Molecular predictors of response to decitabine in advanced chronic myelomonocytic leukemia: a phase 2 trial.
Abstract Hydroxyurea is the standard therapy of chronic myelomonocytic leukemia (CMML) presenting with advanced myeloproliferative and/or myelodysplastic features. Response to hypomethylating agents has been reported in heterogeneous series of CMML. We conducted a phase 2 trial of decitabine (DAC) in 39 patients with advanced CMML defined according to a previous trial. Median number of DAC cycles was 10 (range, 1-24). Overall response rate was 38% with 4 complete responses (10%), 8 marrow responses (21%), and 3 stable diseases with hematologic improvement (8%). Eighteen patients (46%) demonstrated stable disease without hematologic improvement, and 6 (15%) progressed to acute leukemia. With…
A role for caspases in the differentiation of erythroid cells and macrophages
Several cysteine proteases of the caspase family play a central role in many forms of cell death by apoptosis. Other enzymes of the family are involved in cytokine maturation along inflammatory response. In recent years, several caspases involved in cell death were shown to play a role in other cellular processes such as proliferation and differentiation. In the present review, we summarize the current knowledge of the role of caspases in the differentiation of erythroid cells and macrophages. Based on these two examples, we show that the nature of involved enzymes, the pathways leading to their activation in response to specific growth factors, and the specificity of the target proteins th…
TET2 gene mutation is a frequent and adverse event in chronic myelomonocytic leukemia
Background Acquired somatic deletions and loss-of-function mutations in one or several codons of the TET2 ( Ten-Eleven Translocation-2 ) gene were recently identified in hematopoietic cells from patients with myeloid malignancies, including myeloproliferative disorders and myelodys-plastic syndromes. The present study was designed to determine the prevalence of TET2 gene alterations in chronic myelomonocytic leukemias. Design and Methods Blood and bone marrow cells were collected from 88 patients with chronic phase chronic myelomonocytic leukemia and from 14 with acute transformation of a previously identified disease. Polymerase chain reaction analysis and direct sequencing were used to se…
Role of GATA-1 and HSP70 in the Dyserythropoiesis of Early Myelodysplastic Syndromes.
Abstract Abstract 3823 Poster Board III-759 Myelodysplastic syndromes (MDS) are heterogeneous hematopoietic stem cell disorders characterized by a hypercellular dysplastic bone marrow (BM) with peripheral blood cytopenias, mainly anemia. Early MDS with less than 10% BM blasts which belong in most cases to low and intermediate-1 (int-1) risk groups according to the International Prognostic Scoring System (IPSS), usually demonstrate dyserythropoiesis. The growth of erythroid progenitors is altered, with increased caspase activation leading to excessive cell death, and cellular dysplasia characterized, in liquid culture of CD34+-derived erythroid progenitors, by a delayed expression of the gly…
Vitamin K antagonism impairs the bone marrow microenvironment and hematopoiesis
Abstract Vitamin K antagonists (VKAs) have been used in 1% of the world’s population for prophylaxis or treatment of thromboembolic events for 64 years. Impairment of osteoblast function and osteoporosis has been described in patients receiving VKAs. Given the involvement of cells of the bone marrow microenvironment (BMM), such as mesenchymal stem cells (MSCs) and macrophages, as well as other factors such as the extracellular matrix for the maintenance of normal hematopoietic stem cells (HSCs), we investigated a possible effect of VKAs on hematopoiesis via the BMM. Using various transplantation and in vitro assays, we show here that VKAs alter parameters of bone physiology and reduce funct…
Heat shock proteins: essential proteins for apoptosis regulation
Abstract Many different external and intrinsic apoptotic stimuli induce the accumulation in the cells of a set of proteins known as stress or heat shock proteins (HSPs). HSPs are conserved proteins present in both prokaryotes and eukaryotes. These proteins play an essential role as molecular chaperones by assisting the correct folding of nascent and stress-accumulated misfolded proteins, and by preventing their aggregation. HSPs have a protective function, that is they allow the cells to survive to otherwise lethal conditions. Various mechanisms have been proposed to account for the cytoprotective functions of HSPs. Several of these proteins have demonstrated to directly interact with compo…
Defective nuclear localization of Hsp70 is associated with dyserythropoiesis and GATA-1 cleavage in myelodysplastic syndromes.
Abstract Normal human erythroid cell maturation requests the transcription factor GATA-1 and a transient activation of caspase-3, with GATA-1 being protected from caspase-3–mediated cleavage by interaction with the chaperone heat shock protein 70 (Hsp70) in the nucleus. Erythroid cell dysplasia observed in early myelodysplastic syndromes (MDS) involves impairment of differentiation and excess of apoptosis with a burst of caspase activation. Analysis of gene expression in MDS erythroblasts obtained by ex vivo cultures demonstrates the down-regulation of a set of GATA-1 transcriptional target genes, including GYPA that encodes glycophorin A (GPA), and the up-regulation of members of the HSP70…
Alpha-defensins secreted by dysplastic granulocytes inhibit the differentiation of monocytes in chronic myelomonocytic leukemia.
Abstract Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic disorder that occurs in elderly patients. One of the main diagnostic criteria is the accumulation of heterogeneous monocytes in the peripheral blood. We further explored this cellular heterogeneity and observed that part of the leukemic clone in the peripheral blood was made of immature dysplastic granulocytes with a CD14−/CD24+ phenotype. The proteome profile of these cells is dramatically distinct from that of CD14+/CD24− monocytes from CMML patients or healthy donors. More specifically, CD14−/CD24+ CMML cells synthesize and secrete large amounts of alpha-defensin 1-3 (HNP1-3). Recombinant HNPs inhibit macrophage co…
Immune responses during COVID-19 infection
International audience; Over the past 16 years, three coronaviruses (CoVs), severe acute respiratory syndrome CoV (SARS-CoV) in 2002, Middle East respiratory syndrome CoV (MERS-CoV) in 2012 and 2015, and SARS-CoV-2 in 2020, have been causing severe and fatal human epidemics. The unpredictability of coronavirus disease-19 (COVID-19) poses a major burden on health care and economic systems across the world. This is caused by the paucity of in-depth knowledge of the risk factors for severe COVID-19, insufficient diagnostic tools for the detection of SARS-CoV-2, as well as the absence of specific and effective drug treatments. While protective humoral and cellular immune responses are usually m…
Caspase-8 prevents sustained activation of NF-kappaB in monocytes undergoing macrophagic differentiation.
Abstract Caspases have demonstrated several nonapoptotic functions including a role in the differentiation of specific cell types. Here, we show that caspase-8 is the upstream enzyme in the proteolytic caspase cascade whose activation is required for the differentiation of peripheral-blood monocytes into macrophages. On macrophage colony-stimulating factor (M-CSF) exposure, caspase-8 associates with the adaptor protein Fas-associated death domain (FADD), the serine/threonine kinase receptor-interacting protein 1 (RIP1) and the long isoform of FLICE-inhibitory protein FLIP. Overexpression of FADD accelerates the differentiation process that does not involve any death receptor. Active caspase…
Spontaneous and Fas-induced apoptosis of low-grade MDS erythroid precursors involves the endoplasmic reticulum
Spontaneous apoptosis of bone marrow erythroid precursors accounts for the anemia that characterizes most low-grade myelodysplastic syndromes (MDS). We have shown that death of these precursors involved the Fas-dependent activation of caspase-8. To explore the pathway leading from caspase-8 activation to apoptosis, we transduced MDS bone marrow CD34(+) cells with a lentivirus encoding wild-type (WT) or endoplasmic reticulum (ER)-targeted Bcl-2 protein before inducing their erythroid differentiation. Both WT-Bcl-2 and ER-targeted Bcl-2 prevented spontaneous and Fas-dependent apoptosis in MDS erythroid precursors. ER-targeted Bcl-2 inhibited mitochondrial membrane depolarization and cytochrom…
HSP70 sequestration by free α-globin promotes ineffective erythropoiesis in β-thalassaemia
International audience; β-Thalassaemia major (β-TM) is an inherited haemoglobinopathy caused by a quantitative defect in the synthesis of β-globin chains of haemoglobin, leading to the accumulation of free α-globin chains that form toxic aggregates. Despite extensive knowledge of the molecular defects causing β-TM, little is known of the mechanisms responsible for the ineffective erythropoiesis observed in the condition, which is characterized by accelerated erythroid differentiation, maturation arrest and apoptosis at the polychromatophilic stage. We have previously demonstrated that normal human erythroid maturation requires a transient activation of caspase-3 at the later stages of matur…
Identification of proteins cleaved downstream of caspase activation in monocytes undergoing macrophage differentiation.
We have shown previously that caspases were specifically involved in the differentiation of peripheral blood monocytes into macrophages while not required for monocyte differentiation into dendritic cells. To identify caspase targets in monocytes undergoing macrophagic differentiation, we used the human monocytic leukemic cell line U937, whose macrophagic differentiation induced by exposure to 12-O-tetradecanoylphorbol 13-acetate (TPA) can be prevented by expression of the baculovirus caspase-inhibitory protein p35. A comparative two-dimensional gel proteomic analysis of empty vector- and p35-transfected cells after 12 h of exposure to 20 nm TPA, followed by mass spectrometry analysis, iden…
Heat shock proteins in hematopoietic malignancies
Inducible heat shock proteins are molecular chaperones whose expression is increased after many different types of stress. They have a protective function helping the cell to cope with lethal conditions. Their basal expression is low in nonstressed, normal and nontransformed cells. However, in cancer cells and particularly in hematological malignancies, they are surprisingly abundant. Malignant cells have to rewire their metabolic requirements and therefore have a higher need for chaperones. This cancer cell addiction for HSPs is the basis for the use of HSP inhibitors in cancer therapy. HSPs have been shown to interact with different key apoptotic proteins. As a result, HSPs can essentiall…