bluuebunny/crossref_metadata_2025_split huggingface dataset:
GATA1 mutations in transient leukemia and acute megakaryoblastic leukemia of Down syndrome
Authors: Hitzler Johann K. , Cheung Joseph , Li Yue , Scherer Stephen W. , Zipursky Alvin 
Published: May 2003

Abstract
Children with constitutional trisomy 21 (Down syndrome) have an approximately 500-fold increased risk of developing acute megakaryoblastic leukemia (AMKL), a form of acute myeloid leukemia. Unique to newborn infants with Down syndrome is a transient leukemia (TL), also referred to as transient myeloproliferative syndrome, that undergoes spontaneous remission in the majority of cases but in approximately 20% is followed by AMKL later in life. Recently mutations of the gene encoding the hematopoietic transcription factor GATA1 were shown to be specific for AMKL of Down syndrome. Here, we demonstrate that GATA1 mutations are present in blasts of TL and show the identical GATA1 mutation in sequential samples collected from a patient during TL and subsequent AMKL. These findings suggest a model of malignant transformation in Down syndrome AMKL in which GATA1 mutations are an early event and AMKL arises from latent TL clones following initial apparent remission.
Cappuccino, a mouse model of Hermansky-Pudlak syndrome, encodes a novel protein that is part of the pallidin-muted complex (BLOC-1)
Authors: Ciciotte Steven L. , Gwynn Babette , Moriyama Kengo , Huizing Marjan , Gahl William A. , Bonifacino Juan S. , Peters Luanne L. 
Published: May 2003

Abstract
Hermansky-Pudlak syndrome (HPS) is a disorder of organelle biogenesis affecting 3 related organelles—melanosomes, platelet dense bodies, and lysosomes. Four genes causing HPS in humans (HPS1-HPS4) are known, and at least 15 nonallelic mutations cause HPS in the mouse. Where their functions are known, the HPS-associated proteins are involved in some aspect of intracellular vesicular trafficking, that is, protein sorting and vesicle docking and fusion. Biochemical and genetic evidence indicates that the HPS-associated genes encode components of at least 3 distinct protein complexes: the adaptor complex AP-3; the HPS1/HPS4 complex; and BLOC-1 (biogenesis of lysosome-related organelles complex-1), consisting of the proteins encoded at 2 mouse HPS loci, pallid (pa) and muted (mu), and at least 3 other unidentified proteins. Here, we report the cloning of the mouse HPS mutation cappuccino (cno). We show that the wild-type cno gene encodes a novel, ubiquitously expressed cytoplasmic protein that coassembles with pallidin and the muted protein in the BLOC-1 complex. Further, we identify a frameshift mutation in mutant cno/cno mice. The C-terminal 81 amino acids are replaced with 72 different amino acids in the mutant CNO protein, and its ability to interact in BLOC-1 is abolished. We performed mutation screening of patients with HPS and failed to identify any CNO defects. Notably, although defects in components of the HPS1/HPS4 and the AP-3 complexes are associated with HPS in humans, no defects in the known components of BLOC-1 have been identified in 142 patients with HPS screened to date, suggesting that BLOC-1 function may be critical in humans.
Regulation of plasminogen activation: a role for melanotransferrin (p97) in cell migration
Authors: Demeule Michel , Bertrand Yanick , Michaud-Levesque Jonathan , Jodoin Julie , Rolland Yannève , Gabathuler Reinhard , Béliveau Richard 
Published: May 2003

AbstractWe recently reported that human recombinant melanotransferrin (p97) presents a high transport rate across the blood-brain barrier that might involve the low-density lipoprotein receptor–related protein (LRP). We now report new interactions between p97 and another LRP ligand, the urokinase plasminogen activator (uPA) complex. By using biospecific interaction analysis, both pro-uPA and plasminogen are shown to interact with immobilized p97. Moreover, the activation of plasminogen by pro-uPA is increased by soluble p97. Because the uPA system plays a crucial role in cell migration, both in cancer and in angiogenesis, we also measured the impact of both endogenous membrane-bound and exogenous p97 on cell migration. The monoclonal antibody L235 (which recognizes a conformational epitope on p97) inhibited the migration of human microvascular endothelial cells (HMECs-1) and of human melanoma SK-MEL-28 cells, indicating that endogenous membrane-bound p97 could be associated with this process. In addition, low concentrations of exogenous p97 (10 and 100 nM) inhibited HMEC-1 and SK-MEL28 cell migration by more than 50%. These results indicate that membrane-bound and soluble p97 affect the migration capacity of endothelial and melanoma cells and suggest that p97 could be involved in the regulation of plasminogen activation by interacting with pro-uPA and plasminogen.
Myeloid cell expansion elicited by the progression of spontaneous mammary carcinomas in c-erbB-2 transgenic BALB/c mice suppresses immune reactivity
Authors: Melani Cecilia , Chiodoni Claudia , Forni Guido , Colombo Mario P. 
Published: May 2003

AbstractTransgenic female mice expressing the transforming rat oncogene c-erbB-2 (HER-2/neu) under the mouse mammary tumor virus (MMTV) promoter (BALB-neuT) spontaneously develop mammary carcinomas with a progression resembling that of human breast cancer. In these mice, activating antitumor immunotherapy fails to induce T cell–mediated cytotoxicity, suggesting a suppression of the immune response. We found a direct correlation between tumor multiplicity and an increased proportion of Gr-1+ (Ly6G)/Mac-1+(CD11b)/ER-MP12+(CD31) immature myeloid cells in the peripheral blood (PB) and spleen, suggesting that tumor load profoundly affects overall BALB-neuT hematopoiesis. In fact, myeloid colony formation was increased in bone marrow (BM) and spleen. The immature myeloid cells displayed suppressive activity on host T lymphocytes, which progressively failed to respond to alloantigens and CD3 triggering, while maintaining the ability to proliferate in response to nonspecific mitogens. Transplantation of normal BM into BALB-neuT mice readily resulted in hypertrophic hematopoiesis with myeloid cell expansion. This persistent influence of the tumor was mediated through the release of vascular endothelial growth factor (VEGF) but not granulocyte-macrophage colony-stimulating factor (GM-CSF), and was down-modulated when tumor load was reduced but not when BM was transplanted. Together, the data obtained in the BALB-neuT model of naturally occurring carcinogenesis show that tumor-associated immune suppression is secondary to a more general alteration of host hematopoiesis, conditioned by tumor-secreted soluble factors.
IL-15 drives neonatal T cells to acquire CD56 and become activated effector cells
Authors: Cookson Sharon , Reen Denis 
Published: May 2003

AbstractExpression of one or more natural killer (NK) receptors on T cells may correlate with effector function. This study investigated the frequency of neonatal NK receptor–positive (NKR+) T cells and their expansionary properties with interleukin-2 (IL-2), IL-7, or IL-15. While cord blood contains significantly decreased frequencies of NKR+ T cells compared with adult blood, newborn CD56+CD3+ cells could be expanded 200-fold during culture with IL-15. By depleting CD56+ cells, we were able to determine that this expansion was due to a subpopulation of T cells acquiring CD56 expression. Moreover, CD56 acquisition was associated with a distinct CD8+CD25+ interferon γ–positive (IFN-γ+) phenotype. This property could therefore be exploited during bone marrow reconstitution and may partially account for the resilience of the newborn to infection.
Transgenic mice overexpressing erythropoietin adapt to excessive erythrocytosis by regulating blood viscosity
Authors: Vogel Johannes , Kiessling Isabel , Heinicke Katja , Stallmach Thomas , Ossent Pete , Vogel Olga , Aulmann Michael , Frietsch Thomas , Schmid-Schönbein Holger , Kuschinsky Wolfgang , Gassmann Max 
Published: May 2003

AbstractSevere elevation of red blood cell number is often associated with hypertension and thromboembolism resulting in severe cardiovascular complications. However, some individuals such as high altitude dwellers cope well with an increased hematocrit level. We analyzed adaptive mechanisms to excessive erythrocytosis in our transgenic (tg) mice that, due to hypoxia-independent erythropoietin (Epo) overexpression, reached hematocrit values of 0.8 to 0.9 without alteration of blood pressure, heart rate, or cardiac output. Extramedullar erythropoiesis occurred in the tg spleen, leading to splenomegaly. Upon splenectomy, hematocrit values in tg mice decreased from 0.89 to 0.62. Tg mice showed doubled reticulocyte counts and an increased mean corpuscular volume. In tg mice, plasma volume was not elevated whereas blood volume was up to 25% of the body weight compared with 8% in wild-type (wt) siblings. Although plasma viscosity did not differ between tg and wt mice, tg whole-blood viscosity increased to a lower degree (4-fold) than expected from corresponding hemoconcentrated wt blood (8-fold). This moderate increase in viscosity is explicable by the up to 3-fold higher elongation of tg erythrocytes at physiologic shear rates. Apart from the nitric oxide–mediated vasodilation we reported earlier, adaptation to high hematocrit levels in tg mice involves regulated elevation of blood viscosity by increasing erythrocyte flexibility.
Heme and lipid peroxides in hemoglobin-modified low-density lipoprotein mediate cell survival and adaptation to oxidative stress
Authors: Asatryan Liana , Ziouzenkova Ouliana , Duncan Roger , Sevanian Alex 
Published: May 2003

AbstractLow-density lipoprotein (LDL) oxidation mediated by a variety of catalysts in atherosclerotic lesions plays a crucial role in the genesis and evolution of atherosclerotic plaques. In this study we focused on oxidative properties of hemoglobin (Hb)–modified LDL because Hb is present in atherosclerotic lesions. Under low oxygen tensions Hb was previously found to modify apolipoprotein B100 with covalent binding of Hb fragments and formation of electronegative LDL particles (LDL–). Here we show that HbLDL is highly susceptible to oxidation, but is not cytotoxic to vascular cells, as was found for LDL– isolated from human plasma. HbLDL and LDL– have similar levels of oxidized lipid products and low uptake rates; however, the virtual absence of HbLDL-induced toxicity depends on a marked adaptive oxidative stress response. This was evidenced by a time- and dose-dependent induction of heme oxygenase (HO-1). Cell survival was significantly decreased in the presence of HO-1 inhibitor, tin protoporphyrin (SnPPIX). HO-1 induction by HbLDL increased resistance of cells to toxic doses of hemin or t-BuOOH. The high sensitivity to oxidation and HO-1 induction was largely dependent on lipid hydroperoxides and heme associated with HbLDL. Reduction of pre-existing lipid peroxides using ebselen delayed HbLDL kinetics and inhibited HO-1 induction. Moreover, heme inactivation or its degradation inhibited HO-1 induction and provided an additive inhibitory effect to ebselen. We conclude that Hb-catalyzed reactions may modulate vascular cell survival and oxidative stress adaptation due to the presence of peroxides and heme, thus providing a possible mechanism for the evolution of atherosclerotic and hemorrhagic lesions.
Mechanisms for T-cell selective cytotoxicity of arabinosylguanine
Authors: Rodriguez Carlos O. , Stellrecht Christine M. , Gandhi Varsha 
Published: May 2003

AbstractNelarabine, prodrug of arabinosylguanine (ara-G), has demonstrated T-lymphoblastic antileukemic activity in cell lines and in the clinic. To investigate the mechanism for lineage-specific toxicity, the effects of ara-G were compared in CEM (T-lymphoblast), Raji (B-lymphoblast), and ML-1 (myeloid) cell lines. CEM cells were the most sensitive to ara-G–induced apoptosis and accumulated the highest levels of ara-G triphosphate (ara-GTP). However, compared with myeloid and B-lineage cell lines, CEM cells incorporated fewer ara-G molecules—which were at internucleotide positions in all 3 cell lines— into DNA. Ara-G induced an S-phase arrest in both Raji and ML-1, while in CEM the S-phase cells decreased with a concomitant increase in the sub-G1 population. Within 3 hours of ara-G treatment, the levels of soluble Fas ligand (sFasL) in the medium increased significantly in CEM cultures. In parallel, an induction of FasL gene expression was observed by real-time reverse transcriptase–polymerase chain reaction (RT-PCR). Pretreatment of CEM cells with a Fas antagonistic antibody inhibited ara-G–mediated cell death. These results demonstrate that high ara-GTP accumulation in T cells results in an S phase–dependent apoptosis induced by ara-G incorporation into DNA, which may lead to a T cell–specific signal for the induction and liberation of sFasL. Subsequently, the sFasL induces an apoptotic response in neighboring non–S-phase cells. In contrast, myeloid and B cells accumulated lower levels of ara-GTP and arrested in S phase, blocking any apoptotic signaling.
BAALC expression predicts clinical outcome of de novo acute myeloid leukemia patients with normal cytogenetics: a Cancer and Leukemia Group B Study
Authors: Baldus Claudia D. , Tanner Stephan M. , Ruppert Amy S. , Whitman Susan P. , Archer Kellie J. , Marcucci Guido , Caligiuri Michael A. , Carroll Andrew J. , Vardiman James W. , Powell Bayard L. , Allen Steven L. , Moore Joseph O. , Larson Richard A. , Kolitz Jonathan E. , de la Chapelle Albert , Bloomfield Clara D. 
Published: May 2003

AbstractCytogenetic aberrations are important prognostic factors in acute myeloid leukemia (AML). Of adults with de novo AML, 45% lack cytogenetic abnormalities, and identification of predictive molecular markers might improve therapy. We studied the prognostic impact of BAALC (Brain And Acute Leukemia, Cytoplasmic), a novel gene involved in leukemia, in 86 de novo AML patients with normal cytogenetics who were uniformly treated on Cancer and Leukemia Group B 9621. BAALC expression was determined by comparative real-time reverse transcriptase–polymerase chain reaction in pretreatment blood samples, and patients were dichotomized at BAALC's median expression into low and high expressers. Low expressers had higher white counts (P = .03) and more frequent French-American-British M5 morphology (P = .007). Compared to low expressers, high BAALC expressers showed significantly inferior overall survival (OS; median, 1.7 vs 5.8 years, P = .02), event-free survival (EFS; median, 0.8 vs 4.9 years, P = .03), and disease-free survival (DFS; median, 1.4 vs 7.3 years, P = .03). Multivariable analysis confirmed high BAALC expression as an independent risk factor. For high BAALC expressers the hazard ratio of an event for OS, EFS, and DFS was respectively 2.7, 2.6, and 2.2. We conclude that high BAALC expression predicts an adverse prognosis and may define an important risk factor in AML with normal cytogenetics.
Recombinant human activated protein C (rhAPC; drotrecogin alfa [activated]) has minimal effect on markers of coagulation, fibrinolysis, and inflammation in acute human endotoxemia
Authors: Derhaschnig Ulla , Reiter Rosemarie , Knöbl Paul , Baumgartner Magdalena , Keen Priska , Jilma Bernd 
Published: May 2003

Abstract
Inflammatory and procoagulant host responses are closely related in sepsis. The protein C pathway serves as a regulatory pathway with anti-inflammatory and anticoagulant properties. Recently, recombinant human activated protein C (rhAPC) was shown to reduce mortality in severe sepsis. Nevertheless, the effects of rhAPC in humans are still ill defined. The infusion of low endotoxin doses into humans provides a standardized model to study inflammatory and hemostatic mechanisms. Thus, we investigated whether rhAPC acts as an anticoagulant or anti-inflammatory drug in human endotoxemia. There were 24 volunteers randomized to receive either 24 μg/kg per hour rhAPC or placebo intravenously for 8 hours. Lipopolysaccharide (LPS, 2 ng/kg) was administered 2 hours after starting the infusions. rhAPC decreased basal tissue factor (TF)–mRNA expression, and thrombin formation and action. In contrast, rhAPC did not significantly blunt LPS-induced thrombin generation. Consistently, rhAPC did not reduce LPS-induced levels of TF-mRNA or D-dimer and had no effect on fibrinolytic activity or inflammation. Finally, endogenous APC formation was enhanced during endotoxemia and appeared to be associated with inflammation rather than thrombin formation. In conclusion, even low-grade endotoxemia induces significant protein C activation. Infusion of rhAPC decreases “spontaneous” activation of coagulation but does not blunt LPS-induced, TF-mediated coagulation in healthy volunteers, which is in contrast to a number of anticoagulants.
Ex vivo characterization of human CD8+ T subsets with distinct replicative history and partial effector functions
Authors: Rufer Nathalie , Zippelius Alfred , Batard Pascal , Pittet Mikaël J. , Kurth Isabel , Corthesy Patricia , Cerottini Jean-Charles , Leyvraz Serge , Roosnek Eddy , Nabholz Markus , Romero Pedro 
Published: May 2003

Abstract
After antigenic challenge, naive T lymphocytes enter a program of proliferation and differentiation during the course of which they acquire effector functions and may ultimately become memory cells. In humans, the pathways of effector and memory T-cell differentiation remain poorly defined. Here we describe the properties of 2 CD8+ T-lymphocyte subsets, RA+CCR7–27+28+ and RA+CCR7–27+28–, in human peripheral blood. These cells display phenotypic and functional features that are intermediate between naive and effector T cells. Like naive T lymphocytes, both subsets show relatively long telomeres. However, unlike the naive population, these T cells exhibit reduced levels of T-cell receptor excision circles (TRECs), indicating they have undergone additional rounds of in vivo cell division. Furthermore, we show that they also share effector-type properties. At equivalent in vivo replicative history, the 2 subsets express high levels of Fas/CD95 and CD11a, as well as increasing levels of effector mediators such as granzyme B, perforin, interferon γ, and tumor necrosis factor α. Both display partial ex vivo cytolytic activity and can be found among cytomegalovirus-specific cytolytic T cells. Taken together, our data point to the presence of T cells with intermediate effector-like functions and suggest that these subsets consist of T lymphocytes that are evolving toward a more differentiated effector or effector-memory stage.
Iron, manganese, and cobalt transport by Nramp1 (Slc11a1) and Nramp2 (Slc11a2) expressed at the plasma membrane
Authors: Forbes John R. , Gros Philippe 
Published: May 2003

AbstractMutations in the Nramp1 gene (Slc11a1) cause susceptibility to infection by intracellular pathogens. The Nramp1 protein is expressed at the phagosomal membrane of macrophages and neutrophils and is a paralog of the Nramp2 (Slc11a2) iron transporter. The Nramp1 transport mechanism at the phagosomal membrane has remained controversial. An Nramp1 protein modified by insertion of a hemagglutinin epitope into the predicted TM7/8 loop was expressed at the plasma membrane of Chinese hamster ovary cells as demonstrated by immunofluorescence and surface biotinylation. Experiments in Nramp1HA transfectants using the metal-sensitive fluorophors calcein and Fura2 showed that Nramp1HA can mediate Fe2+, Mn2+, and Co2+ uptake. Similar results were obtained in transport studies using radioisotopic 55Fe2+ and 54Mn2+. Nramp1HA transport was dependent on time, temperature, and acidic pH, occurring down the proton gradient. These experiments suggest that Nramp1HA may be a more efficient transporter of Mn2+ compared to Fe2+ and a more efficient Mn2+ transporter than Nramp2HA. The membrane topology and transport properties of Nramp1HA and Nramp2HA were indistinguishable, suggesting that Nramp1 divalent-metal transport at the phagosomal membrane is mechanistically similar to that of Nramp2 at the membrane of acidified endosomes. These results clarify the mechanism by which Nramp1 contributes to phagocyte defenses against infections.
The HIF family member EPAS1/HIF-2α is required for normal hematopoiesis in mice
Authors: Scortegagna Marzia , Morris Margaret A. , Oktay Yavuz , Bennett Michael , Garcia Joseph A. 
Published: May 2003

AbstractHypoxic stress plays a role in pathophysiologic states such as myocardial infarction and cerebral vascular events as well as in normal physiologic conditions including development and hematopoiesis. Members of the hypoxia inducible factor (HIF) family function as transcriptional regulators of genes involved in the hypoxic response. After generating adult mice that globally lack endothelial PAS domain protein 1 (EPAS1, also known as HIF-2α/HRF/HLF/MOP3), the second member of the HIF family, characterization of the hematopoietic cell population indicated that the loss of EPAS1/HIF-2α resulted in pancytopenia. Using bone marrow reconstitution experiments of lethally irradiated hosts, we have defined the extent and site of hematopoietic impairment in the EPAS1/HIF-2α null mice. These data suggest a critical role for EPAS1/HIF-2α in maintaining a functional microenvironment in the bone marrow for effective hematopoiesis.
Mechanisms of donor-specific transfusion tolerance: preemptive induction of clonal T-cell exhaustion via indirect presentation
Authors: Quezada Sergio A. , Fuller Bruce , Jarvinen Lamis Z. , Gonzalez Mercedes , Blazar Bruce R. , Rudensky Alexander Y. , Strom Terry B. , Noelle Randolph J. 
Published: May 2003

AbstractInduction of transplantation tolerance to alloantigens without general immunosuppression remains an enduring challenge. Injecting a donor-specific transfusion (DST) of spleen cells together with blocking αCD154 antibody prior to graft transplantation is an effective way to induce long-lived graft acceptance. Using a novel T-cell receptor (TCR) transgenic (Tg) model of CD4+ T-cell–mediated rejection, this study sheds new insights into the cellular basis for enhanced graft survival induced by DST and αCD154. The study shows that DST and αCD154 induce an early, robust, abortive expansion of the Tg T cells that results in profound anergy. This is contrasted with the more delayed, regional, productive response elicited by an allogeneic graft. Studies show that the induction of tolerance to the allograft induced by DST is mediated by indirect presentation by host antigen-presenting cells. Based on these observations, we conclude that DST and αCD154 preemptively tolerize the alloreactive T-cell compartment to prohibit subsequent responses to the immunogenic allograft.