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Vav1 exhibits two signal transducing properties as an adaptor protein and a regulator of cytoskeleton organization through its Guanine nucleotide Exchange Factor module. Although the expression of Vav1 is restricted to the hematopoietic lineage, its ectopic expression has been unraveled in a number of solid tumors. In this study, we show that in lung cancer cells, as such in hematopoietic cells, Vav1 interacts with the Spleen Tyrosine Kinase, Syk. Likewise, Syk interacts with β-catenin and, together with Vav1, regulates the phosphorylation status of β-catenin. Depletion of Vav1, Syk or β-catenin inhibits Rac1 activity and decreases cell migration suggesting the interplay of the three effectors to a common signaling pathway. This model is further supported by the finding that in turn, β-catenin regulates the transcription of Syk gene expression. This study highlights the elaborated connection between Vav1, Syk and β-catenin and the contribution of the trio to cell migration.

// Stephane Saint-Georges 1,2 , Maude Quettier 1,2 , Marouane Bouyaba 3 , Stephanie Le Coquil 1,2 , Vanessa Lauriente 1,2 , Lionel Guittat 1,2 , Vincent Levy 3 , Florence Ajchenbaum-Cymbalista 1,2,4 , Nadine Varin-Blank 1,2 , Christine Le Roy 1,2,* and Dominique Ledoux 1,2,* 1 INSERM U978, Bobigny, France 2 Universite Paris 13, Sorbonne Paris Cite, Labex “Inflamex”, Bobigny, France 3 Assistance Publique-Hopitaux de Paris, Hopital Avicenne, Unite de Recherche Clinique, Bobigny, France 4 Assistance Publique-Hopitaux de Paris, Hopital Avicenne, Service d’Hematologie Biologique, Bobigny, France * These authors are co-senior authors Correspondence to: Christine Le Roy, email: // Nadine Varin-Blank, email: // Keywords : CLL, lymphadenopathy, B-cell receptor, CXCR4/CXCR5, protein kinase D Received : December 23, 2015 Accepted : April 16, 2016 Published : April 26, 2016 Abstract In Chronic Lymphocytic Leukemia (CLL), infiltration of lymph nodes by leukemic cells is observed in patients with progressive disease and adverse outcome. We have previously demonstrated that B-cell receptor (BCR) engagement resulted in CXCR4 down-regulation in CLL cells, correlating with a shorter progression-free survival in patients. In this study, we show a simultaneous down-regulation of CXCR4, CXCR5 and CD62L upon BCR triggering. While concomitant CXCR4 and CXCR5 down-regulation involves PKDs, CD62L release relies on PKC activation. BCR engagement induces PI3K-δ-dependent phosphorylation of PKD2 and 3, which in turn phosphorylate CXCR4 Ser 324/325 . Moreover, upon BCR triggering, PKD phosphorylation levels correlate with the extent of membrane CXCR4 decrease. Inhibition of PKD activity restores membrane expression of CXCR4 and migration towards CXCL12 in BCR-responsive cells in vitro . In terms of pathophysiology, BCR-dependent CXCR4 down-regulation is observed in leukemic cells from patients with enlarged lymph nodes, irrespective of their IGHV mutational status. Taken together, our results demonstrate that PKD-mediated CXCR4 internalization induced by BCR engagement in B-CLL is associated with lymph node enlargement and suggest PKD as a potential druggable target for CLL therapeutics.

The electrochemical behavior of complexes [FeMo(CO) 5 (κ 2 -dppe)(μ-pdt)] (1) and [FeMo(CO) 4 (MeCN)( κ 2 -dppe)(μ-pdt)] (2), in the absence and in the presence of acid, has been investigated. The reduction of 1 follows at slow scan rates, in CH 2 Cl 2 -[NBu 4 ][PF 6 ] and acid-free media, an EC rev E mechanism that is supported by cyclic voltammetry (CV) experiments and digital CV simulations. In MeCN-[NBu 4 ][PF 6 ], the electrochemical reduction of 1 is the same as in dichloromethane and follows an ECE mechanism at slow scan rates, but with a positive shift of the redox potentials. In contrast, the oxidation of 1 is strongly solvent-dependent. In dichloromethane, the oxidation of 1 is reversible and involves a single electron, while in acetonitrile, it is irreversible at moderate and slow scan rates (v ≤ ca. 1 V s -1 ), and some chemical reversibility is apparent at higher scan rates (v = 10 V s -1 ). Density functional theory calculations revealed that the chemical step in the EC rev E mechanism corresponds to the dissociation of one PPh 2 end of the diphosphine ligand and the transfer of the semibridging CO to the Fe atom, similarly to the mechanism observed in the FeFe analogue complex. However, in the case of 1, the subsequent coordination of the phosphine ligand to the other metal is an unfavorable process.

Only a minority of chronic lymphocytic leukemia (CLL) patients harboring a positive direct antiglobulin test (DAT) will develop autoimmune hemolytic anemia (AIHA). In a single institution cohort of 378 CLL patients, 56 patients (14.8%) had at least one positive DAT during the course of the disease, either at diagnosis or later. We found no relationship between the time of the first positive DAT and overall survival (OS). However, patients with a positive DAT who did not develop AIHA had the same adverse outcome as patients who developed AIHA. Of the patients who were in Binet stage A at diagnosis, those with a positive DAT had a significantly shorter OS, regardless of their IGHV mutational status, however, there was a strong association with VH1-69. By multivariate analysis, a positive DAT was found to be an independent adverse prognostic factor for OS. Thus, DAT represents a strong adverse prognostic factor and its determination should be repeated during follow-up.

International audience; Dimolybdenum thiolate-bridged complexes [Mo2Cp2(μ-SMe)2(μ-SCH2CH2E)] (E = O (2) or NH (4)) with a proton-dependent protecting device have been synthesized by reaction of [Mo2Cp2(μ-SMe)2(μ-Cl)2] (1) with SCH2CH2EH. The reactivity of the resultant quadruply bridged complexes with acid was investigated in the absence and in the presence of a potential ligand (N2, MeCN, RNC). While the protonation of complexes 2 and 4 under N2 in dichloromethane produced only the oxidized derivatives instead of the desired diazenido compound, ligand binding was observed in MeCN or in the presence of RNC (R = t-Bu, Xyl). Whereas acetonitrile loss from [Mo2Cp2(μ-SMe)2(μ-SCH2CH2OH)(MeCN)2]+ (8+) prevented the isolation and characterization of this species, the t-BuNC analogue (6+) could be characterized by an X-ray crystal structure. The electrochemistry of 2 and 2+ was investigated in CH2Cl2 and in MeCN, both in the absence and in the presence of acid. While the addition of HBF4·Et2O to a dichloromethane solution of 2 only produced 2+ (and presumably H2), 8+ was the major product of the protonation in MeCN.

B-cell antigen receptor (BCR)–mediated signaling plays a critical role in chronic lymphocytic leukemia (CLL) pathogenesis and gives an in vitro survival advantage to B cells isolated from patients with unfavorable prognostic factors. In this study, we undertook to elucidate the signaling intermediates responsible for this biologic alteration. In responding cells only, in vitro BCR engagement triggers global phosphorylation of Syk, activation of phospholipase Cγ2, and intracellular calcium mobilization, reflecting competency of BCR signaling. The calcium–calcineurin-dependent transcription factor NFAT2 is up-regulated and to some extent constitutively activated in all CLL B cells. In contrast, its DNA-binding capacity is enhanced on IgM stimulation in responding cells only. NFAT inhibition using the VIVIT peptide prevents induction of CD23 target gene and IgM-induced survival, converting responding cells to unresponsive status. At the opposite, ionomycin-induced NFAT activity allows survival of nonresponding cells. These results demonstrate that the functional heterogeneity relies on variability of protein levels establishing BCR-dependent thresholds and NFAT-dependent activation. Finally, status of the BCR-NFAT pathway for each patient reveals its relevance for CLL clinical outcome and points out to BCR-NFAT intermediates as promising functional therapeutic targets.

Common in ageing patient, the solar lentigo is a macular hyperpigmented skin lesion that results from chronic exposure to ultraviolet irradiations. Despite sharing numerous features with other pigmented spots, the diagnostic of this benign lesion is well characterized at the tissue level. Recent studies shed lights on several factors and their pathogenic mechanisms involved in the development of the solar lentigo. This review summarizes how diverse experimental approaches allowed the identification of several biomarkers, which contribute to a better understanding on the initiation and the maintenance of this pigmentary disorder.

Mixed μ-phosphido or μ-thiolato μ-halo-dimolybdenum(III) compounds [Mo 2 Cp 2 (μ-SMe) 2 (μ-X)(μ-Y)] (X = PPh 2 , Y = Cl ( 1 ); X = SCH 3 , Y = Br ( 3 ), I( 4 )) have been studied. Syntheses and X-ray structures of the new bromo and iodo analogues of [Mo 2 Cp 2 (μ-SMe) 3 (μ-Cl)] ( 2 ) are reported. While preparing 3 a side-product 5 was obtained and structurally characterised as the Mo 5 system [{Mo 2 Cp 2 Br(μ-O)(μ-SMe) 2 } 2 (μ-MoO 4 )], containing a {Mo IV –Mo IV –O–(Mo VI O 2 )–O–Mo IV –Mo IV } unit. The influence of the bridging groups on the structures and electrochemical behaviour of the complexes [Mo 2 Cp 2 (μ-SMe) 2 (μ-X)(μ-Y)] 1 – 4 has been investigated. In MeCN–[NBu 4 ][PF 6 ] the first oxidation of [Mo 2 Cp 2 (μ-SMe) 2 (μ-PPh 2 )(μ-Cl)] ( 1 ) is quasi-reversible, contrasting with the essentially irreversible first oxidation of the thiolate analogue [Mo 2 Cp 2 (μ-SMe) 3 (μ-Cl)] ( 2 ) under similar conditions. The effects of lowering the temperature or increasing the scan rate on the oxidation of 1 were examined: the initial quasi-reversible oxidation at first became irreversible but at still higher scan rates or lower temperatures the oxidation was again quasi-reversible. This suggests that the oxidation of 1 in MeCN is followed by reversible coordination of acetonitrile to afford the species [Mo 2 Cp 2 (μ-SMe) 2 (μ-PPh 2 )(Cl)(MeCN)] + ( 7 + ). Cyclic voltammetry of [Mo 2 Cp 2 (μ-SMe) 3 (μ-Y)](Y = Br ( 3 ) or I ( 4 )) showed two quasi-reversible diffusion-controlled oxidation steps in CH 2 Cl 2 –[NBu 4 ][PF 6 ] or thf–[NBu 4 ][PF 6 ]. In acetonitrile, the fast loss of the halide ligands results in the formation of [Mo 2 Cp 2 (μ-SMe) 3 (MeCN) 2 ] + species.

cited By 10; International audience; A series of chemical and electrochemical transformations of systems in which a Mo2Cp2(μ-SMe)3 core is bridged by a μ-C2HnR ligand (n = 0-4) are described in this paper. The reaction of the alkylidene complex [Mo2Cp2(μ-SMe) 3(μ-η1:η2-CHCH2Tol)] (BF4) (1) with LiBun at 0°C produces the μ-σ,π-vinyl complex [Mo2Cp2(μ-SMe) 3(μ-η1:η2-CH=CHTol] (2) in good yield. The molecular structure of 2 has been confirmed by X-ray analysis. Upon treatment with NaBEL4 1 is readily converted into the semibridging alkyl species [Mo2Cp2(μ-SMe)3(μ-CH 2CH2Tol)] (3), which is also formed by electrochemical reduction of 1 in acidic medium. NMR and X-ray diffraction studies of 3 are consistent with, but do not definitively establish, the presence of a η1 α-agostic interaction. Density functional theory has been used to confirm the presence of agostic interactions in both 1 and 3 and also to explore the exchange pathways for these hydrocarbyl dimolybdenum systems. Electrochemical transformation of the μ-alkylidene complex 1 gives 3 as the major product when acid is present and a mixture of 2 and 3 when acid is absent, production of 2 being favored by low initial concentrations of 1. Theoretical, spectroscopic, and diffraction data are used to explain the formation and structures of closely related [Mo2Cp 2(μ-SMe)3(μ-C2HnR] z- complexes (n = 0-4 and z = 0, 1), including 1-3. © 2005 American Chemical Society.

Treatment of [Mo2(Cp)2(μ-SMe)3(MeCN)2]+ (1+) with NO3– or NO2– results in the conversion of one terminally bound acetonitrile ligand into an amidato bridge. The reaction produces [Mo2(Cp)2(μ-SMe)3{μ-η1,η1-OC(Me)NH}]0/+ (20/+) and involves the formation of an intermediate, which was detected by cyclic voltammetry but which could not be isolated, and which likely arises from the substitution of the NOx anion for one MeCN ligand. The electrochemical behaviour of 2+ was studied by cyclic voltammetry in THF and MeCN. The reduction of 2+ in the presence of acid (HBF4/H2O or HBF4/Et2O) in these solvents leads to the release of the amidate bridge. Controlled-potential electrolysis of 2+ in MeCN in the presence of acid produces 1+ quantitatively; the charge consumed (>1 F mol–1 of 1+) indicates that electrons are also used to reduce protons. This was confirmed by the formation of 2+ (in variable amounts depending on the conditions) on treating 2 with acid. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The internalization of various cargo proteins and lipids from the mammalian cell surface occurs through the clathrin and lipid-raft endocytic pathways. Protein-lipid and protein-protein interactions control the targeting of signalling molecules and their partners to various specialized membrane compartments in these pathways. This functions to control the activity of signalling cascades and the termination of signalling events, and therefore has a key role in defining how a cell responds to its environment.

The reduction of [Mo2(Cp)2(µ-SMe)3(µ-O)]+ (1+) has been investigated by cyclic voltammetry and controlled-potential electrolysis in THF- and MeCN/NBu4PF6 without added acid or in the presence of various acids HX (HX: HTsO, CF3CO2H, HBF4). Reduction in the presence of acid follows an ECrevE mechanism in which the intermediate chemical step is an acid-base equilibrium between 1 and [Mo2(Cp)2(µ-SMe)3(µ-OH)]+ (2+). This electrochemical process is followed by protonation of the neutral µ-hydroxo complex 2 to afford different products which depend both on the solvent (THF or MeCN) and on the nature of the acid. Controlled-potential electrolysis of 1+ in the presence of HX (2 equiv.) leads to the generation of binding sites and finally gives products identical to those obtained from protonation of 2 by HX. The complex [Mo2(Cp)2(µ-SMe)3(µ-η1,η1-OCOCF3)] (3) which can be obtained either by protonation of 2 by CF3CO2H or by reduction of 1+ in the presence of CF3CO2H, has been characterized crystallographically. In the presence of HBF4 protonation of 1+ gives 22+. The reactivity of 2+ and of the complexes [Mo2(Cp)2(µ-SMe)3(H2O)(TsO)] (4) and [Mo2(cp)2(µ-SMe)3(H2O)L]+ (L = H2O or THF) (6+), all of which contain a terminal aqua ligand, has also been investigated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Only a minority of chronic lymphocytic leukemia (CLL) patients harboring a positive direct antiglobulin test (DAT) will develop autoimmune hemolytic anemia (AIHA). In a single institution cohort of 378 CLL patients, 56 patients (14.8%) had at least one positive DAT during the course of the disease, either at diagnosis or later. We found no relationship between the time of the first positive DAT and overall survival (OS). However, patients with a positive DAT who did not develop AIHA had the same adverse outcome as patients who developed AIHA. Of the patients who were in Binet stage A at diagnosis, those with a positive DAT had a significantly shorter OS, regardless of their IGHV mutational status, however, there was a strong association with VH1-69. By multivariate analysis, a positive DAT was found to be an independent adverse prognostic factor for OS. Thus, DAT represents a strong adverse prognostic factor and its determination should be repeated during follow-up.

The purpose of this study was to evaluate the time-course effect of a 36-h treatment with ACTH (10−8m), transforming growth factor-β1 (TGFβ1; 10−10m), angiotensin II (AngII; 10−7m), and insulin-like growth factor I (IGF-I; 10−8m) on the steroidogenic capacity of bovine adrenocortical cells (BAC) and on messenger RNA (mRNA) levels of ACTH receptor, cytochrome P450c17, 3β-hydroxysteroid dehydrogenase (3βHSD), steroidogenic acute regulatory protein (StAR), and StAR protein. ACTH and IGF-I enhanced, in a time-dependent manner, the acute 2-h ACTH-induced cortisol production, whereas TGFβ1 and AngII markedly reduced it. ACTH, IGF-I, and AngII increased ACTH receptor mRNA, but the opposite was observed after TGFβ1 treatment. ACTH and IGF-I increased P450c17 and 3βHSD mRNAs, whereas AngII and TGFβ1 had the opposite effects. However, the effects of the four peptides on ACTH-induced cortisol production appeared before any significant alterations of the mRNA levels occurred. The most marked and rapid effect of the four peptides was on StAR mRNA. The stimulatory effect of ACTH was seen within 1.5 h, peaked at 4–6 h, and declined thereafter, but at the end of the 36-h pretreatment, the levels of StAR mRNA and protein were higher than those in control cells. IGF-I also enhanced StAR mRNA levels within 1.5 h, and these levels remained fairly constant. The effects of AngII on StAR mRNA expression were biphasic, with a peak within 1.5–3 h, followed by a rapid decline to almost undetectable levels of both mRNA and protein. TGFβ1 had no significant effect during the first 3 h, but thereafter StAR mRNA declined, and at the end of the experiment the StAR mRNA and protein were almost undetectable. Similar results were observed when cells were treated with ACTH plus TGFβ1. A 2-h acute ACTH stimulation at the end of the 36-h pretreatment caused a higher increase in StAR mRNA and protein in ACTH- or IGF-I-pretreated cells than in control cells, which, in turn, had higher levels than cells pretreated with TGFβ1, ACTH plus TGFβ1, or AngII.These results and the fact that the stimulatory (IGF-I) or inhibitory (AngII and TGFβ1) effects on ACTH-induced cortisol production were more pronounced than those on the ability of cells to transform pregnenolone into cortisol strongly suggest that regulation of StAR expression is one of the main factors, but not the only one, involved in the positive (IGF-I) or negative (TGFβ1 and AngII) regulation of BAC for ACTH steroidogenic responsiveness. A high correlation between steady state mRNA level and acute ACTH-induced cortisol production favors this conclusion.

Transforming growth factor beta (TGFbeta) has been reported to be a potent growth inhibitor of epithelial cells. The purpose of the present work was to study in vitro and in vivo the effects of overexpression of a dominant-negative type II TGFbeta receptor on the proliferation and differentiation of Y-1 cells. Stable transfections were performed with a mutant TbetaRII (TbetaRII-KR) fused with the Enhanced Fluorescent Green Protein (EGFP). The expression of this fusion protein and its overexpression were demonstrated by northern blot and immunoblot with EGFP and TbetaRII probes and antibodies respectively. The membrane localization of this fusion protein was confirmed by confocal microscopy. The functionality of this fusion protein was demonstrated by its blocking effects on TGFbeta action on DNA synthesis and on Y-1 expression of steroidogenic acute regulatory protein (StAR) and 3beta-hydroxysteroid dehydrogenase (3beta-HSD). Moreover, in nude mice the tumorigenicity of cells stably transfected with the fusion protein was higher than that of cells stably transfected with EGFP alone. Taken together, the present results show that TbetaRII-KR/EGFP blocks the effects of TGFbeta1 on Y-1 cells and acts as a potent dominant-negative receptor preventing TGFbeta signaling.

Transforming growth factor beta 1 (TGF beta 1) is a potent inhibitor of several differentiated functions in bovine adrenal fasciculata cells (BAC). In addition, these cells express and secrete this factor. To determine whether this peptide plays an autocrine role in BAC, cells were transfected with 10 microM unmodified sense (SON) or antisense (AON) oligonucleotide complementary to the translation initiation region of the TGF beta 1 mRNA in an attempt to inhibit TGF beta 1 protein synthesis. We investigated first, the cellular uptake, the stability, and the intracellular distribution of 32P-labeled TGF beta 1 AON and SON; and second, the effects of both oligonucleotides on BAC specific functions. We have demonstrated that in BAC, the TGF beta 1 AON uptake reached a plateau after 8 h of transfection (16% of the radioactivity added) and remained fairly constant for at least 24 h. In contrast, the uptake of TGF beta 1 SON reached a plateau after 2 h of transfection (8% of the radioactivity added), remained stable for only 3 h, and then declined. After 8 h of transfection, followed by 44 h of culture without oligonucleotides, the intracellular level of TGF beta 1 AON was still high with about 8% of the radioactivity added, whereas that of TGF beta 1 SON represented only 1.2%. Moreover, AON was present in the cytoplasmic and nuclear fractions, and it was hybridized in both compartments. However, TGF beta 1 SON was present mainly in the cytoplasmic fraction where it was not hybridized. Neither TGF beta 1 AON nor SON modified TGF beta 1 mRNA levels; however, TGF beta 1 AON, but not SON, caused the disappearance of TGF beta 1 immunoreactivity inside the cells. Finally, the steroidogenic responsiveness of BAC transfected with TGF beta 1 AON increased about 2-fold, and this was associated with a 2-fold increase of the mRNA levels of both cytochrome P450 17 alpha-hydroxylase and 3 beta-hydroxysteroid dehydrogenase. Neither TGF beta 1 SON nor a scrambled oligonucleotide containing the same number of G nucleotides as TGF beta 1 AON had any effect on these parameters. Thus, these studies demonstrate that TGF beta 1 has an autocrine inhibitory effect on BAC differentiated functions, an effect that can be overcome by TGF beta 1 AON.

Technological developments of multiparametric flow cytometry come along with the generation of new dyes. The APC-tandem dyes, which combine the fluorophores APC and Cy7/H7, allow the detection of a specific signal in the APC-Cy7/H7 channel along with an unexpected nonspecific signal in the APC channel. Depending on the magnitude of the latter, it may be a handicap for interpreting the data of multicolor labeling experiments. We investigated the alteration of the APC-tandem dyes by labeling peripheral blood cells with antibodies directed toward leukocyte surface proteins and by analyzing cells by flow cytometry. Our results show that the APC-Cy7/H7 tandem fluorochromes degraded over time. Nonspecific APC signal was observed with the various antibodies tested only upon cell attachment but not under bead linkage. Moreover, the percentage of degradation of the APC-Cy7/H7 dyes was dependent on the cell type analyzed. Interestingly, nonspecific APC signal strongly decreased when the metabolic activity of immunolabeled cells was inhibited or when cells were incubated with vitamin C. This study demonstrates that the APC-tandem dyes are the target of cell-dependent degradation, which may be antagonized. These findings will allow cytometer users to optimize their multicolor panels.

Signaling by the transforming growth factor-β (TGF-β) family of growth factors involves cell surface receptor serine/threonine kinases and downstream components such as SARA and Smurfs, which bind the receptor substrates called the Smad proteins. These components partition between two endocytic pathways, which lead to two separate functions in TGF-β signaling. On the one hand, clathrin-dependent endocytosis promotes signaling by leading the receptor to the early endosome where SARA is localized. On the other, non-clathrin pathways, which are enriched for the Smurf ubiquitin ligases, lead the receptor to degradation. However, in polarized cells, ligand addition induces TGF-β receptor trafficking into junctional regions of the cell where activation of Smad-dependent and -independent pathways mediates the process of epithelial-to-mesenchymal transition, which is critical during development and tumorigenesis. In this chapter, we will focus on how compartmentalization of TGF-β receptors and their downstream components controls TGF-β signaling and its biological functions

The conjugation of ubiquitin to proteins involves a cascade of activating (E1), conjugating (E2), and ubiquitin-ligating (E3) type enzymes that commonly signal protein destruction. In TGFbeta signaling the inhibitory protein Smad7 recruits Smurf2, an E3 of the C2-WW-HECT domain class, to the TGFbeta receptor complex to facilitate receptor degradation. Here, we demonstrate that the amino-terminal domain (NTD) of Smad7 stimulates Smurf activity by recruiting the E2, UbcH7, to the HECT domain. A 2.1 A resolution X-ray crystal structure of the Smurf2 HECT domain reveals that it has a suboptimal E2 binding pocket that could be optimized by mutagenesis to generate a HECT domain that functions independently of Smad7 and potently inhibits TGFbeta signaling. Thus, E2 enzyme recognition by an E3 HECT enzyme is not constitutively competent and provides a point of control for regulating the ubiquitin ligase activity through the action of auxiliary proteins.

The Golgi enzyme β1,6 N-acetylglucosaminyltransferase V (Mgat5) is up-regulated in carcinomas and promotes the substitution of N-glycan with poly N-acetyllactosamine, the preferred ligand for galectin-3 (Gal-3). Here, we report that expression of Mgat5 sensitized mouse cells to multiple cytokines. Gal-3 cross-linked Mgat5-modified N-glycans on epidermal growth factor and transforming growth factor–β receptors at the cell surface and delayed their removal by constitutive endocytosis. Mgat5 expression in mammary carcinoma was rate limiting for cytokine signaling and consequently for epithelial-mesenchymal transition, cell motility, and tumor metastasis. Mgat5 also promoted cytokine-mediated leukocyte signaling, phagocytosis, and extravasation in vivo. Thus, conditional regulation of N-glycan processing drives synchronous modification of cytokine receptors, which balances their surface retention against loss via endocytosis.

Endocytosis of cell surface receptors is an important regulatory event in signal transduction. The transforming growth factor beta (TGF-beta) superfamily signals to the Smad pathway through heteromeric Ser-Thr kinase receptors that are rapidly internalized and then downregulated in a ubiquitin-dependent manner. Here we demonstrate that TGF-beta receptors internalize into both caveolin- and EEA1-positive vesicles and reside in both lipid raft and non-raft membrane domains. Clathrin-dependent internalization into the EEA1-positive endosome, where the Smad2 anchor SARA is enriched, promotes TGF-beta signalling. In contrast, the lipid raft-caveolar internalization pathway contains the Smad7-Smurf2 bound receptor and is required for rapid receptor turnover. Thus, segregation of TGF-beta receptors into distinct endocytic compartments regulates Smad activation and receptor turnover.

Introduction and hypothesis : B-acute lymphoblastic leukemia (B-ALL) expressing the fusion transcript ETV6/RUNX1 is one of the most frequent subtype of childhood leukemia. This disease is associated with a good survival rate but 5 to 10% of patients relapse more than five years after treatment most notably in extra-hematopoietic sanctuary sites like testis. CD9, a protein member of the tetraspanin family, has been shown to be under-expressed in ETV6/RUNX1 B-ALL. This protein is involved in hematopoietic stem cell engraftment. Its expression has also been correlated with the risk of metastasis and is associated with a poor clinical outcome in various types of cancer. Our hypothesis is that CD9, through its functional properties on migration and homing, could be a key actor of ETV6/RUNX1 leukemia relapse. The purpose of our study was to investigate the effect of CD9 expression on motility and engrafment of pre-B lymphocytes. Methods and results : We used the human pre-B lymphoblastic REH cell line which express CD9. By lentiviral transduction of small hairpin RNAs targeting CD9 mRNA, we generated REH cells depleted in CD9 protein. We performed engraftment assays in vivo using Nod Scid Gamma immunodeficient mice. Mice injected with REH cells depleted in CD9 had a longer survival rate than mice injected with REH control cells. In vitro analysis of adhesion on fibronectin demonstrated that cellular adhesion is dependent of membrane expression of CD9. As well, the more CD9 is expressed, the higher migration rate in response to CXCL12 chemokine is. F‐actin labelling after CXCL12 stimulation showed also an increased F‐actin polymerization in CD9‐positive cells and the formation of actin extensions where CD9 and actin are colocalized. No modifications in CXCR4 (receptor of CXCL12) internalization has been found in CD9 depleted cell lines, which suggests that CD9 does not affect the receptor itself but the signalling pathway downstream the receptor. We investigated the activation of RAC1 protein, a Rho GTPase known to induce the formation of actin-rich lamellipodia in diverse cellular functions including migration. We demonstrated that cells depleted in CD9 have lost their ability to activate RAC1 in response to CXCL12. The inhibition and the depletion of RAC1 respectively have the same effect as CD9 depletion on the migration in response to CXCL12 in vitro and on the survival in vivo. Finally, we tested the ability of REH cells and REH depleted in CD9 cells to migrate to testis in vivo after xenograft in mouse model. We showed that only CD9 positive-REH cells were found in testis tissue after xenograft. Moreover we tested in vitro, the ability of testis tissue to induce the migration of REH cells in a Boyden chamber model. We showed that testis tissue induced the migration of REH cells and this migration was strongly decreased using either an inhibitor of CXCR4, an inhibitor of RAC1 or an antibody targeting specifically CD9. Conclusion : Our data show that CD9 is a key actor in pre‐B lymphoblasts adhesion, CXCL12 dependant migration and actin remodelling. We show for the first time in pre-B cells a link between CD9, RAC1 pathway and homing in testis which is a preferential site of late relapse. This work is supported by CNRS, University of Rennes 1, University Hospital of Rennes, Ligue Régionale contre le Cancer (sections 22, 35 and 56) (MPA, VG, MBT), Région Bretagne (MPA, MBT, VG), SFR Biosit UMS 3480 (VG, MBT), Association Laurette Fugain (VG). Disclosures No relevant conflicts of interest to declare.

The expression and the maintenance of specific differentiated function of Leydig cells are regulated not only by gonadotropin but by locally produced factors, which may act as autocrine regulators. Many factors, in particular growth factors, have been postulated to have such a type of effect on testicular cells, but very few fulfilled the three criteria required to establish a paracrine/autocrine role: (a) presence of receptors and biological action on local cells; (b) local secretion regulated by physiological signals; and (c) blockade of the factor or its receptors must modify the function of local cells. In the present work we demonstrate that two factors, insulin-like growth factor 1 (IGF-I) and transforming growth factor beta1 (TGFbeta1) fulfilled the three criteria: (a) IGF-I stimulates the transcription of the genes encoding Leydig cell differentiated function, leading to an enhanced steroidogenic responsiveness to LH/hCG; (b) Leydig cells (LC) express and secrete IGF-I and this secretion is enhanced by hCG; and (c) incubation of LC with IgG anti-IGF-I, but not with IgG-control, markedly reduced the steroidogenic responsiveness to LH/hCG. In contrast to IGF-I, TGFbeta is a potent inhibitor of LC differentiated function. Moreover, LC express TGFbeta1 mRNA and secrete this peptide. To prove that the locally produced TGFbeta has an autocrine role, LC were transfected with 10 microM of an antisense oligonucleotide (AON) complementary to the translation initiation region of TGFbeta1 mRNA. Transfection with AON but not with sense deoxynucleotide induces a complete disappearance of TGFbeta immunoreactivity in LC and an enhanced hCG-induced testosterone production by LC. This increased steroidogenic responsiveness was associated with a significant enhancement of both LH/hCG receptor mRNA and P450c17 mRNA. Taken together, the above results show that both factors play an autocrine role, although opposite, on Leydig cell function.

Cellular movement from one place to another is regulated by various guidance cues. The precise perception of these signals in the three-dimensional environment of a multicellular organism is remarkably complex. Recent work is now revealing that guided cell movement also requires spatial control of signaling events by endocytic dynamics.

Autoimmune cytopenias represent a well-known complication of chronic lymphocytic leukemia (CLL). The most frequent one is autoimmune haemolytic anemia (AIHA), occurring in about 5% of the patients during the course of the disease. The prognostic significance of autoimmune cytopenias remains uncertain and controversial. In previous studies, a positive direct antiglobulin test (DAT) was found in up to 35% of CLL cases, however only a minority of the patients would develop AIHA at any time of the disease. The aim of this monocentric study was to explore the clinical and biological characteristics and the outcome of CLL patients showing a positive direct antiglobulin test at any time during the course of the disease. We reviewed all CLL patients seen at our institution who had at least one positive DAT between January 2007 and May 2013. Fifty-four patients were found, representing about 10% of our CLL cohort. The sex ratio was 1,8 (35M/19F). Median age at diagnosis was 66,2 years (range 44,7 to 87,3). According to the Binet classification, 41 (76 %) patients were in stage A, 7 in stage B, and 6 in stage C. Study of usual prognostic parameters evidenced that these patients represented a very high risk group: 82% of cases harbored unmutated IGHV, and CD38 was expressed in 60% cases. Cytogenetic alterations were studied by FISH analysis: 11q deletion, trisomy 12 and 17p deletion were found in 12,5%, 22,9% and 14,3% cases respectively. In this cohort, with a median follow up of 85 months, 41 (76 %) patients required treatment. The first line of treatment was initiated for CLL progression in 33 cases, for symptomatic AIHA along with CLL progression in 5, and for symptomatic AIHA (without CLL progression) in 3. The median time to first treatment was very short (16 months), and the median overall survival of this cohort was 84 months. In 22 cases, the DAT was positive from the time of diagnosis, while in 34 patients it became positive later during the course of CLL. Only 19 patients (35%) developed symptomatic AIHA. DAT specificity was IgG, IgG+ C or C for respectively 36, 10 and 8 patients. Interestingly, there was no impact of the time of first positive DAT during the course of the disease (at diagnosis or later). Moreover, occurrence of a symptomatic AIHA had no impact on treatment free survival or overall survival when compared with cases with positive DAT only. Among these cases, 41 were in stage A at diagnosis and up to 78% harbored unmutated IGHV (as compared with 30 % in our institutional stage cohort). In order to evaluate the impact of a positive DAT on a homogenous population, we focused on the 31 IGHV unmutated stage A cases and compared them with our cohort of IGHV unmutated stage A with consistently negative DAT. We found a significant prevalence of VH1-69 and VH 3-21 use (43 %) and a high percentage belonging to a stereotyped subset (34%). The majority of the cases (19/28 tested) were responders to in vitro B-cell receptor stimulation by anti IgM. In this population, time to first treatment (26 months) was slightly shorter but median overall survival (55 months) was significantly reduced highlighting the poor response to treatment. In conclusion, occurrence of a positive DAT at any time of the course of CLL is associated with poor outcome and has the same adverse prognostic impact as the onset of a symptomatic AIHA. Moreover, study of B-Cell receptor (BCR stimulation by anti-IgM, CDR3 stereotypy) show that these patients may represent a pathophysiological distinct subgroup in which antigen stimulation is likely to play a major role. Disclosures: No relevant conflicts of interest to declare.

Introduction CD9 is a membrane protein, member of the tetraspanin family. Recent publications have reported the role of CD9 on engraftment of hematopoietic stem cells, and on cancer stem cell potential. The expression of CD9 has been correlated to the risk of metastases and to a poor clinical outcome in various types of cancer. Surprisingly, CD9 protein is downregulated in ETV6/RUNX1 pre-B acute lymphoblastic leukemia. The purpose of our study is to investigate the effect of CD9 expression on migration and engraftment abilities of pre-B lymphocytes. Materials and Methods The CD9-positive Nalm6 and REH (ETV6/RUNX1) pre-B cells were used. By lentiviral transduction of shRNA targeting mRNA, we generated Nalm6 and REH cell lines depleted in CD9 protein. Engraftment tests were performed in vivo using Nod Scid Gamma immunodeficient mice. REH and Nalm6 cells were detected in bone marrow by CD10 and respectively CD19 or HLA-DR labelling. Ability of the different cell lines to adhere on fibronectin and to migrate through double chambers system in response to CXCL12 were measured in vitro. We also investigated the presence of membrane villosities on REH and REH shCD9 cell surface by scanning electron microscopy. Finally, F-actin polymerization after CXCL12 stimulation was measured by rhodamin-phalloidin labelling. Results In vivo engrafments tests showed that the human cells detected in bone marrow is strongly enriched in CD9 positive cells compared to the initially injected population. This result suggests that CD9 facilitates pre-B lymphobasts homing. An in vitro analysis of adhesion on fibronectin demonstrated that cellular adhesion is dependent on membrane expression of CD9. As well, the more CD9 is expressed, the higher the migration rate in response to CXCL12 chemokine is. The analysis of membrane villosities on REH cell surface revealed that cells over expressing CD9 had longer villosity than shCD9 transducted cell lines. Moreover, F-actin labelling after CXCL12 stimulation showed an increased F-actin polymerization in CD9-positive cells and the formation of actin extensions. Conclusion We provide novel evidence that CD9 is a key player of pre-B lymphoblasts engraftment, adhesion and CXCL12 dependant migration. CD9 expression is related to actin remodelling. We are now investigating a potential link between CD9 and RAC1 activation in response to CXC12. Therefore, the expression level of CD9 could impact leukemic blasts abilities to spread and be responsible of relapses. This work is supported by CNRS, University of Rennes 1, University Hospital of Rennes, la Ligue Régionale contre le Cancer (committee 22, 35 and 56) (MPA, VG, MBT), SFR Biosit UMS 3480 (VG, MBT), Association Laurette Fugain (VG) and Europe Career Integration Grant (MBT). Disclosures: No relevant conflicts of interest to declare.

Cells communicate through signals that must be propagated from cell surface to nucleus. Tracking the signals generated by the transforming growth factor-β protein reveals a surprising partner in this process.

Antigen-driven signals are involved in the pathogenesis and progression of CLL with a particular occurrence within the lymph node microenvironment. We have previously shown that ex-vivo BCR engagement promoted simultaneous down-regulation of CXCR4 and CD62L membrane expressions in CLL cells from patients at risk of disease progression only. Functionally, cells down-regulating CXCR4 and CD62L in response to BCR triggering displayed both a reduction in migration toward CXCL12 and in adhesion to lymphatic endothelial cells. We studied a cohort of 73 previously untreated patients, 36 of whom were IGHV mutated and 37 were IGHV unmutated. The distribution of the extent of CXCR4 down-regulation was identical among CXCR4 responders, whether IGHV mutated (median 49% [Q1:28-Q3:62]) or unmutated (median 43% [Q1:31-Q3:66]). We also studied the expression of another chemokine receptor, CXCR5, which is also expressed at the membrane of CLL cells and plays an important role in the homing and trafficking of lymphocytes to the lymphoid follicles. Sustained antigenic stimulation of CLL cell samples (n=25) promoted down-regulation of CXCR4 and CXCR5 in a strictly correlated manner (r= 0,9) i.e. in the same subsets of cells. The extent of BCR-dependent decrease of the two proteins was strikingly representative of the heterogeneous capacity of the B-CLL cells to respond to BCR engagement in a given patient. Moreover, treatment with the specific PKD inhibitor CID755673 blocked significantly both CXCR4 and CXCR5 BCR-mediated decrease (n=11), demonstrating that PKDs specifically target these 2 molecules, whereas CD62L down-regulation was not significantly affected by the PKD inhibitor. At the functional level, treatment with the PKD inhibitor restored CLL cell migration capacity in response to CXCL12. PKD phosphorylation/activation in response to BCR stimulation, which involvesPI3K-d, was required for CXCR4-phosphorylation and its down-regulation. We then studied the clinical relevance of CXCR4 down-regulation after BCR engagement. The capacity to down-regulate CXCR4 was significantly related to shorter PFS (p=0.043). This cohort allowed exploring the link with IGHV mutational status. 36/37 unmutated IGHV cases had a significant CXCR4 down-regulation after in vitro BCR stimulation, in concordance with the ultimately constant progression of the disease. Conversely, IGHV mutated cases fell into two groups: a) one group of 14/36 patients, with very low ( In conclusion, the capacity of cells to down-regulate cell surface chemokine receptors and L-selectin is reflecting the size of the cell subset responding to BCR signaling. Interestingly, BCR signaling capacity to down-regulate CXCR4 is variable among IGHV mutated samples and strongly linked to the presence of lymph nodes as well as disease progression with time. It is tempting to speculate that depending on the BCR-mediated CXCR4/CXCR5 down-regulation capacity, some IGHV mutated patients might not benefit from Btk or PI3K-d inhibitors. Given the crucial importance of down-regulation of these two chemokine receptors after BCR engagement, we suggest that PKD could be promising new therapeutic target in CLL. Disclosures Levy: Roche: Honoraria; Janssen: Honoraria; Gilead: Honoraria. Cymbalista:Janssen: Honoraria, Research Funding; Gilead: Honoraria; Roche: Honoraria; Karyopharm: Honoraria.