Le cancer de la vessie représente le 4ième cancer en terme d’incidence. La mortalité de ce cancer est principalement due à la formation de métastases secondaires. Actuellement, aucun des médicaments disponibles sur le marché ne permet d’éviter la rechute ni de contrôler la dissémination métastatique. L’enjeu thérapeutique principal dans ce cancer est donc le contrôle de la dissémination métastatique. Le mécanisme de formation des métastases est connu et implique la transition épithélio-mésenchymateuse (EMT) qui permet aux cellules épithéliales d’acquérir les caractéristiques des cellules mésenchymateuse, ainsi que la capacité d’invasion. Dans ce travail, nous nous sommes posés 2 questions. Twist1 protéine connue comme régulateur central dans l’EMT, peut-elle être une cible pronostique et pharmacologique dans le cancer de la vessie ? L’utilisation d’un nouvel anti-invasif le saracatinib, peut il être un nouveau traitement dans le cancer de la vessie. Pour répondre à ces questions, nous avons caractérisé nos lignées de cancer de vessie, pour la protéine Twist1, mais aussi pour les principaux marqueurs de l’EMT (E-cadhérine, N-cadhérine, vimentine). Puis nous avons testé pharmacologiquement (cytotoxicité et invasivité) nos lignées pour le saracatinib. L’expression de la molécule Twist1 a été décevante, seulement une lignée exprime Twist1, de manière faible, et non homogène. Twist n’est donc pas une cible potentielle dans le cancer de la vessie. La sensibilité d’un point de vue cytotoxique au saracatinib est liée à l’expression de la E-cadhérine. Cependant il n’existe pas de relation entre l’expression de la E-cadhérine et l’action anti-invasive du saracatinib. Toutes les lignées sont sensibles. Dans la lignée SD48 (E-cadhérine positive), il y a une augmentation de la protéine E-cadhérine, ainsi qu’une nette relocalisation à la membrane sous traitement saracatinib. La voie du saracatinib semble passer par la E-cadherine, mais cette dernière n’explique pas en totalité son action. / Bladder cancer is the 4th cancer in the world. The mortality is principally caused by metastatic dissemination. Currently, no medicine can controle the relapse, and the metastatic dissemination. The principal therapeutic stategy is the contrôle of dissemination. Le mecanisme of metastate synthesis is knowed, and implicate the epithelial to mesenchymal transition (EMT) who change epithelial cells in mesenchymental cell and acquisition of invasivity. In this work, 2 questions are asking. The Twist1 protein who‘s a central regulator of EMT, can be a new prognostic, diagnostic, and therapeutic target in bladder cancer ? The use of a new anti-invasif drug saracatinib, can be a new treatment in the bladder cancer. To answer at this questions, we carcaterise your cells lines for Twist1 and main EMT marquers (E-cadhérine, N-cadhérine, vimentine). Than we test pharmacology response (cytotoxicity and anti-invasivity) of cells lines for saracatinib. The Twist1 expression is very disappointing, only one cells line is expressing Twist1, poorly, and non homogenous. Twist1 is not a good target in bladder cancer. The cytotoxic sensibility is linked to E-cadherin expression. However, there is no relation between E-cadherin expression and anti-invasive action for saracatinib. All the cells lines are sensitive. In the cells line SD48 (E-cadherin positive), there is an increase of E-cadherin protein, and a localisation at the membrane under saracatinib treatment. The saracatinib seem to use E-cadherin pathway, but thys way not expliquate all the action.

The master-regulators of an epithelial-mesenchymal transition (MR-EMT) have a pivotal role in the regulation of carcinoma development, promoting transformation and generating a migratory and invasive phenotype. Within epithelial cells, the ZEB proteins are co-regulated, jointly repressed by the miR-200 family of microRNAs. However, here it is demonstrated that the expression and regulation of the MR-EMT in malignant melanoma cell lines appears to be fundamentally different, with a hierarchical organisation identified. ZEB2 and SNAIL2 were found to be expressed in melanocytes, whilst ZEB1 and TWIST1 expression was acquired by a sub-set of malignant melanoma cell lines. Melanoma-initiating mutations within B-RAF and NRAS were shown to reversibly promote expression of ZEB1 and TWIST1 at the expense of ZEB2 and SNAIL2. Additionally, ZEB2 and SNAIL2 were identified up-stream of ZEB1 and TWIST1 within the MAPK signalling cascade, with ZEB2 functioning as a repressor of ZEB1. Furthermore, ZEB2 and SNAIL2 were found to positively regulate expression of MITF, a marker of melanocyte differentiation. In contrast, ZEB1 repressed expression of MITF and was the primary transcriptional repressor of E-cadherin, an adhesion molecule vital for the interaction between differentiated melanocytes and keratinocytes. Previously, within epithelial cell lines, all the MR-EMT have been identified as transcriptional repressors of E-cadherin. However, ZEB2 and SNAIL2 were co-expressed with E-cadherin within melanocytes and melanoma cell lines and, along with TWIST1, were not able to independently induce E-cadherin re-activation following repression. Surprisingly, ZEB2 became a repressor of E-cadherin in conjunction with ZEB1. Finally, E-cadherin expression was also shown to be controlled in a ZEB1-dependent manner by the transcriptional co-repressor BRG1, the ATPase subunit of the SWI/SNF chromatin remodelling complex, and by the presence of DNA methylation at the E-cadherin promoter. Indeed, DNA methylation was identified as a possible factor controlling the success rate of metastatic colonisation in melanoma cells, allowing for the dynamic re-expression of E-cadherin at the secondary site. These data demonstrate that in malignant melanoma the expression and regulation of the MREMT is fundamentally different to that of epithelial tumours, with the MR-EMT structured hierarchically, with opposing regulatory functions.

During tumor progression and development of distant metastases, a subset of cancer cells undergoes transformation programs, such as epithelial-mesenchymal transition (EMT), to acquire enhanced migratory attributes to commence the metastatic cascade with the intension of achieving an active cell adhesion molecule-mediated organ-specific homing. Similarly, naive T cells reform the assemblage of their surface adhesion molecules during differentiation to activated T cells in order to successfully home to sites of inflammation and other extra-lymphoid organs for surveillance purposes. Sialyl-Lewis X (sLex) is well-known for mediating the homing of epithelial circulating tumor cellss (CTCs) and activated T cells to target sites through the interaction with endothelial selectins. Since glycan structures are not directly encoded by the genome, their expression is dependent on the glycosyltransferase (GT) expression and activity. Yet, the modulation of GTs during breast cancer transformation and in different molecular subtypes is still unknown. In addition, although the regulation of GTs during T cell activation is well-understood, the regulation at the epigenetic level is lacking. O-glycan-type sLex expression and E-selectin binding under static and flow conditions varies among molecular subtypes of breast cancer and upon the induction of EMT which is linked to the expression patterns of GTs. GTs displayed a significant prognostic value of in the association with the patients' survival profiles and in the ability to predict the breast cancer molecular subtypes from the expression data of a random patient sample. Also, GTs were able to differentiate between tumor and their normal counterparts as well as cancer types and glioblastoma subtypes. On the other hand, we studied the regulation of GTs in human CD4+ memory T cells compared to the naive cells at the epigenetic level. Memory T cell subsets demonstrated differential chromatin accessibility and histone marks within the promoters of the GTs genes. Moreover, they showed differential binding of pioneer and nonpioneer transcription factors (TFs). We proposed a model for the regulation of FUT7 during T cell activation that relies on the interplay between chromatin-remodeling and cell-fate-specifying TFs. Furthermore, we developed a fluorescent multiplex cell rolling (FMCR) assay to study the cell adhesion properties under physiological conditions. Compared to the conventional parallel plate flow chamber (PPFC) assay, the novel technique posses a high-throughput capacity which helps eliminate the inter-experimental variation problem by running multiple samples simultaneously and under competitive settings. We also developed a real-time analysis pipeline that enhanced the statistical power of the assay. Overall these modifications to the traditional parallel plate assay improves the reliability and results along with saving time and effort.

The breast tumor suppressor hCLCA2 is a putative chloride regulator that is expressed in normal breast epithelial cells and frequently down-regulated in breast cancers. The first CLCA protein was described as a calcium-activated, plasma-membrane chloride channel having four or five transmembrane pass structure that could form a channel pore. However, CLCA topology is inconsistent with chloride channel function. We showed that hCLCA2 itself is unlikely to form a channel as it has only a single transmembrane segment with a short cytoplasmic tail and is mostly extracellular. Moreover, the N-terminal 109-kDa ectodomain is cleaved at the cell surface and shed into the medium while the 35-kDa C-terminal product is retained by the cell membrane. The general goal of my project was to study the function of this novel protein and its role in breast cancer. In addition to its role in chloride regulation, hCLCA2 behaves as a tumor suppressor gene that is frequently down-regulated in breast cancer. We previously demonstrated that murine homologs of hCLCA2 are transcriptionally induced during mammary involution, when the gland shuts down and 80% of the mammary epithelial cells die by apoptosis. In cell culture, conditions that cause G1 arrest such as contact inhibition and depriving cells of growth factors and anchorage induced these genes. Therefore, one of the goals of this project was to find if this is true of hCLCA2 in human breast epithelial cells. We found that hCLCA2 was induced by the above mentioned stresses and by pharmacological blockage of cell survival signaling. In addition, we found that DNA-damaging agents doxorubicin and aphidicolin potently induced hCLCA2 in p53-positive cell lines such as MCF-7 but not in p53-deficient cells such as MDA-MB231. An adenovirus encoding p53 induced hCLCA2 expression in a broad spectrum of breast cancer cell lines while a control virus did not, suggesting that hCLCA2 is a p53-inducible gene. To further test the hypothesis, we performed chromatin immunoprecipitation (ChIP) to determine whether p53 bound to the hCLCA2 promoter. This analysis showed that p53 binds directly to the hCLCA2 promoter between -157 and -359bp upstream of the translation initiation site. This segment was required for the p53-dependent expression of an hCLCA2-luciferase fusion gene. Point mutation of the p53 consensus binding motif abolished this induction. Induction of hCLCA2 in MCF-7 cells by doxorubicin was inhibited by p53 knockdown and by p53 inhibitor pifithrin, indicating that p53 activates the endogenous hCLCA2 promoter in response to DNA damage. An adenovirus encoding hCLCA2 induced a cell cycle lag in G0/G1 phase, decreased intracellular pH from 7.49 to 6.7, caused Bax and Bad translocation to the mitochondria, activated caspases, induced PARP cleavage, and promoted apoptosis. Conversely, hCLCA2 knockdown enhanced proliferation of epithelial MCF10A cells and reduced sensitivity to doxorubicin. These results reveal the molecular mechanism of hCLCA2 induction and downstream events that may provide protection from tumorigenesis. Epithelial cells acquire mesenchymal characteristics by undergoing phenotypic and genotypic changes during cancer progression. An early step in the epithelial to mesenchymal transition (EMT) is the disruption of intercellular connections due to loss of epithelial cadherins. We find that expression of tumor suppressor hCLCA2 is strongly associated with epithelial differentiation and that induction of EMT by mesenchymal transcription factors represses its expression. Moreover, we found that knockdown of hCLCA2 by RNA interference results in disruption of cell-cell junctions by downregulating E-cadherin. This also imparts invasiveness and anoikis-resistance to epithelial cells but is insufficient to induce full EMT. However, activation of Ras oncogene in combination with hCLCA2 knockdown is sufficient to induce full EMT in vitro. These findings indicate that, like E-cadherin, hCLCA2 is required for epithelial differentiation and that its loss during tumor progression may contribute to metastasis.

Accounting for 14% of all new cancer diagnosis in the United States, prostate cancer is the most commonly diagnosed cancer and the second leading cause of cancer related death in the United States. Prognosis for patients diagnosed with metastatic disease is especially poor, since no effective treatments have been developed (1). In this study, we examined the expression and function of POU5F1B, a protein-encoding pseudogene of the homeodomain transcription factor Oct4, in prostate cancer. POU5F1B is located at 8q24, a "gene desert" containing numerous alleles associated with prostate cancer risk. A recent study has indicated that a number of these risk alleles are correlated with POU5F1B expression and prostate cancer susceptibility. The role of POU5F1B in prostate cancer carcinogenesis and progression, however, is not known. In our study, we found that POU5F1B expression is upregulated in prostate cancers and highly overexpressed by high grade (Gleason ≥8) and metastatic prostate cancers. We cloned POU5F1B from prostate cancer cell lines, which contains prostate cancer risk associated SNPs, including a missense mutation inside the homeobox DNA binding domain, to study the functional effects of POU5F1B overexpression in prostate cancers. Here, we report that POU5F1B from prostate tumor encodes functional proteins that exhibit gene transactivation activity comparable to its parent gene, Oct4. Further, we report that POU5F1B overexpression in prostate cancer cell lines increases prostate cancer cell proliferation, migration, anchorage independent growth, and drug resistance in vitro and tumor xenograft growth in vivo. Conversely, shRNA mediated knockdown of endogenous POU5F1B expression in prostate cancer cells inhibit cell proliferation in vitro and tumor growth in vivo, as well as prolong tumor free survival in animal models. The data provide compelling evidence that POU5F1B is an important mediator of prostate cancer progression. We further examined the molecular mechanism behind POU5F1B driven prostate cancer progression. Our studies found that POU5F1B overexpression suppresses E-Cadherin expression at both mRNA and protein levels. Our studies further found POU5F1B overexpression in prostate cancer cells increases Wnt1, TCF1, and TCF4 expression, as well as increased Wnt/β-Catenin signaling - indicating the induction of epithelial-to-mesenchymal transition (EMT) in POU5F1B overexpressing cells(2). Consistently, qPCR analysis found that POU5F1B overexpression significantly increased the expressions of numerous EMT related genes and prostate cancer stem cell markers. Functional studies further confirmed that the transactivation activity of Nanog, another stem cell related transcription factor, is dramatically increased in POU5F1B overexpressing cells. Taken together, our data strongly suggests that POU5F1B overexpression drives prostate cancer progression through the induction of EMT and conferment of stem-cell properties to tumor cells. In summary, our data demonstrated that POU5F1B is overexpressed in prostate tumors, especially high-grade and metastatic tumors, and is a functional driver of prostate cancer progression by inducing EMT in prostate cancer cells. Our study also showed that POU5F1B can potentially be targeted to treat prostate cancer. Based on our findings, depletion of POU5F1B may reduce the risk of metastatic disease or tumor recurrence when used with concurrent therapies in early state tumors and may attenuate treatment resistance in diseases at advanced stages.

No description available.

Dans ce manuscrit, nous démontrons par le biais de dimères forcés que toutes les propriétés oncogéniques de la protéine TWIST1, telles qu'évaluées par le biais de nombreux tests in vitro (tests de complémentation, inhibition de la sénescence oncogénique, induction de l'EMT et tests de coopération oncogénique…), sont spécifiquement attribués au complexe TWIST1-E12. L'insertion de mutations ponctuelles, définies d'après l'analyse de modèles de simulation in silico développés au sein du laboratoire (Bouard et al., 2013) et perturbant la dimérisation du complexe ou encore son interaction avec l'ADN conduit à une perte complète de l'activité, validant l'importance des deux partenaires dans l'activité oncogénique de la protéine de fusion. La détection du complexe TWIST1-E12 dans des carcinomes mammaires canalaires in situ humains, récapitulant les phases précoces de l'initiation tumorale, par la technique de Proximity Ligation Assay (PLA) ainsi que la sensibilité accrue de souris transgéniques à développer des carcinomes mammaires lorsque le complexe hétérodimérique est exprimé dans les cellules épithéliales luminales mammaires, renforce la conclusion que le complexe TWIST1-E12 est la (ou l'une des) forme(s) active(s) de la protéine TWIST1 dans le cadre de la carcinogenèse mammaire / Among embryonic transcription factors, TWIST proteins (TWIST1 and TWIST2) display the particularity to behave as master regulators of both RB and p53-oncosuppressive pathways. These embryonic transcription factors annihilate the induction of numerous cyclin-kinase inhibitors, including p16INK4A, p15INK4B and p21CIP1, abrogating thereby cell commitment to a senescence program or their death through apoptosis in response to an oncogenic activation. By doing so, TWIST proteins cooperate with mitogenic oncoproteins such as Ras in promoting cell transformation in vitro and breast and lung carcinogenesis in vivo (Ansieau S. et al. Cancer Cell ; Morel A-P. et al., PLoS ONE ; Tran P.T. et al., PLoS Genetics). Strikingly, TWIST depletion in numerous cancer cell types associates with a reactivation of failsafe programs, suggesting that some tumor cells remain addictive to TWIST for survival and proliferation (Ansieau et al., 2008). In support of this hypothesis, silencing TWIST expression in a TWIST + RAS-driven lung carcinogenesis mouse model displays a cytostatic effect (Tran P.T. et al., PLoS Genetics). Based on these observations, we aim at identifying TWIST specific inhibitors and evaluate the efficiency of such molecules in eradicating tumor cells in vitro as well as in vivo. TWIST proteins either behave as homodimeric (TT) or heterodimeric (TE) complexes (in association with E2A proteins), both complexes displaying distinct and sometimes even antagonistic functions during the embryonic development (Firulli B.A. et al., Nature Genetics ; Connerney F. et al., Dev. Dynamics). Ongoing experiments, comparing activities of tethered TWIST dimers, strongly support the assumption that an oncogenic potential is specifically allotted to the heterodimer. To screen for specific chemical inhibitors, we first established the in silico structure of the bHLH domain of TWIST complexes bound to their cis-responsive elements, by analogy with the NeuroD/E47 crystallographic structure. Relevance of these models has been confirmed through analysis of Twist1 variants associated with a loss of function in Saethre-Chotzen patients (Bouard et al., J. Biomolecular Structure & Dynamics). Strikingly, structural analysis highlights the importance of lateral loops in stabilizing the protein-DNA complex and in specifying the DNA sequence targeted

The cardiovasculature is the first functional system in the developing embryo and as such, it plays a crucial role in the proper nourishment and formation of all other body regions and organs. A detailed understanding the mechanisms that regulate cardiac morphogenesis is necessary to develop possible strategies for diagnostics and treatment of cardiovascular diseases.One molecule identified as important for the proper formation of the heart is Hyaluronan synthase 2 (Has2), a membrane protein in charge of assembling the glycosaminoglycan hyaluronan (HA). Mouse embryos lacking Has2 do not produce HA, display severe cardiovascular abnormalities and die during early embryogenesis. Thus, Has2 and HA are necessary for the early stages of heart formation, but many questions remain to be answered in regards to their mechanism of action and their role in later events such as the formation of the coronary vessels. Our current study addresses these questions employing two cell lines: NIH-3T3s, as a model of mesenchymal endocardial cushion cells; and epicardial cells, which have an epithelial phenotype.Here we show that HA induces biological activity in embryonic cells in a manner that is dependent on its molecular size. High molecular weight HA (HMW-HA), but not low molecular weight HA (LMW-HA), induces invasion of NIH-3T3 cells while it promotes differentiation and invasion of epicardial cells. We also demonstrate that stimulation of cells with HMW-HA promotes the association of MEKK1 with the HA receptor CD44. This leads to the activation of two distinct pathways, one ERK-dependent and another NFκB-dependent, which are crucial for the induction of cellular responsesFinally, we have demonstrated that the growth factors TGFβ2 and EGF induce Has2 expression and/or phosphorylation. TGFβ2 governs Has2 via MEKK3-dependent mechanisms, while EGF does not require MEKK3. Increased Has2 activity as a result of TGFβ2 and EGF stimulation leads to enhanced HA synthesis. These increased levels of HA are coincident with enhanced cellular differentiation and invasion. Taken together, these findings underscore how EGF, TGFβ2 and HA signals are integrated to form highly complex networks that are crucial for the proper formation of organs and tissues during development.

Gastrulation is a key early developmental event that generates the three primary germ layers (ectoderm, mesoderm, and endoderm) from which organ systems subsequently develop. The physical mechanisms of germ layer formation differ significantly in amniotes (reptiles, birds, and mammals) and anamniotes (e.g. frog and fish), as amniote gastrulation includes an epithelial-mesenchymal transition (EMT) that is absent from anamniote gastrulation. Despite this striking difference, much of our knowledge regarding the mechanisms underlying gastrulation is derived from frog and fish studies. To better understand amniote gastrulation, the work herein investigates three signaling pathways that regulate amniote gastrulation with distinct and overlapping functions. The central hypothesis is that multiple signaling pathways function cooperatively to precisely modulate cell migration through the primitive streak during avian gastrulation.First, I describe a novel function of Fibroblast Growth Factor (FGF) signaling in the preingression epiblast adjacent to the avian primitive streak, where it governs the expression of molecules from diverse signaling pathways and transcription factor families, and which is mediated largely through the Ras/MAPK pathway. Importantly, FGF signaling also regulates cell migration during avian gastrulation.Next, I report the isolation of a novel chicken non-canonical Wnt ligand (Wnt11b) that is specifically expressed in the primitive streak and adjacent preingression epiblast during gastrula stages. In gain and loss of function studies, Wnt11b and Wnt5a/b participate in regulating cell migration through the streak in a largely redundant fashion. Signaling specifically targets the non-canonical pathway, as similar cell migration defects are observed with a non-canonical mutant of Dishevelled, and activating the canonical pathway has no effect on cell migration.Finally, I investigate the function of A-class Eph-ephrin signaling during avian gastrulation, and describe that Eph receptor forward signaling negatively regulates the migration of cells through the primitive streak. This modulation of cell migration occurs independently of the EMT that accompanies avian gastrulation, as cells are able to undergo the normal cadherin transition and the basal lamina is unaffected.Altogether, the work presented herein provides a significant contribution to our understanding of signaling pathways that modulate gene expression and ongoing cell migration during germ layer formation in amniote gastrulation.

Implication de SIP1 (Smad Interacting Protein 1) dans la transition épithélio-mésenchymateuse associée à la progression métastatique