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Activating FGFR1 mutations in sporadic pheochromocytoma
Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
Department of Surgery, Haukeland University Hospital and Department of Clinical Science, University of Bergen, Bergen, Norway.
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2015 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Pheochromocytomas are neuroendocrine tumors of the adrenal glands that cause hypertension. More than a third of the cases are associated with hereditary mutations in a growing list of susceptibility genes, some of which are also somatically altered in sporadic pheochromocytomas. However, for the majority of sporadic pheochromocytomas, a genetic explanation is still lacking. Here we investigated the genomic landscape of sporadic pheochromocytomas with whole-exome sequencing of 16 paired tumor and normal DNA samples, and discovered on average 33 non-silent somatic mutations per tumor. One of the recurrently mutated genes was FGFR1, encoding the fibroblast growth factor receptor 1, which was recently revealed as an oncogene in pilocytic astrocytoma and childhood glioblastoma. Including a subsequent analysis of a larger cohort, activating FGFR1  mutations were detected in three of 80 sporadic pheochromocytomas (3.8%). Gene expression microarray profiling showed that these tumors clustered with NF1- RET- and HRAS-mutated pheochromocytomas, indicating activation of the MAPK and PI3K-AKT signal transduction pathways. The results advance our biological understanding of pheochromocytoma and suggest that somatic FGFR1 activation is an important event in a subset of these tumors.

Place, publisher, year, edition, pages
2015.
National Category
Clinical Medicine
Identifiers
URN: urn:nbn:se:liu:diva-114805OAI: oai:DiVA.org:liu-114805DiVA: diva2:792534
Available from: 2015-03-04 Created: 2015-03-04 Last updated: 2015-03-04Bibliographically approved
In thesis
1. Genetic Alterations in Pheochromocytoma and Paraganglioma
Open this publication in new window or tab >>Genetic Alterations in Pheochromocytoma and Paraganglioma
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Pheochromocytomas and paragangliomas are neuroendocrine tumors that arise from neural crest-derived cells of the adrenal medulla and the extra-adrenal paraganglia. They cause hypertension due to an abnormally high production of catecholamines (mainly adrenaline and noradrenaline), with symptoms including recurrent episodes of headache, palpitations and sweating, and an increased risk of cardiovascular disease. Malignancy in the form of distant metastases occurs in 10-15% of the patients. The malignant cases are difficult to predict and cure, and have a poor prognosis. About a third of pheochromocytomas and paragangliomas are caused by hereditary mutations in a growing list of known susceptibility genes. However, the cause of the remaining, sporadic, tumors is still largely unknown. The aim of this thesis project has been to further characterize the genetic background of pheochromocytomas and paragangliomas, with a focus on the sporadic tumors.

First, we investigated the role of the genes known from the familial tumors in the sporadic form of the disease. By studying mutations, copy number variations, DNA methylation and gene expression, we found that many of the known susceptibility genes harbor somatic alterations in sporadic pheochromocytomas. Particularly, we found that the NF1 gene, which plays an important role in suppressing cell growth and proliferation by regulating the RASMAPK pathway, was inactivated by mutations in more than 20% of the cases. The mutations occurred together with deletions of the normal allele and were associated with a reduced NF1 gene expression and a specific hormone profile. We also detected activating mutations in the gene EPAS1, which encodes HIF-2α, in a subset of sporadic cases. Microarray analysis of gene expression showed that several genes involved in angiogenesis and cell metabolism were upregulated in EPAS1-mutated tumors, which is in agreement with the role of HIF-2α in the cellular response to hypoxia. In order to comprehensively investigate all the known susceptibility genes in a larger patient cohort, we designed a targeted next-generation sequencing approach and could conclude that it was fast and cost-efficient for genetic testing of pheochromocytomas and paragangliomas. The results showed that about 40% of the sporadic cases had mutations in the tested genes. The majority of the mutations were somatic, but some apparently sporadic cases in fact carried germline mutations. Such knowledge of the genetic background can be of importance to facilitate early detection and correct treatment of pheochromocytomas, paragangliomas and potential co-occurring cancers, and also to identify relatives that might be at risk. By sequencing all the coding regions of the genome, the exome, we then identified recurrent activating mutations in a novel gene, in which mutations have previously only been reported in subgroups of brain tumors. The identified mutations are proposed to cause constitutive activation of the encoded receptor tyrosine kinase, resulting in the activation of downstream kinase signaling pathways that promote cell growth and proliferation.

In summary, the studies increase our biological understanding of pheochromocytoma and paraganglioma, and possibly also co-occurring cancers in which the same genes and pathways are involved. Together with the findings of other scientific studies, our results may contribute to the development of future treatment options.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 64 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1439
Keyword
Pheochromocytoma; paraganglioma; genetics; sequencing; cancer; mutation
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-114806 (URN)10.3384/diss.diva-114806 (DOI)978-91-7519-145-4 (ISBN)
Public defence
2015-04-09, Berzeliussalen, Campus US, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2015-03-04 Created: 2015-03-04 Last updated: 2016-04-07Bibliographically approved

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Welander, JennySöderkvist, PeterGimm, Oliver

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