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)

In this study we review our present understanding of the effect of stem cell factor (SCF) on the in vitro growth of hemopoietic progenitors from patients with acquired severe aplastic anemia (SAA). We have run three separate sets of experiments. First, we have tested the expression of receptor mRNAs for granulocyte-macrophage colony stimulating factor/interleukin 3 (GM-CSF/IL-3) and for c-kit protein on bone marrow (BM) cells from SAA patients. Molecular analysis revealed the presence of normal transcripts for alpha and beta chains of GM-CSF/IL-3 receptor and for c-kit protein by Northern blot analysis. Second, we have tested the in vitro response to SCF of BM cells derived from 11 SAA patients: SCF induced a significant enhancement of erythroid burst forming unit (BFU-E) growth (8 to 29, p = 0.01) and allowed the formation of granulocyte/erythroid/macrophage/megakaryocyte (GEMM) colonies which were not scored in baseline culture conditions (0 to 8, p = 0.01). Granulocyte-macrophage colony forming unit (CFU-GM) growth was also enhanced (4 to 20, p = 0.3). This was true for patients both at diagnosis and after antilymphocyte globulin (ALG) treatment. We concluded that SCF can promote the in vitro growth of hemopoietic progenitors in patients with acquired SAA. Third, we have tested the response to SCF of peripheral blood (PB) hemopoietic progenitors collected from patients receiving in vivo long-term treatment with granulocyte CSF (G-CSF). When PB cells were plated directly in the presence of GM-CSF there was no colony formation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:In vitro effect of stem cell factor on colony growth from acquired severe aplastic anemia. 769 24

Cell kinetic studies of acute myeloid leukemia (AML) have provided evidence for the presence of nonproliferating cells. Hemopoietic growth factors (GF) can regulate proliferation of leukemic cells, furnishing new possibilities for recruiting quiescent cells into the cycle and overcoming cytokinetic resistance in AML. To assess the role of the novel identified cytokine, mast cell growth factor (MGF), in enhancing cytosine arabinoside (Ara-C) cytotoxicity, we have primed AML blasts with MGF and then exposed these cells to the S phase specific agent Ara-C. Other growth factors such as PIXY, interleukin 3 (IL-3), granulocyte-macrophage colony stimulating factor (GM-CSF) and granulocyte CSF (G-CSF) and the combination of MGF plus PIXY were also tested. Cytokinetic changes and clonogenic growth of leukemic colony forming unit (CFU-L) cells in methylcellulose were used to detect proliferative and cytotoxic effects on AML blasts. Expression of MGF receptor, the c-kit protein, was also measured by flow cytometry. We report in this preliminary study that MGF is able to increase proliferation in 75% of the samples studied and enhance Ara-C cytotoxicity in some of these cases. When MGF proliferative activity was compared with other GFs, individual cases showed heterogeneity in response, although the combination of MGF plus PIXY was always the most effective.
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PMID:Effects of mast cell growth factor on Ara-C mediated acute myeloid leukemia cell killing. 769 32

We have studied the effects of recombinant human interleukin-11 (rhIL-11), alone and combined with stem cell factor (SCF or c-kit ligand), IL-3, and granulocyte-macrophage colony-stimulating factor (GM-CSF) on the proliferation of highly enriched human hematopoietic CD34+ and CD34+CD33-DR- progenitor cells. CD34+ cells were purified using the avidin-biotin immunoabsorption technique and CD33+DR+ cells were subsequently removed by immuno-magnetic separation. The colony assays were performed in the presence and absence of exogenous serum. IL-11, as a single agent, induced the growth of a small number of colony-forming units-granulocyte/macrophage (CFU-GM) derived from purified CD34+ cells and failed to support the colony growth of CD34+CD33-DR- cells. The addition of erythropoietin (Epo) to IL-11 induced the growth of erythroid progenitors (BFU-E) derived from CD34+ cells but not from the same population depleted of CD33+DR+ cells. The combination of IL-11 with SCF, IL-3, or GM-CSF, in the presence of Epo, resulted in a synergistic or additive increase in the number of CFU cells (CFU-C) derived from both cell fractions. Moreover, the addition of SCF to IL-11 stimulated the development of macroscopic erythroid and multilineage colonies (CFU-GEMM) containing more than 10(4) cells. A combination of three factors (IL-11, SCF, and IL-3) resulted in the increase of the number of colonies arising from CD34+ and CD34+CD33-DR- cells (but not of their size) compared to the cultures treated with IL-11 plus SCF or IL-11 plus IL-3. The pattern of proliferative response of primitive hematopoietic progenitor cells to IL-11 in serum-free conditions was very similar to the cultures grown in serum-containing medium. It is noteworthy that IL-11 and SCF yielded colony formation that was comparable to that observed in the presence of serum. The effects of IL-11 on CD34+CD33-DR- cells were also studied in a short-term suspension culture system, which was shown to be specific for evaluating the proliferation of pluripotent hematopoietic precursors (Delta assay). In this system, IL-11 had a minimal effect on its own, whereas IL-11 plus SCF acted synergistically and their proliferative activity was improved by the addition of GM-CSF. These experiments indicate that IL-11 may be considered a "permissive" cytokine, capable of initiating the proliferation of very primitive human hematopoietic cells, which are then able to respond to late-acting CSFs.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Interleukin-11 stimulates the proliferation of human hematopoietic CD34+ and CD34+CD33-DR- cells and synergizes with stem cell factor, interleukin-3, and granulocyte-macrophage colony-stimulating factor. 769 67

We have established nurse cell-like clones from long-term cultures of the human skin. These human skin nurse cell (HSNC)-like clones were type I collagen+, type IV collagen-, vimentin+, cytokeratin-, CD44+, CD54+, and weakly positive for VCAM-1, and easily identified by the pseudoemperipolesis that allowed T lymphocytes to migrate beneath the HSNCs. HSNCs and various T cell lines formed a typical complex in the hanging drop culture system. The majority of human and murine T cells, and some of the tumor cell lines other than T cells, including B lymphoma and myeloblastoma cells, migrated beneath the HSNC clones. HSNC clones produced various cytokines, including IL-6, IL-7, IL-8, IL-9, granulocyte CSF (G-CSF), granulocyte-macrophage CSF (GM-CSF), macrophage CSF (CSF-1), TGF-beta 1, and c-kit ligand, but could not produce IL-1 alpha, IL-1 beta, IL-2, IL-3, IL-4, TNF-alpha, or TNF-beta. These characteristics were similar to those of nurse cells established from the murine thymus. Furthermore, IFN-gamma-pretreated HSNC clones that expressed MHC class II Ags induced autologous mixed lymphocyte reaction (AMLR) in autologous PBMCs to proliferate and exhibit the cytotoxicity against altered autologous cells and various tumor cells. These results suggest that HSNCs play an important role in the immunoregulation at skin tissues.
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PMID:Establishment and characterization of nurse cell-like clones from human skin. Nurse cell-like clones can stimulate autologous mixed lymphocyte reaction. 808 78

Analysis of the cellular/molecular basis of the early steps of hematopoietic proliferation and differentiation is hindered by the rarity of hematopoietic progenitors and stem cells (HP/HSC). The intensive efforts devoted to the development of purification methods for early HP and HSC, although initially largely unsuccessful, have recently provided a high level of HP/HSC yield and/or recovery. The methodology developed by our group, recently improved, provides not only virtually complete purification, but also abundant recovery of early HP/HSC such as colony forming units granulocyte/erythroid/macrophage/megakaryocyte (CFU-GEMM), burst forming units erythroid (BFU-E), CFU granulocyte/macrophage (CFU-GM)/CFU blast cells (CFU-B), and long-term culture initiating cells (LTC-IC) from adult peripheral and cord blood (CB). We have also developed a serum-free liquid suspension culture for unilineage erythroid (E), granulocytic (G) or monocytic (M) differentiation of stringently purified HP/HSC. These culture systems allow sequential collection and cellular/molecular analysis of discrete populations of hematopoietic cells at a homogenous stage of differentiation specifically along a unilineage pathway. These experimental tools have been utilized to investigate cellular/molecular mechanisms underlying early hematopoiesis. The transcription factor (TF) GATA-1 is considered to be the "master" gene of erythropoiesis. In highly purified HP/HSC undergoing E or GM differentiation, GATA-1 expression is characterized initially by proliferation-dependent activation and at later stages by sustained expression in the E pathway and suppression in the GM pathway. Hypothetically, similar on/off switches of lineage-restricted TF may underlie the binary fate decisions of early HP differentiation. The expression and modulation of hematopoietic growth factor receptors (HGFR) in early hematopoiesis have been extensively analyzed. The results suggest a model of transactivation cascade for HGFR such as interleukin 6 receptor (IL-6R), IL-3R, GM colony stimulating factor receptor (GM-CSFR), and erythropoietin receptor (EpR), whereby each HGF upmodulates the R(s) for distal-acting HGF(s). Finally, we have investigated the effect of HGF on reactivation of hemoglobin F (HbF) in clonogenic or liquid suspension serum-free culture of purified adult HP. The results suggest that c-kit ligand (KL) plays a key role in the reactivation of HbF synthesis in adult life, and IL-3/GM-CSF potentiate this effect at low KL level. The KL-induced HbF reactivation is seemingly related to an enhanced proliferation of early E progenitors in their differentiation pathway.
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PMID:Stringently purified human hematopoietic progenitors/stem cells: analysis of cellular/molecular mechanisms underlying early hematopoiesis. 824 48

A subset of mobilized CD34+ cells present in patient aphereses expresses Thy1 (CDw90). This population contains most long-term culture initiating cells, as assayed with a murine stromal cell line. It also contains a significant proportion of colony-forming unit granulocyte macrophage, but very few burst-forming unit erythroid. The limited differentiation towards the erythroid lineage is further confirmed by the absence of GATA-1 mRNA in the CD34+/Thy1+ subset, and by the low level of c-kit expression. The CD34+/Thy1+ subset appears phenotypically and functionally heterogeneous, a finding consistent with its high representation, compared to phenotypes such as CD34+/CD38-. Therefore, while at least some of CD34+/Thy1+ cells may be infectable by retroviral vectors, as shown by the presence of a transcript for the receptor for murine amphotropic retroviruses, the use of this selection strategy to specifically target human stem cells appears questionable.
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PMID:Phenotypic, molecular, and functional characterization of human peripheral blood CD34+/THY1+ cells. 856 66

We investigated the effects of stem cell factor (SCF) on the growth of blast clonogenic cells from 27 patients with acute myeloblastic leukemia (AML) and 3 patients with chronic myelocytic leukemia in myeloid crisis. SCF alone showed a significant stimulatory activity in 15 of 30 patients (50%). A marked reduction in the number of blast cell colonies supported by SCF alone was noted by the addition of neutralizing antibody (Ab) against granulocyte-macrophage colony-stimulating factor (GM-CSF). Ab against interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) also moderately reduced the number of colonies, whereas Ab against granulocyte CSF (G-CSF) failed to do so. All four Ab together completely abolished the growth in 5 of 6 patients tested. c-kit antisense oligonucleotides reduced the colony formation supported by IL-3 or G-CSF or, in the absence of growth factor, in only 2 of 10 patients tested. SCF caused stimulation by acting synergistically with G-CSF, GM-CSF, IL-3, IL-6, IL-9, IL-11, and IL-12 in 20 of 27 (74%), 17 of 27 (63%), 14 of 28 (50%), 9 of 28 (32%), 1 of 15 (7%), 3 of 28 (11%), and 2 of 15 (13%) patients, respectively. Thus, SCF alone or in combination with some other factor stimulated the growth in 27 of 30 (90%) patients. Of 3 nonresponders, 2 were AML, M3 at presentation. G-CSF at the optimal concentration increased the sensitivity of blasts to SCF. Taken together, SCF acting in combination with other factors, but not alone, stimulates the growth of blast clonogenic cells. GM-CSF, IL-6, and TNF-alpha may be produced endogenously, whereas G-CSF and SCF may be supplied exogenously. Autocrine regulation of the growth of blasts seems to increase the responsiveness of the cells to any of these factors, allowing them to achieve a highly active growth state.
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PMID:Roles of stem cell factor in the in vitro growth of blast clonogenic cells from patients with acute myeloblastic leukemia. 856 3

Stem cell factor (SCF), also termed mast cell growth factor or c-kit ligand, plays a central role in the regulation of hematopoiesis and maintenance of viability of hematopoietic cells. We used a new murine monoclonal antibody (MAb) specific for canine SCF to further dissect the role of SCF in vitro and in vivo. This neutralizing MAb, RG7.6 (IgG1), recognizes the soluble form as well as the membrane-bound form of SCF on marrow-derived stromal cells. Treatment of long-term bone marrow cultures (LTMC) with RG7.6 suppressed or stimulated the production of CFU-GM, depending on the MAb concentration and the time of addition to cultures. At concentrations of 0.1-10 micrograms/ml given on the day of recharge of the LTMC, RG7.6 resulted in sustained suppression of CFU-GM grown from nonadherent cells. In contrast, higher doses of RG7.6 (20-100 micrograms/ml) led to a two- to threefold increase in CFU-GM formation from nonadherent cells after 3 days of RG7.6 exposure; after longer RG7.6 exposure there was a rapid decline in the number of CFU-GM. The early increase of CFU-GM was even more distinct when RG7.6 addition to LTMCs was delayed until 1 day before cells were plated for the CFU-GM assay. The early increase of CFU-GMs in the presence of high-dose RG7.6 was mimicked by the addition of granulocyte colony-stimulating factor (G-CSF) to cultures containing suboptimal concentrations of RG7.6, suggesting the possibility that the "positive" response to high-dose RG7.6 was due to an overriding effect of other growth factors, e.g., G-CSF. In stromal cells expressing the membrane-bound form of SCF, the presence of MAb RG7.6, even at low concentrations, interfered with thymidine uptake and proliferation. RG7.6 was also tested in vivo. RG7.6 was given intravenously immediately (days 0-4) after total body irradiation and autologous bone marrow transplantation, and granulocyte counts were followed. The post-irradiation nadir of peripheral blood granulocytes was indistinguishable from controls at low doses of RG7.6 but became more shallow as higher doses of RG7.6 were infused, again suggesting a positive effect on granulocyte differentiation. Thus, the SCF-specific MAb appears to interfere with both stromal and hematopoietic cell function. While only inhibition was observed at lower concentrations, a transient increase in granulocyte production was seen at higher MAb concentrations.
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PMID:Neutralization of stem cell factor in vitro and in vivo: dose-dependent inhibition of stromal cells and induction of granulocyte/monocyte differentiation. 862 80

We dissected the functions of the microenvironment of bone marrow (BM) and fetal liver (FL) at the cellular level by cloning individual stromal calls and characterizing their phenotypical and functional features. Stromal cell clones derived from FL are large in size (mean forward light scatter intensity [mFSC] of 450), express the surface antigen Thy-1 but not Sca-1 and 6 out of 6 are able to differentiate into fat accumulating adipocytes. BM derived stromal cell clones are either small (mFSC of 250) or large (mFSC of 450), express Sca-1 but not Thy-1 and only 2 out of 7 differentiate towards adipocytes. Heterogeneity in terms of vascular adhesion molecule-1, intracellular adhesion molecule-1 and heat stable antigen expression was found among the different cell clones. Functional assays using long- and short-term cocultures of stromal and hematopoietic calls revealed: (1) the capacity of 8 out of 12 stromal cell clones to support the expansion of primitive hematopoietic progenitors (colony forming unit spleen day 12) more than 10 weeks. Fat accumulation but not expression of stem cell factor by stromal cells did correlate with this supportive function. (2) Better support of granulocyte maturation and proliferation by BM- compared to FL-derived stromal cell clones. However, stromal cell clones from both organs expressed macrophage-colony stimulating factor. (3) The ability of 4 out of 12 stromal cell clones (derived from both, FL and BM) to support the expansion of Interleukin-7 dependent pre-B cells from the BM. Pre-B cell growth stimulating factor was not restricted to supporters. (4) Mutual exclusiveness of myeloid and lymphoid support in that a given stromal cell clone supported either pre B-cell or granulocyte expansion. Experiments comparing the support of BM- and FL-derived hematopoietic progenitors showed identical responses of late (B220+/c-kit-) but strikingly different responses of early (B220+/c-kit+) pre-B cells, revealing different proliferation requirements for FL- versus BM- derived early pre-B cells in vitro.
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PMID:Hematopoietic supportive functions of mouse bone marrow and fetal liver microenvironment: dissection of granulocyte, B-lymphocyte, and hematopoietic progenitor support at the stroma cell clone level. 863 28

Recombinant thrombopoietin has been reported to stimulate megakaryocytopoiesis and thrombopoiesis and it may be quite useful to treat patients with low platelet counts after chemotherapy. As little is known regarding the possible activation of platelets by thrombopoietin, we examined the effects of thrombopoietin on platelet aggregation induced by shear stress and various agonists in native plasma. Using hirudin as an anticoagulant, thrombopoietin (1 to 100 ng/mL) enhanced platelet aggregation induced by 2 micromol/L adenosine-diphosphate (ADP) in a dose dependent fashion. The enhancement was not affected by treatment of platelets with 1 mmol/L aspirin plus SQ-29548 (a thromboxane antagonist, 1 micromol/L) but was inhibited by a soluble form of the thrombopoietin receptor, suggesting that the enhancement was mediated by the specific receptors and does not require thromboxane production. Epinephrine (1 micromol/L), which does not induce platelet aggregation in hirudin platelet rich plasma (PRP), did so in the presence of thrombopoietin (10 ng/mL). Thrombopoietin (10 ng/mL) also enhanced or primed platelet aggregation induced by collagen (0.5 micron.mL),. thrombin, serotonin, and vasopressin. Thrombopoietin does not induce any rise in cytosolic ionized calcium concentration nor activation of protein kinase C, as estimated by phosphorylation of preckstrin, indicating that the priming effects of thrombopoietin does not require those processes. The ADP- or thrombin-induced rise in cytosolic ionized calcium concentration was not enhanced by thrombopoietin (100 ng/mL). Further, shear (ca. 90 dyn/cm2)-induced platelet aggregation was also potentiated by thrombopoietin. The priming effect on epinephrine-induced platelet aggregation in hirudin PRP was unique to thrombopoietin, with no effects seen using interleukin-6 (IL-6), IL-11, IL-3, erythropoietin, granulocyte-colony stimulating factor, granulocyte macrophage-colony stimulating factor, or c-kit ligand. These data indicate that monitoring of platelet functions may be necessary in the clinical trials of thrombopoietin.
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PMID:Thrombopoietin primes human platelet aggregation induced by shear stress and by multiple agonists. 863 35


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