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  • 1
    Publication Date: 2018-10-05
    Description: Adult T-cell leukemia lymphoma (ATLL) is a rare T cell neoplasm that is endemic in Japanese, Caribbean, and Latin American populations. Most North American ATLL patients are of Caribbean descent and are characterized by high rates of chemo-refractory disease and worse prognosis compared with Japanese ATLL. To determine genomic differences between these 2 cohorts, we performed targeted exon sequencing on 30 North American ATLL patients and compared the results with the Japanese ATLL cases. Although the frequency of TP53 mutations was comparable, the mutation frequency in epigenetic and histone modifying genes (57%) was significantly higher, whereas the mutation frequency in JAK/STAT and T-cell receptor/NF-B pathway genes was significantly lower. The most common type of epigenetic mutation is that affecting EP300 (20%). As a category, epigenetic mutations were associated with adverse prognosis. Dissimilarities with the Japanese cases were also revealed by RNA sequencing analysis of 9 primary patient samples. ATLL samples with a mutated EP300 gene have decreased total and acetyl p53 protein and a transcriptional signature reminiscent of p53-mutated cancers. Most importantly, decitabine has highly selective single-agent activity in the EP300-mutated ATLL samples, suggesting that decitabine treatment induces a synthetic lethal phenotype in EP300-mutated ATLL cells. In conclusion, we demonstrate that North American ATLL has a distinct genomic landscape that is characterized by frequent epigenetic mutations that are targetable preclinically with DNA methyltransferase inhibitors.
    Keywords: Lymphoid Neoplasia
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 2
    Publication Date: 2018-11-30
    Description: Myelodysplastic syndromes (MDSs) are clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis. Anemia is the defining cytopenia of MDS patients, yet the molecular mechanisms for dyserythropoiesis in MDSs remain to be fully defined. Recent studies have revealed that heterozygous loss-of-function mutation of DNA dioxygenase TET2 is 1 of the most common mutations in MDSs and that TET2 deficiency disturbs erythroid differentiation. However, mechanistic insights into the role of TET2 on disordered erythropoiesis are not fully defined. Here, we show that TET2 deficiency leads initially to stem cell factor (SCF)–dependent hyperproliferation and impaired differentiation of human colony-forming unit–erythroid (CFU-E) cells, which were reversed by a c-Kit inhibitor. We further show that this was due to increased phosphorylation of c-Kit accompanied by decreased expression of phosphatase SHP-1, a negative regulator of c-Kit. At later stages, TET2 deficiency led to an accumulation of a progenitor population, which expressed surface markers characteristic of normal CFU-E cells but were functionally different. In contrast to normal CFU-E cells that require only erythropoietin (EPO) for proliferation, these abnormal progenitors required SCF and EPO and exhibited impaired differentiation. We termed this population of progenitors "marker CFU-E" cells. We further show that AXL expression was increased in marker CFU-E cells and that the increased AXL expression led to increased activation of AKT and ERK. Moreover, the altered proliferation and differentiation of marker CFU-E cells were partially rescued by an AXL inhibitor. Our findings document an important role for TET2 in erythropoiesis and have uncovered previously unknown mechanisms by which deficiency of TET2 contributes to ineffective erythropoiesis.
    Keywords: Red Cells, Iron, and Erythropoiesis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 3
    Publication Date: 2018-04-20
    Keywords: Myeloid Neoplasia
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 4
    Publication Date: 2018-03-16
    Description: Activated protein C (APC) cleaves protease-activated receptor 1 (PAR1) in vitro at R46 to initiate beneficial cell signaling; however, thrombin and APC can cleave at R41. To elucidate PAR1-dependent aspects of the pharmacologic in vivo mechanisms of APC, we generated C57BL/6 mouse strains carrying QQ41 or QQ46 point mutations in PAR1 ( F2r gene). Using these strains, we determined whether or not recombinant murine signaling-selective APC mutants would reduce septic death or provide neuroprotection against ischemic stroke when mice carried PAR1-homozygous mutations that prevent cleavage at either R41 or R46. Intercrossing PAR1 + /R46Q mice generated expected numbers of PAR1 +/+ , PAR1 + /R46Q, and R46Q/R46Q offspring whereas intercrossing PAR1 + /R41Q mice gave decreased R41Q/R41Q homozygotes (resembling intercrossing PAR1 + /PAR1-knockout mice). QQ41-PAR1 and QQ46-PAR1 brain endothelial cells showed the predicted retention or loss of cellular responses to thrombin receptor-activating peptide, thrombin, or APC for each PAR1 mutation. In sepsis studies, exogenous APC reduced mortality from 50% to 10% in Escherichia coli –induced pneumonia for wild-type (Wt) PAR1 and QQ41-PAR1 mice ( P 〈 .01) but had no benefit for QQ46-PAR1 mice. In transient distal middle cerebral artery occlusion stroke studies, exogenous APC significantly reduced infarct size, edema, and neuronal apoptosis for Wt mice and QQ41-PAR1 mice but had no detectable benefits for mice carrying QQ46-PAR1. In functional studies of forelimb-asymmetry and foot-fault tests at 24 hours after stroke induction, signaling-selective APC was beneficial for Wt and QQ41-PAR1 mice but not QQ46-PAR1 mice. These results support the concept that APC-induced, PAR1-dependent biased signaling following R46 cleavage is central to the in vivo benefits of APC.
    Keywords: Plenary Papers, Thrombosis and Hemostasis, Vascular Biology
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 5
    Publication Date: 2018-03-16
    Description: The pathogenesis of corticosteroid-resistant immune thrombocytopenia (ITP), a clinically challenging condition in which patients exhibit either no response to corticosteroids or are corticosteroid-dependent, remains poorly understood. Murine studies suggest that bone marrow (BM) endothelial progenitor cells (EPCs) play a crucial role in regulating megakaryocytopoiesis. However, little is known regarding the number and function of BM EPCs or how to improve impaired BM EPCs in corticosteroid-resistant ITP patients. In the current case-control study, we evaluated whether the BM EPCs in corticosteroid-resistant ITP differed from those in corticosteroid-sensitive ITP. Moreover, whether atorvastatin could enhance the number and function of BM EPCs derived from corticosteroid-resistant ITP patients was investigated in vitro and in vivo. Reduced and dysfunctional BM EPCs, characterized by decreased capacities of migration and angiogenesis as well as higher levels of reactive oxygen species and apoptosis, were observed in corticosteroid-resistant ITP patients. In vitro treatment with atorvastatin quantitatively and functionally improved BM EPCs derived from corticosteroid-resistant ITP patients by downregulating the p38 MAPK pathway and upregulating the Akt pathway, and rescued the impaired BM EPCs to support megakaryocytopoiesis. Subsequently, a pilot cohort study showed that atorvastatin was safe and effective in corticosteroid-resistant ITP patients. Taken together, these results indicate that reduced and dysfunctional BM EPCs play a role in the pathogenesis of corticosteroid-resistant ITP, and the impaired BM EPCs could be improved by atorvastatin both in vitro and in vivo. Although requiring further validation, our data indicate that atorvastatin represents a promising therapeutic approach for repairing impaired BM EPCs in corticosteroid-resistant ITP patients.
    Keywords: Thrombocytopenia, Platelets and Thrombopoiesis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 6
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    American Society of Hematology (ASH)
    In: Blood
    Publication Date: 2018-05-04
    Keywords: Free Research Articles, BloodWork, Lymphoid Neoplasia
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 7
    Publication Date: 2018-07-06
    Description: Autologous stem cell transplantation (ASCT) is standard of care for patients with Hodgkin lymphoma (HL) who have relapsed/refractory disease after frontline chemotherapy. Achievement of complete remission (CR) with pre-ASCT salvage chemotherapy predicts favorable outcomes post-ASCT. This phase 1/2 study evaluated the combination of brentuximab vedotin (BV) plus bendamustine as a first salvage regimen in relapsed/refractory HL. A total of 55 patients (28 primary refractory and 27 relapsed) were enrolled. Patients received BV (1.8 mg/kg) on day 1 and bendamustine (90 mg/m 2 ) on days 1 and 2 of a 21-day cycle for up to 6 cycles. Patients could undergo ASCT any time after cycle 2. Following ASCT or completion of combination therapy if not proceeding to ASCT, patients could receive BV monotherapy for up to 16 cycles of total therapy. After a median of 2 cycles of combination therapy (range, 1-6), the objective response rate among 53 efficacy-evaluable patients was 92.5%, with 39 patients (73.6%) achieving CR. Forty patients underwent ASCT. Thirty-one patients (25 of whom underwent ASCT) received BV monotherapy (median, 10 cycles; range, 1-14). After a median of 20.9 months of follow-up, the estimated 2-year progression-free survival was 69.8% and 62.6% for patients who received ASCT and all patients, respectively. Thirty-one patients (56.4%) experienced infusion-related reactions (IRRs), with a majority occurring during cycle 2 of combination therapy. A protocol amendment requiring premedication reduced IRR severity. BV plus bendamustine as first salvage therapy in relapsed/refractory HL is highly active with a manageable toxicity profile. This trial was registered at www.clinicaltrials.gov as #NCT01874054.
    Keywords: Lymphoid Neoplasia, Clinical Trials and Observations
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 8
    Publication Date: 2018-06-01
    Description: Dissecting the pathogenesis of classical Hodgkin lymphoma (cHL), a common cancer in young adults, remains challenging because of the rarity of tumor cells in involved tissues (usually 〈5%). Here, we analyzed the coding genome of cHL by microdissecting tumor and normal cells from 34 patient biopsies for a total of ~50 000 singly isolated lymphoma cells. We uncovered several recurrently mutated genes, namely, STAT6 (32% of cases), GNA13 (24%), XPO1 (18%), and ITPKB (16%), and document the functional role of mutant STAT6 in sustaining tumor cell viability. Mutations of STAT6 genetically and functionally cooperated with disruption of SOCS1 , a JAK-STAT pathway inhibitor, to promote cHL growth. Overall, 87% of cases showed dysregulation of the JAK-STAT pathway by genetic alterations in multiple genes (also including STAT3 , STAT5B , JAK1 , JAK2 , and PTPN1 ), attesting to the pivotal role of this pathway in cHL pathogenesis and highlighting its potential as a new therapeutic target in this disease.
    Keywords: Lymphoid Neoplasia
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 9
    Publication Date: 2018-04-27
    Description: Current antithrombotic drugs, including widely used antiplatelet agents and anticoagulants, are associated with significant bleeding risk. Emerging experimental evidence suggests that the molecular and cellular mechanisms of hemostasis and thrombosis can be separated, thereby increasing the possibility of new antithrombotic therapeutic targets with reduced bleeding risk. We review new coagulation and platelet targets and highlight the interaction between integrin α M β 2 (Mac-1, CD11b/CD18) on leukocytes and GPIbα on platelets that seems to distinguish thrombosis from hemostasis.
    Keywords: Thrombosis and Hemostasis, Vascular Biology, Blood Spotlight
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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