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)

Dogs given 920 cGy of total body irradiation (TBI) followed by autologous marrow infusion uniformly achieve sustained hematopoietic reconstitution. We have previously shown that administration of the anti-MHC class II monoclonal antibody (MoAb) H81.98.21 (IgG2a) at 0.6 mg/kg/d immediately after transplantation results in delayed graft failure. A second noncrossblocking anti-MHC class II MoAb, B1F6, of the same isotype, at the same dose, did not interfere with sustained engraftment, suggesting that the observed effect was epitope dependent. Although higher concentrations of B1F6 were required, in the present study both MoAbs interfered with the propagation of long-term marrow cultures. When MoAb B1F6 was given in vivo at 1.2 mg/kg/d, ie, twice the dose used previously, dogs so treated also developed delayed marrow graft failure. Marrow failure with either MoAb involved myeloid, erythroid, and megakaryocytic lineages. Administration of recombinant canine c-kit ligand/stem cell factor (SCF) for 7 or 21 days posttransplant resulted in reversal of graft failure. Although the short course did induce a broad transient early peak of granulocytes, the longer course of SCF was accompanied by earlier sustained recovery than the short course. In conclusion, therefore, marrow graft failure induced by anti-MHC class II MoAb does not appear to be epitope dependent, involves all hematopoietic lineages, and is overcome by the administration of c-kit ligand.
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PMID:Rescue from anti-MHC class II antibody-mediated marrow graft failure by c-kit ligand. 751 46

The mast cell growth factor (MGF) affects migration, proliferation and differentiation of erythroid and myeloid progenitor cells by binding to a transmembrane receptor tyrosine kinase encoded by the c-Kit proto-oncogene. By using MGF-dependent human myeloid cell lines (M-07e and TF-1), here we show that a Kit-related 100 kDa protein is associated with the cell but it undergoes release into the medium upon treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C. Immunological analysis with a series of antibodies to Kit indicated that the released protein (p100Kit) contains the whole glycosylated extracellular portion of the transmembrane Kit protein (p145Kit). The secreted protein retained the ability to specifically bind MGF. Moreover, p100Kit was able to block the mitogenic effect of MGF on cultured M-07e cells, suggesting that the soluble protein may function as a physiological antagonist of MGF.
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PMID:Protein kinase C-dependent release of a functional whole extracellular domain of the mast cell growth factor (MGF) receptor by MGF-dependent human myeloid cells. 751 83

To test whether primitive hematopoietic stem cells (PHSCs) are stimulated by Steel (SI) factor (c-kit ligand) in vivo, donor mice were studied after three or seven daily injections of SI factor. PHSC activity was measured as long-term erythroid and lymphoid competitive repopulating ability. Cells to be tested (usually marrow or spleen cells from treated donors) were mixed with untreated competitor marrow that produces erythrocytes and lymphocytes that are genetically distinguishable from the donors by differences in hemoglobin (Hb) and glucosephosphate isomerase (GPI) markers. These cell mixtures were injected into lethally irradiated hosts, and after 111 to 293 days, functional abilities of donor PHSC populations were assessed and expressed as percentages of donor-type Hb and GPI in the host's circulating erythrocytes and lymphocytes, respectively. A striking increase in splenic PHSC activity occurred after seven daily injections of SI factor, with a much smaller increase after three daily injections. Both three and seven daily injections of SI factor slightly reduced marrow PHSC activity. Rapid cycling greatly increases PHSC vulnerability to 5-fluorouracil (5FU). To test whether SI factor stimulates PHSCs into rapid cycling, donor mice were given a dose of 5FU in addition to SI factor. The increase in splenic PHSCs after 7 days of treatment with SI factor occurred to a similar degree whether donors were or were not treated with 5FU on day 8. However, a dose of 5FU on day 4 of the SI factor treatments almost totally prevented the increase in splenic PHSC activity. Apparently this increased activity requires PHSC cycling throughout the period of SI factor treatment.
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PMID:Splenic primitive hematopoietic stem cell (PHSC) activity is enhanced by steel factor because of PHSC proliferation. 751 1

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

We have studied the effects of recombinant human interleukin-9 (IL-9), alone and combined with stem cell factor (SCF, c-kit ligand), IL-3, and granulocyte-macrophage colony-stimulating factor (GM-CSF) on the clonogenic proliferation of highly enriched human hematopoietic CD34+ and CD34+CD33-DR- progenitor cells. Colony assays were performed under serum-containing and serum-free conditions. IL-9, as a single agent, did not support colony formation. The addition of erythropoietin (Epo) to IL-9 induced the growth of erythroid progenitors (BFU-E) derived from both CD34+ and CD34+CD33-DR- cells. The IL-9-dependent growth of BFU-E derived from CD34+ cells was increased in an additive manner by SCF and, to a lesser extent, by IL-3, whereas CD34+CD33-DR- erythroid precursors were also responsive to GM-CSF in combination with IL-9. The addition of SCF to IL-9 did stimulate the development of CD34+ and CD34+CD33-DR- macroscopic, multicentered BFU-E and multilineage colonies (CFU-GEMM). When IL-9 was used in serum-free conditions, the growth of CD34+ and CD34+CD33-DR- BFU-E was observed in the presence of Epo. Moreover, a marked synergy on BFU-E colony formation was evident when IL-9 was combined with SCF, and their activity was enhanced by the addition of IL-3. IL-9 showed a negligible proliferative activity on colony-forming units-granulocyte/macrophage (CFU-GM). However, it increased the number of CD34+CD33-DR- CFU-GM responsive to IL-3 (37% of the colonies generated by phytohemagglutinin-stimulated lymphocyte conditioned medium [PHA-LCM]). The effects of IL-9 on CD34+CD33-DR- cells were also studied in a short-term suspension culture system, which evaluates the proliferation of progenitors earlier than day 14 CFU-C (Delta assay). In this system, IL-9 had a minimal activity on its own. In combination with SCF, however, it induced a nine-fold expansion of CD34+CD33-DR- cells, which generated a greater number of CFU-GM than BFU-E in secondary methylcellulose cultures. These experiments indicate that IL-9 induces the proliferation of very primitive human erythroid cells, and this effect is potentiated by SCF and other cytokines. Furthermore, IL-9 synergizes in vitro with the c-kit ligand in expanding the pool of early pluripotent hematopoietic progenitor cells.
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PMID:Stem cell factor (c-kit ligand) enhances the interleukin-9-dependent proliferation of human CD34+ and CD34+CD33-DR- cells. 752 Mar 94

The mi locus of mice encodes a novel member of the basic-helix-loop-helix-leucine zipper protein family of transcription factors (hereafter called mi factor). In addition to microphthalmus, osteopetrosis, and lack of melanocytes, mice of mi/mi genotype are deficient in mast cells. Since the c-kit receptor tyrosine kinase plays an important role in the development of mast cells, and since the c-kit expression by cultured mast cells from mi/mi mice is deficient in both mRNA and protein levels, the mast cell deficiency of mi/mi mice has been attributed at least in part to the deficient expression of c-kit. However, it remained to be examined whether the c-kit expression was also deficient in tissues of mi/mi mice. In the present study, we examined the c-kit expression by mi/mi skin mast cells using in situ hybridization and immunohistochemistry. Moreover, we examined the c-kit expression by various cells other than mast cells in tissues of mi/mi mice. We found that the c-kit expression was deficient in mast cells but not in erythroid precursors, testicular germ cells, and neurons of mi/mi mice. This suggested that the regulation of the c-kit transcription by the mi factor was dependent on cell types. Mice of mi/mi genotype appeared to be a useful model to analyze the function of transcription factors in the whole-animal level.
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PMID:Cell type-specific deficiency of c-kit gene expression in mutant mice of mi/mi genotype. 752 30

Multiple cycles of high-dose chemotherapy can be hematologically supported by repeated administration of peripheral blood progenitors obtained after mobilization using cytokine alone or in combination with chemotherapy. We have explored the quality of such cells and their potential to undergo ex vivo expansion. Twenty-five leukapheresis samples from 19 patients who had received extensive prior chemotherapy for stage IV breast cancer were subjected to CD34+ cell selection using immunoaffinity columns of immunomagnetic bead separation. Cells were cultured in suspension in the presence of c-kit ligand, interleukin-3, interleukin-6, erythropoietin, and granulocyte colony-stimulating factor. Ten experiments were performed using weekly exchange of media and cytokines (Delta assay). Median myeloid and erythroid progenitors expanded 15-fold at 7 days (range, 7 to 43), 40-fold at 14 days (range, 18 to 470), 46-fold at 21 days (range, 0 to 118), and 21-fold at 28 days (range, 0 to 61). In a system using gas-permeable bags without exchange of media or cytokine, median progenitors expanded 13-fold at 7 days (range, 7 to 36), 14-fold at 10 days (range, 4 to 61), 14-fold at 12 days (range, 3 to 46), and 10-fold at 14 days (range, 1 to 35). Progenitor expansion less than 10-fold occurred in 8% of experiments at day 7, in 17% at day 10, in 43% at day 12, and in 50% at day 14. When autologous plasma, autologous plasma processed (removal of cryoprecipitate, centrifugation, then filtration), or human serum were substituted for 20% fetal calf serum, the ratio of progenitor expansion at 7 days relative to 20% fetal calf serum for 10% human serum, 20% human serum, and 1% autologous plasma processed was 1.01 (range, 0.62 to 1.33), 0.88 (range, 0.61 to 1.20), and 0.96 (range, 0.55 to 1.64), respectively. These findings support the feasibility of ex vivo expansion in a system free of nonhuman proteins of CD34(+)-derived progenitors obtained from the peripheral blood of patients who have received prior chemotherapy.
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PMID:Optimization of conditions for ex vivo expansion of CD34+ cells from patients with stage IV breast cancer. 752 42

Stem cell factor (SCF) is a determining and crucial element in the development of early hematopoietic cells. The SCF receptor protein has been identified as the product of the protooncogene c-kit and has been detected using monoclonal antibodies (MAbs) on a broad selection of erythroid, myeloid, and lymphoid cell lines as well as on bone marrow mononuclear cells (BMMNC). SCF is known to increase both the number and size of burst-forming unit-erythroid (BFU-E) colonies in normal human BM culture in a dose-dependent fashion. A detailed study of the involvement of SCF and its receptor c-kit in normal erythropoiesis will help elucidate intrinsic irregularities of anemias such as Diamond Blackfan Anemia, an aregenerative congenital anemia. Abnormalities of this heterogeneous disorder are confined to the red cell lineage and are thought to arise through a defect at the stem/progenitor cell level. Our in vitro studies suggest that SCF therapy will influence BFU-E production in at least a portion of these patients, although in another group, SCF response is limited or absent. Additionally, further investigations have shown a possible c-kit signaling defect that clearly necessitates further c-kit characterization. To parallel this, we, therefore, attempted to study the relationship of c-kit with its ligand. This report describes a nonradioactive method for detecting SCF receptors that varies from conventional assays in that the fluorescent label conjugated to the SCF/c-kit complex is connected via an extended-ester linkage that reduces steric influence and promotes full normal structural ligand binding of the SCF to its receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:c-kit protein (stem cell factor receptor) expression on cells with erythroid characteristics and on normal human bone marrow without the use of monoclonal antibodies. 752 82

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

Nonadherent, low-density T-lymphocyte-depleted (NALT-) CD34 cells from normal human cord blood were assessed in suspension culture for the effects of recombinant cytokines on their proliferation, differentiation, and generation of myeloid progenitor cells. In this cell population, 82% of cells expressed c-kit protein as assessed by in situ hybridization, and their cloning efficiency was 85% when cells were plated at low cell numbers with combinations of growth factors. CD34 cells were sorted as 1, 5, or 10 cell(s) per well and also at 5000 cells per dish to initiate stromal-free suspension cultures in the presence of steel factor (SLF), interleukin (IL)-1 alpha, and IL-3. Forty-eight percent of the wells started with a single CD34 cell were positive for growth after 14 days, and the wells contained greater than 5 x 10(3) cells by 21-28 days. Progenitors were assayed weekly with cultures initiated with 1 or 5000 cells. While the fold expansion of nucleated cells was greater in cultures initiated with one cell per well (> 5000 compared to 791-fold expansion for 5000 cells), the fold expansion of progenitors was greater than 5000 cells were used to initiate cultures. Under optimal conditions, there was, respectively, a 160-, 164-, and 57-fold output of high proliferative potential colony-forming cells, granulocyte-macrophage colony-forming units, and erythroid burst-forming units/granulocyte erythroid macrophage megakaryocyte colony-forming units within 1-3 weeks for cultures initiated with 5000 CD34 cells compared with respective fold increases of 29, 16, and 1, for single-initiated cultures. These results demonstrate the expansion capacity of single CD34 cord blood cells and demonstrate that factors in addition to SLF, IL-1 alpha, and IL-3 are necessary for optimal expansion of progenitors from single isolated CD34 cells.
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PMID:Extensive proliferative capacity of single isolated CD34 human cord blood cells in suspension culture. 753 51


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