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- Johansson, Térèse A., 1978-
(author)
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Pancreatic Endocrine Tumourigenesis : Genes of potential importance
- 2008
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Doctoral thesis (other academic/artistic)abstract
- Understanding signalling pathways that control pancreatic endocrine tumour (PET) development and proliferation may reveal novel targets for therapeutic intervention. The pathogenesis for sporadic and hereditary PETs, apart from mutations of the MEN1 and VHL tumour suppressor genes, is still elusive. The protein product of the MEN1 gene, menin, regulates many genes. The aim of this thesis was to identify genes involved in pancreatic endocrine tumourigenesis, with special reference to Notch signalling.Messenger RNA and protein expression of NOTCH1, HES1, HEY1, ASCL1, NEUROG3, NEUROD1, DLK1, POU3F4, PDX1, RPL10, DKK1 and TPH1 were studied in human PETs, sporadic and MEN 1, as well as in tumours from heterozygous Men1 mice. For comparison, normal and MEN1 non-tumourous human and mouse pancreatic specimens were used. Nuclear expression of HES1 was consistently absent in PETs. In mouse tumours this coincided with loss of menin expression, and there was a correlation between Men1 expression and several Notch signalling factors. A new phenotype consisting of numerous menin-expressing endocrine cell clusters, smaller than islets, was found in Men1 mice. Expression of NEUROG3 and NEUROD1 was predominantly localised to the cytoplasm in PETs and islets from MEN 1 patients and Men1 mice, whereas expression was solely nuclear in wt mice. Differences in expression levels of Pou3f4, Rpl10 and Dlk1 between islets of Men1 and wt mice were observed.In addition, combined RNA interference and microarray expression analysis in the pancreatic endocrine cell line BON1 identified 158 target genes of ASCL1. For two of these, DKK1 (a negative regulator of the WNT/β-catenin signalling pathway) and TPH1, immunohistochemistry was performed on PETs. In concordance with the microarray finding, DKK1 expression showed an inverse relation to ASCL1 expression.Altered subcellular localisation of HES1, NEUROD1 and NEUROG3 and down-regulation of DKK1 may contribute to tumourigenesis.
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| 2. |
- Halin Lejonklou, Margareta, 1966-
(author)
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The MEN 1 Pancreas : Tumor Development and Haploinsufficiency
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Multiple Endocrine Neoplasia Type I Syndrome (MEN 1) is a monogenic autosomal dominantly inherited cancer syndrome caused by a heterozygous loss of the MEN1 gene, predisposing for endocrine cell proliferation and tumor formation. MEN 1 carriers classically develop tumors in endocrine organs; the parathyroids, the endocrine pancreas, and the pituitary. Other organs, endocrine and non-endocrine, may also be affected. The most common cause of death in MEN 1 is pancreatic endocrine tumor (PNET), which exhibit inactivation of both MEN1 alleles. The increased proliferation prior to loss of the wild-type allele indicates haploinsufficiency, and little is known concerning the mechanisms behind MEN 1 PNET development. The MEN1 protein, menin, lacking homology with other known proteins, is involved in several aspects of transcriptional regulation and chromatin organization.We report differential expression and subcellular localization of transcription factors important in pancreatic development, in human and mouse MEN 1 pancreas, compared to non-MEN 1 pancreas. A predominantly cytoplasmic localization of Neurogenin3 and NeuroD1 was observed in tumors as well as in MEN 1 non-tumorous pancreas.Notch signaling factor expression and localization were examined in the pancreas of a heterozygous Men1 mouse model, and compared with that of wild-type littermates. Nuclear Hes1 was lost in tumors, concomitant to weaker Notch1 NICD expression, and further, analyzed using qPCR, it was shown that Notch1 was less expressed in heterozygous islets compared to wild-type islets.Performing a global gene expression array, we identified differential gene expression in five-week-old heterozygous Men1 mouse islets, compared to islets from wild-type littermates. The array results for a subset of the differentially regulated genes were corroborated using qPCR, western blotting and in situ PLA. We additionally observed significantly accelerated proliferation in islets from young heterozygous animals.It is often problematic to determine prognosis for individual patients with PNET. This is especially true in the group of patients with well differentiated endocrine carcinomas. In the absence of metastases, morphological signs of malignancy are frequently lacking. We evaluated the expression of nuclear and cytoplasmic survivin in a clinically characterized patient material (n=111), and a high nuclear survivin expression proved to be a significant negative prognostic factor for survival.
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| 3. |
- Ekeblad, Sara, 1980-
(author)
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Pancreatic Endocrine Tumors and GIST - Clinical Markers, Epidemiology and Treatment
- 2007
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Doctoral thesis (other academic/artistic)abstract
- Pancreatic endocrine tumors and gastrointestinal stromal tumors are rare. Evidence regarding prognostic factors, and in the former also treatment, is scarce. We evaluated the survival and prognostic factors in a consecutive series of 324 patients with pancreatic endocrine tumors treated at a single institution. Radical surgery, WHO classification, TNM stage, age and Ki67 ≥2% emerged as independent prognostic factors. Having a non-functioning tumor was not an independent prognostic marker, and neither was hereditary tumor disease. We present the first evaluation of the newly proposed TNM staging system for these patients. A separate analysis of well-differentiated neuroendocrine carcinomas is reported, suggesting tumor size ≥5cm and Ki67 ≥2% as negative prognostic markers in this group. The first 36 patients with advanced neuroendocrine tumors treated with temozolomide at our clinic were evaluated. The median time to progression was seven months. Fourteen percent showed partial regression and 53% stabilization of disease. Side effects were generally mild. Investigation of O6-methylguanine DNA methyltransferase revealed a low expression in a subset of tumors. Four out of five patients responding to treatment had tumors with low expression. Concomitant expression of the orexigen ghrelin and its receptor in pancreatic endocrine tumors is demonstrated. No significant difference in mean plasma ghrelin between patients and controls were found, but elevated plasma ghrelin was seen in five patients. We provide the first report of expression of ghrelin and its receptor in gastrointestinal stromal tumors. Concomitant expression was frequent, indicating the presence of an autocrine loop. The tumors also expressed the neuroendocrine marker synaptic vesicle protein 2. Together, these findings are suggestive of neuroendocrine features.
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