Les œstrogènes, et en particulier l’œstradiol E2, régulent un nombre considérable de fonctions physiologiques au sein de l’organisme et permettent notamment l’établissement et le maintien des fonctions reproductives chez tous les vertébrés. L’E2 agit localement dans de multiples organes cibles via l’intermédiaire de ses récepteurs : ERα et ERβ. Par son action proliférative contribuant au renouvellement de l’épithélium mammaire, l’E2 ainsi que son récepteur ERα ont été associés au développement pathologique de tumeurs mammaires. Celles-ci sont qualifiées d’hormono-dépendantes car elles répondent pour la majorité d’entre elles à l’utilisation de l’hormonothérapie visant à bloquer leur croissance. Malheureusement, on estime que 30 à 40% des tumeurs mammaires finissent par présenter une résistance aux traitements anti-oestrogéniques, par des mécanismes extrêmement complexes. Les travaux présentés dans ce manuscrit ont pour objectifs de mieux comprendre les mécanismes moléculaires et cellulaires impliqués dans le phénomène d’échappement des cellules tumorales mammaires au contrôle hormonal. Dans le cadre de cette thèse, nous nous sommes intéressés à deux facteurs capables de moduler l’activité d’ERα : l’hypoxie, qui désigne l’appauvrissement en oxygène du microenvironnement cellulaire, et la voie RhoA/MKL1 fréquemment mise en place au cours de la transition épithélio-mésenchymateuse. L’hypoxie est une caractéristique majeure des tumeurs solides, et des études lui suggèrent un rôle dans l’apparition de résistance endocrine. Nous montrons que le stress hypoxique inhibe fortement l’expression d’ERα, principalement au niveau protéique, et qu’il abolit la prolifération et la survie cellulaire induites par l’E2. L’analyse transcriptomique démontre qu’un certain nombre de gènes cibles d’ERα sont également régulés par l’hypoxie, qui peut soit réprimer (CXCL12…) ou bien augmenter leur expression (AREG…). Par ailleurs, l’analyse du cistrome d’ERα démontre une perte massive du nombre d’ERBSs (Estrogen Receptor Binding Site) par l’hypoxie, mais également une apparition d’ERBSs hypoxie-spécifiques. Nos résultats suggèrent que le fort recouvrement de régulation entre ERα et l’hypoxie puisse moduler l’efficacité des thérapies antihormonales. Enfin, l’équipe a démontré que l’activation de la voie RhoA/MKL1 provoque une forte inhibition de la fonction AF1 d’ERα. Afin de mieux appréhender les effets de cette voie de signalisation sur l’activité d’ERα, une lignée cellulaire MCF7 exprimant stablement un mutant constitutivement actif du facteur MKL1 a été générée. Nous montrons que son expression modifie profondément le contexte cellulaire en provoquant le basculement d’un phénotype luminal vers un phénotype basal-like. L’analyse transcriptomique de la réponse à l’E2 montre que le changement d’orientation cellulaire induit par MKL1 abolit toute régulation transcriptionnelle des gènes cibles d’ERα. Ce changement d’orientation cellulaire s’accompagne d’une reprogrammation massive du cistrome d’ERα avec une perte importante de ses sites de fixation à la chromatine, mais également de façon inattendue, un enrichissement en nouveaux ERBSs. Enfin, nous montrons une forte augmentation des interactions « non-génomiques » d’ERα avec des partenaires cytoplasmiques tels que PI3K, MSK1 et Src. Ces données suggèrent que dans des cellules agressives de type mésenchymal exprimant ERα, l’activité du récepteur repose majoritairement sur son action « non-génomique ». De façon intéressante, l’utilisation de l’anti-œstrogène pur ICI 182 780 n’a aucun effet inhibiteur sur ces interactions, pour lesquelles un rôle fonctionnel reste à établir. / Estrogens, and in particular estradiol E2, regulate a considerable number of physiological functions in the body and allow the establishment and maintenance of reproductive functions in all vertebrates. E2 acts locally in multiple target organs via its receptors: ERα and ERβ. By its proliferative action contributing to the renewal of the mammary epithelium, E2 as well as its ERα receptor have been associated with the pathological development of mammary tumors. These are qualified as hormone-dependent because they, for the majority of them, respond to the use of hormone therapy to block their growth. Unfortunately, it is estimated that 30-40% of mammary tumors end up with resistance to anti-estrogen treatments, through extremely complex mechanisms. The work presented in this manuscript aims to better understand the molecular and cellular mechanisms involved in the escape of mammary tumor cells to hormonal control. In this thesis, we looked at two factors that can modulate the ERα activity: hypoxia, which refers to oxygen depletion in the cellular microenvironment, and the RhoA/MKL1 pathway that is frequently activated during the epithelial-mesenchymal transition. Hypoxia is a major feature of solid tumors, and studies suggest a role in the development of endocrine resistance in breast cancer. We show that hypoxic stress strongly inhibits the expression of ERα, mainly at the protein level, and that it abolishes E2-induced cell proliferation and survival. Transcriptomic analysis shows that a certain number of ERα target genes are also regulated by hypoxia, which can either repress (CXCL12) or increase their expression (AREG ...). Moreover, the analysis of the ERα cistrome demonstrates a massive loss of the number of ERBSs (Estrogen Receptor Binding Site) by hypoxia, but also an appearance of hypoxia-specific ERBSs. Our results suggest that the strong regulatory overlap between ERα and hypoxia may modulate the efficacy of anti-hormonal therapies. Finally, the team demonstrated that the activation of the RhoA/MKL1 pathway causes a strong inhibition of the ERα AF1 function. In order to better understand the effects of this signaling pathway on ERα activity, an MCF7 cell line stably expressing a constitutively active mutant of the MKL1 factor was generated. We show that its expression profoundly modifies the cellular context by causing the switch from a luminal phenotype to a basal-like phenotype. The transcriptomic analysis of the E2 response shows that the MKL1 induced change in cell fate abolishes any transcriptional regulation of ERα target genes. This change in cellular orientation is accompanied by massive reprogramming of the ERα cistrome with a significant loss of its chromatin binding sites, but also unexpectedly, an enrichment of new ERBSs. Finally, we show a strong increase of "non-genomic" ERα interactions with cytoplasmic partners such as PI3K, MSK1 and Src. These data suggest that in aggressive mesenchymal cells expressing ERα, the receptor activity is mainly based on its "non-genomic" action. Interestingly, the use of pure anti-estrogen ICI 182 780 has no inhibitory effect on these interactions, for which a functional role remains to be established.

Submitted by Rafael Bispo Paschoalini (rbpaschoalini@gmail.com) on 2016-03-08T04:00:33Z No. of bitstreams: 1 Dissertação de mestrado - Rafael Bispo Paschoalini.pdf: 2764983 bytes, checksum: 576265167e590acb2641a540cda6283a (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-03-09T16:26:52Z (GMT) No. of bitstreams: 1 paschoalini_rb_me_bot.pdf: 2764983 bytes, checksum: 576265167e590acb2641a540cda6283a (MD5) / Made available in DSpace on 2016-03-09T16:26:52Z (GMT). No. of bitstreams: 1 paschoalini_rb_me_bot.pdf: 2764983 bytes, checksum: 576265167e590acb2641a540cda6283a (MD5) Previous issue date: 2016-02-26 / O carcinoma de mama é uma doença heterogênea. Pode ser classificado em fenótipos, com diferentes prognósticos, com base na expressão de determinadas proteínas. O fenótipo luminal é o mais frequente, correspondendo a cerca de 70% dos casos, sendo que tratamentos específicos para este fenótipo de carcinoma de mama já estão em estudo, com melhora promissora do prognóstico das pacientes acometidas. Entretanto, ainda não foram definidos critérios citológicos que pudessem predizer este fenótipo no material obtido pela punção aspirativa por agulha fina (PAAF). OBJETIVO: Investigar critérios citológicos individuais presentes na PAAF que possam se associar com o diagnóstico do fenótipo luminal do carcinoma de mama. MÉTODOS: Trata-se de estudo tipo corte-transversal, com componente descritivo e comparativo. As lâminas de PAAF e espécimes de carcinomas de mama invasivos ductais e lobulares, do período de 2000 a 2005, foram selecionados do arquivo do Laboratório de Patologia do Hospital Amaral Carvalho de Jaú/São Paulo, totalizando 297 casos. Dos blocos doadores foram extraídos cilindros de 2mm de diâmetro e depositados nos blocos de parafina receptores, usando Tissue Microarrays (Bencher Instruments®, Silver Spring, Maryland). Nestes cortes, foi feita a pesquisa imunoistoquímica para diferenciação dos fenótipos do carcinoma de mama, segundo a Classificação Molecular. As lâminas obtidas por PAAF, foram revisadas em microscópio de multiobservação (BX50 Olympus®, Japan), por dois médicos patologistas (RMD e FMN), sendo estudados individualmente os cinco critérios citológicos: celularidade, coesão celular, necrose, nucléolo e atipia nuclear. Utilizou-se o teste exato de Fisher para testar a associação entre os critérios citológicos e os fenótipos do carcinoma de mama. RESULTADOS: Dos 297 casos selecionados, 169 foram incluídos, resultando nos seguintes fenótipos - luminal A: 107 (63.3%), luminal B: 39 (23.1%), superexpressão de HER2: 8 (4.7%), e triplo negativo: 15 (8.9%). Os critérios citológicos que se associaram ao fenótipo luminal foram: celularidade baixa ou moderada (40.4%) (OR = 7.12, IC95%: 1.61 - 31.52), nucléolo inconspícuo ou presente (55.5%) (OR = 8.31, IC95%: 2.36 - 29.19) e atipia nuclear discreta ou moderada (44.5%) (OR = 8.42, IC95%: 1.90 - 37.25). Os critérios citológicos associados ao fenótipo luminal A foram: nucléolo inconspícuo ou presente (62.6%) (OR = 2.99, IC95%: 1.39 – 6.41), menor perda de coesão celular (OR = 0.46, IC95%: 0.24 - 0.88), mostrando grupamentos com coesão celular moderada a intensa, e ausência de necrose (40.2%) (OR = 0.32, IC95%: 0.15 – 0.68). CONCLUSÃO: Os critérios citológicos presentes nas lâminas obtidas por PAAF, e que mais se associaram ao fenótipo luminal do carcinoma de mama foram celularidade baixa e moderada, nucléolos inconspícuos ou pequenos e atipia nuclear leve a moderada. Cabe destacar, que para o fenótipo luminal A, os critérios citológicos que mais se associaram foram: nucléolos inconspícuos ou pequenos, coesão celular moderada a intensa e ausência de necrose. A distinção do fenótipo luminal é de relevância clínica, por apresentar melhor prognóstico, relacionado a menor mortalidade e menores taxas de metástase. / Breast carcinoma is a heterogeneous disease. It can be classified into phenotypes based on the expression of certain proteins, with differences in prognosis. The luminal phenotype is the most common, accounting for about 70% of cases. Some specific treatments for this phenotype of breast carcinoma are already being studied, which could improve prognosis of affected patients. However, there is currently no consensus on which cytological criteria could predict the luminal phenotype. OBJECTIVE: To evaluate which cytological criteria in fine-needle aspiration (FNA) biopsy are related with the luminal phenotype of breast carcinoma. METHODS: This was a cross-sectional study with descriptive and comparative component from cases of breast carcinomas, from the Laboratory of Pathology, Hospital Amaral Carvalho de Jaú / São Paulo. FNA biopsy specimens and tissue sections (mastectomy specimens) of invasive ductal and lobular carcinomas of the breast, retrieved from 2000 to 2005, were selected and classified into phenotypes by immunohistochemistry, using tissue microarray technology (Bencher Instruments®, Silver Spring, Maryland): luminal A and B, HER2 overexpression and triple negative. The cytological criteria for all cases were reviewed blindly by two pathologists using a multiobserver microscope (BX50 Olympus®, Japan), according to five cytological criteria: cellularity, cell cohesion, necrosis, nucleoli and nuclear atypia. Exact Fisher test was used to test the association between cytological criteria and phenotypes of breast carcinoma. RESULTS: From 297 selected patients, 169 were included, resulting in the following phenotypes - luminal A: 107 (63.3%), luminal B: 39 (23.1%), HER2 overexpression: 8 (4.7%), and triple negative: 15 (8.9%). The luminal phenotype showed mild or moderate cellularity (40.4%) (OR = 7.12, 95% CI: 1.61 - 31.52), inconspicuous or present nucleoli (55.5%) (OR = 8.31, 95% CI: 2.36 - 29.19) and mild or moderate nuclear atypia (44.5%) (OR = 8.42, 95% CI: 1.90 - 37.25). Inconspicuous or present nucleoli (62.6%) (OR = 2.99, 95% CI: 1.39 - 6.41), less dishesive cells (OR = 0.46, 95% CI: 0.24 - 0.88), showing clusters with moderate to intense cell cohesion (54.2%), and absence of necrosis (40.2%) (OR = 0.32, 95% CI: 0.15 - 0.68) were associated with luminal A phenotype. CONCLUSION: The individual FNA cytological criteria that might indicate the luminal phenotype of breast cancer were mild to moderate cellularity, inconspicuous or little nucleoli and mild to moderate nuclear atypia. Inconspicuous or little nucleoli, moderate to intense cell cohesion and absence of necrosis were associated with luminal A phenotype. The distinction of luminal phenotype of breast carcinoma is clinically relevant, since it has better prognosis, related to lower mortality and lower metastases rate.

Orientador: Rozany Mucha Dufloth / Resumo: O carcinoma de mama é uma doença heterogênea. Pode ser classificado em fenótipos, com diferentes prognósticos, com base na expressão de determinadas proteínas. O fenótipo luminal é o mais frequente, correspondendo a cerca de 70% dos casos, sendo que tratamentos específicos para este fenótipo de carcinoma de mama já estão em estudo, com melhora promissora do prognóstico das pacientes acometidas. Entretanto, ainda não foram definidos critérios citológicos que pudessem predizer este fenótipo no material obtido pela punção aspirativa por agulha fina (PAAF). OBJETIVO: Investigar critérios citológicos individuais presentes na PAAF que possam se associar com o diagnóstico do fenótipo luminal do carcinoma de mama. MÉTODOS: Trata-se de estudo tipo corte-transversal, com componente descritivo e comparativo. As lâminas de PAAF e espécimes de carcinomas de mama invasivos ductais e lobulares, do período de 2000 a 2005, foram selecionados do arquivo do Laboratório de Patologia do Hospital Amaral Carvalho de Jaú/São Paulo, totalizando 297 casos. Dos blocos doadores foram extraídos cilindros de 2mm de diâmetro e depositados nos blocos de parafina receptores, usando Tissue Microarrays (Bencher Instruments®, Silver Spring, Maryland). Nestes cortes, foi feita a pesquisa imunoistoquímica para diferenciação dos fenótipos do carcinoma de mama, segundo a Classificação Molecular. As lâminas obtidas por PAAF, foram revisadas em microscópio de multiobservação (BX50 Olympus®, Japan), por dois médicos p... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Breast carcinoma is a heterogeneous disease. It can be classified into phenotypes based on the expression of certain proteins, with differences in prognosis. The luminal phenotype is the most common, accounting for about 70% of cases. Some specific treatments for this phenotype of breast carcinoma are already being studied, which could improve prognosis of affected patients. However, there is currently no consensus on which cytological criteria could predict the luminal phenotype. OBJECTIVE: To evaluate which cytological criteria in fine-needle aspiration (FNA) biopsy are related with the luminal phenotype of breast carcinoma. METHODS: This was a cross-sectional study with descriptive and comparative component from cases of breast carcinomas, from the Laboratory of Pathology, Hospital Amaral Carvalho de Jaú / São Paulo. FNA biopsy specimens and tissue sections (mastectomy specimens) of invasive ductal and lobular carcinomas of the breast, retrieved from 2000 to 2005, were selected and classified into phenotypes by immunohistochemistry, using tissue microarray technology (Bencher Instruments®, Silver Spring, Maryland): luminal A and B, HER2 overexpression and triple negative. The cytological criteria for all cases were reviewed blindly by two pathologists using a multiobserver microscope (BX50 Olympus®, Japan), according to five cytological criteria: cellularity, cell cohesion, necrosis, nucleoli and nuclear atypia. Exact Fisher test was used to test the association between cy... (Complete abstract click electronic access below) / Mestre

Les cancers du sein de sous-type luminal B sont associés à un mauvais pronostic. Afin de mieux comprendre la biologie de ce sous-type, nous avons étudié au sein de 188 tumeurs mammaires de différents sous-types, les anomalies du nombre de copies, les méthylations de l'ADN, les profils d'expression génique et les mutations somatiques dans 9 gènes sélectionnés. Un total respectif de 237 et 101 oncogènes et gènes suppresseurs de tumeurs (TSG) candidats présentaient une dérégulation de l'expression en relation avec leur CNA. 88% des TSG potentiels étaient localisés sur le bras chromosomique 6q. 101 oncogènes candidats ont été validés sur une série publique de 5765 cancers du sein, et l'expression de 67 gènes était associée à un mauvais pronostic au sein des tumeurs luminales. 24 gènes présentaient une dérégulation de l'expression en relation avec un haut niveau de méthylation de l'ADN. FOXO3, PIK3CA et TP53 étaient les gènes les plus fréquemment mutés parmi les 9 testés. Dans une méta-analyse de séquençage de nouvelle génération regroupant 875 cancers du sein, les gènes les plus fréquemment mutés dans le sous-type luminal B étaient PIK3CA, TP53 et GATA3. Les nombreuses altérations moléculaires ciblaient des voies de signalisation communes, incluant 3 axes pouvant jouer un rôle majeur dans le sous-type luminal B : la voie TP53 et l'instabilité chromosomique, les voies de signalisation PI3K/AKT/MTOR/FOXO et MAPK/JNK, et les altérations des facteurs de transcription et épigénomiques. En conclusion, nous avons établi un répertoire de gènes candidats dans le sous-type luminal B qui pourraient être impliqués dans le développement et/ou l'hormonorésistance de ce sous-type. / Breast cancers (BCs) of the luminal B subtype have a poor prognosis. To better understand this subtype we studied in 188 BCs of various molecular subtypes, DNA copy number aberrations, DNA promoter methylation, gene expression profiles, and somatic mutations in nine selected genes. A total of 237 and 101 luminal B-specific candidate oncogenes and tumor suppressor genes (TSGs) presented a deregulated expression in relation with their CNAs. Interestingly, 88% of the potential TSGs are located within chromosome arm 6q. 101 candidate oncogenes were validated in a public series of 5,765 BCs and the overexpression of 67 was associated with poor survival in luminal tumors. 24 genes presented a deregulated expression in relation with a high DNA methylation level. FOXO3, PIK3CA and TP53 were the most frequent mutated genes among the nine tested. In a meta-analysis of next-generation sequencing data in 875 BCs, PIK3CA, TP53 and GATA3 were the most frequent mutated genes. Numerous molecular alterations targeted common signalling pathway, included 3 ways wich may play a major in the luminal B subtype: TP53 pathway and chromosomal instability, PI3K/AKT/MTOR/FOXO and MAPK/JNK pathway, and epigenomic and transcription factors alterations. In conclusion, we have reported a repertoire of luminal B candidate genes that may be involved in the development and/or hormone resistance of this subtype.

The heterogeneity of breast cancer (disease stage and phenotype) makes it challenging to differentiate between each subtype; luminal A, luminal B, HER2, basal-like and claudin-low, on the basis of a single gene or protein. Therefore, a collection of markers is required that can serve as a signature for diagnosing different types of breast cancer. New developments in proteomics have provided the opportunity to look at phenotype-specific breast cancer cell lines and stage-specific liquid biopsies (nipple aspirate fluid [NAF], plasma samples) to identify disease and phenotype specific signature. An 8-plex iTRAQ quantification strategy was employed to compare proteomic profiles of a range of breast cancer and ‘normal-like’ cell lines with primary breast epithelial cells. From this, 2467 proteins were identified on Orbitrap Fusion and Ultraflex II, of which 1430 were common. Matched pairs of NAF samples from four patients with different stages of breast cancer, were analysed by SCX-LC-MS and a total of 1990 unique gene products were identified. More than double the number of proteins previously published data, were detected in NAF, including 300 not detected in plasma. The NAF from the diseased patients have 138 potential phenotype biomarkers that were significantly changed compared to the healthy volunteer (7 for luminal A, 9 for luminal B, 11 for HER2, 14 for basal-like and 52 for claudin-low type). The average coefficient of variation for triplicate analyses by multiple reaction monitoring mass spectrometry (MRM-MS), was 9% in cell lines, 17 % in tissue biopsies, 22% in serum samples and 24% in NAF samples. Overall, the results provide a strong paradigm to develop a clinical assay based on proteomic changes in NAF samples for the early detection of breast cancer supplementary to established mammography programmes.

<p>After drinking water, the fluid quickly leaves the stomach thereby creating a hypotonic luminal environment in the duodenum. This in turn constitutes a potential threat to the integrity of the duodenal epithelium. It therefore seems highly likely that luminal hypotonicity activates physiological mechanisms that aim to increase luminal osmolality. One such physiological mechanism may be to increase mucosal permeability thereby facilitating the transport of osmolytes into the lumen.</p><p>A draw-back of performing experiments in anesthetized animals is that surgery <i>per se</i> depresses gut functions, such as peristalsis, by mechanisms involving endogenous prostaglandins. In this thesis it is shown that inhibition of cyclooxygenase-2 (COX-2), in animals subjected to an abdominal operation, restore and/or improve duodenal functions such as motility, mucosal bicarbonate secretion, hypotonicity-induced increase in mucosal permeability and the osmolality-adjusting capability.</p><p>Experiments revealed that the stomach is resistant to hypotonic challenge while the jejunum is more sensitive to hypotonicity-induced increase in mucosal permeability than the duodenum. The hypotonicity-induced increase in duodenal mucosal permeability is not due to injury but possibly reflects physiological dilatation of paracellular shunts.</p><p>Luminal perfusion of the duodenum with an isotonic solution lacking Cl^- decreased bicarbonate secretion while the lack of luminal Na⁺ increased mucosal permeability. Stimulation of bicarbonate secretion by COX-2 inhibition is to a large extent dependent on luminal Cl^- while that induced by vasoactive intestinal peptide is not.</p><p>The hypotonicity-induced increase in mucosal permeability involves the release and action of serotonin (5-HT) on 5-HT₃ and 5-HT₄ receptors and stimulation of enteric nerves strongly implicating physiological regulation of this process.</p>

After drinking water, the fluid quickly leaves the stomach thereby creating a hypotonic luminal environment in the duodenum. This in turn constitutes a potential threat to the integrity of the duodenal epithelium. It therefore seems highly likely that luminal hypotonicity activates physiological mechanisms that aim to increase luminal osmolality. One such physiological mechanism may be to increase mucosal permeability thereby facilitating the transport of osmolytes into the lumen. A draw-back of performing experiments in anesthetized animals is that surgery per se depresses gut functions, such as peristalsis, by mechanisms involving endogenous prostaglandins. In this thesis it is shown that inhibition of cyclooxygenase-2 (COX-2), in animals subjected to an abdominal operation, restore and/or improve duodenal functions such as motility, mucosal bicarbonate secretion, hypotonicity-induced increase in mucosal permeability and the osmolality-adjusting capability. Experiments revealed that the stomach is resistant to hypotonic challenge while the jejunum is more sensitive to hypotonicity-induced increase in mucosal permeability than the duodenum. The hypotonicity-induced increase in duodenal mucosal permeability is not due to injury but possibly reflects physiological dilatation of paracellular shunts. Luminal perfusion of the duodenum with an isotonic solution lacking Cl- decreased bicarbonate secretion while the lack of luminal Na+ increased mucosal permeability. Stimulation of bicarbonate secretion by COX-2 inhibition is to a large extent dependent on luminal Cl- while that induced by vasoactive intestinal peptide is not. The hypotonicity-induced increase in mucosal permeability involves the release and action of serotonin (5-HT) on 5-HT3 and 5-HT4 receptors and stimulation of enteric nerves strongly implicating physiological regulation of this process.

The formation of a continuous tubular network in the mammalian urinary system requires the interconnection of two epithelial populations with distinct cellular origins. The proximal component of the renal network is the nephron--a complex tubule responsible for much of the physiological action of the kidney. Nephrons connect to a collecting duct network to transport urine from the kidney to the bladder, via the ureter. I have used high-resolution image analysis of genetically labeled nephron and collecting duct networks together with apical and luminal markers to characterize the epithelial interconnection process in the developing kidney. Morphological protrusions at the distal end of the nephron precursor, adjacent to the tip of the collecting duct epithelium, precede luminal interconnection at the S-shaped body stage. Distal cells in the nephron precursor do not display clear epithelial junction complexes and show upregulation of phospho-myosin light chain, suggestive of a quasi-mesenchymal cell behavior. The close apposition of this group of cells with the collecting duct epithelium is facilitated by the absence on an intervening basal lamina. Live imaging of explanted kidneys suggests that distal cells break through into the lumen of the collecting duct epithelium and undergo cell death. No interconnection is observed upon Notch-mediated proximalization of distal cell fates. Furthermore, distal factor bone morphogenetic protein 2 (Bmp2) expression is lost in proximalized nephron precursor derivatives. Finally, I demonstrate that mice with specific loss of Bmp2 in nephron precursors and their derivatives results in a fraction of disconnected mature nephrons that later results in nephron atrophy and compromised renal function at juvenile stage compared to control mice. These data support a model in which the establishment of distal identity in nephron precursor cells closest to the nascent collecting duct epithelium leads to an active cell invasion that establishes a patent tubular interconnection between the nephron and collecting duct.

The aim of this thesis was to investigate the prognostic role of the proliferation markers cyclin B1 and Phosphorylated Histone 3 (PPH3) in breast cancer (BC). In paper I we used an experimental study design, we compared women dying early from their BC with women free from relapse more than eight years after initial diagnosis. All women had stage I, node-negative and hormone receptor positive disease. None had received adjuvant chemotherapy. We found that low-risk node negative patients with high expression of cyclin B1 had a significantly worse outcome than patients with low expression of cyclin B1. In paper II a population-based case control study was performed to further investigate the prognostic value of cyclin B1. One hundred and ninety women who died from BC were defined as cases and 190 women alive at the time for the corresponding case’s death were defined as controls. Inclusion criteria were tumor size 50 mm, no lymph node metastases, and no adjuvant chemotherapy. Two investigators evaluated the stainings independently. Cyclin B1 was found to be a prognostic factor for BC death that could identify high-risk patients with a good to very good reproducibility. Paper III aimed to investigate the role of proliferation in male breast cancer (MBC). One hundred and ninety-seven MBC tumors were stained for cyclin A, B1, D1 and Ki67. Overexpression of cyclin A and B1 and elevated mitotic count were predictive of breast cancer death. Ki67 was re-evaluated and different cut-offs were used, but no prognostic value could be demonstrated. On the other hand high levels of cyclin D1 were associated with better outcome in MBC. In paper IV we applied the immunohistochemichal panel suggested from international guidelines to the same patient material as in paper II, to discriminate luminal A from luminal B BC. We wanted to evaluate if different cut-off values of Ki67, cyclin A or B1 could more clearly separate luminal A from B. Cyclin A, B1 and Ki67 (cut-off 20%) could detect difference in outcome between these subtypes with cyclin A showing greater prognostic value. The aim of paper V was to examine the prognostic role of PPH3 compared to the proliferation markers Ki67, cyclin A and cyclin B1 with focus on ER positive disease. PPH3 was found to be a prognostic factor for breast cancer death but in the multivariate analysis including all proliferation markers, only cyclin A remained a prognostic factor. Finally, we conclude that both cyclin B1 and PPH3 are prognostic factors for breast cancer death, but are outperformed by cyclin A in ER positive patients. In male breast cancer prognostic factors need to be further studied.

Deux tiers des cancers du sein expriment le récepteur à l’estrogène alpha (REα) et leur croissance dépend des estrogènes alors que l’expression de REα induit la différenciation et la sénescence des cellules humaines mammaires épithéliales normales. Le développement embryonnaire et la différenciation de la glande mammaire adulte sont contrôlés par des facteurs de transcription, dont beaucoup sont aussi impliqués dans la tumorigenèse. Plusieurs études d'association pan-génomiques ont identifié le putatif facteur de transcription TOX high mobility group box family member 3 (TOX3) comme un nouveau gène de prédisposition au cancer du sein.L’objectif de cette étude était la caractérisation fonctionelle de TOX3 dans l’épithélium mammaire normal et le cancer du sein.J’ai examiné l’expression de TOX3 dans des tumeurs du sein humaines et dans le sein normal par analyse des données d’expression issues de puces à ADN. L’effet de TOX3 sur la différenciation des cellules épithéliales mammaires était analysé par des assays CFC et FACS. De plus, j’ai effectué une analyse microarray des cellules luminales cancéreuses MCF-7 exprimant TOX3 afin d’identifier les gènes cibles de TOX3 ainsi que la méthode de purification d’affinité en tandem (TAP) combinée à la spectrométrie de masse afin d’identifier des protéines interactants de TOX3. Finalement, j’ai étudié le potentiel oncogénique de TOX3 dans un modèle de xénogreffe. / Two thirds of breast cancers express the estrogen receptor alpha (ERα) and are estrogen-dependent for growth. In contrast, expression of ERα induces differentiation and senescence in normal human mammary epithelial cells. Both embryonic development and lineage commitment in the adult mammary gland are governed by transcriptional regulators, many of which have also been implicated in tumourigenesis. Genome-wide association studies have identified the previously uncharacterised putative transcription factor TOX high mobility group box family member 3 (TOX3) as a new candidate breast cancer susceptibility gene.In the present study, I aimed to characterise TOX3 function in the normal human mammary epithelium and in breast cancer.I have examined TOX3 expression in primary breast tumours and in the normal mammary gland using micorarray data. The influence of TOX3 expression on lineage commitment was investigated using the colony forming cell (CFC) assay and FACS analysis. I further carried out microarray analysis of luminal breast cancer cells ectopically expressing TOX3 to identify TOX3 target genes as well as tandem affinity purification of TOX3 to identify TOX3 interacting proteins. Finally, the oncogenic potential of TOX3 was investigated in a human-in-mouse xenograft model.