Showing papers on "Myeloid published in 2002"
TL;DR: Although the heterogeneous development of imatinib resistance is challenging, the fact that BCR-ABL is active in many resistant patients suggests that the chimeric oncoprotein remains a good therapeutic target.
Abstract: Selective inhibition of the BCR-ABL tyrosine kinase by imatinib (STI571, Glivec/Gleevec) is a promising new therapeutic strategy in patients with chronic myelogenous leukemia (CML). Despite significant hematologic and cytogenetic responses, resistance occurs, particularly in patients with advanced disease. We sought to determine the underlying mechanisms. Sixty-six patients with CML in myeloid blast crisis (n = 33), lymphoid blast crisis (n = 2), accelerated phase (n = 16), chronic phase (n = 13), and BCR-ABL-positive acute lymphoblastic leukemia (n = 2) resistant to imatinib were investigated. Median duration of imatinib therapy was 148 days (range 6-882). Patients were evaluated for genomic amplification of BCR-ABL, overexpression of BCR-ABL transcripts, clonal karyotypic evolution, and mutations of the imatinib binding site in the BCR-ABL tyrosine kinase domain. Results were as follows: (1) Median levels of BCR-ABL transcripts, were not significantly changed at the time of resistance but 7/55 patients showed a >10-fold increase in BCR-ABL levels; (2) genomic amplification of BCR-ABL was found in 2/32 patients evaluated by fluorescence in situ hybridization; (3) additional chromosomal aberrations were observed in 19/36 patients; (4) point mutations of the ABL tyrosine kinase domain resulting in reactivation of the BCR-ABL tyrosine kinase were detected in 23/66 patients. In conclusion, although the heterogeneous development of imatinib resistance is challenging, the fact that BCR-ABL is active in many resistant patients suggests that the chimeric oncoprotein remains a good therapeutic target. However, patients with clonal evolution are more likely to have BCR-ABL-independent mechanisms of resistance. The observations warrant trials combining imatinib with other agents.
925 citations
TL;DR: It is shown that the MSC lines potently block in vitro proliferation of T cells stimulated with either mitogen or antigenic peptide, with as few as 3% of MSC cells causing complete suppression.
Abstract: CD11b(+)Gr-1(+) myeloid suppressor cells (MSC) accumulate in lymphoid organs under conditions of intense immune stress where they inhibit T and B cell function. We recently described the generation of immortalized MSC lines that provide a homogeneous source of suppressor cells for dissecting the mechanism of suppression. In this study we show that the MSC lines potently block in vitro proliferation of T cells stimulated with either mitogen or antigenic peptide, with as few as 3% of MSC cells causing complete suppression. Inhibition of mitogenic and peptide-specific responses is not associated with a loss in IL-2 production or inability to up-modulate the early activation markers, CD69 and CD25, but results in direct impairment of the three IL-2R signaling pathways, as demonstrated by the lack of Janus kinase 3, STAT5, extracellular signal-regulated kinase, and Akt phosphorylation in response to IL-2. Suppression is mediated by and requires NO, which is secreted by MSC in response to signals from activated T cells, including IFN-gamma and a contact-dependent stimulus. Experiments with inducible NO synthase knockout mice demonstrated that the inhibition of T cell proliferation by CD11b(+)Gr-1(+) cells in the spleens of immunosuppressed mice is also dependent upon NO, indicating that the MSC lines accurately represent their normal counterparts. The distinctive capacity of MSC to generate suppressive signals when encountering activated T cells defines a specialized subset of myeloid cells that most likely serve a regulatory function during times of heightened immune activity.
633 citations
TL;DR: The results establish a paradigm for the treatment of a genetic disorder by combining therapeutic cloning with gene therapy by restoring normal Rag2 gene structure through homologous recombination.
605 citations
TL;DR: It is suggested that RBP-J, probably by mediating Notch signaling, controls T versus B cell fate decision in lymphoid progenitors.
Abstract: The transcription factor recombination signal binding protein-J (RBP-J) functions immediately downstream of the cell surface receptor Notch and mediates transcriptional activation by the intracellular domain of all four kinds of Notch receptors. To investigate the function of RBP-J, we introduced loxP sites on both sides of the RBP-J exons encoding its DNA binding domain. Mice bearing the loxP-flanked RBP-J alleles, RBP-J(f/f), were mated with Mx-Cre transgenic mice and deletional mutation of the RBP-J gene in adult mice was induced by injection of the IFN-alpha inducer poly(I)-poly(C). Here we show that inactivation of RBP-J in bone marrow resulted in a block of T cell development at the earliest stage and increase of B cell development in the thymus. Lymphoid progenitors deficient in RBP-J differentiate into B but not T cells when cultured in 2'-deoxyguanosine-treated fetal thymic lobes by hanging-drop fetal thymus organ culture. Competitive repopulation assay also revealed cell autonomous deficiency of T cell development from bone marrow of RBP-J knockout mouse. Myeloid and B lineage differentiation appears normal in the bone marrow of RBP-J-inactivated mice. These results suggest that RBP-J, probably by mediating Notch signaling, controls T versus B cell fate decision in lymphoid progenitors.
589 citations
TL;DR: Using parallel reverse transcriptase–PCR and real-time PCR screening, it is found that the common leukemia fusion genes, TEL-AML1 or AML1-ETO, are present in cord bloods at a frequency that is 100-fold greater than the risk of the corresponding leukemia.
Abstract: Studies on monozygotic twins with concordant leukemia and retrospective scrutiny of neonatal blood spots of patients with leukemia indicate that chromosomal translocations characteristic of pediatric leukemia often arise prenatally, probably as initiating events. The modest concordance rate for leukemia in identical twins (≈5%), protracted latency, and transgenic modeling all suggest that additional postnatal exposure and/or genetic events are required for clinically overt leukemia development. This notion leads to the prediction that chromosome translocations, functional fusion genes, and preleukemic clones should be present in the blood of healthy newborns at a rate that is significantly greater than the cumulative risk of the corresponding leukemia. Using parallel reverse transcriptase–PCR and real-time PCR (Taqman) screening, we find that the common leukemia fusion genes, TEL-AML1 or AML1-ETO, are present in cord bloods at a frequency that is 100-fold greater than the risk of the corresponding leukemia. Single-cell analysis by cell enrichment and immunophenotype/fluorescence in situ hybridization multicolor staining confirmed the presence of translocations in restricted cell types corresponding to the B lymphoid or myeloid lineage of the leukemias that normally harbor these fusion genes. The frequency of positive cells (10−4 to 10−3) indicates substantial clonal expansion of a progenitor population. These data have significant implications for the pathogenesis, natural history, and etiology of childhood leukemia.
556 citations
TL;DR: The prospective isolation of early developmental intermediates, the human clonogenic common myeloid progenitors and their downstream progeny, the granulocyte/macrophage and megakaryocyte/erythrocyte progenitor populations are shown.
Abstract: The hierarchical development from hematopoietic stem cells to mature cells of the hematolymphoid system involves progressive loss of self-renewal capacity, proliferation ability, and lineage potentials. Here we show the prospective isolation of early developmental intermediates, the human clonogenic common myeloid progenitors and their downstream progeny, the granulocyte/macrophage and megakaryocyte/erythrocyte progenitors. All three populations reside in the lineage-negative (lin−) CD34+CD38+ fraction of adult bone marrow as well as in cord blood. They are distinguishable by the expression of the IL-3Rα chain, the receptor of an early-acting hematopoietic cytokine, and CD45RA, an isoform of a phosphotyrosine phosphatase involved in negative regulation of cytokine signaling. Multipotent progenitors, early lymphoid progenitors, and the here-defined myeloid progenitors express distinct profiles of hematopoiesis-affiliated genes. The isolation of highly purified hematopoietic intermediates provides tools to better understand developmental programs underlying normal and leukemic hematopoiesis.
539 citations
TL;DR: It is demonstrated that FLT3-ITD mutant proteins are sufficient to induce a myeloproliferative disorder, but are insufficient to recapitulate the AML phenotype observed in humans.
513 citations
TL;DR: The essential roles of the chemokine SDF-1 and its receptor CXCR4 which mediate and regulate stem cell homing and repopulation will be discussed.
Abstract: Hematopoietic stem cells are identified based on their functional ability to migrate via the blood circulation of transplanted recipients, to home to the host bone marrow and to durably repopulate this organ with high levels of maturing myeloid and lymphoid cells. While a small pool of undifferentiated stem cells with the potential to repeat the entire process in serially transplanted recipients is maintained within the bone marrow, maturing cells are continuously released into the circulation. In recent years pre-clinical, functional in vivo models for human stem cells have been developed, using immune-deficient mice or pre-immune, fetal sheep as recipients. The mechanism of human stem cell migration, homing and repopulation in transplanted immune-deficient NOD/SCID and NOD/SCID/B2m(null) mice as well as the accessory mediators that facilitate these processes, will be reviewed. In particular, the essential roles of the chemokine SDF-1 and its receptor CXCR4 which mediate and regulate stem cell homing and repopulation will be discussed.
485 citations
TL;DR: Early lymphocyte progenitors (ELP) are distinct from stem cells, previously described prolymphocytes, or progenitor corresponding to other blood cell lineages, as well as indicating that distinctive early lymphocyte characteristics are not synchronously acquired.
477 citations
TL;DR: The AML1/CBFbeta transcription factor complex, a frequent target of chromosomal translocations in leukemia, is essential for the generation of definitive hematopoietic stem cells.
441 citations
TL;DR: It is demonstrated here that "promiscuous" expression of myeloid or lymphoid genes precedes lineage commitment in hematopoiesis, which may allow flexibility in fate commitments at these multipotent stages.
TL;DR: This study demonstrates the safety, feasibility, and antileukemic effects of 213Bi-HuM195, and it is the first proof-of-concept for systemic targeted α particle immunotherapy in humans.
TL;DR: The data suggest that activated Notch1 signaling plays an important role in the pathobiology of Hodgkin and anaplastic large cell lymphoma and that it might be a potential new target for treatment.
TL;DR: The conclusion is made that CD4(+)CD56(+) malignancies constitute a genuine homogeneous entity and some therapeutic options were clearly identified.
TL;DR: This work reports that Tyr177 recruits the scaffolding adaptor Gab2 via a Grb2/Gab2 complex and identifies Gab2 and its associated proteins as key determinants of the lineage and severity of BCR/ABL transformation.
TL;DR: Compared with controls, recipients of Hoxa9-transduced cells had an about 15-fold increase in transplantable lymphomyeloid long-term repopulating cells, indicating the capacity for this oncogene to confer a growth advantage to hematopoietic stem cells.
TL;DR: The molecular mechanisms that promote the survival of MM cells are examined and a key role is identified for myeloid cell factor-1 (Mcl-1), an antiapoptotic member of the Bcl-2 family, which is likely to be the labile factor governing MM cell survival.
TL;DR: It is shown that HIV+ individuals have a significant decrease in the number of the Lin−HLA-DR+CD123+ and BDCA-2+ PDC compared with uninfected donors and that DC subsets are differentially reconstituted during the immune recovery associated with antiviral therapy.
Abstract: Dendritic cells (DC) have an instrumental role in the activation and function of both innate and adaptive immune responses. In humans, at least two distinct DC subsets have been characterized based on phenotypic markers: the myeloid DC (MDC) and the plasmacytoid DC (PDC). Both subsets are critical producers of cytokines (IL-12 for MDC and type I/II IFNs for PDC) and are functionally different. We show in this study that HIV(+) individuals have a significant decrease in the number of the Lin(-)HLA-DR(+)CD123(+) and BDCA-2(+) PDC compared with uninfected donors (p = 0.0001). HIV(+) individuals also have a sustained impairment in viral-induced IFN-alpha production (p 5000 HIV-1 copies/ml. The inverse association with viral load of the MDC number, but not of IFN-alpha secretion or the number of PDC, suggests a role for MDC in viral control. Our data suggest that DC subsets are differentially reconstituted during the immune recovery associated with antiviral therapy. The persistent impairment of certain DC subsets may result in a sustained defect in DC-mediated innate immune functions despite an effective treatment regimen.
TL;DR: It is concluded that Gfi1 influences the differentiation of myeloid precursors into granulocytes or monocytes and acts in limiting the inflammatory immune response.
Abstract: The transcriptional repressor Gfi1 is a nuclear zinc-finger protein expressed in T-cell precursors in the thymus and in activated mature T lymphocytes1,2,3,4. Previous experiments have shown that Gfi1 is involved in T-cell lymphomagenesis and in the development of T-cell progenitors5,6,7. Here we show that Gfi1 is also expressed outside the lymphoid system in granulocytes and activated macrophages, cells that mediate innate immunity (that is, non-specific immunity). We have generated Gfi1-deficient mice (Gfi1−/−) and show that these animals are severely neutropenic and accumulate immature monocytic cells in blood and bone marrow. Their myeloid precursor cells are unable to differentiate into granulocytes upon stimulation with granulocyte colony–stimulating factor (G-CSF) but can develop into mature macrophages. We found that Gfi1−/− macrophages produce enhanced levels of inflammatory cytokines, such as tumor necrosis factor (TNF), interleukin-10 (IL-10) and IL-1β, when stimulated with bacterial lipopolysaccharide (LPS) and that Gfi1−/− mice succumb to low doses of this endotoxin that are tolerated by wildtype mice. We conclude that Gfi1 influences the differentiation of myeloid precursors into granulocytes or monocytes and acts in limiting the inflammatory immune response.
TL;DR: In patients with chronic myeloids leukemia, acute myeloid leukemia, and myelodysplasia undergoing allogeneic transplantation from matched siblings, the use of peripheral blood instead of bone marrow leads to faster hematologic recovery, similar risk of graft-versus-host disease, and improved survival.
TL;DR: It is shown that expression of BCR-ABL in myeloid precursor cells leads to transcriptional suppression of the granulocyte colony–stimulating factor receptor G-CSF-R (encoded by CSF3R), possibly through down-modulation of C/EBPα—the principal regulator of granulocytic differentiation.
Abstract: The arrest of differentiation is a feature of both chronic myelogenous leukemia cells in myeloid blast crisis and myeloid precursors that ectopically express the p210BCR-ABL oncoprotein; however, its underlying mechanisms remain poorly understood. Here we show that expression of BCR-ABL in myeloid precursor cells leads to transcriptional suppression of the granulocyte colony-stimulating factor receptor G-CSF-R (encoded by CSF3R), possibly through down-modulation of C/EBPalpha-the principal regulator of granulocytic differentiation. Expression of C/EBPalpha protein is barely detectable in primary marrow cells taken from individuals affected with chronic myeloid leukemia in blast crisis. In contrast, CEBPA RNA is clearly present. Ectopic expression of C/EBPalpha induces granulocytic differentiation of myeloid precursor cells expressing BCR-ABL. Expression of C/EBPalpha is suppressed at the translational level by interaction of the poly(rC)-binding protein hnRNP E2 with CEBPA mRNA, and ectopic expression of hnRNP E2 in myeloid precursor cells down-regulates both C/EBPalpha and G-CSF-R and leads to rapid cell death on treatment with G-CSF (encoded by CSF3). Our results indicate that BCR-ABL regulates the expression of C/EBPalpha by inducing hnRNP E2-which inhibits the translation of CEBPA mRNA.
TL;DR: Adult mice deficient in expression of the flt3 ligand (FL) have severely (10-fold) reduced levels of the CLP, accompanied by reductions in the earliest identifiable B and T cell progenitors, indicating a potential autocrine role of FL in regulation of the earliest lymphoid commitment step from HSC.
TL;DR: This study revealed a unique correlation between AML-specific cytogenetic aberrations and gene expression profiles and microarray analyses for gene expression profiling on bone marrow samples of patients with newly diagnosed AML.
Abstract: Acute myeloid leukemia (AML) is a heterogeneous group of genetically defined diseases. Their classification is important with regard to prognosis and treatment. We performed microarray analyses for gene expression profiling on bone marrow samples of 37 patients with newly diagnosed AML. All cases had either of the distinct subtypes AML M2 with t(8;21), AML M3 or M3v with t(15;17), or AML M4eo with inv(16). Diagnosis was established by cytomorphology, cytogenetics, fluorescence in situ hybridization, and reverse transcriptase-PCR in every sample. By using two different strategies for microarray data analyses, this study revealed a unique correlation between AML-specific cytogenetic aberrations and gene expression profiles.
TL;DR: It is suggested that FLT3/ITD may contribute as the initial transforming event in AML, and relapse can reflect the selection and outgrowth of a mutant clone or evolution of a new clone harboring this mutation.
TL;DR: Salvage treatment with chemotherapy before DLI can help some patients with advanced myeloid relapse and is not dependent on GVHD.
Abstract: PURPOSE: Patients with advanced myeloid malignancies who experience relapse after allogeneic bone marrow transplantation (BMT) have a poor prognosis. Long-term survival after chemotherapy alone, second myeloablative transplant, or donor leukocyte infusions (DLIs) alone is unusual. DLIs may have minimal effectiveness in advanced disease because adequate cellular responses are not able to develop in the presence of bulky, fast-growing disease. A chemotherapy strategy was used to debulk disease before administration of granulocyte colony-stimulating factor (G-CSF)–primed DLIs. PATIENTS AND METHODS: Sixty-five patients experiencing hematologic relapse of myeloid malignancy after HLA-matched sibling BMT were prospectively treated with cytarabine-based chemotherapy, then G-CSF–primed DLIs. No prophylactic immunosuppression was provided. RESULTS: Twenty-seven of 57 assessable patients experienced a complete response. Graft-versus-host disease (GVHD) was observed in 56% of the patients. Treatment-related mortalit...
TL;DR: The p14ARF tumor suppressor, a mediator of the p53 oncogene checkpoint, is identified, as a direct transcriptional target of AML1–ETO, a fusion protein consisting of the acute myeloid leukemia-1 transcription factor and the eight-twenty-one corepressor.
Abstract: The t(8;21) is one of the most frequent chromosomal translocations associated with acute leukemia. This translocation creates a fusion protein consisting of the acute myeloid leukemia-1 transcription factor and the eight-twenty-one corepressor (AML1 ETO), which represses transcription through AML1 (RUNX1) DNA binding sites and immortalizes hematopoietic progenitor cells. We have identified the p14(ARF) tumor suppressor, a mediator of the p53 oncogene checkpoint, as a direct transcriptional target of AML1 ETO. AML1 ETO repressed the p14(ARF) promoter and reduced endogenous levels of p14(ARF) expression in multiple cell types. In contrast, AML1 stimulated p14(ARF) expression and induced phenotypes consistent with cellular senescence. Chromatin immunoprecipitation assays demonstrated that AML1 ETO was specifically bound to the p14(ARF) promoter. In acute myeloid leukemia samples containing the t(8;21), levels of p14(ARF) mRNA were markedly lower when compared with other acute myeloid leukemias lacking this translocation. Repression of p14(ARF) may explain why p53 is not mutated in t(8;21)-containing leukemias and suggests that p14(ARF) is an important tumor suppressor in a large number of human leukemias.
TL;DR: Pan-hematopoietic Pax5 expression strongly promoted B cell development at the expense of T lymphopoiesis and interfered with T lineage commitment and early thymocyte development by repressing the transcription of the T cell specification gene Notch1.
TL;DR: The first report of mutations in the PU.1 gene in human neoplasia is reported and suggests that disruption ofPU.1 function contributes to the block in differentiation found in AML patients.
TL;DR: The characterization of a DC-committed precursor population, which has the capacity to generate all the DC subpopulations present in mouse lymphoid organs but which is devoid of myeloid or lymphoid differentiation potential, helps support an alternative model of DC development, in which there is an independent, common DC differentiation pathway.
Abstract: Dendritic cells (DCs) are essential for the establishment of immune responses against pathogens and tumour cells, and thus have great potential as tools for vaccination and cancer immunotherapy trials. Experimental evidence has led to a dual DC differentiation model, which involves the existence of both myeloid- and lymphoid-derived DCs. But this concept has been challenged by recent reports demonstrating that both CD8- and CD8+ DCs, considered in mice as archetypes of myeloid and lymphoid DCs respectively, can be generated from either lymphoid or myeloid progenitors. The issue of DC physiological derivation therefore remains an open question. Here we report the characterization of a DC-committed precursor population, which has the capacity to generate all the DC subpopulations present in mouse lymphoid organs---including CD8- and CD8+ DCs, as well as the B220+ DC subset---but which is devoid of myeloid or lymphoid differentiation potential. These data support an alternative model of DC development, in which there is an independent, common DC differentiation pathway.
TL;DR: It is suggested that Delta-1 can enhance myeloid and lymphoid marrow-repopulating ability and promote the generation of thymus- repopulating T cell precursors.
Abstract: We investigated the effect of Notch signaling, a known regulator of cell fate in numerous developmental systems, on human hematopoietic precursors. We show that activation of endogenous Notch signaling in human CD34+CD38– cord blood precursors with immobilized Delta-1 in serum-free cultures containing fibronectin and hematopoietic growth factors inhibited myeloid differentiation and induced a 100-fold increase in the number of CD34+ cells compared with control cultures. Immobilized Delta-1 also induced a multifold expansion of cells with the phenotype of common lymphoid precursors (CD34+CD7+CD45RA+) and promoted the development of cytoplasmic CD3+ T/NK cell precursors. IL-7 enhanced the promotion of T/NK cell differentiation by immobilized Delta-1, but granulocytic differentiation occurred when G-CSF was added. Transplantation into immunodeficient mice showed a substantial increase in myeloid and B cell engraftment in the marrow and also revealed thymic repopulation by CD3+ T cells due to cells being cultured for a longer period with immobilized Delta-1. These data suggest that Delta-1 can enhance myeloid and lymphoid marrow-repopulating ability and promote the generation of thymus-repopulating T cell precursors.