published_or_final_version / Zoology / Master / Master of Philosophy

published_or_final_version / abstract / Surgery / Master / Master of Philosophy

<p>Midgut carcinoid tumours are rare with an incidence of 0.5-2.1/100 000. The primary tumour is usually small and grows slowly but has almost always set metastases at diagnosis. When radically operated, most patients will eventually recur in their disease. </p><p>We evaluated different methods in detecting recurrent disease in 61 malignant midgut carcinoid tumours that had been radically operated. Thirty-eight patients have been diagnosed with a recurrence. In 32/38 of these patients P-Chromogranin A was the first method to indicate a recurrence. We therefore recommend using P-CgA in the work up in these patients.</p><p>We investigated characteristics, survival and independent factors that could be of bad prognostic value. We found that in our 284 malignant midgut carcinoid tumours, 208/284 (73%) had distant metastases and 30/284 (11%) had carcinoid heart disease. Median survival was 115.5 months and five-year survival was 77%. In a multivariate analysis liver metastases and carcinoid heart disease were poor prognostic factors.</p><p>We performed a phase II study with octreotide pamoate investigating the clinical effect in 12 malignant midgut carcinoid tumours in a progressive phase. We found that 9/12 (75%) were stabilised for a median duration of 12 months. We think that this is a good effect considering the advanced stage.</p><p>We investigated the frequency of four different tyrosine kinase receptors, platelet derived growth factor receptor (PDGR) α and β, epidermal growth factor receptor (EGFR) and c-kit, in 36 malignant midgut carcinoid tumours with immunohistochemistry. We found that 13/34 (38%) tumour samples expressed PDGFRα, 29/33 (88%) PDGFRβ, 24/33 (73%) EGFR, whereas none expressed c-kit. This implicates that midgut carcinoid tumours might be susceptible to treatment with tyrosine kinase receptor inhibitors. </p>

Midgut carcinoid tumours are rare with an incidence of 0.5-2.1/100 000. The primary tumour is usually small and grows slowly but has almost always set metastases at diagnosis. When radically operated, most patients will eventually recur in their disease. We evaluated different methods in detecting recurrent disease in 61 malignant midgut carcinoid tumours that had been radically operated. Thirty-eight patients have been diagnosed with a recurrence. In 32/38 of these patients P-Chromogranin A was the first method to indicate a recurrence. We therefore recommend using P-CgA in the work up in these patients. We investigated characteristics, survival and independent factors that could be of bad prognostic value. We found that in our 284 malignant midgut carcinoid tumours, 208/284 (73%) had distant metastases and 30/284 (11%) had carcinoid heart disease. Median survival was 115.5 months and five-year survival was 77%. In a multivariate analysis liver metastases and carcinoid heart disease were poor prognostic factors. We performed a phase II study with octreotide pamoate investigating the clinical effect in 12 malignant midgut carcinoid tumours in a progressive phase. We found that 9/12 (75%) were stabilised for a median duration of 12 months. We think that this is a good effect considering the advanced stage. We investigated the frequency of four different tyrosine kinase receptors, platelet derived growth factor receptor (PDGR) α and β, epidermal growth factor receptor (EGFR) and c-kit, in 36 malignant midgut carcinoid tumours with immunohistochemistry. We found that 13/34 (38%) tumour samples expressed PDGFRα, 29/33 (88%) PDGFRβ, 24/33 (73%) EGFR, whereas none expressed c-kit. This implicates that midgut carcinoid tumours might be susceptible to treatment with tyrosine kinase receptor inhibitors.

Au sein d'un organisme les cellules se divisent et assurent la croissance, la différentiation et l'homéostasie des tissus. Des travaux récents proposent qu'elles communiquent activement entre voisines au sein des organes solides pour coordonner leur propre division et la préservation de l'intégrité tissulaire. Nous proposons que la signalisation Eph-éphrine, acteur de la communication cellulaire locale, participe à cette coordination entre division cellulaire et cohésion du tissu. Au cours de ma thèse, j'ai démontré dans plusieurs modèles cellulaires que la signalisation Eph-éphrine contrôle la division cellulaire et peut induire des retards dans l'abscission et de la polyploïdie. J'ai prouvé par vidéomicrosocpie que ces défauts d'abscission dépendent du domaine catalytique du récepteur EphB2 et de l'activation de la protéine tyrosine kinase relais c-Src. En cascade, c-Src phosphoryle un régulateur clé de la stabilité du pont intercellulaire, la protéine citron kinase (CitK). J'ai également observé que CitK était anormalement localisé durant la cytocinése en aval de la voie Eph. Par des essais kinase in vitro, j'ai exclu une phosphorylation directe de CitK par le récepteur Eph et identifié c-Src comme capable de phosphoryler directement CitK. J'ai identifié les résidus tyrosines de CitK phosphorylés par c-Src, mutés deux d'entre eux et à l'aide d'analyses de sauvetage phénotypique, démontré que ces résidus étaient nécessaires et suffisants pour induire des défauts d'abscission. J'ai ensuite validé in vivo ce rôle original de la voie Eph-éphrine, dans le contexte du développement neuronal chez la souris. Plusieurs membres de la famille des Eph-éphrines sont exprimés dans les progéniteurs neuraux à l'origine des neurones corticaux et des auteurs ont montrés que CitK contrôle la cytocinèse de ces cellules. En utilisant un système Cre-lox, j'ai spécifiquement éteint la signalisation Eph dans ces progéniteurs et observé une modification de la ploïdie neuronale dans ces animaux. J'ai également observé dans les progéniteurs neuraux une co-localisation physiologique de résidus tyrosines phosphorylés et de la protéine CitK, qui adopte un enrichissement apical caractéristique. Ces résultats suggèrent notamment que la signalisation Eph-éphrine pourrait contrôler l'abscission des progéniteurs neuraux via la phosphorylation de CitK. La cytocinèse est aujourd'hui décrite comme un processus cellulaire autonome orchestré par la machinerie intracellulaire. Les résultats obtenus durant mon doctorat suggèrent que la cytocinèse est également régulée par l'environnement local de la cellule comme j'en ai fait la démonstration avec la signalisation Eph-éphrine. D'autre part, mes travaux suggèrent que la phosphorylation de CitK sert d'interrupteur moléculaire durant la progression à travers la division cellulaire et le contrôle de la ploïdie des neurones. / Cells within an organism successfully divide to ensure growth, differentiation and homeostasie. Recent work suggests that dividing cells actively communicate with neighbours thus spatially and temporally coordinating cell division while maintaining tissue cohesiveness. We hypothesized that Eph-ephrin signalling, a local cell-cell signalling pathway, could participate in coordinating cell division within a tissue. Using vertebrate and invertebrate cell culture models I showed that Eph-signalling controls cell division and induces delay in the abscission of nascent daughter cells as well as polyploidy. Using time-lapse imaging I proved that the Eph-mediated abscission failure depends on the catalytic activity of the receptor via the non receptor tyrosine kinase relay molecule c-Src. Downstream of Eph signalling c-Src phosphorylates the protein citron kinase (CitK) a well known regulator of intercellular bridge stability. I also observed that CitK was abnormally localized during cytokinesis when Eph signalling was active. Further, using in vitro kinase assays, I demonstrated that Eph does not directly phosphorylate CitK but that c-Src could do so. In addition, using Mass Spectrometry I mapped all tyrosine residues directly phosphorylated by c-Src. I mutated two of them located in the Rho binding domain of CitK and demonstrated that phosphorylation of those residues are necessary and sufficient to induce cytokinesis failure. I validated in vivo this novel role of Eph-ephrin signalling in a physiological context in the developing mouse neocortex. Members of the Eph/ephrin family are expressed in neural progenitors that give rise to neurons of the cortex upon neurogenic division. Importantly, CitK has been shown by others to control cytokinesis of these progenitor cells. Using the Cre-lox system, I specifically turned off Eph forward signalling in neural progenitor cells and observed an alteration of neuronal ploidy in these mutant animals. Further, I also observed that CitK which adopts a particular apical localisation in neural progenitors physiologically co-localized with phosphorylated tyrosine residues. Altogether, these results suggest that Eph-ephrin signalling controls abscission of neural progenitors by promoting phosphorylation of CitK. The textbook view of cytokinesis is that it is a cell autonomous event orchestrated by the intracellular machinery. Data obtained during my PhD suggest that cytokinesis is also regulated by local environment, here Eph/ephrin signalling, and that phosphorylation of CitK may represent a molecular switch in the normal progression of cell division and in the control of neuronal ploidy.

<p>We treated 16 patients with somatostatin analogs combined with α-interferon and achieved a biochemical and/or radiological response in 56% (median duration 22 months). We consider this treatment a good alternative for patients who fail during chemotherapy or who do not want to/cannot receive cytotoxic drugs.</p><p>Thirty-six patients with neuroendocrine tumors were treated with cisplatin combined with etoposide. Of 14 patients with evaluable EPTs, 50% responded radiologically and/or biochemically (median duration 9 months). We consider this treatment useful as first-line medical treatment in aggressive EPTs or in patients failing prior chemotherapy.</p><p>Twenty-eight tumor tissues from EPTs were examined with immunohistochemistry regarding expression of somatostatin receptors (ssts) 1 to 5 on tumor cells and in intratumoral vessels. We found that sst₂ and sst₄ were highly expressed on tumor cells and in vessels. However, sst₃ and sst₅ were lacking in half of the tumor tissues and in most of the vessels. Because of the variability in sst expression, we recommend analysis of each individual’s receptor expression before starting treatment.</p><p>Endocrine pancreatic tumors (EPTs) are rare with an incidence of 4 per million inhabitants. In the majority of cases they grow slowly, but there are exceptions with very rapidly progressing malignant carcinomas. First-line medical treatment is streptozotocin combined with 5-fluorouracil.</p><p>We examined 38 tumor samples regarding expression of tyrosine kinase receptors platelet-derived growth factor receptors (PDGFRs), c-kit and epidermal growth factor receptor (EGFR). We found that the receptors were expressed in more than half of the tumor tissues. Further studies will reveal if tyrosin kinase antagonists can be part of the future treatment arsenal.</p>

We treated 16 patients with somatostatin analogs combined with α-interferon and achieved a biochemical and/or radiological response in 56% (median duration 22 months). We consider this treatment a good alternative for patients who fail during chemotherapy or who do not want to/cannot receive cytotoxic drugs. Thirty-six patients with neuroendocrine tumors were treated with cisplatin combined with etoposide. Of 14 patients with evaluable EPTs, 50% responded radiologically and/or biochemically (median duration 9 months). We consider this treatment useful as first-line medical treatment in aggressive EPTs or in patients failing prior chemotherapy. Twenty-eight tumor tissues from EPTs were examined with immunohistochemistry regarding expression of somatostatin receptors (ssts) 1 to 5 on tumor cells and in intratumoral vessels. We found that sst2 and sst4 were highly expressed on tumor cells and in vessels. However, sst3 and sst5 were lacking in half of the tumor tissues and in most of the vessels. Because of the variability in sst expression, we recommend analysis of each individual’s receptor expression before starting treatment. Endocrine pancreatic tumors (EPTs) are rare with an incidence of 4 per million inhabitants. In the majority of cases they grow slowly, but there are exceptions with very rapidly progressing malignant carcinomas. First-line medical treatment is streptozotocin combined with 5-fluorouracil. We examined 38 tumor samples regarding expression of tyrosine kinase receptors platelet-derived growth factor receptors (PDGFRs), c-kit and epidermal growth factor receptor (EGFR). We found that the receptors were expressed in more than half of the tumor tissues. Further studies will reveal if tyrosin kinase antagonists can be part of the future treatment arsenal.

Les acides biliaires sont des composants naturels du tractus gastro-intestinal. La hausse du taux d’acides biliaires dans l’intestin est associée à une carcinogenèse de l’appareil digestif. L’homéostasie des acides biliaires est maintenue par le contrôle de l’expression des gènes impliqués dans le métabolisme tels que SHP, FGF19 et CYP-7A1 par le récepteur nucléaire FXRα. FXRα agit comme facteur de transcription en réponse à l’interaction directe des acides biliaires. Par contre, plusieurs évidences tendent à démontrer le rôle central de FXRα dans la carcinogenèse hépatique. Les récepteurs de la famille EGFR/ErbB sont des récepteurs tyrosine kinase également activés par les acides biliaires, dont la surexpression est associée au développement de plusieurs cancers. Ainsi, le projet vise à déterminer l’impact de la signalisation des récepteurs EGFR/ErbB sur la réponse transcriptionnelle de FXRα. Nous avons identifié un mécanisme d’inhibition de l’activité transcriptionnelle de FXRα et de l’expression de ses gènes cibles par l’activation des récepteurs EGFR/ErbB par leur ligands HRG et EGF et par l’expression du mutant constitutivement actif ErbB2-V659E dans les cellules hépatiques. Nous avons montré que ce processus dépend de la signalisation par la voie MAPK. On observe également que l’activation de FXRα diminue la prolifération des cellules cancéreuses du foie alors que celle du récepteur ErbB2 augmente cette prolifération. Ainsi, cette étude nous a permis d’établir un nouveau mécanisme de l’impact délétère de la suractivation des récepteurs EGFR/ErbB sur la prolifération des cellules cancéreuses du foie qui implique une inhibition du potentiel transcriptionnel du récepteur aux acides biliaires FXRα. / Bile acids are natural components of the gastrointestinal tract. An increase of bile acid levels in the intestine is associated with the carcinogenesis of the digestive system. Bile acid homeostasis is maintained by the nuclear receptor FXRα which regulates the expression of specific genes involved in metabolism such as SHP, FGF19 and CYP-7A1. In this way, FXRα acts as a transcription factor following bile acids binding, allowing its transcriptional activation. On the other hand, several studies established the central role of FXRα activation in liver carcinogenesis. EGFR/ErbB receptors are a family of tyrosine kinase receptors that can be regulated by bile acids. Overexpression of EGFR/ErbB receptors is associated with several cancers. Thus, the project aims to examine the impact of EGFR/ErbB receptors signaling on FXR transcriptional potential. We identify that EGFR/ErbB activation by their ligands HRG and EGF and by the expression of the constitutively active mutant ErbB2-V659E inhibits FXR transcriptional activity and expression of its target genes in liver cells. We demonstrate that this process is dependent on the MAPK signaling pathway. We also show that FXR activation decreases proliferation of liver cancer cells while activation of ErbB2 increases this cellular response. Thus, this study identifies a new mechanism of the deleterious impact of EGFR/ErbB receptors overactivation on liver cancer cells proliferation, involving the inhibition of the transcriptional potential of the bile acid receptor FXRα.