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  • American Society of Hematology (ASH)  (12)
  • 1
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    Fev regulates hematopoietic stem cell development via ERK signaling (2013)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2013-07-19
    Description: Reprogramming of somatic cells to desired cell types holds great promise in regenerative medicine. However, production of transplantable hematopoietic stem cells (HSCs) in vitro by defined factors has not yet been achieved. Therefore, it is critical to fully understand the molecular mechanisms of HSC development in vivo. Here, we show that Fev, an ETS transcription factor, is a pivotal regulator of HSC development in vertebrates. In fev -deficient zebrafish embryos, the first definitive HSC population was compromised and fewer T cells were found in the thymus. Genetic and chemical analyses support a mechanism whereby Fev regulates HSC through direct regulation of ERK signaling. Blastula transplant assay demonstrates that Fev regulation of HSC development is cell autonomous. Experiments performed with purified cord blood show that fev is expressed and functions in primitive HSCs in humans, indicating its conserved role in higher vertebrates. Our data indicate that Fev-ERK signaling is essential for hemogenic endothelium-based HSC development.
    Keywords: Hematopoiesis and Stem Cells
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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  • 2
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    TNF-mediated inflammation represses GATA1 and activates p38 MAP kinase in RPS19-deficient hematopoietic progenitors (2014)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2014-12-12
    Description: Diamond-Blackfan anemia (DBA) is an inherited disorder characterized by defects in erythropoiesis, congenital abnormalities, and predisposition to cancer. Approximately 25% of DBA patients have a mutation in RPS19 , which encodes a component of the 40S ribosomal subunit. Upregulation of p53 contributes to the pathogenesis of DBA, but the link between ribosomal protein mutations and erythropoietic defects is not well understood. We found that RPS19 deficiency in hematopoietic progenitor cells leads to decreased GATA1 expression in the erythroid progenitor population and p53-dependent upregulation of tumor necrosis factor-α (TNF-α) in nonerythroid cells. The decrease in GATA1 expression was mediated, at least in part, by activation of p38 MAPK in erythroid cells and rescued by inhibition of TNF-α or p53. The anemia phenotype in rps19 -deficient zebrafish was reversed by treatment with the TNF-α inhibitor etanercept. Our data reveal that RPS19 deficiency leads to inflammation, p53-dependent increase in TNF-α, activation of p38 MAPK, and decreased GATA1 expression, suggesting a novel mechanism for the erythroid defects observed in DBA.
    Keywords: Hematopoiesis and Stem Cells, Pediatric Hematology, Red Cells, Iron, and Erythropoiesis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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  • 3
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    Epstein-Barr virus LMP2A suppresses MHC class II expression by regulating the B-cell transcription factors E47 and PU.1 (2015)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2015-04-03
    Description: Oncogenic Epstein-Barr virus (EBV) uses various approaches to escape host immune responses and persist in B cells. Such persistent infections may provide the opportunity for this virus to initiate tumor formation. Using EBV-immortalized lymphoblastoid cell lines (LCLs) as a model, we found that the expression of major histocompatibility complex (MHC) class II and CD74 in B cells is repressed after EBV infection. Class II transactivator (CIITA) is the master regulator of MHC class II–related genes. As expected, CIITA was downregulated in LCLs. We showed that downregulation of CIITA is caused by EBV latent membrane protein 2A (LMP2A) and driven by the CIITA-PIII promoter. Furthermore, we demonstrated that LMP2A-mediated E47 and PU.1 reduction resulted in CIITA suppression. Mechanistically, the LMP2A immunoreceptor tyrosine-based activation motif was critical for the repression of E47 and PU.1 promoter activity via Syk, Src, and the phosphatidylinositol 3-kinase/Akt pathway. Elimination of LMP2A in LCLs using a shLMP2A approach showed that the expression levels of E47 , PU.1 , CIITA , MHC class II , and CD74 are reversed. These data indicated that the LMP2A may reduce MHC class II expression through interference with the E47/PU.1-CIITA pathway. Finally, we demonstrated that MHC class II may be detected in tonsils and EBV-negative Hodgkin disease but not in EBV-associated posttransplant lymphoproliferative disease and Hodgkin disease.
    Keywords: Immunobiology, Lymphoid Neoplasia
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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  • 4
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    RAP-011 improves erythropoiesis in zebrafish model of Diamond-Blackfan anemia through antagonizing lefty1 (2015)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2015-08-14
    Description: Diamond-Blackfan Anemia (DBA) is a bone marrow failure disorder characterized by low red blood cell count. Mutations in ribosomal protein genes have been identified in approximately half of all DBA cases. Corticosteriod therapy and bone marrow transplantation are common treatment options for patients; however, significant risks and complications are associated with these treatment options. Therefore, novel therapeutic approaches are needed for treating DBA. Sotatercept (ACE-011, and its murine ortholog RAP-011) acts as an activin receptor type IIA ligand trap, increasing hemoglobin and hematocrit in pharmacologic models, in healthy volunteers, and in patients with β-thalassemia, by expanding late-stage erythroblasts through a mechanism distinct from erythropoietin. Here, we evaluated the effects of RAP-011 in zebrafish models of RPL11 ribosome deficiency. Treatment with RAP-011 dramatically restored hemoglobin levels caused by ribosome stress. In zebrafish embryos, RAP-011 likely stimulates erythropoietic activity by sequestering lefty1 from erythroid cells. These findings identify lefty1 as a signaling component in the development of erythroid cells and rationalize the use of sotatercept in DBA patients.
    Keywords: Red Cells, Iron, and Erythropoiesis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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  • 5
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    Plasma L5 levels are elevated in ischemic stroke patients and enhance platelet aggregation (2016)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2016-03-11
    Description: L5, the most electronegative and atherogenic subfraction of low-density lipoprotein (LDL), induces platelet activation. We hypothesized that plasma L5 levels are increased in acute ischemic stroke patients and examined whether lectin-like oxidized LDL receptor-1 (LOX-1), the receptor for L5 on endothelial cells and platelets, plays a critical role in stroke. Because amyloid β (Aβ) stimulates platelet aggregation, we studied whether L5 and Aβ function synergistically to induce prothrombotic pathways leading to stroke. Levels of plasma L5, serum Aβ, and platelet LOX-1 expression were significantly higher in acute ischemic stroke patients than in controls without metabolic syndrome ( P 〈 .01). In mice subjected to focal cerebral ischemia, L5 treatment resulted in larger infarction volumes than did phosphate-buffered saline treatment. Deficiency or neutralizing of LOX-1 reduced infarct volume up to threefold after focal cerebral ischemia in mice, illustrating the importance of LOX-1 in stroke injury. In human platelets, L5 but not L1 (the least electronegative LDL subfraction) induced Aβ release via IB kinase 2 (IKK2). Furthermore, L5+Aβ synergistically induced glycoprotein IIb/IIIa receptor activation; phosphorylation of IKK2, IBα, p65, and c-Jun N-terminal kinase 1; and platelet aggregation. These effects were blocked by inhibiting IKK2, LOX-1, or nuclear factor–B (NF-B). Injecting L5+Aβ shortened tail-bleeding time by 50% (n = 12; P 〈 .05 vs L1-injected mice), which was prevented by the IKK2 inhibitor. Our findings suggest that, through LOX-1, atherogenic L5 potentiates Aβ-mediated platelet activation, platelet aggregation, and hemostasis via IKK2/NF-B signaling. L5 elevation may be a risk factor for cerebral atherothrombosis, and downregulating LOX-1 and inhibiting IKK2 may be novel antithrombotic strategies.
    Keywords: Free Research Articles, Platelets and Thrombopoiesis, Thrombosis and Hemostasis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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  • 6
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    A FOXO1-induced oncogenic network defines the AML1-ETO preleukemic program (2017)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2017-09-08
    Description: Understanding and blocking the self-renewal pathway of preleukemia stem cells could prevent acute myeloid leukemia (AML) relapse. In this study, we show that increased FOXO1 represents a critical mechanism driving aberrant self-renewal in preleukemic cells expressing the t(8;21)-associated oncogene AML1-ETO (AE). Although generally considered as a tumor suppressor, FOXO1 is consistently upregulated in t(8;21) AML. Expression of FOXO1 in human CD34 + cells promotes a preleukemic state with enhanced self-renewal and dysregulated differentiation. The DNA binding domain of FOXO1 is essential for these functions. FOXO1 activates a stem cell molecular signature that is also present in AE preleukemia cells and preserved in t(8;21) patient samples. Genome-wide binding studies show that AE and FOXO1 share the majority of their binding sites, whereby FOXO1 binds to multiple crucial self-renewal genes and is required for their activation. In agreement with this observation, genetic and pharmacological ablation of FOXO1 inhibited the long-term proliferation and clonogenicity of AE cells and t(8;21) AML cell lines. Targeting of FOXO1 therefore provides a potential therapeutic strategy for elimination of stem cells at both preleukemic and leukemic stages.
    Keywords: Myeloid Neoplasia
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    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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  • 7
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    The full transforming capacity of MLL-Af4 is interlinked with lymphoid lineage commitment (2017)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2017-08-18
    Description: Chromosome rearrangements involving the mixed-lineage leukemia gene (MLL) create MLL-fusion proteins, which could drive both acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). The lineage decision of MLL-fusion leukemia is influenced by the fusion partner and microenvironment. To investigate the interplay of fusion proteins and microenvironment in lineage choice, we transplanted human hematopoietic stem and progenitor cells (HSPCs) expressing MLL-AF9 or MLL-Af4 into immunodeficient NSGS mice, which strongly promote myeloid development. Cells expressing MLL-AF9 efficiently developed AML in NSGS mice. In contrast, MLL-Af4 cells, which were fully oncogenic under lymphoid conditions present in NSG mice, displayed compromised transformation capacity in a myeloid microenvironment. MLL-Af4 activated a self-renewal program in a lineage-dependent manner, showing the leukemogenic activity of MLL-Af4 was interlinked with lymphoid lineage commitment. The C-terminal homology domain (CHD) of Af4 was sufficient to confer this linkage. Although the MLL-CHD fusion protein failed to immortalize HSPCs in myeloid conditions in vitro, it could successfully induce ALL in NSG mice. Our data suggest that defective self-renewal ability and leukemogenesis of MLL-Af4 myeloid cells could contribute to the strong B-cell ALL association of MLL-AF4 leukemia observed in the clinic.
    Keywords: Myeloid Neoplasia, Lymphoid Neoplasia, Brief Reports
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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  • 8
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    The thrombopoietin/MPL/Bcl-xL pathway is essential for survival and self-renewal in human preleukemia induced by AML1-ETO (2012)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2012-07-27
    Description: AML1-ETO (AE) is a fusion product of translocation (8;21) that accounts for 40% of M2 type acute myeloid leukemia (AML). In addition to its role in promoting preleukemic hematopoietic cell self-renewal, AE represses DNA repair genes, which leads to DNA damage and increased mutation frequency. Although this latter function may promote leukemogenesis, concurrent p53 activation also leads to an increased baseline apoptotic rate. It is unclear how AE expression is able to counterbalance this intrinsic apoptotic conditioning by p53 to promote survival and self-renewal. In this report, we show that Bcl-xL is up-regulated in AE cells and plays an essential role in their survival and self-renewal. Further investigation revealed that Bcl-xL expression is regulated by thrombopoietin (THPO)/MPL-signaling induced by AE expression. THPO/MPL-signaling also controls cell cycle reentry and mediates AE-induced self-renewal. Analysis of primary AML patient samples revealed a correlation between MPL and Bcl-xL expression specifically in t(8;21) blasts. Taken together, we propose that survival signaling through Bcl-xL is a critical and intrinsic component of a broader self-renewal signaling pathway downstream of AML1-ETO–induced MPL.
    Keywords: Plenary Papers, Myeloid Neoplasia
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    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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  • 9
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    Suppression of inhibitor formation against FVIII in a murine model of hemophilia A by oral delivery of antigens bioencapsulated in plant cells (2014)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2014-09-05
    Description: Hemophilia A is the X-linked bleeding disorder caused by deficiency of coagulation factor VIII (FVIII). To address serious complications of inhibitory antibody formation in current replacement therapy, we created tobacco transplastomic lines expressing FVIII antigens, heavy chain (HC) and C2, fused with the transmucosal carrier, cholera toxin B subunit. Cholera toxin B-HC and cholera toxin B-C2 fusion proteins expressed up to 80 or 370 µg/g in fresh leaves, assembled into pentameric forms, and bound to GM1 receptors. Protection of FVIII antigen through bioencapsulation in plant cells and oral delivery to the gut immune system was confirmed by immunostaining. Feeding of HC/C2 mixture substantially suppressed T helper cell responses and inhibitor formation against FVIII in mice of 2 different strain backgrounds with hemophilia A. Prolonged oral delivery was required to control inhibitor formation long-term. Substantial reduction of inhibitor titers in preimmune mice demonstrated that the protocol could also reverse inhibitor formation. Gene expression and flow cytometry analyses showed upregulation of immune suppressive cytokines (transforming growth factor β and interleukin 10). Adoptive transfer experiments confirmed an active suppression mechanism and revealed induction of CD4 + CD25 + and CD4 + CD25 – T cells that potently suppressed anti-FVIII formation. In sum, these data support plant cell-based oral tolerance for suppression of inhibitor formation against FVIII.
    Keywords: Thrombosis and Hemostasis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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  • 10
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    Regulation of EBV LMP1-triggered EphA4 downregulation in EBV-associated B lymphoma and its impact on patients survival (2016)
    American Society of Hematology (ASH)
    In: Blood
    Details
    Publication Date: 2016-09-23
    Description: Epstein-Barr virus (EBV), an oncogenic human virus, is associated with several lymphoproliferative disorders, including Burkitt lymphoma, Hodgkin disease, diffuse large B-cell lymphoma (DLBCL), and posttransplant lymphoproliferative disorder (PTLD). In vitro, EBV transforms primary B cells into lymphoblastoid cell lines (LCLs). Recently, several studies have shown that receptor tyrosine kinases (RTKs) play important roles in EBV-associated neoplasia. However, details of the involvement of RTKs in EBV-regulated B-cell neoplasia and malignancies remain largely unclear. Here, we found that erythropoietin-producing hepatocellular receptor A4 (EphA4), which belongs to the largest RTK Eph family, was downregulated in primary B cells post-EBV infection at the transcriptional and translational levels. Overexpression and knockdown experiments confirmed that EBV-encoded latent membrane protein 1 (LMP1) was responsible for this EphA4 suppression. Mechanistically, LMP1 triggered the extracellular signal-regulated kinase (ERK) pathway and promoted Sp1 to suppress EphA4 promoter activity. Functionally, overexpression of EphA4 prevented LCLs from proliferation. Pathologically, the expression of EphA4 was detected in EBV – tonsils but not in EBV + PTLD. In addition, an inverse correlation of EphA4 expression and EBV presence was verified by immunochemical staining of EBV + and EBV – DLBCL, suggesting EBV infection was associated with reduced EphA4 expression. Analysis of a public data set showed that lower EphA4 expression was correlated with a poor survival rate of DLBCL patients. Our findings provide a novel mechanism by which EphA4 can be regulated by an oncogenic LMP1 protein and explore its possible function in B cells. The results provide new insights into the role of EphA4 in EBV + PTLD and DLBCL.
    Keywords: Lymphoid Neoplasia
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology (ASH)
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