Expression de la protéine anti-apoptotitque MCL-1 dans le myélome multiple (corrélation avec l'activité de la maladie)

Le myélome multiple (MM) est une hémopathie maligne caractérisée par l'expansion clonale de plasmocytes tumoraux qui s'accumulent dans la moelle osseuse. La protéine anti-apoptotique Mcl-1 est un facteur de survie des plasmocytes de MM. Nous avons quantifié en cytométrie en flux, par quadruple marquage, l'expression de Mcl-1 chez 45 patients atteints de MM. Nous avons étudié en parallèle à Mcl-1, l'expression de la protéine Bcl-2, autre protéine anti-apoptotique. Nos résultats montrent que Mcl-1, contrairement à Bcl-2, est davantage exprimé dans les plasmocytes de MM que dans les plasmocytes normaux et que cette hyper-expression est essentiellement cantonnée au compartiment le plus proliférant CD45 Fort. L'étude de corrélation entre l'expression de Mcl-1 et la prolifération ne montrent pas, contrairement à Bcl-2, de corrélation significative. Aussi, l'hyper-expression constitutive de Mcl-1, essentiellement dans le compartiment CD45 Fort, est probablement liée directement à la malignité intrinsèque de la tumeur. Nous avons aussi montré que l'expression de Mcl-1 est liée à l'activité de la maladie. En effet cette protéine est plus exprimée dans les MM en rechutes que dans les MM au diagnostic. Aussi, la protéine Mcl-1 à probablement une valeur pronostic dans la progression du MM.NANTES-BU Médecine pharmacie (441092101) / SudocSudocFranceF

Expression et régulation de la protéine anti-apoptotique Mcl-1 dans le myélome multiple (implications clinico-biologiques)

La protéine anti-apoptotique Mcl-1 joue un rôle majeur dans la survie des cellules myélomateuses. Nous montrons que la surexpression de Mcl-1 est corrélée à la rechute et à une survie plus courte des patients. Le complexe Mcl-1/Bim est important dans la régulation de l'apoptose dans les plasmocytes malins. En effet, Mcl-1 se lie à Bim et neutralise son effet pro-apoptotique. De plus, l'interaction de Mcl-1 et Bina confère aux deux protéines une stabilité mutuelle par protection de l'ubiquitination et de la dégradation par le protéasome. En effet, la diminution de l'expression de Bim ou de Mcl-1 par shRNA interférence induit une augmentation de la dégradation de Mcl-1 et de Bim dans les cellules shBim et shMcl-1 respectivement. Le Bortézomib est un inhibiteur spécifique du protéasome nouvellement introduit dans le traitement des myélomes multiples (MM) en rechute. L'apoptose induite par le Bortézomib est associée à un clivage de Mcl-1 et à la modification de ses interactions avec les protéines BH3 seulement . En effet, le Bortézomib induit une accumulation de Noxa, une augmentation du complexe Mcl-1/Noxa et une diminution du complexe Mcl-1/Bim. Ainsi, la sensibilité au Bortézomib des cellules myélomateuses peut être expliquée par le déplacement de Bim, BH3 seulement activatrice, par Noxa, BH3 seulement sensibilisatrice, du complexe Mcl-1/Bim, ce qui induit l'activation de Bax/Bak. La régulation de Mcl-1 via son clivage ou via ses interactions protéiques avec les protéines BH3 seulement contribue à réguler l'apoptose des plasmocytes myélomateux.Mcl-1 is a major survival protein for multiple myeloma (MM) cells. Mcl-1 overexpression of Mcl-1 in vivo is correlated with relapse and shorter survival. Mcl-1/Bim complexes are critical in myeloma cells. Mcl-1 neutralizes the pro-apoptotic function of Bim and prevents activation of death effectors. The interaction between Mcl-1 and Bim confers to themselves mutual protection. Indeed, down-regulation of Mcl-1 by sh- RNA leads to unligated Bim to ubiquitin-proteasome- degradation and reciprocally for unliganded Mcl-1 in shBim cells. Bortezomib, a specific proteasome inhibitor, has been approved for the treatment of relapsed or refractory MM. Bortezomib-induced apoptosis, in MM cells, was associated with Mcl-1 cleavage, Noxa induction and caspase activation. Under Bortezomib treatment, Mcl-1/Noxa complexes were highly increased and Mcl-1/Bim interaction were disrupted. Thus, in MM cells, the mechanistic basis for bortezomib sensitivity can be explained mainly by a model in which the sensitizer Noxa can displace Bim, a BH3-only activator, from Mcl-1, thus leading to Bax/Bak activation. The regulation of Mcl-1 via its cleavage or its interactions with "BH3 only" proteins contributes to control apoptosis induction in MM.NANTES-BU Médecine pharmacie (441092101) / SudocSudocFranceF

Platelet Counting: Ugly Traps and Good Advice. Proposals from the French-Speaking Cellular Hematology Group (GFHC).

Despite the ongoing development of automated hematology analyzers to optimize complete blood count results, platelet count still suffers from pre-analytical or analytical pitfalls, including EDTA-induced pseudothrombocytopenia. Although most of these interferences are widely known, laboratory practices remain highly heterogeneous. In order to harmonize and standardize cellular hematology practices, the French-speaking Cellular Hematology Group (GFHC) wants to focus on interferences that could affect the platelet count and to detail the verification steps with minimal recommendations, taking into account the different technologies employed nowadays. The conclusions of the GFHC presented here met with a "strong professional agreement" and are explained with their rationale to define the course of actions, in case thrombocytopenia or thrombocytosis is detected. They are proposed as minimum recommendations to be used by each specialist in laboratory medicine who remains free to use more restrictive guidelines based on the patient's condition

Baseline dysmegakaryopoiesis in inherited thrombocytopenia/platelet disorder with predisposition to haematological malignancies

International audienc

Molecular Signature of 18 F-FDG PET Biomarkers in Newly Diagnosed Multiple Myeloma Patients: A Genome-Wide Transcriptome Analysis from the CASSIOPET Study

International audienceThe International Myeloma Working Group recently fully incorporated 18F-FDG PET into multiple myeloma (MM) diagnosis and response evaluation. Moreover, a few studies demonstrated the prognostic value of several biomarkers extracted from this imaging at baseline. Before these 18F-FDG PET biomarkers could be fully endorsed as risk classifiers by the hematologist community, further characterization of underlying molecular aspects was necessary. Methods: Reported prognostic biomarkers (18F-FDG avidity, SUVmax, number of focal lesions, presence of paramedullary disease [PMD] or extramedullary disease) were extracted from 18F-FDG PET imaging at baseline in a group of 139 patients from CASSIOPET, a companion study of the CASSIOPEIA cohort (ClinicalTrials.gov identifier NCT02541383). Transcriptomic analyses using RNA sequencing were realized on sorted bone marrow plasma cells from the same patients. An association with a high-risk gene expression signature (IFM15), molecular classification, progression-free survival, a stringent clinical response, and minimal residual disease negativity were explored. Results:18F-FDG PET results were positive in 79.4% of patients; 14% and 11% of them had PMD and extramedullary disease, respectively. Negative 18F-FDG PET results were associated with lower levels of expression of hexokinase 2 (HK2) (fold change, 2.1; adjusted P = 0.04) and showed enrichment for a subgroup of patients with a low level of bone disease. Positive 18F-FDG PET results displayed 2 distinct signatures: either high levels of expression of proliferation genes or high levels of expression of GLUT5 and lymphocyte antigens. PMD and IFM15 were independently associated with a lower level of progression-free survival, and the presence of both biomarkers defined a group of "double-positive" patients at very high risk of progression. PMD and IFM15 were related neither to minimal residual disease assessment nor to a stringent clinical response. Conclusion: Our study confirmed and extended the association between imaging biomarkers and transcriptomic programs in MM. The combined prognostic value of PMD and a high-risk IFM15 signature may help define MM patients with a very high risk of progression

A new cytokine‐based dynamic stratification during induction is highly predictive of survivals in acute myeloid leukemia

International audienceThe aim of this study was to assess the potential impact of the kinetics of serum levels of seven cytokines during induction in acute myeloid leukemia (AML) patients. Indeed, the role of cytokines, in the pathophysiology and response to therapy of AML patients, remains under investigation. Here, we report on the impact of peripheral levels of two cytokines, the Fms-like tyrosine kinase 3 ligand (FL) and interleukin-6 (IL-6), evaluated during first-line intensive induction. A new risk stratification can be proposed, which supersedes the ELN 2017 classification to predict survivals in AML patients by examining the kinetic profile of these cytokines during the induction phase. It segregates three groups of, respectively, high-risk, characterized by a stagnation of low FL levels, intermediate risk, with dynamic increasing FL levels and high IL-6 at day 22, and favorable risk with increasing FL levels but low IL-6 at day 22

Perls' Stain Guidelines from the French-Speaking Cellular Hematology Group (GFHC).

In order to standardize cellular hematology practices, the French-speaking Cellular Hematology Group (Groupe Francophone d'Hématologie Cellulaire, GFHC) focused on Perls' stain. A national survey was carried out, leading to the proposal of recommendations on insoluble iron detection and quantification in bone marrow. The criteria presented here met with a "strong professional agreement" and follow the suggestions of the World Health Organization's classification of hematological malignancies