Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04141 (granulocyte-macrophage colony-stimulating factor)
 6,790 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Basic fibroblast growth factor (bFGF), a multifunctional growth factor produced by bone marrow stromal cells, is known to be a potent modulator of hematopoiesis. Because bFGF is present in both human megakaryocytes (MKs) and platelets, we have hypothesized that this growth factor might affect human megakaryocytopoiesis. To test this hypothesis, either low density bone marrow (BM) cells (LDBM), a human BM subpopulation (CD34+ DR+) enriched for the colony-forming unit megakaryocyte (CFU-MK) or a BM subpopulation (CD34+ DR-) enriched for the more primitive burst-forming unit megakaryocyte (BFU-MK) were assayed in the presence of this growth factor. The effect of bFGF on MK colony formation differed according to the cell population assayed. bFGF alone had on MK colony-stimulating activity (MK-CSA) when either CD34+ DR+ or CD34+ DR- BM cells were cloned, but exhibited MK-CSA equivalent to that of interleukin-3 (IL-3) when LDBM cells were used as the target cell population. The MK-CSA of bFGF was inhibited by the addition of neutralizing antisera to either IL-3 and/or granulocyte-macrophage colony-stimulating factor (GM-CSF) but not IL-6. The addition of excess amounts of either IL-3 or GM-CSF to cultures containing bFGF plus anti-IL-3 or anti-GM-CSF reversed the inhibition by the corresponding antisera. The addition of bFGF and IL-3 to assays containing CD34+ DR+ or CD34+ DR- cells increased the size of both CFU-MK- and BFU-MK-derived colonies, respectively, when compared with assays containing IL-3 alone. This increase in MK colony size mediated by bFGF was not affected by addition of either an anti-GM-CSF or anti-IL-6 neutralizing antisera. When LDBM cells were assayed, bFGF alone increased CFU-MK-derived colony size when compared with control values. However, this potentiation of MK colony size by bFGF could be reversed by the addition of either anti-IL-3 or anti-GM-CSF but not anti-IL-6 antisera. In addition, the effects of bFGF and IL-3 on the size of MK colonies cloned from LDBM were not additive. These results suggest that bFGF affects human megakaryocytopoiesis by directly promoting MK progenitor cell proliferation and stimulating BM accessory cells to release growth factor(s) with MK-CSA, such as IL-3 and GM-CSF. We conclude that bFGF, likely produced by cellular components of the BM microenvironment, plays an important role in the control of human megakaryocytopoiesis.
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PMID:Basic fibroblast growth factor promotes the proliferation of human megakaryocyte progenitor cells. 832 1

In humans and nonhuman primates, the in vivo administration of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) consistently results in marked increase of megakaryocyte ploidy and size similar to that observed with interleukin-6 (IL-6). However, whereas the administration of IL-6 also results in an increase in circulating platelets, there is no predictable corresponding increase in peripheral blood platelets following treatment with rhGM-CSF. To determine whether the failure of rhGM-CSF to produce thrombocytosis is secondary to cytokine-related increased platelet activation and consumption in vivo, we quantified autologous platelet survival time and in vivo platelet activation before and during 5 days of administration of rhGM-CSF to two rhesus monkeys. Platelet survival was measured using autologous platelets labeled with 111Indium-oxine. Platelet activation was assessed by flow cytometric determination of the expression of the major platelet membrane glycoprotein (GP) IIb/IIIa complex, and an activation-dependent epitope on GPIIb/IIIa (recognized by monoclonal antibodies [MABs] LJ-P4 and PAC1, respectively). Platelet activation was also assessed by dose-response aggregometry using adenosine diphosphate (ADP). While megakaryocyte ploidy increased during rhGM-CSF administration, peripheral platelet counts were 418 x 10(9)/L and 525 x 10(9)/L before and 402 x 10(9)/L and 508 x 10(9)/L during cytokine treatment in animals 1 and 2, respectively. No changes were observed in the mean platelet volume. 111Indium-labeled platelet recovery in circulation was similar before (94.7%, 91.8%) and during (92.9%, 92.8%) rhGM-CSF administration, which indicates that cytokine-related in vivo sequestration of platelets does not occur. Autologous platelet survival was 5.6 and 6.2 days before and 5.0 and 5.4 days during the rhGM-CSF treatment (p = 0.07), without significant change in the corresponding platelet turnover rate (derived from the platelet count and survival time). The flow cytometric analysis showed no increase in the binding of either LJ-P4 or PAC1 MABs to the platelet membrane during rhGM-CSF administration. The aggregometry studies demonstrated similar concentrations of ADP inducing half-maximal aggregation (ED50). Overall, the above data indicate that treatment with rhGM-CSF is not associated with in vivo activation, sequestration, or increased consumption of platelets. The data suggest that the failure of rhGM-CSF-stimulated megakaryocytes to increase peripheral platelet count is a manifestation of ineffective megakaryocytopoiesis resulting from inability to increase platelet delivery to the circulation.
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PMID:Effects of recombinant human granulocyte-macrophage colony-stimulating factor on platelet survival and activation using a nonhuman primate model. 840 39

Interleukin-4 (IL-4) is a cytokine with pleiotropic activities. In normal bone marrow cultures grown in the presence of either granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3), IL-4 suppresses granulocyte-macrophage colony-forming unit (CFU-GM) proliferation but it enhances the colony-stimulatory effect of granulocyte colony-stimulating factor (G-CSF). We studied the effect of IL-4 on chronic myelogenous leukemia (CML) bone marrow or peripheral blood cells from 30 patients using the CFU-granulocyte-erythrocyte-monocyte-megakaryocyte colony culture assay. In several repetitive experiments, IL-4 inhibited CFU-GM colony replication by 24 to 65% in a dose-dependent fashion at concentrations ranging from 0.01 to 10 micrograms/ml when patients' cells were cultured in the presence of erythropoietin alone or with phytohemagglutinin-conditioned medium, GM-CSF, or IL-3. The addition of 100 U/ml of IL-1 beta to the CML cultures partially reversed the inhibitory effect of IL-4. Incubation of CML low-density peripheral blood cells with IL-4 resulted in down-regulation of IL-1 beta and IL-6 production in three of four samples, suggesting that the suppressive effect of IL-4 is mediated by inhibition of IL-1 and by other mechanisms including inhibition of IL-6 production. In contrast to the stimulatory effect exerted by IL-4 on G-CSF-dependent CFU-GM progenitor proliferation in normal marrow, the addition of IL-4 to CML cultures grown in the presence of G-CSF resulted in a divergent effect: suppression of CML CFU-GM in two, stimulation in three, and no significant effect in two CML patients' samples. It is therefore possible that IL-4 may have an in vivo antiproliferative effect in a subpopulation of CML patients.
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PMID:Suppression of chronic myelogenous leukemia colony growth by interleukin-4. 842 75

Azidothymidine (AZT) has been demonstrated to increase platelet counts in patients suffering from acquired immunodeficiency syndrome (AIDS). However, the ability of long-term AZT treatment to sustain increases in platelet counts is controversial. We have recently demonstrated that AZT elevates the levels of circulating platelets in both normal C57BL/6 mice and mice made immunodeficient by infection with LP-BM5 murine leukemia virus (MAIDS mice). We therefore studied the effect of long-term AZT administration on platelet formation in both normal and MAIDS mice. Peripheral blood indices, levels of femoral and splenic megakaryocyte colony forming units (CFU-MK), and plasma levels of cytokines important in platelet formation-interleukin-6 (IL-6) and granulocyte-macrophage colony-stimulating factor (GM-CSF)--were examined. Platelet counts remained elevated throughout a 120-day AZT treatment period. Splenic CFU-MK were not significantly changed in MAIDS mice, except at day 15 when they were elevated. Splenic CFU-MK were significantly decreased in normal mice at days 8 and 120, and increased at day 30. Bone marrow CFU-MK were increased by AZT treatment at all time points tested in both normal and MAIDS mice. Plasma levels of GM-CSF were unchanged by AZT treatment in both normal and MAIDS mice. Plasma levels of IL-6 were unchanged in AZT-treated normal mice but decreased in AZT-treated MAIDS mice. These results indicate that long-term AZT treatment maintains elevated levels of platelets in both normal and MAIDS mice and affects CFU-MK colony formation. Our studies add to a growing body of work suggesting that AZT can ameliorate thrombocytopenia associated with HIV disease.
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PMID:Sustained elevation of platelet counts by long-term azidothymidine treatment of immunosuppressed mice. 845 34

Amegakaryocytic thrombocytopenia (AMT) is a rare and often fatal disorder of infancy and childhood presenting with isolated thrombocytopenia that progresses to marrow failure. The defect in thrombopoiesis is not well understood nor is the etiology of the progressive marrow failure. No standard modality of treatment exists. Here, we evaluated the capacity of marrow cells isolated from five patients with AMT and progressive marrow failure to generate megakaryocyte progenitor cells (CFU-MK). These in vitro studies demonstrated assayable numbers of CFU-MK from all patient bone marrows that responded in vitro to the addition of interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or the combination of both. These findings suggest that the defect in AMT might be partially correctable by the administration of these cytokines. A Phase I/II trial of in vivo administration of these same hematopoietins in the identical patients was conducted in which no significant toxicity was observed. IL-3 but not GM-CSF administration resulted in improved platelet counts in two patients and decreased bleeding and transfusion requirement in the remaining three. No clinical benefit was observed when GM-CSF was administered after IL-3 pretreatment. Prolonged IL-3 administration has resulted in platelet increases in an additional two patients. In vitro responsiveness of CFU-MK to either cytokine did not predict the degree of clinical response. Although the optimal dose and schedule of IL-3 either alone or in combination remains to be established, this study suggests that IL-3 may contribute to the treatment of patients with AMT.
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PMID:Effects of interleukin-3 and granulocyte-macrophage colony-stimulating factor on thrombopoiesis in congenital amegakaryocytic thrombocytopenia. 846 59

The human homolog of the murine flt3/flk2 gene product is a tyrosine kinase receptor that plays a role in regulating the proliferation and differentiation of cells in the hematopoietic system. Using a plasma-clot clonal assay and a long-term bone marrow culture (LTBMC) system, we studied the effects of the recently cloned human flt3 ligand (FL) alone and in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), or stem cell factor (c-kit ligand [KL]) on human megakaryocytopoiesis. The effects of FL on the primitive megakaryocyte (MK) progenitor cell, the burst-forming unit-megakaryocyte (BFU-MK), and the more differentiated colony-forming unit-megakaryocyte (CFU-MK) were determined. FL alone had no megakaryocytic colony-stimulating activity (MK-CSA), but was capable of augmenting the MK-CSA of both GM-CSF and IL-3. FL synergized with IL-3 at the level of both CFU-MK and BFU-MK and with GM-CSF and KL at the level of CFU-MK. Although FL alone exhibited a limited potential in sustaining long-term megakaryocytopoiesis in vitro, it synergistically augmented the ability of IL-3 and KL, alone or in association, to promote long-term megakaryocytopoiesis. These data indicate that multiple cytokines are necessary to optimally stimulate the proliferation of both classes of MK progenitor cells and that FL plays a significant role in this process by amplifying the MK-CSA of GM-CSF, IL-3, and KL.
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PMID:The effects of human FLT3 ligand on in vitro human megakaryocytopoiesis. 864 63

Interleukin-3 (IL-3) is a glycoprotein produced primarily by activated T-lymphocytes. As a hematopoietic growth factor it affects the proliferation, maturation, and survival of progenitor cells of the myeloid, erythroid, and megakaryocyte lineages. Initial studies in cancer patients with normal bone marrow using IL-3 doses of > 5 micrograms/kg daily produced a doubling of the neutrophil count within 2-3 days and that of platelet counts by days 10-12. Phase I-II clinical trials have examined the response to IL-3 in various clinical states, and ongoing phase III studies are currently assessing the clinical relevance. In the treatment of relapsed lymphoma, small-cell lung cancer, and breast and ovarian cancer, IL-3 at doses of 5-10 micrograms/kg daily given mainly subcutaneously for 5-10 days has been shown to maintain chemotherapy schedules while preserving adequate granulocyte and platelet numbers in the peripheral blood. At these doses, side effects were uncommon. The translation of these observations into clinical phase III studies has been disappointing, with no clear-cut clinical advantage being observed in the treated group. This reflects the relative lack of myelosuppression seen with most current regimens for solid tumors. The role of combined treatment with IL-3 in association with granulocyte colony-stimulating factor or granulocyte-macrophage colony-stimulating factor after cytotoxic treatment has yet to be established. However, it has been shown that they may act synergistically, resulting in significantly higher numbers of progenitor cells in the peripheral blood than when either is used alone. Combinations with IL-6 are also under study, as is the use of "cocktails" for ex vivo expansion of progenitors. This latter approach would allow single, small collections to be used for multiple infusions of progenitors and could support significant dose-intensification regimens by relieving myelosuppression. It is clear that the place of these newer cytokines in current treatment remains to be clarified.
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PMID:Is interleukin 3 active in anticancer drug-induced thrombocytopenia? 876 24

The recently cloned factor thrombopoietin (TPO) has been shown to exhibit megakaryocyte colony-stimulating activity in vitro. In this investigation, to further evaluate the action of TPO on megakaryocyte progenitor cells (colony-forming units-megakaryocyte [CFU-MK]), GpIIb/IIIa+ and GpIIb/IIIa- populations of CFU-MK were prepared from rat bone marrow cells based on their reactivity with P55 antibody, a monoclonal antibody against rat GpIIb/IIIa, and their responsiveness to recombinant human TPO (rhTPO) and recombinant rat interleukin-3 (rrIL-3) was examined using a megakaryocyte colony-forming assay (Meg-CSA). rhTPO supported only megakaryocyte colony growth from both fractions in a dose-dependent fashion. The mean colony size observed with the GpIIb/IIIa+ population was smaller than that seen with the GpIIb/IIIa- population. With the optimal concentration of either rhTPO or rrIL-3, similar numbers of megakaryocyte colonies were formed from the GpIIb/IIIa+ population previously shown to be highly enriched for CFU-MK. In contrast, the maximum number of megakaryocyte colonies from the GpIIb/IIIa- population stimulated by rhTPO was only 24.2% of that achieved with rrIL-3. Morphologic analysis of rhTPO-promoted megakaryocyte colonies from the GpIIb/IIIa+ population showed that the average colony size was smaller but that the mean diameter of individual megakaryocytes was larger than in megakaryocyte colonies promoted with rrIL-3. rhTPO plus rrIL-3, each at suboptimal concentrations, had an additive effect on proliferation of CFU-MK in the GpIIb/IIIa+ fraction, whereas rhTPO plus murine IL-6 or murine granulocyte-macrophage colony-stimulating factor (mG-M-CSF) modestly but significantly reduced megakaryocyte colony growth. These results indicate that TPO preferentially acts on GpIIb/IIIa+ late CFU-MK with lower proliferative capacity and interacts with some other cytokines in CFU-MK development.
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PMID:GpIIb/IIIa+ subpopulation of rat megakaryocyte progenitor cells exhibits high responsiveness to human thrombopoietin. 876 96

Platelets and megakaryocytes express Fc receptors for IgG which are encoded by the Fc gamma RIIA gene. In an effort to establish a cellular model for induction of Fc gamma RIIA expression during megakaryocyte development by hematopoietic growth factors, steady-state Fc gamma RIIA mRNA levels were monitored in c-kit receptor-positive megakaryocytic cells (M07e, HEL, and Dami) in response to c-kit ligand (KL; also known as stem cell factor, mast cell growth factor, or Steel factor). Northern blot analysis showed that exposure of cells to KL led to significant increases in Fc gamma RIIA levels in M07e (15 x at 24 hours), with smaller increases in HEL (1.9 x at 2 hours) and Dami (1.6 x at 24 hours) cells. K562 cells, which lack c-kit receptor, showed no effect of KL on modulating Fc gamma RIIA mRNA levels. The effects of KL were specific for Fc gamma RIIA, as there were no effects on platelet factor 4 (PF4), gamma-globin, or GATA-1 mRNA levels. Effects of KL, alone and in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF) and gamma-interferon (IFN-gamma), on surface Fc gamma RIIA expression were assessed by flow cytometry using anti-Fc gamma RII monoclonal antibody IV.3. In M07e cells, KL alone and in combination led to significant increases in the percentage of cells positive for surface Fc gamma RIIA and the mean cell fluorescence intensity. Transient transfection studies of an Fc gamma RIIA promoter-luciferase reporter gene in the presence or absence of KL showed increased reporter gene expression in KL-treated cells, with the largest increase (3.7-fold) in the M07e cells. In HEL and Dami cells, other cytokines active in megakaryocytopoiesis when used alone (interleukin-3 [IL-3], IL-6, IL-11, GM-CSF) had negligible activity in increasing reporter gene activity. These results suggest that increased levels of Fc gamma RIIA mRNA after KL treatment of M07e cells are a result, in part, of increased Fc gamma RIIA gene transcription. Our results indicate that M07e cells represent a cellular model for KL-induced Fc gamma RIIA expression in early megakaryocyte development.
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PMID:Human c-kit ligand (stem cell factor) induces platelet Fc receptor expression in megakaryoblastic cells. 876 99

Thrombopoietin (Tpo), the ligand for c-mpl, has been shown to be the principal regulator of megakaryocytopoiesis and platelet production. The ability of Tpo to potently stimulate the growth of committed megakaryocyte (Mk) progenitor cells has been studied in detail. Murine fetal liver cells, highly enriched in primitive progenitors, have been shown to express c-mpl, but little is known about the ability of Tpo to stimulate the growth and differentiation of primitive multipotent bone marrow (BM) progenitor cells. Here, we show that Tpo alone and in combination with early acting cytokines can stimulate the growth and multilineage differentiation of Lin- Sca-1+ BM progenitor cells. In particular, Tpo potently synergized with the ligands for c-kit (stem cell factor [SCF]) and flt3 (FL) to stimulate an increase in the number and size of clones formed from Lin- Sca-1+ progenitors. When cells were plated at 1 cell per well, the synergistic effect of Tpo was observed both in fetal calf serum-supplemented and serum-depleted medium and was decreased if the addition of Tpo to cultures was delayed for as little as 24 hours, suggesting that Tpo is acting directly on the primitive progenitors. Tpo added to SCF + erythropoietin (Epo)-supplemented methylcellulose cultures potently enhanced the formation of multilineage colonies containing granulocytes, macrophages, erythrocytes, and Mks. SCF potently enhanced Tpo-stimulated production of high-ploidy Mks from Lin- Sca-1+ progenitors, whereas the increased growth response obtained when combining Tpo with FL did not translate into increased Mk production. The ability of Tpo and SCF to synergistically enhance the growth of Lin- Sca-1+ progenitors was predominantly observed in the more primitive rhodamine 123(lo) fraction. Tpo also enhanced growth of Lin- Sca-1+ progenitors when combined with interleukin-3 (IL-3) and IL-11 but not with IL-12, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, or Epo. Epo, which has high homology to Tpo, was unable to stimulate the growth of Lin- Sca-1+ progenitors alone or in combination with SCF or FL, suggesting that c-mpl is expressed on more primitive stages of progenitors than the Epo receptor. Thus, the present studies show the potent ability of Tpo to enhance the growth of primitive multipotent murine BM progenitors in combination with multiple early acting cytokines and documents its unique ability to synergize with SCF to enhance Mk production from such progenitors.
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PMID:Thrombopoietin, but not erythropoietin, directly stimulates multilineage growth of primitive murine bone marrow progenitor cells in synergy with early acting cytokines: distinct interactions with the ligands for c-kit and FLT3. 897 40


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