor and stromal cell co-culture prevent apoptosis in a subculture of the megakaryoblastic cell line, UT-7. 879 93

Aqueous extracts prepared from the murine kidney (MKE) promoted colony formation derived from murine hematopoietic progenitor cells in serum-free cultures stimulated by interleukin-3 (IL-3) and erythropoietin (Epo). MKE itself did not stimulate any colony formation. MKE preferentially enhanced granulocyte-macrophage colony forming units (CFU-GM), but did not promote any erythroid colony formation. The CFU-GM colony promotion by MKE was observed at day 6 after the culture started, and the colony-promoting activity (CPA) was maintained at the same level until day 16. MKE showed no CPA in the cultures using cells obtained from 5-FU-injected mice and from c-kit(+)-enriched treatment. Furthermore, MKE acted synergistically with granulocyte-colony-stimulating factor (CSF), macrophage-CSF, IL-6 and IL-11 on colony formation, but did not act with GM-CSF, stem cell factor and Epo. From the results of various experiments and gel-filtration chromatography, it is estimated that the colony-promoting factor detected in MKE is a heat stable protein with about 20 KDa molecular weight. These results suggest that MKE promotes colony formation by murine myeloid progenitor cells, and that the target cell populations of MKE are relatively mature in the hematopoietic differentiation pathway.
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PMID:[Biological properties of the colony-promoting activity in extracts prepared from murine kidney]. 885 17


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