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)

The effects of human recombinant megakaryocyte growth and development factor (MGDF) (also known as thrombopoietin (TPO)), alone or in combination with other growth factors, on the proliferation and on the clonal growth of clonogenic progenitors from 24 acute myeloblastic leukemia (AML) patients were evaluated. A significant proliferative response to MGDF alone (proliferation index > 1.5) was observed in nine of 23 cases; the responding cases belonged to all FAB subtypes. However, the greatest response (proliferation index > 7) was found in one M6 and in one M7 case. MGDF also enhanced interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), c-kit ligand (KL) and FLT3 ligand (FL) stimulated blast cell proliferation. MGDF as a single factor induced or significantly enhanced colony formation by clonogenic precursor cells in 12 of 14 AML cases. MGDF strongly increased KL-induced leukemic colony growth in seven cases, whereas it only moderately enhanced IL-3- or GM-CSF-induced colony growth. The analysis of tyrosine phosphorylated protein(s) upon MGDF stimulation in fresh AML cells was also performed. The results demonstrated a band of approximately 90 kDa phosphorylated protein(s) upon MGDF stimulation in AML responsive cases, but not in unresponsive ones. Taken together the present findings suggest that, in a consistent proportion of AML cases, MGDF stimulates blast cell growth and induces tyrosine protein phosphorylation.
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PMID:Megakaryocyte growth and development factor (MGDF)-induced acute leukemia cell proliferation and clonal growth is associated with functional c-mpl. 909 94

Hematopoiesis is a complex process of regulated cellular proliferation and differentiation from the primitive stem cells to the final fully differentiated cell. The long and extensive search for a factor specifically regulating megakaryocytopoiesis led to the cloning of a hormone, here called thrombopoietin (TPO), that specifically promotes proliferation and differentiation of the megakaryocytic lineage. The availability of recombinant TPO and its imminent clinical use has made a more detailed understanding of its effects on hematopoietic cells more urgent. Normal megakaryocyto- and thrombopoiesis occurs predominantly in the bone marrow, a difficult organ to study in situ, particularly in humans, due to the low numbers of megakaryocytic progenitors and the consequent difficult isolation as pure populations. Thus, we developed an in vitro system which may allow us to address questions regarding the biology of TPO. The acute myeloid leukemia (AML)-derived cell lines HU-3, M-07e, M-MOK and TF-1 have absolute dependence on granulocyte-macrophage colony-stimulating factor (GM-CSF). We cultured these cells long term (> 6 months) in the continuous presence of TPO (omitting GM-CSF). TPO alone supported the maintenance and expansion of these sister cell lines, HU-3/TPO, M-07e/TPO, M-MOK/TPO and TF-1/TPO, that displayed somewhat longer doubling times, a larger cell size, and a higher percentage of polynucleated giant cells and slightly adherent cells than the corresponding countercultures grown with GM-CSF. In the absence of TPO the cells died quickly, within a few days; thus, the TPO-grown cell lines have an absolute dependence on this factor, but could all be switched back to growth with GM-CSF. In comparison with the GM-CSF-treated cells, the receptors for GM-CSF and interleukin-3 (IL-3) were down-regulated and the receptors for stem cell factor (SCF) and TPO were up-regulated in the TPO-exposed cells. A short-term proliferation assay showed a stronger response of the TPO-cell lines to erythropoietin, GM-CSF, IL-3, PIXY-321, SCF and TPO than the GM-CSF-cell lines. Flow cytometric analysis of the GM-CSF-and TPO-cultured lines displayed an up-regulation of the megakaryocytic surface markers CD41, CD42 and CD61, and a down-regulation of the erythroid marker glycophorin A in the latter cell lines, suggesting some differentiation along the megakaryocytic lineage. Thus, in long-term exposure, TPO appears to have both a proliferative and a differentiative effect on responsive cells. Under serum-deprived culture conditions, TPO acted as a survival factor on the TPO-cell lines. Taken together, these findings indicate that the TPO-dependent cell lines represent important biological reagents for further characterization of the biology of TPO and should also provide a great aid for future in vitro experiments aimed at elucidating megakaryocyto- and thrombopoiesis.
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PMID:Thrombopoietin supports the continuous growth of cytokine-dependent human leukemia cell lines. 909 95

UT-7 is a human megakaryoblastic leukemia cell line with absolute dependence on interleukin-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), or erythropoietin (EPO) for growth and survival. We isolated a novel subline, UT-7/GM after long-term culture of UT-7 with GM-CSF. The hemoglobin concentration and gamma-globin and EPO-receptor mRNA levels were significantly higher in EPO-treated UT-7/GM cells than in untreated cells. In contrast, the platelet factor 4 and glycoprotein IIb mRNA levels were much higher in thrombopoietin (TPO)-treated UT-7/GM cells than in untreated cells. Some TPO-treated cells had morphologically mature megakaryocytic characteristics such as a developed demarcation membrane in the cytoplasm and multilobular nuclei. These findings indicate that UT-7/GM is a bipotential cell line that can be induced to differentiate into erythroid and megakaryocytic lineages by EPO and TPO, respectively. Moreover, a minority of UT-7/GM cells acquired a high hemoglobin concentration by treatment with TPO, suggesting that TPO in part induced the erythroid differentiation of the UT-7/GM cells. Interestingly, GM-CSF inhibited the EPO- or TPO-induced erythroid differentiation and the TPO-induced megakaryocytic differentiation of UT-7/GM cells. These results support the hypothesis that cytokines influence the programming of gene expression required for lineage commitment or differentiation.
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PMID:In vitro development of erythroid and megakaryocytic cells from a UT-7 subline, UT-7/GM. 916 41

Prostacyclin (prostaglandin I2, PGI2) is a potent vasodilator and inhibitor of platelet aggregation. Although it is well known that the specific receptor for prostacyclin (PGI2-R) is abundantly expressed on platelets, PGI2-R expression in megakaryocytes is poorly understood. In this study, we examined its expression in leukemic or normal megakaryocytes. PGI2-R mRNA was expressed in human leukemic cell lines of megakaryocytic nature as evaluated by Northern blot analysis. Phorbol 12-myristate 13-acetate (PMA), interleukin-1 (IL-1), IL-3, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), thrombopoietin (TPO), and tumor necrosis factor-alpha (TNF-alpha) enhanced PGI2-R mRNA expression. The enhancement of PGI2-R expression by PMA and TPO was associated with the upregulation of platelet factor 4 or glycoprotein IIb mRNA expression. Iloprost, an agonist of prostacyclin, induced significant cyclic (c)AMP synthesis in these leukemic cells indicating that interaction of PGI2-R and its ligand can induce postreceptor signal transduction. Furthermore, iloprost-induced cAMP synthesis was enhanced by the pretreatment with PMA or the cytokines that promoted PGI2-R expression. PMA and TPO also increased the specific binding of [3H]iloprost to these cells. Pooled normal megakaryocytic colonies from TPO-containing semisolid culture of purified human CD34+ cells expressed PGI2-R, which were increased as the megakaryocytes matured with the peak expression before proplatelet formation, as evaluated by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). These results indicate that PGI2-R is expressed in human megakaryocytes and is upregulated by cytokines involved in thrombopoiesis or inflammation. Also, it was indicated that megakaryocytic maturation accompanies enhancement of PGI2-R expression.
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PMID:Expression of prostacyclin receptor in human megakaryocytes. 924 34

We examined the effects of recombinant human thrombopoietin (TPO, c-Mpl ligand) on the proliferation and differentiation of human haemopoietic progenitors other than megakaryocytic progenitors using serum-free cultures. TPO alone supported the generation of not only megakaryocytic (MK) but also blast cell (blast) colonies from cord blood CD34+ cells. Delayed addition of a cytokine cocktail (cytokines; interleukin (IL)-3, IL-6, stem cell factor, erythropoietin, granulocyte-macrophage colony-stimulating factor, and TPO) to cultures with TPO alone on day 7 induced various colonies including granulocyte-macrophage (GM) colonies, erythroid bursts (E), granulocyte-erythrocyte-macrophage-megakaryocyte (GEMM) colonies. Replating experiments of blast colonies supported by TPO alone for culture with cytokines revealed that approximately 60% of the blast colonies contained various haemopoietic progenitors. Single cell cultures of clone-sorted CD34+ cells indicated that TPO supported the early proliferation and/or survival of both primitive and committed haemopoietic progenitors. In serum-free suspension cultures, TPO alone significantly stimulated the production of progenitors for MK, GM, E and GEMM colonies as well as long-term culture-initiating cells. These effects were completely abrogated by anti-TPO antibody. These results suggest that TPO is an important cytokine in the early proliferation of human primitive as well as committed haemopoietic progenitors, and in the ex vivo manipulation of human haemopoietic progenitors.
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PMID:Thrombopoietin alone stimulates the early proliferation and survival of human erythroid, myeloid and multipotential progenitors in serum-free culture. 926 17

Protein kinase C (PKC) has been implicated in signal transduction events elicited by several hematopoietic growth factors. Thrombopoietin (TPO) is the major regulator of megakaryocytic lineage development, and its receptor, c-Mpl, transduces signals for the proliferation and differentiation of hematopoietic progenitors. In this study we have examined the effect of TPO on the subcellular distribution of PKC (a measure of enzyme activation) in a growth factor-dependent pluripotent hematopoietic cell line that was engineered to express the c-Mpl receptor (UT-7/mpl). In addition, we have assessed the significance of this activation for the induction of both mitogenesis and differentiation. Using a PKC translocation assay, TPO was found to stimulate a time- and dose-dependent increase in the total content of PKC activity present in the membrane fraction of UT-7/mpl cells (maximum increase = 2.3-fold above basal level after 15 minutes with 40 ng/mL TPO, EC50 = 7 ng/mL). Accordingly, a decrease of PKC content in the cytosolic fraction was observed. Immunoblot analysis using PKC isotype-specific antibodies showed that TPO treatment led to a marked increase of the Ca2+/diacylglycerol-sensitive PKC isoforms alpha and beta found in the membrane fraction. In contrast, the subcellular distribution of these isoforms did not change after treatment with granulocyte-macrophage colony-stimulating factor (GM-CSF). Exposure of UT-7/mpl cells to the selective PKC inhibitor GF109203X completely inhibited the PKC activity associated to the membrane fraction after TPO treatment, and blocked the mitogenic effect of TPO. In contrast, GF109203X had no effect on the TPO-induced expression of GpIIb, a megakaryocytic differentiation antigen. Downregulation of PKC isoforms alpha and beta to less than 25% of their initial level by treatment with phorbol 12,13-dibutyrate also abolished the TPO-induced mitogenic response, but had no significant effect when this response was induced by GM-CSF. Taken together, these findings suggest that (1) TPO stimulates the activation of PKC, (2) PKC activation mediates the mitogenic action of TPO, and (3) PKC activation is not required for TPO-induced expression of megakaryocytic surface markers.
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PMID:Protein kinase C mediates the mitogenic action of thrombopoietin in c-Mpl-expressing UT-7 cells. 944 41

With the identification and recombinant production of the hematopoietic growth factors, these cytokines have been evaluated in the treatment of primary bone marrow failure states and following myelosuppressive chemotherapy or radiotherapy. An increasing number of clinical trials with hematopoietic factors have been performed in patients with haematological and oncological diseases. Granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), erythropoietin and, in phase I/II trials, thrombopoietin (TPO) are available for the clinical use. Most studies have been performed with G-CSF and GM-CSF, their beneficial effects are proven regarding acceleration of hematopoietic recovery following chemotherapy. This results in a marked reduction of infectious risks and a shortening of drug- and radiation-induced myelosuppression. CSFs are most important in mobilizing peripheral blood progenitor cells (PBPC) and have allowed high-dose therapy combined with stem cell support in gynecological malignancies, e.g. ovarian carcinoma and breast cancer. However, evidence based, clinical practical guidelines for the use of hematopoietic growth factors in gynecological malignancies are not for all circumstances available.
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PMID:[Current status of clinical indications for hematopoietic growth factors after chemo-/radiotherapy in gynecology]. 948 9

Vascular endothelial growth factor (VEGF) production was analysed in megakaryocytic cell lines and CD34+ haematopoietic progenitors following treatment with thrombopoietin (TPO). In CMK cells TPO caused a time- and dose-dependent increase in the levels of VEGF released into the medium. A similar effect was observed in UT-7/mpl cells transfected with the TPO receptor c-Mpl, but not in parental UT-7 cells. In CD34+ haematopoietic progenitor cell cultures TPO stimulated VEGF mRNA expression and VEGF protein release. Production of VEGF in CD34+ cultures increased with TPO-induced megakaryocytic differentiation, but not with erythroid or myelomonocytic differentiation induced respectively by erythropoietin and granulocyte-macrophage colony-stimulating factor. These results demonstrate that TPO stimulates VEGF release in c-Mpl-expressing cells and suggest that this process is an integral feature of the megakaryocytic differentiation programme.
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PMID:Thrombopoietin stimulates VEGF release from c-Mpl-expressing cell lines and haematopoietic progenitors. 950 32

UT-7 is a human megakaryoblastic leukemia cell line with absolute dependence on interleukin-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), or erythropoietin (EPO) for growth and survival. Among its sublines, UT-7/GM, which remains undifferentiated in the presence of GM-CSF, has a bipotency showing differentiation into erythroid or megakaryocytic cell lineages in the presence of EPO or thrombopoietin (TPO), respectively. To investigate the mechanism underlying determination of cell differentiation, we investigated the role of signal transducers and activators of transcription (STAT) in EPO-induced erythroid differentiation. UT-7 cells grow in response to GM-CSF and EPO but do not differentiate into mature cells. UT-7/GM cells grow in response to GM-CSF and differentiate into erythroid cells by EPO. In UT-7 cells, both GM-CSF and EPO induced the activation of Stat1 alpha, Stat3 and Stat5. In UT-7/GM cells, EPO activated Stat5 alone, although the activation of Stat1 alpha, Stat3, and Stat5 was induced by GM-CSF or TPO. In addition, GM-CSF inhibited EPO-induced erythroid differentiation and concomitantly activated Stat1 alpha and Stat3 in UT-7/GM cells even in the presence of EPO. Further we transfected Stat1 alpha, Stat3 cDNA or both into UT-7/GM cells. Hemoglobin-positive cells were decreased in the stable transfectants stimulated with EPO. These results indicate that Stat1 alpha and Stat3 have an inhibitory effect on the EPO-induced erythroid differentiation, and more complicated combination of transcription factors may play an important role in the decision of cell differentiation.
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PMID:Regulation of both erythroid and megakaryocytic differentiation of a human leukemia cell line, UT-7. 958 1

We previously reported the aberrant growth of granulocyte-macrophage (GM) progenitors induced by a combination of stem cell factor (SCF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in juvenile chronic myelogenous leukemia (JCML). We examined here the effects of thrombopoietin (TPO) on the proliferation and differentiation of hematopoietic progenitors in JCML. In serum-deprived single-cell cultures of normal bone marrow (BM) CD34+CD38high cells, the addition of TPO to the culture containing SCF + GM-CSF resulted in an increase in the number and size of GM colonies. In the JCML cultures, in contrast, the number of SCF + GM-CSF-dependent GM colonies was not increased by the addition of TPO. However, the TPO addition caused an enlargement of GM colonies in cultures from the JCML patients to a significantly greater extent compared with the normal controls. There was no difference in the type of the constituent cells of GM colonies with or without TPO grown by JCML BM cells. A flow cytometric analysis showed that the c-Mpl expression was found on CD13+ myeloid cells generated by CD34+CD38high BM cells from JCML patients, but was at an undetectable level in normal controls. The addition of TPO to the culture containing SCF or SCF + GM-CSF caused a significant increase in the production of GM colony-forming cells by JCML CD34+CD38neg/low population, indicating the stimulatory effects of TPO on JCML primitive hematopoietic progenitors. Normal BM cells yielded a significant number of megakaryocytes as well as myeloid cells in response to a combination of SCF, GM-CSF, and/or TPO. In contrast, megakaryocytic cells were barely produced by the JCML progenitors. Our results may provide a fundamental insight that the administration of TPO enhances the aberrant growth of GM progenitors rather than the recovery of megakaryocytopoiesis.
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PMID:Thrombopoietin enhances the production of myeloid cells, but not megakaryocytes, in juvenile chronic myelogenous leukemia. 959 51


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