Cyclin D1 targets hexokinase 2 to control aerobic glycolysis in myeloma cells.

Cancer cells are characterized by the Warburg effect, a shift from mitochondrial respiration to oxidative glycolysis. We report here the crucial role of cyclin D1 in promoting this effect in a cyclin-dependent kinase (CDK)4/6-independent manner in multiple myeloma (MM) cells. We show that the cyclin D1 oncoprotein targets hexokinase 2 (HK2), a major glycolysis regulator, through two original molecular mechanisms in the cytoplasmic and nuclear compartments. In the cytoplasm, cyclin D1 binds HK2 at the outer mitochondrial membrane, and in the nucleus, it binds hypoxia-inducible factor-1α (HIF1α), which regulates HK2 gene transcription. We also show that high levels of HK2 expression are correlated with shorter event-free survival (EFS) and overall survival (OS) in MM patients. HK2 may therefore be considered as a possible target for antimyeloma therapy.

Lysyl oxidase activity regulates oncogenic stress response and tumorigenesis.

Cellular senescence, a stable proliferation arrest, is induced in response to various stresses. Oncogenic stress-induced senescence (OIS) results in blocked proliferation and constitutes a fail-safe program counteracting tumorigenesis. The events that enable a tumor in a benign senescent state to escape from OIS and become malignant are largely unknown. We show that lysyl oxidase activity contributes to the decision to maintain senescence. Indeed, in human epithelial cell the constitutive expression of the LOX or LOXL2 protein favored OIS escape, whereas inhibition of lysyl oxidase activity was found to stabilize OIS. The relevance of these in vitro observations is supported by in vivo findings: in a transgenic mouse model of aggressive pancreatic ductal adenocarcinoma (PDAC), increasing lysyl oxidase activity accelerates senescence escape, whereas inhibition of lysyl oxidase activity was found to stabilize senescence, delay tumorigenesis, and increase survival. Mechanistically, we show that lysyl oxidase activity favors the escape of senescence by regulating the focal-adhesion kinase. Altogether, our results demonstrate that lysyl oxidase activity participates in primary tumor growth by directly impacting the senescence stability.

Ptf1a/Rbpj complex inhibits ganglion cell fate and drives the specification of all horizontal cell subtypes in the chick retina.

During development, progenitor cells of the retina give rise to six principal classes of neurons and the Müller glial cells found within the adult retina. The pancreas transcription factor 1 subunit a (Ptf1a) encodes a basic-helix-loop-helix transcription factor necessary for the specification of horizontal cells and the majority of amacrine cell subtypes in the mouse retina. The Ptf1a-regulated genes and the regulation of Ptf1a activity by transcription cofactors during retinogenesis have been poorly investigated. Using a retrovirus-mediated gene transfer approach, we reported that Ptf1a was sufficient to promote the fates of amacrine and horizontal cells from retinal progenitors and inhibit retinal ganglion cell and photoreceptor differentiation in the chick retina. Both GABAergic H1 and non-GABAergic H3 horizontal cells were induced following the forced expression of Ptf1a. We describe Ptf1a as a strong, negative regulator of Atoh7 expression. Furthermore, the Rbpj-interacting domains of Ptf1a protein were required for its effects on cell fate specification. Together, these data provide a novel insight into the molecular basis of Ptf1a activity on early cell specification in the chick retina.

HIF-2alpha specifically activates the VE-cadherin promoter independently of hypoxia and in synergy with Ets-1 through two essential ETS-binding sites.

The mechanisms that are responsible for the restricted pattern of expression of the VE-cadherin gene in endothelial cells are not clearly understood. Regulation of expression is under the control of an approximately 140 bp proximal promoter that provides basal, non-endothelial specific expression. A larger region contained within the 2.5 kb genomic DNA sequence located ahead of the transcription start is involved in the specific expression of the gene in endothelial cells. We show here that the VE-cadherin promoter contains several putative hypoxia response elements (HRE) which are able to bind endothelial nuclear factors under normoxia. The VE-cadherin gene is not responsive to hypoxia but hypoxia-inducible factor (HIF)-2alpha specifically activates the promoter while HIF-1alpha does not. The HRE, that are involved in this activity have been identified. Further, we show that HIF-2alpha cooperates with the Ets-1 transcription factor for activation of the VE-cadherin promoter and that this synergy is dependent on the binding of Ets-1 to DNA. This cooperative action of HIF-2alpha with Ets-1 most probably participates to the transcriptional regulation of expression of the gene in endothelial cells. This mechanism may also be involved in the expression of the VE-cadherin gene by tumor cells in the process of vascular mimicry.

PCR-restriction fragment length polymorphism analysis of a diagnostic 452-base-pair DNA fragment discriminates between Cryptosporidium parvum and C. meleagridis and between C. parvum isolates of human and animal origin.

Genomic DNAs from human Cryptosporidium isolates previously typed by analysis of the 18S ribosomal DNA locus (Cryptosporidium parvum bovine genotype, C. parvum human genotype, Cryptosporidium meleagridis, and Cryptosporidium felis) were used to amplify the diagnostic fragment described by Laxer et al. (M. A. Laxer, B. K. Timblin, and R. J. Patel, Am. J. Trop. Med. Hyg., 45:688-694, 1991). The obtained 452-bp amplified fragments were sequenced and aligned with the homologous Cryptosporidium wrairi sequence. Polymorphism was exploited to develop a restriction fragment length polymorphism method able to discriminate Cryptosporidium species and C. parvum genotypes.

Molecular characterization of Cryptosporidium isolates obtained from humans in France.

Cryptosporidium parvum is usually considered the agent of human cryptosporidiosis. However, only in the last few years, molecular biology-based methods have allowed the identification of Cryptosporidium species and genotypes, and only a few data are available from France. In the present work, we collected samples of whole feces from 57 patients from France (11 immunocompetent patients, 35 human immunodeficiency virus [HIV]-infected patients, 11 immunocompromised but non-HIV-infected patients) in whom Cryptosporidium oocysts were recognized by clinical laboratories. A fragment of the Cryptosporidium 18S rRNA gene encompassing the hypervariable region was amplified by PCR and sequenced. The results revealed that the majority of the patients were infected with cattle (29 of 57) or human (18 of 57) genotypes of Cryptosporidium parvum. However, a number of immunocompromised patients were infected with C. meleagridis (3 of 57), C. felis (6 of 57), or a new genotype of C. muris (1 of 57). This is the first report of the last three species of Cryptosporidium in humans in France. These results indicate that immunocompromised individuals are susceptible to a wide range of Cryptosporidium species and genotypes.

The Ets family contains transcriptional activators and repressors involved in angiogenesis.

The Ets family contains a growing number of transcriptional activators and inhibitors, which activity is regulated by phosphorylation and protein-protein interactions. Among these factors, Ets1, Erg1 and Fli1 are expressed in endothelial cells during angiogenesis in normal and pathological development. The expression of these transcription factors is regulated by angiogenic factors in cultured endothelial cells, as well as by various stresses occurring during angiogenesis. Transfection experiments and transgenic mice analysis revealed that Ets family members are involved in the transcriptional regulation of endothelial specific genes such as those encoding Tie1 and -2, VEGFR1 and -2 and VE-Cadherin. In vitro studies plead for a role of Ets family members in endothelial cell adhesion, spreading and motility. Gene inactivation experiments show that Ets1 is dispensable for embryonic development. The phenotype of knocked-out embryos indicates that Tel is required for maintenance of the developing vascular network in the yolk sac. Altogether, we suggest that Ets family members act both positively and negatively during the different steps of the angiogenic process. The regulation of the initiation of gene transcription arises from the combined activity of different transcriptional regulators. Therefore very few transcription factors are specific for a physiological process, or a given cell type. The transcriptional network that regulates blood vessel formation involves transcription factors which are expressed in a variety of situations. The Lung Kruppel Like Factor (LKLF) which is required for blood vessel stabilisation during murine development is also expressed in the primitive vertebrae and in the lung of the adult (C.T. Kuo, M.L. Veselits, K.P. Barton, M.M. Lu, C. Clendenin, J.M. Leiden, The LKLF transcription factor is required for normal tunica media formation and blood vessel stabilisation during murine embryogenesis, Genes Dev. 11 (22) (1997) 2996-3006). Scl/Tal1 which is essential for angiogenic remodelling of the yolk sac capillary network (J.E. Visvader, Y. Fujiwara, S.H. Orkin, Unsuspected role for the T-cell leukemia protein SCL/tal-1 in vascular development, Genes Dev. 12 (4) (1998) 473-479), is involved in blood cell development and is also expressed in the developing brain. The EPAS transcription factor which was thought to be endothelial cell specific in the mouse embryo (H. Tian, S.L. McKnight, D.W. Russell, Endothelial PAS domain protein 1 (EPAS1), a transcription factor selectively expressed in endothelial cells, Genes Dev. 11 (1) (1997) 72-82) is also expressed in the liver, kidney and cells of the sympathetic nervous system of the chick embryo (J. Favier, H. Kempf, P. Corvol, J.M. Gasc, Cloning and expression pattern of EPAS1 in the chicken embryo. Colocalization with tyrosine hydroxylase, FEBS Lett. 462 (1-2) (1999) 19-24). Ets1, which expression was originally detected in lymphoid cells of adult tissues, has been the first transcription factor to be identified in endothelial cells during angiogenesis in the embryo (B. Vandenbunder, L. Pardanaud, T. Jaffredo, M.A. Mirabel, D. Stehelin, Complementary patterns of expression of c-etsl, c-myb and c-myc in the blood-forming system of the chick embryo, Development 107 (1989) 265-274 [5]) and in tumours (N. Wernert, M.B. Raes, P. Lassalle, M.P. Dehouck, B. Gosselin, B. Vandenbunder, D. Stehelin, The c-ets 1 proto-oncogene is a transcription factor expressed in endothelial cells during tumor vascularisation and other forms of angiogenesis in man, Am. J. Path. 140 (1992) 119-127 [6]). Since then, the Ets family has extended and this review will emphasise the relationships between these factors and angiogenesis.

The ciliary neurotrophic factor receptor alpha component induces the secretion of and is required for functional responses to cardiotrophin-like cytokine.

Ciliary neurotrophic factor (CNTF) is involved in the survival of a number of different neural cell types, including motor neurons. CNTF functional responses are mediated through a tripartite membrane receptor composed of two signalling receptor chains, gp130 and the leukaemia inhibitory factor receptor (LIFR), associated with a non-signalling CNTF binding receptor alpha component (CNTFR). CNTFR-deficient mice show profound neuronal deficits at birth, leading to a lethal phenotype. In contrast, inactivation of the CNTF gene leads only to a slight muscle weakness, mainly during adulthood, suggesting that CNTFR binds to a second ligand that is important for development. Modelling studies of the interleukin-6 family member cardiotrophin-like cytokine (CLC) revealed structural similarities with CNTF, including the conservation of a site I domain involved in binding to CNTFR. Co-expression of CLC and CNTFR in mammalian cells generates a secreted composite cytokine, displaying activities on cells expressing the gp130-LIFR complex on their surface. Correspondingly, CLC-CNTFR activates gp130, LIFR and STAT3 signalling components, and enhances motor neuron survival. Together, these observations demonstrate that CNTFR induces the secretion of CLC, as well as mediating the functional responses of CLC.

Signaling pathways recruited by the cardiotrophin-like cytokine/cytokine-like factor-1 composite cytokine: specific requirement of the membrane-bound form of ciliary neurotrophic factor receptor alpha component.

Ciliary neurotrophic factor (CNTF) is a cytokine supporting the differentiation and survival of a number of neural cell types. Its receptor complex consists of a ligand-binding component, CNTF receptor (CNTFR), associated with two signaling receptor components, gp130 and leukemia inhibitory factor receptor (LIFR). Striking phenotypic differences between CNTF- and CNTFR-deficient mice suggest that CNTFR serves as a receptor for a second developmentally important ligand. We recently demonstrated that cardiotrophin-like cytokine (CLC) associates with the soluble orphan receptor cytokine-like factor-1 (CLF) to form a heterodimeric cytokine that displayed activities only on cells expressing the tripartite CNTF receptor on their surface. In this present study we examined the membrane binding of the CLC/CLF composite cytokine and observed a preferential interaction of the cytokine with the CNTFR subunit. Signaling pathways recruited by the CLC/CLF complex in human neuroblastoma cell lines were also analyzed in detail. The results obtained showed an activation of Janus kinases (JAK1, JAK2, and TYK2) leading to a tyrosine phosphorylation of the gp130 and LIFR. The phosphorylated signaling receptors served in turn as docking proteins for signal transducing molecules such as STAT3 and SHP-2. In vitro analysis revealed that the gp130-LIFR pathway could also stimulate the phosphatidylinositol 3-kinase and the mitogen-activated protein kinase pathways. In contrast to that reported before for CNTF, soluble CNTFR failed to promote the action CLC/CLF, and an absolute requirement of the membrane form of CNTFR was required to generate a functional response to the composite cytokine. This study reinforces the functional similarity between CNTF and the CLC/CLF composite cytokine defining the second ligand for CNTFR.

[Role of the ETS transcription factors in the control of endothelial-specific gene expression and in angiogenesis]. / Rôle des facteurs de transcription ETS dans le contrôle de la spécificité d'expression endothéliale et l'angiogenèse.

The transcription factors of the ETS family are involved in the control of the endothelial-specific expression of genes that are important for the formation of new blood vessels. The analysis of the expression pattern of ets1, the gene inactivation of tel and fli1, the in vitro analysis of potential target genes of ETS factors in endothelial cells, the in vivo studies of the promoter regions of endothelial-specific genes all demonstrate a role for ETS factors in this specificity. However, the precise role of individual ETS factors in the endothelial identity and in angiogenesis in general remains difficult to understand in vivo.

[Cryptosporidium and wildlife: a risk for humans?]. / Cryptosporidium et faune sauvage: un risque pour l'homme?

The present review underlines the knowledge of Cryptosporidium, especially its biodiversity and transmission. The presence of the parasite in different mammal host species is discussed with real, potential risk of transmission to humans. The potential role of insects in mechanical transmission of the parasite is evaluated by experimental protocols. The cost of cryptosporidiosis at health and economic levels are mentioned, which emphasises the importance of detection and identification of the parasite in the environment and in wild mammal species, using specific molecular tools. Potential measures to be accomplished in order to fight off cryptosporidiosis are also noted.

CLF associates with CLC to form a functional heteromeric ligand for the CNTF receptor complex.

Ciliary neurotrophic factor (CNTF) is a cytokine supporting the differentiation and survival of various cell types in the peripheral and central nervous systems. Its receptor complex consists of a non-signaling alpha chain, CNTFR, and two signaling beta chains, gp130 and the leukemia inhibitory factor receptor (LIFR). Striking phenotypic differences between CNTF- and CNTFR-deficient mice suggest that CNTFR serves as a receptor for a second, developmentally important ligand. We have identified this factor as a stable secreted complex of cardiotrophin-like cytokine (CLC) and the soluble receptor cytokine-like factor-1 (CLF). CLF expression was required for CLC secretion, and the complex acted only on cells expressing functional CNTF receptors. The CLF/CLC complex activated gp130, LIFR and signal transducer and activator of transcription 3 (STAT3) and supported motor neuron survival. Our results indicate that the CLF/CLC complex is a second ligand for CNTFR with potentially important implications in nervous system development.

ETS1 lowers capillary endothelial cell density at confluence and induces the expression of VE-cadherin.

Ets1 is a transcription factor expressed in endothelial cells during angiogenesis but its target genes and function in blood vessel formation are still unknown. We have over-expressed Ets1 as a tagged protein in brain capillary endothelial cells and in 3T3 fibroblasts using a retroviral vector. Over-expression of Ets1 reduced by nearly half cell density at confluence of endothelials but not of fibroblasts. As density at confluence is controlled in part by cadherins, this growth arrest could be due to the up-regulation of these cell contact molecules. Indeed, Ets1 increased the expression of the endothelial-specific VE-cadherin without affecting N-cadherin expression levels. In parallel, both a dominant negative mutant of Ets members and an Ets1 anti-sense oligonucleotide inhibited VE-cadherin expression in endothelial cells. Ets1 bound to two Ets-binding sites located in the proximal region of the VE-cadherin promoter. Mutation of these sites abolished Ets1-induced transactivation of the promoter. The present work is the first demonstration of a function of Ets1 in the regulation of a specific endothelial marker based on its endogenous gene and protein expression.

Development of an ultralow-light-level luminescence image analysis system for dynamic measurements of transcriptional activity in living and migrating cells.

We have developed an approach to study in single living epithelial cells both cell migration and transcriptional activation, which was evidenced by the detection of luminescence emission from cells transfected with luciferase reporter vectors. The image acquisition chain consists of an epifluorescence inverted microscope, connected to an ultralow-light-level photon-counting camera and an image-acquisition card associated to specialized image analysis software running on a PC computer. Using a simple method based on a thin calibrated light source, the image acquisition chain has been optimized following comparisons of the performance of microscopy objectives and photon-counting cameras designed to observe luminescence. This setup allows us to measure by image analysis the luminescent light emitted by individual cells stably expressing a luciferase reporter vector. The sensitivity of the camera was adjusted to a high value, which required the use of a segmentation algorithm to eliminate the background noise. Following mathematical morphology treatments, kinetic changes of luminescent sources were analyzed and then correlated with the distance and speed of migration. Our results highlight the usefulness of our image acquisition chain and mathematical morphology software to quantify the kinetics of luminescence changes in migrating cells.

Identification of a gp130 cytokine receptor critical site involved in oncostatin M response.

Gp130 cytokine receptor is involved in the formation of multimeric functional receptors for interleukin-6 (IL-6), IL-11, leukemia inhibitory factor (LIF), oncostatin M (OSM), ciliary neurotrophic factor, and cardiotrophin-1. Cloning of the epitope recognized by an OSM-neutralizing anti-gp130 monoclonal antibody identified a portion of gp130 receptor localized in the EF loop of the cytokine binding domain. Site-directed mutagenesis of the corresponding region was carried out by alanine substitution of residues 186-198. To generate type 1 or type 2 OSM receptors, gp130 mutants were expressed together with either LIF receptor beta or OSM receptor beta. When positions Val-189/Tyr-190 and Phe-191/Val-192 were alanine-substituted, Scatchard analyses indicated a complete abrogation of OSM binding to both type receptors. Interestingly, binding of LIF to type 1 receptor was not affected, corroborating the notion that in this case gp130 mostly behaves as a converter protein rather than a binding receptor. The present study demonstrates that positions 189-192 of gp130 cytokine binding domain are essential for OSM binding to both gp130/LIF receptor beta and gp130/OSM receptor beta heterocomplexes.

Structural and functional properties of membrane and secreted IgD.

More than 35 years ago, study of an unknown immunoglobulin (Ig) in the serum from a myeloma patient led to the discovery of IgD. Subsequently, the finding that it also exists as a membrane-bound Ig stimulated a large number of studies during the 70s. Then, the interest on IgD shrank, largely because of the lack of known function of secretory IgD (secIgD) and of a stagnating knowledge of the functions of surface IgD. In the recent years, very significant advances followed the tremendous accumulation of data on the physiology of the B cell receptor, of which IgD is the major component, on the role of secIgD in normal and diseased individuals. This review, which is focused on human IgD but integrates data in the mouse and other species when needed, summarizes present data on the structure, synthesis and functions of both membrane and secIgD, IgD receptors and the involvement of IgD in various diseases, especially the hyperIgD syndrome.

T(h)2 cytokine dependence of IgD production by normal human B cells.

IgD is a minor component of serum Ig and the control of IgD secretion is virtually unknown. We measured concentrations of IgD (and IgE and IgM as controls) in culture supernatants of peripheral blood mononuclear cells (PBMC) from 60 normal donors as well as mononuclear cells from 10 tonsils following culture in the absence or presence of CD40 mAb and cytokines. Low levels of IgD were measured in cultures of PBMC, either unstimulated or stimulated by anti-CD40 antibodies. IL-4 and IL-10 significantly increased IgD production by CD40 mAb-stimulated cells in the majority of normal subjects studied, whereas in a limited number of individuals, spontaneous IgD production was either low or high, but with no increase upon stimulation. Spontaneous IgD production by tonsil-derived mononuclear cells was higher than by PBMC and increased after CD40 stimulation and even more in the presence of IL-10, but not IL-4. IL-2 and IFN-gamma exerted a dose-dependent inhibition on spontaneous as well as CD40- and cytokine-induced IgD production by PBMC, but not by tonsil mononuclear cells. Activation by IL-4 of CD40-stimulated purified B cells from tonsil and PBMC, and by IL-10 of tonsil B cells increased IgD production, whereas IL-2 and IFN-gamma had no detectable inhibitory effect. This suggests that accessory cells indirectly regulate IgD synthesis. IgD production induced in PBMC by IL-4 or IL-10 appeared to result from an active synthesis, and correlated with an increase in the number of IgD-containing plasma cells as demonstrated by immunofluorescence and increased expression of secreted IgD transcripts. These findings suggest that IgD production by normal peripheral blood human B cells is regulated positively by T(h)2 cytokines and negatively by T(h)1 cytokines.

Receptor recognition sites of cytokines are organized as exchangeable modules. Transfer of the leukemia inhibitory factor receptor-binding site from ciliary neurotrophic factor to interleukin-6.

Interleukin-6 (IL-6) and ciliary neurotrophic factor (CNTF) are "4-helical bundle" cytokines of the IL-6 type family of neuropoietic and hematopoietic cytokines. IL-6 signals by induction of a gp130 homodimer (e.g. IL-6), whereas CNTF and leukemia inhibitory factor (LIF) signal via a heterodimer of gp130 and LIF receptor (LIFR). Despite binding to the same receptor component (gp130) and a similar protein structure, IL-6 and CNTF share only 6% sequence identity. Using molecular modeling we defined a putative LIFR binding epitope on CNTF that consists of three distinct regions (C-terminal A-helix/N-terminal AB loop, BC loop, C-terminal CD-loop/N-terminal D-helix). A corresponding gp130-binding site on IL-6 was exchanged with this epitope. The resulting IL-6/CNTF chimera lost the capacity to signal via gp130 on cells without LIFR, but acquired the ability to signal via the gp130/LIFR heterodimer and STAT3 on responsive cells. Besides identifying a specific LIFR binding epitope on CNTF, our results suggest that receptor recognition sites of cytokines are organized as modules that are exchangeable even between cytokines with limited sequence homology.

Determination of melatonin in biological fluids in the presence of the melatonin agonist S 20098: comparison of immunological techniques and GC-MS methods.

Immunoassays were investigated for the determination of melatonin in biological samples in the presence of a naphthalenic structural analogue S 20098, which is currently under development as a melatonin agonist. The lack of specificity of commercially available antibodies in the presence of closely related molecules led us to develop an LC-RIA procedure with a quantification limit set at 15 pg/ml(-1). Because this technique was not sensitive enough and difficult to use on a routine basis, a more sensitive GC-MS technique was developed. This method involved automated solid-phase extraction (plasma) or liquid-liquid extraction (saliva), derivatization of the indolic moiety and GC separation with an automated switching device before MS detection. The method was validated over the range 1-100 pg/ml(-1), with a quantification limit set at 1 pg/ml(-1) in human plasma and saliva. Intra-assay and inter-assay precision and accuracy were within 16% for all concentrations investigated and each biological matrix. The stability of melatonin in plasma and saliva under various storage conditions was also determined. The specificity of the assay for the analysis of melatonin in the presence of S 20098 and its metabolises was demonstrated. The method was subsequently applied for the determination of endogenous melatonin concentrations in plasma and saliva samples from clinical studies performed with S 20098 to provide pharmacodynamic data.