Les mutations du gène MEN1 prédisposent au syndrome des Néoplasies Endocriniennes Multiples de type 1 (NEM1), caractérisé par des tumeurs endocrines multiples. Les souris hétérozygotes pour Men1 développent des tumeurs similaires, ainsi que des cancers de la prostate et des glandes mammaires, avec une incidence faible. J’ai pu montrer que l’expression de la protéine menin, codée par ce gène, est totalement inactivée dans les carcinomes prostatiques développés chez ces souris et est associée à une dérégulation de l’expression du récepteur aux androgènes et une inactivation de l’inhibiteur des CDK p27, un gène cible connu de menin. Des souris WapCre-Men1 F/F, où le gène Men1 est invalidé dans les cellules mammaires, développent des néoplasies intraépithéliales mammaires (MIN) avec une forte incidence à partir de 9 mois. Une fuite d’expression du transgène WapCre dans l’hypophyse entraîne en plus le développement de prolactinomes chez ces souris, les conduisant à une mort prématurée. Par diverses analyses, j’ai pu déterminer que l’augmentation de l’incidence de ces lésions ne pouvait pas être seulement expliquée par l’influence des prolactinomes. De manière intéressante, j’ai pu mettre en évidence une nette diminution du marquage membranaire de beta-caténine, un partenaire connu de menin, ainsi que de E-cadhérine dans les lésions MIN, suggérant une altération de la cohésion cellulaire en absence de menin. L’ensemble des données obtenues pendant ma thèse indiquent un rôle potentiel de l’invalidation du gène Men1 dans le développement de carcinomes prostatiques et de néoplasies mammaires chez la souris / Mutations of the MEN1 gene predispose to multiple endocrine neoplasia type 1 (MEN1) syndrome, characterized by the occurrence of multiple endocrine tumours. Heterozygous Men1 mutant mice not only recapitulate MEN1 pathology, but also display prostatic and mammary carcinomas with a low incidence. I showed that the expression of menin, coded by the Men1 gene, was completely inactivated in the prostatic carcinomas developed in these mice. Deregulated expression of androgen receptor and the inactivation of p27 CDK inhibitor, a menin target gene, were also found in these lesions. In addition, my data demonstrated that mammary-specific disruption of the Men1 gene in mice led to high incidence of mammary intraepithelial neoplasia (MIN) from 9 months of age in the mutant mice. An unexpected leakage activity of the WapCre transgene in pituitary resulted in the development of prolactinomas and premature death in the mutant mice. Several analyses provided evidence showing that the increased incidence of MIN lesions could not be simply explained by the influence of prolactinomas. Interestingly, we observed a strong reduction of beta-catenin, a known menin partner, and E-cadherin membrane expression in these lesions, suggesting an alteration of cellular adhesion in the absence of menin. On the whole, these data indicate a potential implication of Men1 disruption in the development of prostate carcinomas and mammary intraepithelial neoplasia in mice

Beyond its essential roles in embryonic development, the Wnt-mediated signal transduction cascade is critically implicated in homeostasis of adult tissues. In the gastrointestinal epithelium, the threshold of active Wnt signaling is kept in a physiological range by a spectrum of regulatory networks and loops, thereby balancing the opposing processes of cell fate determination, proliferation and stem cell self-renewal. Furthermore, compelling evidence undoubtedly link an aberrant Wnt activity to the onset of bowel cancer. Understanding the principle causes and effects secondary to excessive Wnt signaling can provide valuable insights into the pathology of the malignant transformation of the colorectum. The proposed thesis attempts to focus on novel modes of the Wnt pathway modulation; both general and context-specific nuances of the Wnt level adjustment are thereby delineated. The results are presented in three distinct research publications and one review article. The first study examines the contribution of the distinct post-translational modifications, which the Wnt proteins undergo, to their proper processing, secretion and signaling activity. First, we investigated the sequential order and mutual interdependence of cysteine and serine-linked fatty acylation and N-linked glycosylation of murine...

L’hyperplasie bilatérale macronodulaire des surrénales (HBMS) conduit au développement de nodules corticosurrénaliens bilatéraux entraînant un syndrome de Cushing diagnostiqué souvent au cours de la cinquième décennie. L’étiologie de cette maladie n’était que partiellement connue mais le caractère bilatéral de l’atteinte surrénalienne et l’observation de cas familiaux suggéraient, au début de ce travail, une origine génétique. L’analyse de l’ADN tumoral et leucocytaire d’une série de 33 patients opérés a permis de mettre en évidence chez 25% des patients une perte d’hétérozygotie neutre en nombres de copies (LOH) de tout le bras court du chromosome 16 (16p) au niveau du tissu surrénalien. Un séquençage complet du génome de 5 patients (ADN germinal et tumoral) a permis de mettre en évidence une mutation du gène ARMC5 localisé en 16p pour 4 patients. Le séquençage direct des parties codantes d’ARMC5 à partir de l’ADN somatique et germinal de l’ensemble des patients opérés de la cohorte a montré qu’au total, 55% des patients avaient une mutation d’ARMC5. L’inactivation du gène se fait selon la théorie de Knudson (un événement germinal inactivant le premier allèle associé à un autre événement somatique inactivant le second allèle) ce qui laisse supposer qu’ARMC5 est un gène suppresseur de tumeur. L’analyse de la cohorte d’HBMS de nos collaborateurs américains au National Institute Health (laboratoire de CA. Stratakis, Bethesda, USA) a permis de confirmer que les mutations d’ARMC5 étaient un événement fréquent. Des variants de ce gène sont aussi associés à l’hypertension à rénine basse chez les patients noirs-américains. Afin de déterminer des corrélations génotype-phénotype, notre cohorte initiale a été élargie pour constituer une série consécutive de 98 cas index de patients présentant des formes légères à sévères de la maladie, opérées ou non. Vingt-quatre patients (25%) présentaient une altération d’ARMC5. Par ailleurs, 31 nodules surrénaliens de 19 patients ont été analysés en somatique. Le second événement était une mutation dans 68% des cas et une LOH du locus pour les 32% restant. Chez un même patient, le second événement était différent dans chaque nodule présenté. Les patients mutés avaient un syndrome de Cushing plus sévère cliniquement et biologiquement par rapport aux patients non mutés. La taille de leurs surrénales étaient plus grandes avec un plus grand nombre de nodules. Les patients mutés étaient aussi plus jeunes au diagnostic et plus souvent hypertendus. Ces patients étaient ainsi plus souvent opérés. La fonction de la protéine ARMC5 n’était pas connue lors de son identification comme gène de l’HBMS. In vitro, la surexpression du gène sauvage induit l’apoptose. La surexpression des mutants faux-sens et du mutant p.F700del retrouvés chez les patients entraîne moins d’apoptose qu’ARMC5 sauvage. La protéine ARMC5 contient des domaines Armadillo et BTB, connus pour être impliqués dans l’interaction protéine-protéine. En physiologie, l’ACTH stimule la production d’AMPc et la voie de la protéine kinase A (PKA) est impliquée dans différentes pathologies corticosurrénaliennes. Nous avons pu montrer qu’ARMC5 interagissait avec la sous-unité catalytique alpha de la PKA. L’invalidation d’ARMC5 conduit in vitro à une diminution de l’expression d’enzymes de la stéroïdogénèse, de la production de cortisol et une diminution de l’activité PKA. Ainsi, l’hypothèse pour expliquer les HBMS liées à une inactivation d’ARMC5 est que la perte d’apoptose conduit à une hyperplasie nodulaire du tissu corticosurrénalien et que, même si la production de cortisol est diminuée à l’échelle unicellulaire, l’effet de masse global conduit au total à un hypercortisolisme. Nos travaux ont donc identifié et caractérisé un premier gène causal, ARMC5, fréquemment impliqué dans l’HBMS et associé à des formes plus sévères de la maladie. Cette découverte ouvre des perspectives pour le diagnostic familial et la prise en charge des patients. (...) / Primary bilateral macronodular adrenal hyperplasia (PBMAH) is a rare cause of adrenal Cushing’s syndrome and bilateral adrenal tumors. We suspected a genetic origin of the disease on the basis of the report of some familial cases and the involvement of both adrenal glands. The aim of this study was to find a genetic cause of non syndromic PBMAH. To look at chromosomal abnormalities, we use single-nucleotide polymorphism (SNP) arrays and microsatellite markers analysis in a first series of 33 patients all operated for PBMAH. We realize whole genome sequencing of 5 patients (blood and tumor DNAs matched). Then we genotyped by Sanger sequencing the gene Armadillo Repeat Containing 5 (ARMC5) in this first series and 66 additional patients. Clinical data were collected to establish genotype-phenotype correlation. In addition, the cohort of patients of our collaborators at the National Institute Health (Dr. Stratakis, Bethesda, USA) was studied. The effects of ARMC5 inactivation and overexpression and the partners of the protein were sought in cell-culture models. The most frequent somatic alteration was a loss of heterozygosity at 16p observed in tumors of 25% of the patients. The gene ARMC5, located at 16p11.2, was the most frequently mutated by whole genome sequencing: a mutation was found in 4/5 patients. 55% of the patients of the first cohort (33 patients treated by adrenalectomy for PBMAH) had ARMC5 alteration. One patient presented with germline microdeletion of the locus identified by SNP array. Every patient had two events: either a mutation or a deletion at the germline level, either a second mutation or a LOH at the somatic level. We showed that the two events were present on different alleles suggesting that ARMC5 is a tumor suppressor gene. In addition, we showed for several patients that the second hit was different in each adrenal nodules of a same patient. This first cohort included only operated patients with serious forms of the disease. The study of the American cohort and the analysis of the total cohort of our lab including non-operated patients and milder forms showed an alteration of ARMC5 in about 25% of the patients. Genotype-phenotype correlation showed that ARMC5 defects are associated with younger age at the diagnosis, higher hypercortisolism, bigger adrenals and higher number of nodules. In addition, a mutation of ARMC5 was shown in a patient with a PBMAH secreting both aldosterone and cortisol. Analysis of a series of patient affected by primary hyperaldosteronism suggested that ARMC5 may be associated with hypertension especially in African-American subjet. Overexpression of ARMC5 leads in vitro to cell apoptosis. We showed that this apoptosis was reduced when transfecting vector harboring missense mutations or single amino-acid deletion found in our cohort. Invalidation of ARMC5 leads to a decreased steroidogenic enzymes expression, cortisol production and reduced protein kinase A (PKA) activity. We showed that ARMC5 interacts with the calaytic subunit alpha of the PKA dissociated from the cAMP-bound regulatory subunits. More than one quarter of sporadic PBMAH patients present a pathogenic germline ARMC5 defect and these index cases present a more severe disease. Systematic genotyping of ARMC5 may help for early diagnosis of PBMAH, familial counseling, and patients’ management. ARMC5 appears to be a new regulator of PKA and might represent a new target for the development of pharmacological agents controlling PKA function and cortisol production.

A expressão do gene RECK é ubíqua em tecidos normais e não detectável nas linhagens celulares tumorais testadas e em fibroblastos transformados por diversos oncogenes. Inicialmente isolado como um gene indutor da reversão fenotípica tumoral→normal em fibroblastos transformados por v-Ki-ras, o gene RECK codifica uma glicoproteína de membrana que suprime a invasão tumoral e metástase através da regulação da metaloprotease de matriz-9. Para entender os mecanismos de inibição da expressão do gene RECK, mediada por oncogenes, isolou-se e caracterizou-se a região 5\'- flanqueadora do gene RECK de camundongo (mRECK). Ensaios de atividade promotora utilizando mutantes de deleção da região 5\' - flanqueadora e o gene repórter luciferase, revelaram que a sequência de 52 pb, imediatamente \"upstream\" ao gene, possui uma atividade promotora que é suprimida pelo produto do oncogene Ha-ras (V12). Esta sequência contém dois sítios de ligação a Sp1 (SplA e SplB), um sítio de ligação a cEBPb e um CAAT box. EMSAs e ensaios de atividade promotora, utilizando mutantes pontuais nestes sítios, revelaram que as proteínas Spl e Sp3 se ligam a ambos os sítios Spl, e que a resposta a Ras é mediada apenas pelo sítio SplB. Análise por Southern blot utilizando uma enzima de restrição sensível à metilação e por Northern blot de mRNA extraído de células tratadas com um agente desmetilante, sugeriram que o mecanismo de metilação de DNA não está envolvido na regulação transcricional do gene RECK. O envolvimento de RECK em diversos sistemas de proliferação, invasão e reversão celular foi analisado através de Northern blot. Os resultados sugerem que a expressão de RECK é regulada por soro na linhagem A3l de fibroblastos normais de camundongo. / The RECK gene is ubiquitously expressed in normal human tissues, but is downregulated both in tumor cell lines and in oncogenically transformed fibroblasts. Initially isolated as a tumor→normal phenotypic reversioninducing gene in v-ki-ras-transformed fibroblast, RECK encodes a membrane-anchored glycoprotein that suppresses tumor invasion and metastasis by regulating the matrix metalloproteinase-9. In order to understand the mechanism of oncogene-mediated suppression of RECK gene expression, we have isolated and characterized the 5\'-flanking region of the mouse RECK gene (mRECK). Deletion mutants constructs of this 5\' -flanking region with the luciferase reporter gene, revealed that the 52 base pairs upstream displays promoter activity which is suppressed by the Ha-ras (V12) oncogene. This region contains two Spl-binding motifs (SplA and SplB), one cEBPb-binding motif, and one CAAT box. Gel shift analysis and reporter gene assays, in combination with site-directed point mutations in these elements, revealed that both Spl sites associate with Spl as well as Sp3 proteins, although Ras- responsiveness seems to be mediated only by the downstream Spl site (SplB). Southern blot analysis using a methylation-sensitive restriction enzyme and Northern blot analysis with mRNA extracted from cells treated with a demethylating agent, indicated that the mechanism of DNA methylation is not involved in the regulation of RECK gene transcription. The role of RECK in several systems of cell proliferation, invasion and reversion, analysed by Northern blot, suggested that RECK expression is cell cycle regulated by serum in normal A3l mouse fibroblast cell line.

O complexo da esclerose tuberosa (TSC) é um transtorno genético, sistêmico, com expressividade variável e herança autossômica dominante. Clinicamente manifesta-se devido ao desenvolvimento de hamartomas e hamártias em diferentes tecidos, principalmente no cérebro, rins, coração, pele e pulmões, podendo causar disfunção do órgão. Mutação em um de dois genes supressores tumorais, TSC1 ou TSC2, são responsáveis pelo TSC. Os genes TSC1 e TSC2 codificam para hamartina e tuberina, respectivamente. Ambas as proteínas interagem fisicamente formando um complexo citosólico que inibe mTOR (mammalian target of rapamycin). Testes moleculares para TSC1 e TSC2 são úteis para auxiliar no diagnóstico de casos clínicos difíceis, em aconselhamento genético e estudos de associação genótipo-fenotípica, além de permitirem a caracterização molecular de mecanismos patogenéticos da formação dos hamartomas e análises funcionais de seus produtos gênicos. Apesar de o diagnóstico de TSC ser basicamente clínico, a partir da revisão de seus critérios em 2012 por um grupo de especialistas, o achado de uma mutação em TSC1 ou TSC2 passou a ser considerado suficiente para o diagnóstico definitivo da doença. O estudo apresentado aqui é parte de um projeto em andamento para estabelecer condições ao desenvolvimento de análise de mutações causadoras de TSC nos genes TSC1 e TSC2. Nosso objetivo neste trabalho foi avaliar por sequenciamento de Sanger o DNA genômico de 28 pacientes brasileiros com diagnóstico definitivo de TSC, procedentes dos estados de São Paulo ou Paraná, tendo como alvo a sequência codificadora do gene TSC1, parte de seus segmentos intrônicos, o promotor basal, bem como o segmento imediatamente a 5\' deste. Sete pacientes (25%) apresentaram mutações de sentido trocado (nonsense) ou com deslocamento da leitura à tradução (frameshift) no gene TSC1. Entre 31 outras variantes de DNA encontradas, 23 são polimorfismos conhecidos e oito apresentaram frequência inferior a 1%, como verificado in silico entre mais de mil sequências de genomas humanos. Entre essas oito variantes de DNA novas ou raras, quatro foram detectadas em pacientes para os quais uma mutação patogênica havia sido identificada e, por isso, foram reclassificadas como polimorfismos. Duas e uma variantes de DNA do mesmo paciente flanqueavam um sítio de ligação em potencial para um fator de transcrição específico, a 5\' do promotor basal de TSC1. Por fim, uma nova variante de DNA na região não codificadora do éxon 2 do gene TSC1 foi predita com potencial para alterar um elemento candidato a acentuador de splicing. Em resumo, como observado em estudos anteriores, descrevemos aqui 25% dos pacientes com TSC apresentando mutações patogênicas na sequência codificadora do gene TSC1. Nossos dados mostraram quatro novas variantes de DNA em regiões potencialmente reguladoras da expressão do gene TSC1, que podem revelar-se como mutações patogênicas e, portanto, necessitam ser testadas experimentalmente / Tuberous sclerosis complex (TSC) is a multisystem disorder, with variable expression and autosomal dominant inheritance. Clinically it is due to hamartia and hamartoma development in different tissues, notably in the brain, kidneys, heart, skin and lungs, causing organ dysfunction. Mutations in either tumor suppressor gene, TSC1 or TSC2, are responsible for TSC. TSC1 and TSC2 genes code for hamartin and tuberin, respectively. Both proteins physically interact forming a cytosolic complex that inhibits the mammalian target of rapamycin (mTOR). TSC1 and TSC2 molecular testing has been useful in diagnosing clinically challenging cases, in genetic counseling and genotype/phenotype association studies, besides evaluation of the molecular basis of hamartoma formation and functional analyses of both gene products. Although TSC diagnosis is basically clinical, since the 2012 specialist panel review the finding of a TSC1 or TSC2 mutation has been considered sufficient for the definite diagnosis of the disease. The results presented here are part of an ongoing project to establish conditions for TSC1 and TSC2 mutation studies. Our first aim is to evaluate by Sanger sequencing TSC1 coding sequence, and an average of 132 base pairs of intronic regions next to exon boundaries from TSC patients, in addition to the gene core promoter. We present preliminary results of a sample of 28 patients with definite TSC diagnosis, from São Paulo and Paraná states. Seven patients (25%) displayed TSC1 nonsense or frameshift mutations. Among 31 other DNA variants identified, 23 were known polymorphisms, and eight had frequencies below 1% as verified in silico among more than a thousand human genomes. Out of eight novel or rare DNA variants, four were detected in patients for whom a pathogenic mutation had been found. Two and one additional DNA point variants from the same patient flanked a putative transcription factor binding site. Finally, a novel DNA variant residing in the TSC1 noncoding exon 2 was predicted to change the sequence potential to behave as a splicing enhancer. In summary, similar to previous studies, we describe 25% of TSC patients with mutations in the TSC1 coding sequence. Differently from other reports, our data disclose four novel DNA variants in TSC1 potentially regulatory regions that are likely to unravel novel pathogenic mutations, and thus need to be experimentally tested

O complexo da esclerose tuberosa (TSC) é um transtorno genético, sistêmico, com expressividade variável e herança autossômica dominante. Clinicamente manifesta-se devido ao desenvolvimento de hamartomas e hamártias em diferentes tecidos, principalmente no cérebro, rins, coração, pele e pulmões, podendo causar disfunção do órgão. Mutação em um de dois genes supressores tumorais, TSC1 ou TSC2, são responsáveis pelo TSC. Os genes TSC1 e TSC2 codificam para hamartina e tuberina, respectivamente. Ambas as proteínas interagem fisicamente formando um complexo citosólico que inibe mTOR (mammalian target of rapamycin). Testes moleculares para TSC1 e TSC2 são úteis para auxiliar no diagnóstico de casos clínicos difíceis, em aconselhamento genético e estudos de associação genótipo-fenotípica, além de permitirem a caracterização molecular de mecanismos patogenéticos da formação dos hamartomas e análises funcionais de seus produtos gênicos. Apesar de o diagnóstico de TSC ser basicamente clínico, a partir da revisão de seus critérios em 2012 por um grupo de especialistas, o achado de uma mutação em TSC1 ou TSC2 passou a ser considerado suficiente para o diagnóstico definitivo da doença. O estudo apresentado aqui é parte de um projeto em andamento para estabelecer condições ao desenvolvimento de análise de mutações causadoras de TSC nos genes TSC1 e TSC2. Nosso objetivo neste trabalho foi avaliar por sequenciamento de Sanger o DNA genômico de 28 pacientes brasileiros com diagnóstico definitivo de TSC, procedentes dos estados de São Paulo ou Paraná, tendo como alvo a sequência codificadora do gene TSC1, parte de seus segmentos intrônicos, o promotor basal, bem como o segmento imediatamente a 5\' deste. Sete pacientes (25%) apresentaram mutações de sentido trocado (nonsense) ou com deslocamento da leitura à tradução (frameshift) no gene TSC1. Entre 31 outras variantes de DNA encontradas, 23 são polimorfismos conhecidos e oito apresentaram frequência inferior a 1%, como verificado in silico entre mais de mil sequências de genomas humanos. Entre essas oito variantes de DNA novas ou raras, quatro foram detectadas em pacientes para os quais uma mutação patogênica havia sido identificada e, por isso, foram reclassificadas como polimorfismos. Duas e uma variantes de DNA do mesmo paciente flanqueavam um sítio de ligação em potencial para um fator de transcrição específico, a 5\' do promotor basal de TSC1. Por fim, uma nova variante de DNA na região não codificadora do éxon 2 do gene TSC1 foi predita com potencial para alterar um elemento candidato a acentuador de splicing. Em resumo, como observado em estudos anteriores, descrevemos aqui 25% dos pacientes com TSC apresentando mutações patogênicas na sequência codificadora do gene TSC1. Nossos dados mostraram quatro novas variantes de DNA em regiões potencialmente reguladoras da expressão do gene TSC1, que podem revelar-se como mutações patogênicas e, portanto, necessitam ser testadas experimentalmente / Tuberous sclerosis complex (TSC) is a multisystem disorder, with variable expression and autosomal dominant inheritance. Clinically it is due to hamartia and hamartoma development in different tissues, notably in the brain, kidneys, heart, skin and lungs, causing organ dysfunction. Mutations in either tumor suppressor gene, TSC1 or TSC2, are responsible for TSC. TSC1 and TSC2 genes code for hamartin and tuberin, respectively. Both proteins physically interact forming a cytosolic complex that inhibits the mammalian target of rapamycin (mTOR). TSC1 and TSC2 molecular testing has been useful in diagnosing clinically challenging cases, in genetic counseling and genotype/phenotype association studies, besides evaluation of the molecular basis of hamartoma formation and functional analyses of both gene products. Although TSC diagnosis is basically clinical, since the 2012 specialist panel review the finding of a TSC1 or TSC2 mutation has been considered sufficient for the definite diagnosis of the disease. The results presented here are part of an ongoing project to establish conditions for TSC1 and TSC2 mutation studies. Our first aim is to evaluate by Sanger sequencing TSC1 coding sequence, and an average of 132 base pairs of intronic regions next to exon boundaries from TSC patients, in addition to the gene core promoter. We present preliminary results of a sample of 28 patients with definite TSC diagnosis, from São Paulo and Paraná states. Seven patients (25%) displayed TSC1 nonsense or frameshift mutations. Among 31 other DNA variants identified, 23 were known polymorphisms, and eight had frequencies below 1% as verified in silico among more than a thousand human genomes. Out of eight novel or rare DNA variants, four were detected in patients for whom a pathogenic mutation had been found. Two and one additional DNA point variants from the same patient flanked a putative transcription factor binding site. Finally, a novel DNA variant residing in the TSC1 noncoding exon 2 was predicted to change the sequence potential to behave as a splicing enhancer. In summary, similar to previous studies, we describe 25% of TSC patients with mutations in the TSC1 coding sequence. Differently from other reports, our data disclose four novel DNA variants in TSC1 potentially regulatory regions that are likely to unravel novel pathogenic mutations, and thus need to be experimentally tested

The phosphorylation and dephosphorylation of the tyrosine amino-acids in proteins play an important role in the regulation of many cellular processes in all eukariotic organisms, including the regulation of cell cycle control, growth control, cellular differentiation and gene and synaptic transmission. The involvement of the phosphatase genes in human carcinogenesis was long-suspected, but PTEN is the first important phosphatase gene proven to be a true tumour suppressor. The basic function of normal PTEN is the dephosphorylation of the kinases and inhibition of the integrin and growth factor mediated kinase signalling pathways. The central hypothesis of this study is that PTEN plays an important role in tumours of the upper female genital tract. The involvement of aberrations in the coding regions of this gene was studied in specific gynaecologic tumours and tissues using polymerase chain reaction based mutation analysis. The research model was to study both the malignant tumour and the closest available pre-malignant or benign counterpart to demonstrate different levels of involvement of PTEN in the evolving steps. The PTEN gene was found to be intimately involved in endometrial carcinogenesis. Involvement was demonstrated in hyperplasia and was common in endometroid carcinoma (54%). Pathogenic PTEN mutations were much more common in cancer than in hyperplasia (10%). Multiple mutations were found in some late stage tumours, suggesting that the already malignant tumour cells accumulate more genetic mutations over time. All tumours with more than one pathogenic mutation occurred in African patients. The latter twofindings are unique to the current study. Selective involvement of the PTEN gene was demonstrated in uterine soft tissue tumours. PTEN involvement was neither found in benign soft tissue tumours nor significantly in leiomyosarcoma or endometrial stromal sarcoma. However, PTEN plays a significant role in uterine carcinosarcoma (13%) and specifically in tumours with an endometroid epithelial component, where mutations were found in 17%. This finding is a highly significant and unique research result which supports the hypothesis of the endometrial origin of these tumours. It also supports the observation of a strong link between this gene and endometroid differentiation, with morphology strongly linked to cellular genetics. PTEN gene mutation was demonstrated in ovarian endometroid carcinoma in ~29% of cases investigated. This finding confirms PTEN involvement in carcinogenesis in this tumour type. The finding suggests that PTEN involvement is linked to endometroid epithelial morphology. We could not sufficiently test the involvement of the gene in benign or pre-malignant ovarian endometroid lesions and thus cannot comment on the chronology of mutations in this tissue type. When all tumour types were included, there was a tendency towards a lower frequency ofPTEN mutations in African women. PTEN mutations correlated with endometroid histology. In combination, these results confirm the racial disparity in tumour type distribution or morphology. In summary this study demonstrated significant though highly selective PTEN gene involvement and a strong and interesting association between genotype and histological phenotype was confirmed. The findings enhance our understanding of carcinogenesis and should lead to translational research into new anti-neoplastic drugs. AFRIKAANS: Fosforilering en defosforilering van die tirosien aminosure in proteine speel ‘n belangrike rol in die regulering van sellulêre prosesse in alle eukariotiese organismes. Dit sluit die regulering van selsikluskontrole, groeikontrole, sellulêre differensiasie sowel as genetiese en sinaptiese oordrag in. Dit word lank reeds gespekuleer dat die fosfatase-gene betrokke is in menslike karsinogenese, maar die PTEN geen is die eerste fosfatase geen wat bewys word om ‘n ware tumoronderdrukker geen te wees. As basiese funksie defosforileer normale PTEN die kinases en inhibeer dit die kinase sinjaal kontrolepaaie wat deur integrien en groeifaktor beheer word. Die sentrale hipotese van hierdie studie is dat PTEN ‘n belangrike rol speel in tumore van die boonste genitale traktus. Die frekwensie van abnormaliteite in die koderingsareas van hierdie geen is bestudeer in spesifieke ginekologiese tumore en weefsels met die gebruik van polimerase kettingreaksie gebaseerde mutasie-analise. Die maligne tumore sowel as die mees verwante pre-maligne of benigne weefsel- of tumortipes wat beskikbaar was, is gebruik as navorsingsmateriaal om sodoende die verskillende vlakke van PTEN betrokkenheid in die ontwikkeling van neoplasie te demonstreer.Intieme betrokkenheid van die PTEN geen is gevind in endometriële karsinogenese. PTEN mutasies is in hiperplasie gevind en dit was algemeen in endometroiede karsinoom (54%). Patogene mutasies was baie meer algemeen in kanker as in hiperplasie (10%). Veelvuldige mutasies is in sommige laat stadium tumore aangetoon, wat suggereer dat reeds maligne selle meer genetiese mutasies oor tyd verkry. Alle tumore waar meer as een patogeniese mutasie gevind is het voorgekom by swart pasiënte. Die laaste twee bevindinge is uniek tot hierdie studie.Selektiewe betrokkenheid van die PTEN geen is gevind in die ontwikkeling van sagte weefsel tumore van die uterus. PTEN mutasies is nie in benigne sagte weefsel tumore gevind nie en geen betekenisvolle betrokkenheid is in leiomiosarkome of endometriële stromale sarkome aangetoon nie. PTEN was egter betekenisvol betrokke in karsinosarkome van die uterus (13%) en veral in tumore met ‘n endometrioiede epiteelkomponent waar mutasies in 17% gevind is. Hierdie bevinding is ‘n hoogs betekenisvolle en unieke navorsingsbevinding wat die hipotese ondersteun dat hierdie tumore uit die endometrium ontstaan. Dit onderskryf ook die indruk dat ‘n sterk band bestaan tussen hierdie geen en endometroiede differensiasie, met morfologie sterk gekoppel aan sellulêre genetika.Mutasie in die PTEN geen is aangetoon in ovariële endometroiede karsinoom in ~29% van gevalle wat ondersoek is. Die bevinding bevestig PTEN betrokkenheid in karsinogenese in hierdie tumortipe. Weereens toon die resultaat dat PTEN betrokkenheid gekoppel is aan endometroiede morfologie. Die ondersoek van benign of pre-maligne letsels in hierdie orgaan was nie voldoende om kommentaar oor die tydsberekening van mutasie te kan lewer nie.Met alle tumortipes in ag genome, is daar ‘n tendens aangetoon van minder PTEN mutasies in swart vroue. PTEN mutasies korreleer met endometroiede histologie. In kombinasie bevestig hierdie resultaat ‘n rasse-diskrepansie in die distribusie van tumourtipe of morfologie. In opsomming is die bevinding van hierdie studie dat daar betekenisvolle dog hoogs selektiewe PTEN geen betrokkenheid in boonste genitale traktus tumore is. ‘n Sterk en interessante verband is bevestig tussen genotipe en histologiese fenotipe. Hierdie resultate verbeter die begrip van karsinogenese en behoort ‘n bydrae te lewer in die soeke na nuwe anti-neoplastiese middels. / Thesis (PhD)--University of Pretoria, 2011. / Obstetrics and Gynaecology / unrestricted

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.

As part of an International Cooperative Biodiversity Group (ICBG), extracts of plants from Suriname and Madagascar were bioassayed for cytotoxicity and antimalarial activity. Six cytotoxic extracts and one potential antimalarial were selected for fractionation, and yielded a number of bioactive compounds which were characterized by spectroscopy methods. Craspidospermum verticillatum (Apocynaceae) yielded four known indole alkoids. Casimirella sp (Icacinaceae) gave three new and five known diterpenoids. Pentopetia androsaemifolia (Apocynaceae) afforded one new and three known cardenolide glycosides. Physalis angulata (Solanaceae) yielded seven known physalins. Roupellina boivinnii (Apocynaceae) yielded four known and three new cardenolide glycosides, and three known cucurbitacins were isolated from Octolepis aff. dioica (Thymelaeaceae). In addition to these structural studies, a synthetic approach to lucilactaene, a cell cycle inhibitor was developed. / Ph. D.

Brust- und Ovarialkarzinome gehören zu den häufigsten sporadischen Tumorerkrankungen bei der Frau. Die Progression von benignen Neoplasien zu malignen Karzinomen werden von spezifischen Veränderungen der Genexpression begleitet. Durch die bioinformatische Auswertung von vier Millionen ESTs aus cDNA-Bibliotheken von Normalgeweben und der korrespondierenden Tumore wurden Hunderte von differenziell exprimierten Genen selektiert. Nach der chromosomalen Kartierung der Kandidatengene erfolgten weitere Untersuchungen für Gene aus den chromosomalen Regionen 1q32-q41 und 11q12-q23, die häufig in Brust- und Ovarialkarzinomen als aberrant beschrieben wurden. Die Validierung der in-silico Expressionsdaten erfolgte über Northernblot- und cDNA-Array-Analysen von unselektierten und mikrodissezierten Tumorproben. Es konnte für einige der Gene die differenzielle Expression in Brusttumoren bestätigt und dadurch neue Kandidatengene für die untersuchten Genloci identifiziert werden. Das Expressionsmuster einer Acyltransferase in 11q13 als potenzielles Tumorsuppressorgen erbrachte den Hinweis auf eine mögliche Involvierung in den Retinol-Metabolismus und könnte auf einen Mechanismus der Inhibierung der Karzinogenese im Brustepithel hindeuten. / Breast and ovarian cancers have become major tumor diseases among woman. The progression of benign neoplasia to malignant carcinoma is characterized by specific changes of gene expression. By using an in-silico strategy to analyze four million ESTs available in cDNA libraries of normal and the corresponding tumor tissues, we selected hundreds of differentially expressed genes. After chromosomal assignment of the candidate genes, further experiments were focussed on these genes located in the specific regions 1q32-q41 and 11q13-q23 often described to be aberrant in breast and ovarian cancer specimen. The in-silico expression analysis was verifyed by Northern blot and cDNA-Array techniques of unselected and microdissected tumor samples. We could confirm the in-silico expression pattern of some genes and identified novel tumor associated candidate genes for the investigated loci. According to the expression pattern, an acyltransferases located in 11q13 may represent a tumor suppressor gene, which could possibly inhibit breast carcinogenesis by involving in retinol metabolism.