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  • American Society of Hematology (ASH)  (10)
  • 2010-2014  (10)
  • 1990-1994
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  • 1
    Publication Date: 2013-04-26
    Description: Recombinant adeno-associated virus (rAAV) vectors encoding human factor VIII (hFVIII) were systematically evaluated for hemophilia A (HA) gene therapy. A 5.7-kb rAAV-expression cassette (rAAV-HLP-codop-hFVIII-N6) containing a codon-optimized hFVIII cDNA in which a 226 amino acid (aa) B-domain spacer replaced the entire B domain and a hybrid liver-specific promoter (HLP) mediated 10-fold higher hFVIII levels in mice compared with non–codon-optimized variants. A further twofold improvement in potency was achieved by replacing the 226-aa N6 spacer with a novel 17-aa peptide (V3) in which 6 glycosylation triplets from the B domain were juxtaposed. The resulting 5.2-kb rAAV-HLP-codop-hFVIII-V3 cassette was more efficiently packaged within AAV virions and mediated supraphysiologic hFVIII expression (732 ± 162% of normal) in HA knock-out mice following administration of 2 x 10 12 vector genomes/kg, a vector dose shown to be safe in subjects with hemophilia B. Stable hFVIII expression at 15 ± 4% of normal was observed at this dose in a nonhuman primate. hFVIII expression above 100% was observed in 3 macaques that received a higher dose of either this vector or the N6 variant. These animals developed neutralizing anti-FVIII antibodies that were abrogated with transient immunosuppression. Therefore, rAAV-HLP-codop-hFVIII-V3 substantially improves the prospects of effective HA gene therapy.
    Keywords: Thrombosis and Hemostasis, Gene Therapy
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 2
    Publication Date: 2012-03-09
    Description: The coagulopathy of acute promyelocytic leukemia (APL) is mainly related to procoagulant substances and fibrinolytic activators of APL blasts, but the fate of these leukemic cells is unknown. The aim of this study was to investigate the removal of APL blasts by macrophages and endothelial cells in vitro and consequent procoagulant and fibrinolytic activity of APL cells. We found that human umbilical vein endothelial cells as well as THP-1 and monocyte-derived macrophages bound, engulfed, and subsequently degraded immortalized APL cell line NB4 and primary APL cells. Lactadherin promoted phagocytosis of APL cells in a time-dependent fashion. Furthermore, factor Xa and prothrombinase activity of phosphatidylserine-exposed target APL cells was time-dependently decreased after incubation with phagocytes (THP-1–derived macrophages or HUVECs). Thrombin production on target APL cells was reduced by 40%-45% after 2 hours of coincubation with phagocytes and 80% by a combination of lactadherin and phagocytes. Moreover, plasmin generation of target APL cells was inhibited 30% by 2 hours of phagocytosis and ~ 50% by lactadherin-mediated engulfment. These results suggest that engulfment by macrophages and endothelial cells reduce procoagulant and fibrinolytic activity of APL blasts. Lactadherin and phagocytosis could cooperatively ameliorate the clotting disorders in APL.
    Keywords: Myeloid Neoplasia, Phagocytes, Granulocytes, and Myelopoiesis, Thrombosis and Hemostasis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 3
    Publication Date: 2012-02-17
    Description: A close homologue to protein disulfide isomerase (PDI) called ERp57 forms disulfide bonds in glycoproteins in the endoplasmic reticulum and is expressed on the platelet surface. We generated 2 rabbit Abs to ERp57. One Ab strongly inhibited ERp57 in a functional assay and strongly inhibited platelet aggregation. There was minimal cross-reactivity of this Ab with PDI by Western blot or in the functional assay. This Ab substantially inhibited activation of the αIIbβ3 fibrinogen receptor and P-selectin expression. Furthermore, adding ERp57 to platelets potentiated aggregation. In contrast, adding a catalytically inactive ERp57 inhibited platelet aggregation. When infused into mice the inactive ERp57 prolonged the tail bleeding times. We generated 2 IgG2a mAbs that reacted with ERp57 by immunoblot. One of these Abs inhibited both ERp57 activity and platelet aggregation. The other Ab did not inhibit ERp57 activity or platelet aggregation. The inhibitory Ab inhibited activation of αIIbβ3 and P-selectin expression, prolonged tail bleeding times, and inhibited FeCl 3 -induced thrombosis in mice. Finally, we found that a commonly used mAb to PDI also inhibited ERp57 activity. We conclude that a glycoprotein-specific member of the PDI family, ERp57, is required for platelet aggregation, hemostasis, and thrombosis.
    Keywords: Platelets and Thrombopoiesis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 4
    Publication Date: 2014-09-19
    Keywords: Free Research Articles, Myeloid Neoplasia, Clinical Trials and Observations
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 5
    Publication Date: 2014-09-05
    Description: Cyclooxygenases (COXs) and their prostanoid products play important roles in a diverse range of physiological processes, including in the immune system. Here, we provide evidence that COX-1 is an essential regulator in early stages of B-cell development. COX-1–deficient mice displayed systematic reduction in total B cells, which was attributed to the arrest of early B-cell development from pro-B to pre-B stage. We further demonstrated that this defect was mediated through downregulation of the Janus kinase/signal transducer and activator of transcription 5 (JAK/STAT5) signaling and its target genes, including Pax5, in COX-1 –/– mice. Mechanistic studies revealed that COX-1–derived thromboxane A 2 (TxA 2 ) could regulate JAK3/STAT5 signaling through the cyclic adenosine monophosphate-protein kinase A pathway, via binding with its receptor thromboxane A2 receptor (TP). Administration of the TP agonist could rescue the defective B-cell development and JAK/STAT5 signaling activity in COX-1–deficient mice. Moreover, administration of low-dose aspirin caused a significant reduction in total B cells in peripheral blood of healthy human volunteers, coincidentally with reduced TxA 2 production and downregulation of JAK/STAT5 signaling. Taken together, our results demonstrate that COX-1–derived TxA 2 plays a critical role in the stage transition of early B-cell development through regulation of JAK/STAT5 signaling and indicate a potential immune-suppressive effect of low-dose aspirin in humans.
    Keywords: Hematopoiesis and Stem Cells, Immunobiology
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 6
    Publication Date: 2012-12-07
    Description: Understanding the process of myeloid differentiation offers important insights into both normal and abnormal developmental processes but is limited by the dearth of experimental models. Here we show that myeloid progenitors can be derived from embryonic stem cells, immortalized, and applied to the study of the mechanisms underlying myeloid differentiation. The embryonic stem cell–derived myeloid progenitors, when immortalized with estrogen-regulated Hoxb8 protein, demonstrate normal karyotyping, are genetically tractable, and can be differentiated into functional neutrophils. Using this model, we identified mammalian target of rapamycin complex 1 as a critical regulator of myeloid differentiation. Together, our studies led to a convenient, karyotypically normal, and genetically manipulatable cellular system, which can be used to shed new light on the mechanisms for myeloid differentiation.
    Keywords: Hematopoiesis and Stem Cells, Phagocytes, Granulocytes, and Myelopoiesis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 7
    Publication Date: 2013-01-18
    Description: t(8;21) is one of the most frequent chromosomal translocations occurring in acute myeloid leukemia (AML) and is considered the leukemia-initiating event. The biologic and clinical significance of microRNA dysregulation associated with AML1/ETO expressed in t(8;21) AML is unknown. Here, we show that AML1/ETO triggers the heterochromatic silencing of microRNA-193a ( miR-193a ) by binding at AML1-binding sites and recruiting chromatin-remodeling enzymes. Suppression of miR-193a expands the oncogenic activity of the fusion protein AML-ETO, because miR-193a represses the expression of multiple target genes, such as AML1/ETO , DNMT3a , HDAC3 , KIT , CCND1 , and MDM2 directly, and increases PTEN indirectly. Enhanced miR-193a levels induce G 1 arrest, apoptosis, and restore leukemic cell differentiation. Our study identifies miR-193a and PTEN as targets for AML1/ETO and provides evidence that links the epigenetic silencing of tumor suppressor genes miR-193a and PTEN to differentiation block of myeloid precursors. Our results indicated a feedback circuitry involving miR-193a and AML1/ETO/DNMTs/HDACs , cooperating with the PTEN /PI3K signaling pathway and contributing to leukemogenesis in vitro and in vivo, which can be successfully targeted by pharmacologic disruption of the AML1/ETO/DNMTs/HDACs complex or enhancement of miR-193a in t(8;21)–leukemias.
    Keywords: Myeloid Neoplasia
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 8
    Publication Date: 2013-11-22
    Description: The platelet protein disulfide isomerase called ERp57 mediates platelet aggregation, but its role in thrombus formation is unknown. To determine the specific role of platelet-derived ERp57 in hemostasis and thrombosis, we generated a megakaryocyte/platelet-specific knockout. Despite normal platelet counts and platelet glycoprotein expression, mice with ERp57-deficient platelets had prolonged tail-bleeding times and thrombus occlusion times with FeCl 3 -induced carotid artery injury. Using a mesenteric artery thrombosis model, we found decreased incorporation of ERp57-deficient platelets into a growing thrombus. Platelets lacking ERp57 have defective activation of the αIIbβ3 integrin and platelet aggregation. The defect in aggregation was corrected by the addition of exogenous ERp57, implicating surface ERp57 in platelet aggregation. Using mutants of ERp57, we demonstrate the second active site targets a platelet surface substrate to potentiate platelet aggregation. Binding of Alexa 488–labeled ERp57 to thrombin-activated and Mn 2+ -treated platelets lacking β3 was decreased substantially, suggesting a direct interaction of ERp57 with αIIbβ3. Surface expression of ERp57 protein and activity in human platelets increased with platelet activation, with protein expression occurring in a physiologically relevant time frame. In conclusion, platelet-derived ERp57 directly interacts with αIIbβ3 during activation of this receptor and is required for incorporation of platelets into a growing thrombus.
    Keywords: Platelets and Thrombopoiesis, Thrombosis and Hemostasis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 9
    Publication Date: 2014-01-17
    Description: Mobilization of hematopoietic stem and progenitor cells (HSPCs) from bone marrow into the blood circulation has been widely used for hematopoietic transplantation. However, the current methods of cytokine- or small-molecule–stimulated HSPC mobilization are far from satisfactory. New mobilizing agents are needed to increase the number of stem cells in peripheral blood for effective reconstitution of hematopoiesis. Here, we report that the molecule Me6TREN (Me6) can induce rapid mobilization of hematopoietic progenitor cells and that Me6 exhibits more significant effects than granulocyte colony-stimulating factor (G-CSF) or AMD3100. Me6 also mobilizes long-term repopulating cells, which successfully engraft and expand in a multilineage fashion in primary and secondary transplant recipients. Mechanistically, Me6 inhibits both the SDF-1α–induced migration and VLA-4–mediated adhesion of mouse and human hematopoietic cells. Me6 appears to mobilize HSPCs by activating MMP-9 expression and disrupting the SDF-1α/CXCR4 axis. Therefore, Me6 may become a new potent and efficacious mobilizing agent of HSPCs.
    Keywords: Hematopoiesis and Stem Cells, Transplantation
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    Electronic ISSN: 1528-0020
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  • 10
    Publication Date: 2014-01-24
    Description: ASXL1 is mutated/deleted with high frequencies in multiple forms of myeloid malignancies, and its alterations are associated with poor prognosis. De novo ASXL1 mutations cause Bohring-Opitz syndrome characterized by multiple congenital malformations. We show that Asxl1 deletion in mice led to developmental abnormalities including dwarfism, anophthalmia, and 80% embryonic lethality. Surviving Asxl1 –/– mice lived for up to 42 days and developed features of myelodysplastic syndrome (MDS), including dysplastic neutrophils and multiple lineage cytopenia. Asxl1 –/– mice had a reduced hematopoietic stem cell (HSC) pool, and Asxl1 –/– HSCs exhibited decreased hematopoietic repopulating capacity, with skewed cell differentiation favoring granulocytic lineage. Asxl1 +/– mice also developed mild MDS-like disease, which could progress to MDS/myeloproliferative neoplasm, demonstrating a haploinsufficient effect of Asxl1 in the pathogenesis of myeloid malignancies. Asxl1 loss led to an increased apoptosis and mitosis in Lineage – c-Kit + (Lin – c-Kit + ) cells, consistent with human MDS. Furthermore, Asxl1 –/– Lin – c-Kit + cells exhibited decreased global levels of H3K27me3 and H3K4me3 and altered expression of genes regulating apoptosis ( Bcl2 , Bcl2l12 , Bcl2l13 ). Collectively, we report a novel ASXL1 murine model that recapitulates human myeloid malignancies, implying that Asxl1 functions as a tumor suppressor to maintain hematopoietic cell homeostasis. Future work is necessary to clarify the contribution of microenvironment to the hematopoietic phenotypes observed in the constitutional Asxl1 –/– mice.
    Keywords: Myeloid Neoplasia
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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