Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0023473 (chronic myeloid leukemia)
 18,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endoglin is a glycoprotein expressed predominantly on human endothelial cells. It was first identified with mAb 44G4, produced against the pre-B acute lymphoblastic HOON cell line. We now report that four mAbs independently produced against human umbilical vein endothelial cells (HUVECs), chronic myelogenous leukemia in blast crisis, or U-937 pro-monocytic cells stimulated with phorbol myristate acetate also react with endoglin. High levels of reactivity of all mAbs were observed with HUVEC, while intermediate levels were seen with HOON and U-937 cells. By sequential immunoprecipitation from HUVEC and U-937 cell extracts, it was established that RMAC8, HEC-19, 8E11, and 1G2 mAbs react with the same protein as 44G4. Three distinct epitopes recognized by 44G4, RMAC8, and 1G2 mAbs were identified by competitive radioimmunoassay and flow cytometry. The HEC-19 epitope is spatially related to the 44G4 epitope, whereas the 8E11 epitope is most closely related to the 1G2 epitope. Western blot analysis showed that all antibodies react with the endoglin dimer (Mr = 170,000) purified from placenta. Immunostaining of sections of full-term placenta revealed reactivity not only with fetal vessels but also with the syncytiotrophoblast, the fetal cell layer which interfaces with maternal blood. When HUVEC monolayers were treated with the different mAbs to endoglin, prior to incubation with U-937 cells, a 5- to 10-fold stimulation of adhesion was observed. A fibronectin hexapeptide containing RGD, but not the corresponding RGE peptide, was capable of inhibiting the increased adhesion, when tested with mAb 44G4 and RMAC8. However, the same peptides had no effect on the binding of any of the five anti-endoglin mAbs to cells. Since 44G4 and RMAC8 recognize two distinct epitopes of endoglin, and since all five mAbs stimulated adhesion, the results suggest that a signal has been triggered through endoglin on HUVECs. Endoglin might be implicated either directly, by binding to a specific integrin-like ligand, or indirectly, by regulating the level of adhesion between certain integrins and their receptors.
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PMID:Identification of distinct epitopes of endoglin, an RGD-containing glycoprotein of endothelial cells, leukemic cells, and syncytiotrophoblasts. 137 94

We studied the adhesion of primitive and committed progenitors from chronic myelogenous leukemia (CML) and normal bone marrow to stroma and to several extracellular matrix components. In contrast to benign primitive progenitors from CML or normal bone marrow, Ph1-positive primitive progenitors from CML bone marrow fail to adhere to normal stromal layers and to fibronectin and its proteolytic fragments, but do adhere to collagen type IV, an extracellular matrix component of basement membranes. Similarly, multilineage colony-forming unit (CFU-MIX) progenitors from CML bone marrow do not adhere to fibronectin or its adhesion promoting fragments but adhere to collagen type IV. Unlike committed progenitors from normal bone marrow, CML single-lineage burst-forming units-erythroid and granulocyte/macrophage colony-forming units fail to adhere to fibronectin or its components but do adhere to both collagen type IV and laminin. Evaluation of adhesion receptor expression demonstrates that fibronectin receptors (alpha 4, alpha 5, and beta 1) are equally present on progenitors from normal and CML bone marrow. However, a fraction of CML progenitors express alpha 2 and alpha 6 receptors, associated with laminin and collagens, whereas these receptors are absent from normal progenitors. These observations indicate that the premature release of malignant Ph1-positive progenitors into the circulation may be caused by loss of adhesive interactions with stroma and/or fibronectin and acquisition of adhesive interactions with basement membrane components. Further study of the altered function of cell-surface adhesion receptors characteristic of the malignant clone in CML may lead to a better understanding of the mechanisms underlying both abnormal expansion and abnormal circulation of malignant progenitors in CML.
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PMID:Mechanisms underlying abnormal trafficking of malignant progenitors in chronic myelogenous leukemia. Decreased adhesion to stroma and fibronectin but increased adhesion to the basement membrane components laminin and collagen type IV. 138 71

Using a sensitive transfection-tumorigenicity assay, we have isolated a novel transforming gene from the DNA of two patients with chronic myelogenous leukemia. Sequence analysis indicates that the product of this gene, axl, is a receptor tyrosine kinase. Overexpression of axl cDNA in NIH 3T3 cells induces neoplastic transformation with the concomitant appearance of a 140-kDa axl tyrosine-phosphorylated protein. Expression of axl cDNA in the baculovirus system results in the expression of the appropriate recombinant protein that is recognized by antiphosphotyrosine antibodies, confirming that the axl protein is a tyrosine kinase. The juxtaposition of fibronectin type III and immunoglobulinlike repeats in the extracellular domain, as well as distinct amino acid sequences in the kinase domain, indicate that the axl protein represents a novel subclass of receptor tyrosine kinases.
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PMID:axl, a transforming gene isolated from primary human myeloid leukemia cells, encodes a novel receptor tyrosine kinase. 165 20

In the present study plasma fibronectin levels were determined in patients with hematopoietic malignancy, particularly leukemias, in an effort to clarify their clinical implications. Among leukemia patients, those with AML, ALL, ATL or CLL had various plasma fibronectin levels that were higher in some cases, while lower in others, as compared to normal control values. An elevation of the fibronectin level was noted often in APL, while lower fibronectin values were observed in many instances of CML. In these types of leukemia, acute exacerbation as well as supervention of infection tended to be associated with lower than normal levels of fibronectin. An especially marked depression of fibronectin occurred, when leukemia was complicated by sepsis or DIC, in which a good parallel was noted between the progress of disease and the fibronectin level. In lymphoproliferative diseases, the fibronectin value varied widely, but low fibronectin levels were frequently associated with intercurrent infection or an extreme deterioration of the general physical conditions.
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PMID:Variation of plasma fibronectin levels in leukemia patients. 248 45

The maintenance of hemopoietic precursors in long-term liquid bone marrow cultures (LTBMC) is associated with the presence of an adherent stromal layer composed of heterogeneous cell populations. We have used a culture assay to promote the growth of one of its cellular components and characterize its properties. Freshly obtained bone marrow cells and cells derived from the adherent layer of LTBMC were grown in methylcellulose-clotted plasma in the presence of phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM), hydrocortisone (HC), and citrated normal human plasma. Both sources contained cells (CFU-RF) that gave rise to colonies of cells with a reticulofibroblastoid appearance. In the presence of HC, most colonies contained lipid-laden cells. Colonies could be further propagated as adherent layers when transferred into liquid cultures. These cells produced laminin, fibronectin, and collagen types I, III, IV, and V. They were negative for Von Willebrand factor VIII. The ability to synthesize laminin and collagen type IV distinguished these cells from a population of previously described bone marrow fibroblasts (CFU-F). The relationship of CFU-RF to hemopoietic precursors was investigated using patients with chronic myeloid leukemia and bone marrow transplant recipients. Cells within CFU-RF-derived colonies were uniformly negative for the Philadelphia chromosome, thus making it unlikely that they belonged to the malignant hemopoietic clone. CFU-RF-derived colonies in bone marrow transplant recipients were found to be exclusively of host origin. Both observations support the view that CFU-RF is not part of the repertoire of hemopoietic stem cells.
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PMID:Characterization of reticulofibroblastoid colonies (CFU-RF) derived from bone marrow and long-term marrow culture monolayers. 308 97

Chronic myeloproliferative disorders (MPD) are clonal diseases of the pluripotent hematopoietic stem cell frequently associated with myelofibrosis (MF). There is only indirect evidence indicating that the increased deposition of collagen in bone marrow matrix is a secondary phenomenon. A liquid culture system for cloning and growing bone marrow fibroblasts has permitted us to approach more directly the understanding of the pathogenesis of myelofibrosis by comparing the biophysical, growth, and functional characteristics of fibroblasts from normals, MPD patients without MF, and those with MF. In patients with MF, marrow fibroblast colony (CFU-F) formation could not be studied; fibroblasts were grown from marrow explants. CFU-E from normals and MPD patients exhibited similar cell density distribution and similar cell sedimentation rates. These similarities contrasted sharply with the differences seen when the erythroid and granulocyte-macrophage progenitors were studied by the same methods. There was a marked light density shift and a rapidly sedimenting shift of MPD hematopoietic colony-forming cells. Marrow fibroblasts from MPD patients with and without MF displayed the same in vitro growth characteristics as fibroblasts from normals. Both types of fibroblasts exhibited anchorage and serum dependence, and contact inhibition of growth. Marrow fibroblasts were also characterized for the presence and distribution of fibronectin and collagen types by immunofluorescent staining using monospecific antibodies. Extracellular matrix, membrane-, and cytoplasm-associated fibronectin, type I, type III, and type V collagen showed a similar staining pattern in both normal and myelofibrotic marrow fibroblasts. Plasminogen-dependent fibrinolytic activity elicited from normal and myelofibrotic marrow fibroblasts were equivalent. Chromosomal analysis of hematopoietic cells and marrow fibroblasts from Philadelphia chromosome positive chronic myelocytic leukemia patients with and without MF showed that the Philadelphia chromosome was present only in hematopoietic cells. The results of these studies taken together demonstrate that bone marrow collagen-producing cells from MPD patients with and without MF behave in vitro as do those from normals. These findings support the hypothesis that that the marrow fibrosis observed in patients with MPD results from a reactive process rather than from a primary disorder affecting the marrow collagen-producing cells.
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PMID:Characteristics of bone marrow fibroblast colony-forming cells (CFU-F) and their progeny in patients with myeloproliferative disorders. 704 2

Recirculation of normal and neoplastic lymphocytes occurs via binding to the endothelial luminar surface, followed by extravasation and the subsequent interaction of the cells with components of the underlying basement membrane and stromal extracellular matrix (ECM). To identify matrix constituents that could be involved in the tissue dissemination of neoplastic B cells, we have examined the ability of three lymphoma B-cell lines and one Philadelphia chromosome (Ph1)-positive cell line established from the lymphoid transformation of a chronic myeloid leukemia (CML) to adhere to a range of purified ECM molecules. Immunophenotyping with a panel of markers suggested that the lines derived from cells that had undergone transformation at distinct stages of B-cell maturation. The four cell lines displayed a differential ability to adhere to the ECM molecules tested. BV-173, Ci-1, and Sc-1 cells attached to various degrees to fibronectin (FN). Ri-1, Ci-1, and Sc-1 cells attached to human laminin (LN) variants, whereas only Ci-1 and Sc-1 cells showed some affinity for collagen (Col) type VI. All four cell lines interacted with fibrillar Col I, but only BV-173 and Ri-1 cells attached to fibrillar Col III. The subendothelial Col VIII only was active as a substratum for BV-173 cells. In all cases, cells bound to fibrillar collagens when they were assembled into polymeric fibrils, and were incapable of adhering to monomeric and denatured collagen. In contrast to cell adhesion to FN and LN, which showed a plateau at high substrate concentrations, adhesion to fibrillar Col I reached a peak at intermediary concentrations and decreased thereafter, suggesting that cells respond to a definite macromolecular arrangement of collagenous fibrils. Adhesion to individual ECM molecules was not directly correlated with the apparent maturation state of the cells, nor with the relative density of known ECM receptors. Taken together, these results suggest that interaction of neoplastic B cells with selected matrix components may influence their dispersion throughout tissues. We further suggest that the use of quantitative cell adhesion assays in vitro may provide means of defining the behavioral traits of neoplastic B cells in vivo.
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PMID:Differential attachment of human neoplastic B cells to purified extracellular matrix molecules. 812 49

CML is often associated with myelofibrosis, and fibrosis in the accelerated phase is one of the diagnostic criteria for this accelerated phase. In this review, the mechanism of myelofibrosis associated with CML is discussed with emphasis on the cell origin of the production and release of platelet derived growth factor (PDGF) and its interaction with marrow fibroblasts. In the initial stage of myelofibrosis in chronic phase CML, atypical small megakaryocytes might leak PDGF, possibly PDGF-AB, together with other growth factors. As the clinical phase of the disease progresses to accelerated or blastic phase, a larger quantity of PDGF-AB or PDGF-BB might be secreted from blastic cells with myeloid phenotype. In addition some fibroblasts may be attracted by the PDGF and proliferate, and deposit collagen as well as fibronectin in the bone marrow stroma.
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PMID:Platelet derived growth factor expression, myelofibrosis and chronic myelogenous leukemia. 853 88

Migration patterns of leukemic cells in bone marrow are largely regulated by cell contacts between leukemic cells and stromal cells or extra-cellular matrix. The mechanism of this interaction with bone-marrow stromal cells was studied in a human in vitro model. Migration behavior of erythroleukemia cell line K562, derived from a patient with chronic myeloid leukemia, was compared with that of the erythroleukemia cell line HEL92.1.7 and the promyelocytic leukemia cell line HL60 from acute leukemias. Interaction varied between low binding affinity (K562) to intensive cell interaction (HEL92.1.7) followed by invasion into the stromal cell monolayer. Some of the HL60 cells adhered to stromal cells, while the remainder migrated into the stromal cell monolayer. The role of adhesion molecules in these cell interactions was determined. Distinct expression of beta1-integrins ICAM-1, CD44 and VCAM-1 was detected on the different cell lines. Inhibition studies pointed to a dominant role of VLA-4- and VLA-5-mediated interactions. K562 lacked VLA-4 and a low binding affinity of the VLA-5 on these cells resulted in an absence of binding to the bone-marrow stroma. These results indicate the VLA-5/fibronectin, VLA-4/fibronectin and the VLA-4/VCAM-1 interaction pathways between leukemic cells and bone-marrow stroma.
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PMID:beta1-Integrins dominate cell traffic of leukemic cells in human bone-marrow stroma. 860 16

Chronic myelogenous leukemia (CML) progenitors show decreased adhesion to stroma and fibronectin (FN) through beta 1 integrin receptors. We have previously shown that interferon-alpha (IFN-alpha) restores beta 1 integrin-mediated adhesion of CML progenitors to stroma. Because beta1 integrins transmit proliferation inhibitory signals from the microenvironment to normal hematopoietic progenitors, we hypothesized that decreased integrin-mediated adhesion of CML progenitors contributes to their continuous proliferation when in contact with stroma and that IFN-alpha treatment, by restoring integrin-mediated adhesion, also restores integrin-mediated microenvironmental inhibition of CML progenitor proliferation. We show here that, in contrast to normal colony-forming cells (CFC), the percentage of malignant CML CFC in S-phase was not significantly reduced following coculture with stromal layers. However, IFN-alpha treatment resulted in a significant reduction in the proliferation of CML CFC on coculture with stroma. This effect was not because of a direct antiproliferative effect of IFN-alpha on CML CFC because the proliferation of IFN-alpha treated CML CFC kept in suspension culture was not reduced. We examined the role of restored signaling through beta 1 integrin receptors in IFN-alpha induced inhibition of CML progenitors in two sets of experiment. In the first set of experiments, we demonstrated that proliferation of IFN-alpha-treated CML CFC, but not untreated CML CFC, was significantly reduced following coculture with 33/66-kD and 75-kD FN fragments, recognized by alpha 4 beta 1 and alpha 5 beta 1 integrins respectively. In a second set of experiments, we demonstrate that direct stimulation of integrin receptors by crosslinking with blocking antibodies to alpha 4, alpha 5, and beta 1 integrins and secondary goat antimouse antibodies resulted in significant reduction in proliferation of normal and IFN-alpha treated CML progenitors but not untreated CML CFC. These studies indicate that CML hematopoietic progenitors are unresponsive to beta 1-integrin mediated proliferation inhibition and that IFN-alpha not only restores beta 1 integrin-mediated adhesion but also beta1-mediated microenvironmental inhibition of CML progenitor proliferation. These observations may explain, at least in part, the therapeutic efficacy of IFN-alpha in CML.
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PMID:Interferon-alpha restores normal beta 1 integrin-mediated inhibition of hematopoietic progenitor proliferation by the marrow microenvironment in chronic myelogenous leukemia. 861 16


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