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

In this report, a novel approach is described to physically separate erythroid progenitors from monocyte and granulocyte progenitors, based on the expression of CD34 and Kit. Using biotin-labeled human Kit ligand (KL) and flow cytometry, Kit was detectable on 2% to 3% of the nucleated cells in rhesus monkey bone marrow. Combination of biotin-KL with CD34 monoclonal antibodies (MoAb) showed that Kit was expressed on subsets of CD34low and CD34pos cells. Our data clearly demonstrate that CD34pos cells are more heterogeneous with respect to Kit expression than observed in studies using Kit MoAb. A small cluster, approximately 7% of the CD34pos cells, expressed CD34 at submaximal levels and stained brightly with biotinylated KL. This CD34pos/kithi fraction contained predominantly erythroid progenitors (burst-forming units-erythroid; BFU-E). The majority of the granulocytic and monocytic progenitors (colony-forming units-granulocyte/macrophage; CFU-GM) were CD34pos/kitmed. Some BFU-E were also detected in the CD34pos/kitmed and CD34low/kitpos fractions at low frequency. In the latter subset, most erythroid colony-forming units (CFU-E) were recovered. Using three-color flow cytometry, we analyzed expression of Kit in relation to that of CD34 and the class II major histocompatibility antigen, RhLA-DR. The most immature bone marrow cells that can be identified in vitro, ie, CD34pos/RhLA-DRlow cells, were kitmed. The CD34pos/kithi and CD34pos/kitneg subsets predominantly contained the more mature RhLA-DRbright cells. Our results demonstrate that erythroid precursors express c-kit at much higher levels than monomyeloid precursors and pluripotent progenitors. The difference in expression levels of CD34 and c-kit can be exploited to isolate BFU-E populations that are virtually devoid of nonerythroid cells.
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PMID:Separation of myeloid and erythroid progenitors based on expression of CD34 and c-kit. 749 63

The effect of the v-ski oncogene on the transformation of chicken hematopoietic cells was examined. In initial experiments viruses encoding the v-ski oncoprotein did not transform chicken bone marrow cells. However, whereas viruses encoding the ts-v-sea oncoprotein transform solely erythroid cells, viruses encoding both the v-ski and the ts-v-sea oncogenes were found capable of transforming myeloid cells from the monocytic and/or granulocytic lineages in addition to erythroid cells. Analysis of cell clones transformed by the v-ski/ts-v-sea virus identified one clone that no longer expressed the v-sea protein, indicating that this protein was necessary for the initiation but not the maintenance of transformation. Subsequent experiments testing the effects of various growth factors on transformation of bone marrow cells by the v-ski oncogene product alone identified the avian c-kit ligand (stem cell factor; SCF) as being able to co-operate with the v-ski protein to cause transformation of chicken hematopoietic cells of both myeloid and erythroid lineages.
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PMID:Transformation of chicken bone marrow cells by the v-ski oncogene. 750 31

We found a K562 subclone (K562YO) that highly expressed the c-kit gene. K562YO had a higher capability of erythroid differentiation by hemin and cytosine arabinoside (Ara-C) than its parent K562 (KIT-). We obtained the transfectant expressing c-kit by introducing c-kit cDNA into K562 (KIT-). The differentiation of the transfectant was similar to that of the parent cell. Thus the difference described above was not due to the expression of c-kit. Next, we investigated the effects of stem cell factor (SCF) on the differentiation of the K562 cell expressing c-kit. SCF did not enhance the cell growth of K562YO. On the other hand, SCF suppressed induction of benzidine-positive cells when c-kit-positive cells were treated with hemin and Ara-C, especially at a low concentration. Furthermore, c-kit mRNA and protein were down-regulated during erythroid differentiation. SCF also downregulated the c-kit proteins. Our results suggest that the SCF/c-kit signals could act negatively for erythroid differentiation of the K562 cells expressing c-kit. K562YO is also useful for studying the mechanism that controls the expression of the c-kit gene because there is a K562 counterpart cell line that does not express this gene.
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PMID:Inhibition of erythroid differentiation by stem cell factor in K562 cells expressing the c-kit gene. 750 74

Using monoclonal antibody (MAB) YB5.B8, we have examined the expression of the c-kit protein, the receptor for the hematopoietic cytokine stem cell factor (SCF), on primitive hematopoietic cells. Bone marrow mononuclear cells (BMMNC) enriched for immature cells by differential agglutination using the lectin soybean agglutinin (SBA) were subjected to multiparameter fluorescence activated cell sorting (FACS) based on light-scattering properties, the expression of the c-kit protein and the CD34 antigen, and the retention of the vital fluorescent dye, Rhodamine 123 (Rh123). Sorted populations were assayed for their content of directly clonogenic progenitor cells (colony-forming units-granulocyte/macrophage [CFU-GM], burst-forming units-erythroid [BFU-E], and multipotential colony-forming units [CFU-Mix]) and for the presence of more primitive progenitor cells ("pre-CFU"). The latter were assayed by (1) their ability to initiate and sustain hematopoiesis in a standard stromal cell-dependent culture system and (2) their capacity for de novo generation of clonogenic progenitors in response to a combination of six recombinant hematopoietic cytokines in a stroma-independent suspension culture assay. A mean of 76% of CD34+ cells were found to coexpress c-kit. The majority of directly clonogenic cells (98% of CFU-GM, 98% of CFU-Mix, and 85% of BFU-E) were found in the CD34+c-kit+ fraction. Similarly, all pre-CFU were recovered in the CD34+c-kit+Rh123dull fraction, irrespective of whether the cells were maintained on marrow stromal cells or in cytokine-supplemented liquid culture. A mean of 87% (range 70-100%) of the CD34+Rh123dull cells also expressed c-kit. Since SCF has been reported to act as a growth factor for early lymphoid cells as well as myeloid cells, we looked for coexpression of c-kit and early lymphoid markers in the CD34+ population by multiparameter flow cytometry. Coexpression of c-kit on a minority of cells with markers of B or T lineages was observed. The majority of early lymphoid cells, however, appeared to lack c-kit expression. This was confirmed by the finding that only 4% of c-kit+CD34+ cells showed terminal deoxynucleotidyl transferase (TdT) activity, compared with 25% of the c-kit-CD34+ cells.
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PMID:c-kit is expressed by primitive human hematopoietic cells that give rise to colony-forming cells in stroma-dependent or cytokine-supplemented culture. 750 57

Stem cell factor (SCF), the ligand of the c-kit receptor, is a potent enhancing cytokine for haematopoietic cells in the presence of IL-3, GM-CSF and erythropoietin (Epo). In the clonogenic assays of 63 MDS patients, the addition of rh-SCF + GM-CSF and/or IL-3 induced a significant increase (p < 0.001) in the number and size of CFU-GM. Never reaching the levels of controls, this increase was seen in all FAB subtypes, but particularly in RA. There was no significant increase in cluster formation, even in RAEB or RAEBt. Rh-SCF (10 ng/ml) led to mean increases of up to 26 times in the number of Epo-dependent BFU-E colonies, particularly in RA (p < 0.001) and RAEB (p < 0.05). Individual responses varied widely (especially in RA) from no response to supranormal levels. Added to the weekly refeed of 37 MDS LTBMC, SCF (10 ng/ml) induced only a 7% mean increase in both cell output and the number of clonogenic cells recovered in the supernatant. Immunohistochemical examination of the supernatant showed significant increases in differentiating myeloid cells in all examined cases, and in erythroid cells in 3 cases; blast cells increased in only 3 cases. These data suggest that rh-SCF is capable of at least partially reversing defective MDS myeloid haematopoiesis, and leads no overt risk of leukaemic transformation. Its potent effect on erythroid cells is encouraging for future clinical applications in patients, particularly if they are selected by means of in vitro tests.
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PMID:Effects of recombinant human stem cell factor (rh-SCF) on colony formation and long-term bone marrow cultures (LTBMC) in patients with myelodysplastic syndromes. 750 65

We examined the effects of interleukin-3 (IL-3) and c-kit ligand (KL) on the survival of differentiated hematopoietic progenitor cells (HPC), the burst-forming unit-erythroid (BFU-E); colony-forming unit-granulocyte, erythroid, monocyte, megakaryocyte (CFU-GEMM); and CFU-granulocyte-monocyte (CFU-GM) and more primitive hematopoietic cells that give rise to these progenitor cells (pre-colony-forming cells [pre-CFC]). CD34+ HLA-DR+ cells, which are highly enriched for committed HPC, and CD34+ HLA-DR- c-kit+ cells, which contain the most primitive assayable hematopoietic cells, including long-term bone marrow culture-initiating cells, high proliferative potential-CFC, the CFU-blast, and the BFU-megakaryocyte, were suspended in serum-free medium in the presence or absence of IL-3 or KL. CD34+ HLA-DR+ cells incubated under serum-free conditions or in the presence of KL for 96 hours lost greater than 90% of assayable unilineage or multilineage HPC, whereas those cells incubated in the presence of IL-3 retained 40% of the number of HPC present at time 0. The effect of IL-3 on HPC survival was most pronounced on the BFU-E and CFU-GEMM present within CD34+ HLA-DR+ cells. Addition of IL-3, but not of KL, to CD34+ HLA-DR+ cells delayed the appearance of morphologic changes and DNA fragmentation patterns associated with cell death occurring by apoptosis. CD34+ HLA-DR-c-kit+ cells were incubated under similar serum-free conditions in the presence or absence of IL-3 or KL, and the frequency of pre-CFC was determined by limiting dilution analysis. The frequency of pre-CFC in cells incubated for 48 hours in the absence of serum was similar to that of cells incubated in the presence of IL-3 and approximately doubled when CD34+ HLA-DR- c-kit+ cells were incubated in the presence of KL. Addition of KL to serum-free suspension cultures of CD34+ HLA-DR- c-kit+ cells delayed the appearance of DNA fragmentation patterns associated with apoptosis to a greater extent than did the addition of IL-3. These studies suggests that IL-3, but not KL, promotes HPC survival, whereas KL plays a greater role than IL-3 in sustaining more primitive HPC, such as pre-CFC. The effects of both cytokines in mediating HPC and primitive hematopoietic cell survival appear to be related, in part, to their ability to suppress apoptosis.
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PMID:Effects of interleukin-3 and c-kit ligand on the survival of various classes of human hematopoietic progenitor cells. 751 Jan 43

To examine the in vivo role of c-kit receptor in B lymphopoiesis we have evaluated precursor B cell populations expressing c-kit in mouse bone marrow and the effects on B cell genesis of administering a neutralizing anti-c-kit mAb, ACK2. Double immunofluorescence labeling and mitotic arrest were used to examine bone marrow cells from BALB/c mice. Almost one-half of TdT+ cells and one-quarter of B220+ cells coexpressed c-kit, mainly at low intensities, and were actively proliferating in vivo. c-kit+ cells that lacked B lineage markers expressed c-kit in high intensities and entered mitosis at an exceptionally rapid rate. In ACK2-treated mice, erythroid and granulocytic cells were almost completely absent from the bone marrow, whereas, in contrast, B lymphopoiesis was stimulated. Pre-B cells expressing cytoplasmic mu-chains; as well as TdT+B220+ cells before mu expression, were increased two- to fourfold in number and production rate. IgM-bearing B lymphocytes were increased in bone marrow and spleen. The results demonstrate that many early precursor B cells in mouse bone marrow constitutively express c-kit receptor. The failure of ACK2 treatment to block B lymphopoiesis, however, suggests that c-kit receptor function is not essential for precursor B cell development in vivo, but can be replaced by alternative signaling systems. The stimulation of B cell genesis by ACK2 treatment may reflect a conferred advantage in the competition for microenvironmental factors which underlies the balance between B lymphopoiesis and other hemopoietic lineages in vivo.
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PMID:c-kit expression by B cell precursors in mouse bone marrow. Stimulation of B cell genesis by in vivo treatment with anti-c-kit antibody. 751 30

The effects of recombinant human stem cell factor (SCF/c-kit ligand), interleukin-3 (IL-3) and granulocyte/macrophage colony-stimulating factor (GM-CSF) on erythroid colony formation by non-phagocytic mononuclear cells (MNC) and CD34+ cells derived from normal human bone marrow (BM), peripheral blood (PB) and umbilical cord blood (CB) were studied using a methylcellulose culture containing recombinant human erythropoietin (Epo). BM-MNC generated the largest number of total erythroid colonies consisting of erythroid bursts and erythroid mixed colonies (E-Mix) in the presence of SCF, whereas PB-MNC produced the largest number with IL-3. No additive effect between SCF and IL-3 was observed in the erythroid colony formation by BM- or PB-MNC. These observations were reproducible in cultures with several independent samples and purified CD34+ cells, suggesting that in normal human adults the erythroid progenitors supported by SCF alone mainly reside in the BM but those supported by IL-3 alone are mainly circulating. IL-3 was the most potent promoter of the total erythroid colony formation by CB-MNC, but it had no cooperation with SCF. In contrast, SCF supported large numbers of E-Mix and showed significant cooperative activity with IL-3 in E-Mix formation. These findings were also confirmed using independent specimens and CD34+ cells. Outstanding E-Mix formation by the CB cells indicated that newborn infants contain significantly more immature circulating erythroid progenitors than adults. These observations will stimulate interest in the role of the c-kit-SCF system as an adhesion molecule in the ontogenetic development of hemopoiesis.
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PMID:Different responses of human marrow and circulating erythroid progenitors to stem cell factor, interleukin-3 and granulocyte/macrophage colony-stimulating factor. 751 46

The purpose of this study was to define the effects of recombinant human Steel factor (rhSF) (c-kit ligand) on early and late cord blood hematopoietic progenitors. In the presence of recombinant human erythropoietin (rhEpo), rhSF supported the development of granulocyte/macrophage, erythroid, and mixed colonies from CD34-positive cord blood cells. With increasing concentrations of rhSF, an increase in the number of mixed colonies was observed. This increase was paralleled by a decrease in the number of erythroid colonies, such that the total number of the two colony types was always constant. Similar results were observed when CD34+ cells were cultured in the presence of a combination of rhEpo, rhSF, and rhIL-3. These results indicate that the presence of rhSF enhanced the detectability of the nonerythroid components of mixed colonies. The effect of rhSF on early progenitors (pre-colony-forming units [pre-CFU]) was studied in a two-step assay. In this assay, cells positive for CD34 and resistant to treatment with 4-hydroperoxycyclophosphamide (CD34+/4-HCres) were cultured in suspension for 7 days with rhSF, rhIL-3, or rhSF plus rhIL-3 and then plated in clonogenic assays. Before suspension culture, CD34+/4-HCres cells had a low clonogenic potential (0.37%). After being cultured in suspension, however, these cells gave rise to a large number of colonies of all types when replated. Cells cultured in suspension with the combination of rhSF and rhIL-3 increased significantly in number and gave rise to more colonies, when compared to cells cultured with either factor alone (synergistic effect). In identical experiments, such as effect had not been observed with combinations of rhIL-3 and either rhIL-1 or rhIL-6. Thus, rhSF supports the expansion and differentiation of early progenitors in human cord blood.
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PMID:Effects of recombinant human Steel factor (c-kit ligand) on early cord blood hematopoietic precursors. 751 47

A panel of 164 continuous human leukemia-lymphoma cell lines was analyzed for expression of c-kit using Northern blotting and reverse transcriptase-polymerase chain reaction (RT-PCR). The c-kit transcripts were detectable in cell lines assigned to the myeloid (in 7 of 29 by Northern blotting and in 4 of 8 by RT-PCR), monocytic (in 1 of 24 by Northern blotting and in 3 of 6 by RT-PCR), erythroid (in 6 of 8 by Northern blotting and in 5 of 5 by RT-PCR), and megakaryoblastic (in 10 of 10 by Northern blotting) lineages, c-kit expression was not seen by Northern blotting or RT-PCR analysis in any of the 93 lymphoid leukemia, myeloma, or lymphoma cell lines. Treatment of four megakaryoblastic cell lines with protein kinase C activators (phorbol ester 12-O-tetradecanoylphorbol 13-acetate and Bryostatin 1) led to terminal differentiation as assessed by morphologic alterations, changes in the surface marker profile, and growth arrest. These effects were associated with enhanced c-kit mRNA expression. Exposure to all-trans retinoic acid down-regulated c-kit mRNA levels, while simultaneously causing morphologic alterations in all four cell lines. Stimulation with growth factors (interleukin-3, granulocyte macrophage-colony stimulating factor, and insulin-like growth factors I and II), used to assess any role of c-kit in proliferative processes, did not lead to significant upregulation or downregulation of c-kit expression. The finding of constitutive and high expression of c-kit mRNA in all megakaryoblastic leukemia cell lines and its modulation by various reagents might further contribute to the understanding of megakaryopoietic proliferation, differentiation, and leukemogenesis.
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PMID:c-kit expression in human megakaryoblastic leukemia cell lines. 751 41


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