A New α5β1 Integrin-Dependent Survival Pathway Through GSK3β Activation in Leukemic Cells

Cell survival mediated by integrin engagement has been implicated in cell adhesion-mediated drug resistance. We have recently demonstrated that the activation of glycogen synthase kinase 3 beta (GSK3beta) is a new pathway supporting the chemoresistance of leukemic cells adhered to fibronectin.We show here that in conditions of serum starvation, the fibronectin receptor alpha(5)beta(1) integrin, but not alpha(4)beta(1), induced activation of GSK3beta through Ser-9 dephosphorylation in adherent U937 cells. The GSK3beta-dependent survival pathway occurred in adherent leukemic cells from patients but not in the HL-60 and KG1 cell lines. In adhesion, activated GSK3beta was found in the cytosol/plasma membrane compartment and was co-immunoprecipitated with alpha(5) integrin, the phosphatase PP2A and the scaffolding protein RACK1. PP2A and its regulatory subunit B' regulated the Ser-9 phosphorylation of GSK3beta. In adherent leukemic cells, alpha(5)beta(1) integrin but not alpha(4)beta(1) upregulated the resistance to TNFalpha-induced apoptosis. Both extrinsic and intrinsic apoptotic pathways were under the control of alpha(5)beta(1) and GSK3beta.Our data show that, upon serum starvation, alpha(5)beta(1) integrin engagement could regulate specific pro-survival functions through the activation of GSK3beta

Thrombin modifies growth, proliferation and apoptosis of human colon organoids: a protease-activated receptor 1- and protease-activated receptor 4-dependent mechanism

International audienceExperimental Approach: Crypts were isolated from human colonic resections and cultured for 6 days, forming human colon organoids. Cultured organoids were exposed to 10 and 50 mU·mL−1 of thrombin, in the presence or not of protease‐activated receptor (PAR) antagonists. Organoid morphology, metabolism, proliferation and apoptosis were followed.Key Results: Thrombin favoured organoid maturation leading to a decreased number of immature cystic structures and a concomitant increased number of larger structures releasing cell debris and apoptotic cells. The size of budding structures, metabolic activity and proliferation were significantly reduced in organoid cultures exposed to thrombin, while apoptosis was dramatically increased. Both PAR1 and PAR4 antagonists inhibited apoptosis regardless of thrombin doses. Thrombin‐induced inhibition of proliferation and metabolic activity were reversed by PAR4 antagonist for thrombin's lowest dose and by PAR1 antagonist for thrombin's highest dose.Conclusions and Implications: Overall, our data suggest that the presence of thrombin in the vicinity of human colon epithelial cells favours their maturation at the expense of their regenerative capacities. Our data point to thrombin and its two receptors PAR1 and PAR4 as potential molecular targets for epithelial repair therapies

Regulation des activites phosphoinositide kinases dans la plaquette sanguine

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 84728 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

GSK3β, a Master Kinase in the Regulation of Adult Stem Cell Behavior

In adult stem cells, Glycogen Synthase Kinase 3β (GSK3β) is at the crossroad of signaling pathways controlling survival, proliferation, adhesion and differentiation. The microenvironment plays a key role in the regulation of these cell functions and we have demonstrated that the GSK3β activity is strongly dependent on the engagement of integrins and protease-activated receptors (PARs). Downstream of the integrin α5β1 or PAR2 activation, a molecular complex is organized around the scaffolding proteins RACK1 and β-arrestin-2 respectively, containing the phosphatase PP2A responsible for GSK3β activation. As a consequence, a quiescent stem cell phenotype is established with high capacities to face apoptotic and metabolic stresses. A protective role of GSK3β has been found for hematopoietic and intestinal stem cells. Latters survived to de-adhesion through PAR2 activation, whereas formers were protected from cytotoxicity through α5β1 engagement. However, a prolonged activation of GSK3β promoted a defect in epithelial regeneration and a resistance to chemotherapy of leukemic cells, paving the way to chronic inflammatory diseases and to cancer resurgence, respectively. In both cases, a sexual dimorphism was measured in GSK3β-dependent cellular functions. GSK3β activity is a key marker for inflammatory and cancer diseases allowing adjusted therapy to sex, age and metabolic status of patients

La glycogène synthase kinase 3 bêta (une nouvelle voie de survie des cellules souches de leucémies aiguës myéloïdes)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Rôle de la voie Wnt/b-caténine dans la prolifération et la chimiorésistance des leucémies aiguës myéloïdes

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Progrès dans l’étude du cancer de la prostate : la culture cellulaire en trois dimensions reproduit ex vivo les caractéristiques des tumeurs prostatiques

Malgré les progrès thérapeutiques, le cancer de la prostate (CaP) reste un enjeu de santé publique par son incidence et sa mortalité élevée. Les difficultés de la recherche sur le CaP viennent du manque de modèles précliniques in vitro et in vivo capables de reproduire ses caractéristiques. Actuellement, les cultures de lignées cellulaires de CaP in vitro en 2D sont les plus répandues, mais elles ont de nombreuses limites. Elles ne reproduisent pas la morphologie cellulaire, l’architecture tissulaire, et ne reflètent pas l’hétérogénéité tumorale entre les patients et au sein même de la tumeur. De plus, elles sont dépourvues du microenvironnement tumoral et des cellules souches cancéreuses qui sont deux acteurs incontournables du CaP. Les modèles in vivo murins du CaP ne représentent pas le spectre des altérations génétiques de la maladie et ont des difficultés à reproduire le processus métastatique. Par conséquent, la physiologie de ces modèles in vitro et in vivo est extrêmement éloignée de celle des tumeurs prostatiques des patients. Les modèles de culture cellulaire en 3D s’affranchissent de ces limites en partageant les caractéristiques des tumeurs in vivo tout en en gardant la reproductibilité expérimentale des modèles in vitro. Les modèles en 3D du CaP comprennent les sphéroïdes qui dérivent des lignées cellulaires tumorales, et les organoïdes issus des tumeurs primaires ou des métastases du CaP. Dans ces structures, la morphologie cellulaire est conservée, une matrice extracellulaire entoure les cellules et les interactions cellules-cellules et cellules-matrice sont préservées. De plus, les organoïdes conservent les altérations génétiques des tumeurs prostatiques dont ils dérivent et ils permettent l’étude des cellules souches cancéreuses au sein d’un microenvironnement. Les organoïdes ouvrent la perspective de tests thérapeutiques couvrant le large spectre des phénotypes du CaP. Les organoïdes générés à partir de biopsies de patients pourraient de plus, mener vers une médecine personnalisée.Despite new therapeutics options, Prostate Cancer (PCa) remains a public health challenge because of its high incidence and mortality. Limits in PCa research come from the lack of in vitro and in vivo models that mimic the human disease. Currently, 2D in vitro tissue culture models of PCa are widely used but they present numerous limits. They do not reproduce cellular morphology, tissue architecture, inter-patients and intratumor heterogeneity. Furthermore, they lack two key components of PCa tumors, the tumoral microenvironment and the cancer stem cells. In vivo murine models of PCa cannot be representative of all the genetic alterations known in prostate tumors and they hardly reproduce the pathophysiology of human metastatic progression. Consequently, the physiology of these in vitro and in vivo models do not well represent patients tumors. 3D cell cultures overcome many of these limits by sharing morphologic characteristics with in vivo tumors as well as reproducibility of in vitro models. 3D models of PCa include spheroids derived from tumor cell lines, and organoids, derived from patient. In 3D cell cultures, cell fitness is maintained, the physiological cells-cells and cell-matrix interactions are restored and an extracellular matrix surrounds the cells. Organoids, generated from PCa primary tumors or metastases, allow studies on cancer stem cells and their microenvironment. Moreover, organoids retain genetic integrity of PCa tumors. PCa organoid model is an innovative tool that offers great perspectives of therapeutic screening. In the future, organoids generated from patients’ biopsies may also lead to personalized medicine

Sustainable positive response to sirolimus in juvenile polyposis of infancy

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Cucurbitacins from the Leaves of Citrullus colocynthis (L.) Schrad

International audienceTwo new tetracyclic cucurbitane-type triterpene glycosides were isolated from an ethyl acetate extract of Citrullus colocynthis leaves together with four known cucurbitacins. Their structures were established on the basis of their spectroscopic data (mainly NMR and mass spectrometry). Evaluation of the in vitro cytotoxic activity of the isolated compounds against two human colon cancer cell lines (HT29 and Caco-2) and one normal rat intestine epithelial cell line (IEC6), revealed that one of the isolated compounds presented interesting specific cytotoxic activity towards colorectal cell lines