Les récepteurs à dépendance présentent la particularité d’induire deux voies de signalisation différentes selon la disponibilité de leur ligand. En présence de leur ligand, ils transduisent une voie de signalisation favorisant notamment la survie cellulaire (signalisation positive), tandis qu’en son absence, ils induisent activement l’apoptose des cellules (signalisation négative). La dualité fonctionnelle de ces récepteurs pourrait leur conférer un rôle central au cours du développement embryonnaire, mais aussi dans le maintien de l’homéostasie cellulaire chez l’adulte. En effet, du fait de leur signalisation pro-apoptotique, les récepteurs à dépendance pourraient limiter le nombre de cellules (en fonction de la disponibilité en ligand), et réguler leur migration (dans des zones dépourvues de ligand), au cours des processus développementaux mais aussi en cas de prolifération tumorale et de dissémination métastatique. Au cours de ma thèse, j’ai donc développé différentes thématiques de recherche visant à préciser le rôle du contrôle apoptotique exercé par les couples nétrine-1/récepteurs à dépendance (DCC et UNC5B) au cours de la tumorigenèse et du développement embryonnaire. Dans ce cadre, nous avons montré que les souris exprimant une forme mutée du récepteur DCC, ayant perdu la capacité d’induire l’apoptose des cellules en absence de son ligand la nétrine-1, étaient prédisposées à la survenue de (1) cancers colorectaux dans un contexte prédisposant, et de (2) lymphomes non hodgkiniens (LNH) dans un modèle de vieillissement. Ces résultats suggèrent que DCC puisse agir comme un suppresseur de tumeur conditionnel, via sa voie de signalisation négative, en absence de son ligand nétrine-1. De plus, nous avons montré qu’il existe un gain de nétrine-1 dans une fraction significative de LNH de type B (LNH-B) chez l’Homme, gain qui leur confère un avantage sélectif en bloquant constitutivement l’apoptose induite par le récepteur DCC. Réciproquement, nous avons montré que l’utilisation d’un anticorps ciblant la nétrine-1 était capable de restaurer l’apoptose induite par le récepteur DCC non lié, dans des lignées tumorales humaines de LNH-B in vitro et ex-vivo dans un modèle de xénogreffe. Ainsi, nos résultats suggèrent que cibler l’interaction nétrine-1/DCC dans les LNH-B pourrait être une stratégie thérapeutique prometteuse. La partie « développement » de mon travail de thèse est encore préliminaire. Elle se focalise sur le rôle du contrôle apoptotique exercé par les couples nétrine-1/récepteurs à dépendance (DCC et UNC5B) au cours de la mise en place des réseaux vasculaire et nerveux chez l’embryon de souris / Dependence receptors share the common property of inducing two types of signaling cascades according to the availability of their ligand. In presence of their ligand, they induce a positive signal allowing cell survival whereas in its absence, they induce cell death by apoptosis. Dependence receptors dual functionality could play a major role both during the embryonic development and in the regulation of tissue homeostasis in adult. Indeed, apoptosis induced by dependence receptors would be a safeguard mechanism which regulates the number of cells and their migration during developmental or tumorigenic process. Thus, during my PhD, I have investigated the involvement of netrin- 1/dependence receptors (DCC and UNC5B) apoptotic control during tumorigenesis and embryonic development. We observed that DCC-mutant mice in which DCC pro-apoptotic signaling is genetically silenced show a higher propensity to develop colorectal cancers in a predisposing context and B-cell type non-Hodgkin lymphoma (B-NHL) with age, suggesting than DCC could act as a conditional tumor suppressor gene through its pro-apoptotic signaling, in absence of netrin-1. Moreover, we show that netrin-1 is overexpressed in a significant fraction of Human B-NHL, which confers tumor cells a selective advantage by blocking DCC-induced apoptosis. Reciprocally, we showed that inhibiting the interaction between netrin-1 and its DCC receptor restore apoptosis in lymphoma cells in vitro and in vivo in xenografts experiments, suggesting that targeting netrin-1 and DCC interaction in lymphoma could represent a promising anti-tumor therapeutic strategy. The "developmental" part of my PhD work is in progress and we obtained only few preliminary data. It focuses on the role of apoptotic control mediated by netrin1-/dependence receptor (DCC/UNC5B) during the development of vascular and neural networks in the mouse embryo

The thesis uses mathematical modeling and analysis to provide insights into the transmission dynamics of Human papillomavirus (HPV), and associated cancers and warts, in a community. A new deterministic model is designed and used to assess the community-wide impact of mass vaccination of new sexually-active susceptible females with the anti-HPV Gardasil vaccine. Conditions for the existence and asymptotic stability of the associated equilibria are derived. Numerical simulations show that the use of Gardasil vaccine could lead to the effective control of the spread of HPV in the community if the vaccine coverage is at least 78%. The model is extended to include the dynamics of the low- and high-risk HPV types and the combined use of the Gardasil and Cervarix anti-HPV vaccines. Overall, this study shows that the prospect of the effective community-wide control of HPV using the currently-available anti-HPV vaccines are encouraging.

The thesis uses mathematical modeling and analysis to provide insights into the transmission dynamics of Human papillomavirus (HPV), and associated cancers and warts, in a community. A new deterministic model is designed and used to assess the community-wide impact of mass vaccination of new sexually-active susceptible females with the anti-HPV Gardasil vaccine. Conditions for the existence and asymptotic stability of the associated equilibria are derived. Numerical simulations show that the use of Gardasil vaccine could lead to the effective control of the spread of HPV in the community if the vaccine coverage is at least 78%. The model is extended to include the dynamics of the low- and high-risk HPV types and the combined use of the Gardasil and Cervarix anti-HPV vaccines. Overall, this study shows that the prospect of the effective community-wide control of HPV using the currently-available anti-HPV vaccines are encouraging.

Les objectifs de cette thèse étaient d’étudier les tendances du risque de second cancer primitif (SPC) selon l’année de diagnostic d’un premier cancer des voies aéro-digestives supérieures (VADS) dans le Bas-Rhin, de produire les premières estimations de l’incidence des SPC à l’échelle nationale en France et d’estimer la survie des patients atteints d’un cancer des VADS selon la présence d’antécédents de cancer. Ce travail a montré que : 1) L’excès de risque de SPC des VADS et de l’œsophage a diminué de 53% entre 1975 et 2006 dans le Bas-Rhin, mais que le risque de SPC du poumon est resté stable ; 2) Le risque de SPC en France est augmenté de 36% chez les patients atteints de cancer par rapport à la population générale ; 3) La survie des hommes atteints d’un cancer des VADS était fortement associée à la présence d’antécédents de cancer. Des perspectives se dégagent de ce travail en termes de recherche épidémiologique, de recherche clinique et de politiques de santé publique. / The objectives of this PhD thesis were: to study the trends of the risk of second primary cancer (SPC) among patients with a head and neck (HNSCC) cancer in Bas-Rhin, to provide first nationwide estimates of the risk of SPC in France and to assess the survival of patients with a HNSCC depending on their history of cancer. This work showed that : 1) The excess risk of SPC of head and neck and esophagus sites decreased by 53% over three decades among patients with a HNSCC, and that the excess risk of SPC of the lung did not change significantly. 2) The risk of SPC among cancer survivors in France was increased by 36% compared to the general population. 3) History of cancer was strongly associated with survival among HNSCC patients. Several epidemiological and clinical research perspectives can be established based on this work. These results also present an interest in a public health perspective in the framework of the third cancer plan.

published_or_final_version / abstract / Pathology / Doctoral / Doctor of Philosophy

Philosophiae Doctor - PhD / Introduction: Globally, there are over 190,000 new reported cases of ovarian cancers per annum. This comprises 3% to 4% of all cancers in women. Ovarian cancer is one of the leading causes of deaths in women. Ovarian cancer is the second most diagnosed gynaecological malignancy and over all the fifth cause leading to death among all types of cancer in the UK in 2004. More than 70% of epithelial ovarian cancers are diagnosed at an advanced stage. Consequently, the prognosis is poor and the mortality rate high. Thus, the survival rate is affected by how far the disease has progressed or spread. A dire need exists to identify ovarian cancer biomarkers, which could be used as good indicators of expression in ovarian cancer cells in vitro Aim: The aim of this study was to analyse selected cancer biomarkers, which are currently under intense investigation for their suitability to diagnose epithelial ovarian cancer at an early stage. These biomarkers were analysed in terms of their in vitro expression in normal epithelial cells and ovarian cancer cell lines, which allows for their genomic and proteomic classification. The expression analysis of each biomarker is related to the malignancy of a tumour and, therefore, advocates its use for potential future improvement of sensitive tumour markers. Methods: The primary human ovarian surface epithelial cell line (HOSEpiC), SKOV-3 cells and the OAW42 human epithelial ovarian tumour cell lines were used to evaluate the selected cancer biomarkers. Cells were cultured using appropriate media and supplements, and real-time quantitative polymerase chain reaction (RT-PCR) utilized to validate expression levels of the following genes: HDAC1, HDAC2, HDCA3, HDAC5, HDAC6, HDAC7, HDAC8, LPAR1, LPAR2, MUC16 and FOSL1, against normal housekeeping genes GAPDH and HPRT. In addition, immunocytochemistry was also used in the validation process of the aforementioned genes. Significance: ovarian cancer cells express gene signatures, which pose significant challenges for cancer drug development, therapeutics, prevention and management. The present study is an effort to explore ovarian cancer biomarkers to provide a better diagnostic method that may offer translational therapeutic possibilities to increase five- year survival rate. Results: HDAC5, HDAC6, LPAR1, LPAR2 and MUC16 expressed distinctively in ovarian cancers matched to other tissues or cancer types have already been identified by RT-QPCR and confirmed by immunocytochemistry and efforts to generate monoclonal antibodies to the other six genes (HDAC1, HDAC2, HDAC3, HDAC7, HDAC8 and FOSL1) encoded proteins are underway. Conclusions: here we provide strong evidence suggesting that HDAC5, HDAC6, LPAR1, LPAR2, except MUC16 are up regulated in ovarian cancer. These data were confirmed by examining Human Protein Atlas (HPA) databases, in addition to protein expression of HDAC5, HDAC6, LPAR1, LPAR2 and MUC16 in cells cytoplasm. For future prospective, using other techniques that assess the variant expression that could explain the release of these gene candidates into the circulation with serum tumour markers, and protein expression will be strengthened.

Previous data have unveiled a novel autoregulatory feedback loop between iASPP and p63 in the stratified epithelia; this involves two microRNAs, miR-574-3p and miR-720, and is critical for epidermal homeostasis. The iASPP oncoprotein, an inhibitory member of the ASPP (apoptosis stimulating protein of p53) family, is a key inhibitor of p53 and NF-κB and is highly expressed in many cancers. Non-melanoma skin cancer, comprising of cutaneous squamous carcinoma (cSCC) and basal cell carcinoma, is currently the most common malignancy in the UK. In view of this newly-identified iASPP-p63 axis, I hypothesised a potential role for dysregulation of this feedback loop in the pathogenesis of cSCC and aimed to assess the role of iASPP in human cSCC. Protein and mRNA expression patterns were assessed in a panel of 10 cSCC cell lines generated by our group. In addition, immunostaining of iASPP and p63 was performed in 107 cSCC clinical samples of variable differentiation status. The data reveal an overall increase in expression of iASPP and ΔNp63 in cSCC but also suggest a significant alteration of the cellular localisation of iASPP dependent on the differentiation status of the tumour. To further assess the effects mediated by the iASPP/p63 axis, iASPP and p63 have been silenced by RNAi technology in a subset of cSCC cell lines. Whilst data shows the direct effects of iASPP and p63 upon each other's expression are maintained in cSCC, epigenetic dysregulation of the feedback loop at the microRNA level may be occurring via a novel p63 regulator, miR-211-5p. Functionality of iASPP in cSCC (proliferation, apoptosis, cell motility/migration and invasiveness) provides evidence for a role of iASPP in preventing epithelial-mesenchymal transition in cSCC via a p63/miR-205-5. These findings provide potential future directions for development of clinical biomarkers and novel therapeutic targets for cSCC and may ultimately provide the tools for tackling the increasing morbidity and mortality associated with this malignancy.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

Cisplatin (CDDP; cis-diamminedichloroplatinum) resistance presents a major impediment in the treatment of several gynecologic solid tumors, including ovarian and cervical tumors. p53, a critical regulator of cellular apoptosis, is a determinant of CDDP sensitivity. In our study, we have observed that the dysregulation of p53 regulators, checkpoint kinase 1 (Chk1) and protein phosphatase magnesium-dependent 1 (PPM1D), significantly reduced CDDP responsiveness in human cancer cells. Isogenic wt-p53 CDDP-sensitive (OV2008) and -resistant (C13*) cervical cancer cells, and isogenic wt-p53 CDDP-sensitive (A2780s) and p53 mutant resistant (A2780cp) ovarian cancer cells, along with CDDP-resistant ovarian cancer cell lines (OCC-1 and OVCAR-3, mutant p53; SKOV-3, p53 null) were used to elucidate the mechanisms of p53 regulation in human gynecologic cancer cells. We have complemented our study with a xenograft model (A2780s) and a tissue microarray of human ovarian tumors to validate our in vitro observations. We have demonstrated that CDDP differentially regulated the p53 activator Chk1 in sensitive and resistant cancer cells; it enhances Chk1 activation in sensitive but not resistant cells. This differential regulation also extended to PPM1D, whereby CDDP enhanced PPM1D content in resistant but not sensitive cells. PPM1D knockdown sensitized resistant cells to CDDP, which was associated with up-regulation of Chk1 and p53 activations, while PPM1D over-expression had the opposite effect. We have also shown that CDDP sensitivity in response to PPM1D down-regulation was p53-dependent. Moreover, CDDP promotes PPM1D nuclear localization in resistant cells and nuclear exclusion in sensitive cells and xenograft tumors. Enhanced PPM1D expression in human ovarian tumors is significantly associated with tumor aggression. Dysregulation of the oncogene Akt has been implicated in a variety of human malignancies, including ovarian cancer. We have demonstrated that Akt regulates PPM1D stability, since activated Akt over-expression in sensitive cells rescued PPM1D from CDDP-induced proteasomal degradation and Akt down-regulation in resistant cells lead to PPM1D de-stabilization and down-regulation. We have shown for the first time that PPM1D is downstream of Akt through which it can modulate CDDP sensitivity in human cancer cells. These findings extend the current knowledge on the molecular basis of CDDP resistance in gynecological cancers and may help in developing effective therapeutic strategies.

Breast cancers fall into two major classes depending on their estrogen receptor (ER) status. ER+ and ER- tumors have very different molecular phenotypes, and may have distinct cells of origin. ER- tumors generally fail to respond to endocrine therapy and have a poorer prognosis. To develop a comprehensive understanding of the gene networks active in ER+ compared to ER- breast cancers, we performed a meta-analysis of Grade 3 breast cancers from five published datasets. A measure of association with ER status taking into account intra- and inter-study variability was calculated for every probe set. The meta-analysis revealed that ER-/Grade 3 tumors show increased expression of proliferation-associated functional categories when compared to ER+/Grade 3 tumors. Using Gene Set Enrichment Analysis we show that transcript levels of direct transcriptional targets of ER are lower in ER- tumors, but that expression of other estrogen-induced genes is higher in ER- tumors. Transcript levels of both direct and other targets of the estrogen-regulated MYC gene and the E2F family of genes are significantly higher in ER- tumors. The increased expression of targets of MYC and E2F is particularly pronounced in the "basal" subgroup of ER- tumors. This suggests that a study assessing the association of these genes with clinical outcome in ER- patients is warranted, but is not currently feasible due to lack of suitable publicly available data. The contribution of genes regulated or bound by estrogen, MYC or E2F to increased risk of relapse in ER+ tamoxifen-treated patients was assessed in a pilot study using Cox proportional hazards models and Gene Set Enrichment Analysis. The high expression of several gene sets containing genes induced by estrogen and/or MYC and direct targets of MYC and E2F was correlated with poor outcome in these patients. We conclude that over-expression or constitutive activation of MYC, possibly in conjunction with elevated E2F activity, may lead to the induction of a set of genes characteristic of the estrogen response thereby contributing to increased proliferation in ER- breast tumors, particularly in the basal subgroup. A pilot survival study indicated that MYC- and E2F-activity may play a role in tamoxifen-resistance.