| 1. |
- Kiss, Nimrod G B
(author)
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DNA methylation and gene expression patterns in adrenal medullary tumors
- 2009
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Doctoral thesis (other academic/artistic)abstract
- Pheochromocytomas and abdominal paragangliomas are neuroendocrine tumors of the autonomous nervous system, arising in adrenal medulla and sympathetic ganglia throughout the abdomen. These tumors originate from catecholamine-producing chromaffin cells. Neuroblastomas are common childhood tumors in the adrenal medulla and abdominal ganglia. They derive from an unidentified subset of immature sympathetic nerve cells. Like most other cancers, pheochromocytomas, paragangliomas and neuroblastomas arise as a result of a vast array of genetic and epigenetic events that allow them to circumvent the normal mechanisms governing cell growth and death. It is the purpose of this thesis and the works contained herein to further elucidate the mechanisms that propel the development of these tumors. It was the purpose of Paper I to assess the involvement of the CDKN2A gene locus and its two resident tumor suppressor genes (TSGs), p16INK4A and p14ARF, previously implicated in the pathogenesis of pheochromocytomas and paragangliomas. p16INK4A promoter hypermethylation was prominent in a subset of malignant paragangliomas, and sequence alterations were observed in the gene. Suppressed p16INK4A RNA and protein expression was also evident in these tumors. SDHB gene mutation status was assessed, and overlapped fully with p16INK4A hypermethylation. In contrast, we found little evidence for p14ARF involvement in pheochromocytomas and paragangliomas. In Paper II we assessed global and gene specific methylation levels in pheochromocytomas and paragangliomas in relation to clinical phenotype. CpG islands in the promoter regions of 11 tumor suppressor genes were assessed using a quantitative method. A CpG island methylator phenotype (CIMP; defined as hypermethylation in three or more of the assessed TSGs) was found in the same subset of paragangliomas that displayed p16INK4A hypermethylation in Paper I. In Paper III we strived to verify concerted TSG promoter hypermethylation in a subset of malignant paragangliomas with SDHB mutation in an independent sample series, and to shed light on the temporal occurrence of genetic and epigenetic events in these tumors. Epigenetic changes in the new tumor set mirrored the results from Papers I and II. As in the previous papers, TSG hypermethylation was strongly associated with SDHB mutation, and we show that mutation precedes aberrant TSG methylation and tumor formation. The purpose of Paper IV was to evaluate the involvement of two RAS effector proteins with tumor suppressor functions, RASSF1A and NORE1A, in pheochromocytomas and paragangliomas. Suppressed RASSF1A and NORE1A mRNA were observed in tumors in comparison to normal reference. In agreement with the previous papers we found RASSF1A hypermethylation in malignant paragangliomas. Reconstitution of Nore1a in rat pheochromocytoma cell line suppressed the ability to grow in soft agar and induced apoptosis, supporting a tumor suppressive function for Nore1a in pheochromocytoma. In Paper V we assessed global and gene specific methylation of 14 TSGs in neuroblastomas in relation to clinical phenotype. Frequent TSG hypermethylation was observed with neuroblastomas, but no clear-cut correlations could be made with specific tumor features. In Paper VI we assessed expression and gene methylation of the TSG RIZ in neuroblastomas. We observed suppressed RIZ1 expression in a subset of neuroblastomas with adverse features. In conclusion we find substantial evidence for epigenetic involvement in TSG inactivation in paragangliomas and neuroblastomas. In light of these findings we propose the evaluation of demethylating agents in the treatment of these tumors.
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| 2. |
- Lee, Jia-Jing, et al.
(author)
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Array-CGH identifies cyclin D1 and UBCH10 amplicons in anaplastic thyroid carcinoma.
- 2008
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In: Endocrine-Related Cancer. - 1479-6821 .- 1351-0088. ; 15:3, s. 801-815
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Journal article (peer-reviewed)abstract
- Anaplastic thyroid cancer (ATC) is a rare but highly aggressive disease with largely unexplained etiology and molecular pathogenesis. In this study, we analyzed genome-wide copy number changes, BRAF (V-raf sarcoma viral oncogene homolog B1) mutations, and p16 and cyclin D1 expressions in a panel of ATC primary tumors. Three ATCs harbored the common BRAF mutation V600E. Using array-comparative genomic hybridisation (array-CGH), several distinct recurrent copy number alterations were revealed including gains in 16p11.2, 20q11.2, and 20q13.12. Subsequent fluorescence in situ hybridization revealed recurrent locus gain of UBCH10 in 20q13.12 and Cyclin D1 (CCND1) in 11q13. The detection of a homozygous loss encompassing the CDKN2A locus in 9p21.3 motivated the examination of p16 protein expression, which was undetectable in 24/27 ATCs (89%). Based on the frequent gain in 11q13 (41%; n=11), the role of CCND1 was further investigated. Expression of cyclin D1 protein was observed at varying levels in 18/27 ATCs (67%). The effect of CCND1 on thyroid cell proliferation was assessed in vitro in ATC cells by means of siRNA and in thyroid cells after CCND1 transfection. In summary, the recurrent chromosomal copy number changes and molecular alterations identified in this study may provide an insight into the pathogenesis and development of ATC.
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| 3. |
- Sandgren, Johanna, et al.
(author)
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Recurrent genomic alterations in benign and malignant pheochromocytomas and paragangliomas revealed by whole-genome array comparative genomic hybridization analysis
- 2010
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In: Endocrine-Related Cancer. - 1351-0088 .- 1479-6821. ; 17:3, s. 561-579
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Journal article (peer-reviewed)abstract
- Pheochromocytomas and abdominal paragangliomas are adrenal and extra-adrenal catecholamine-producing tumours. They arise due to heritable cancer syndromes, or more frequently occur sporadically due to an unknown genetic cause. The majority of cases are benign, but malignant tumours are observed. Previous comparative genomic hybridization (CGH) and loss of heterozygosity studies have shown frequent deletions of chromosome arms 1p, 3q and 22q in pheochromocytomas. We applied high-resolution whole-genome array CGH on 53 benign and malignant pheochromocytomas and paragangliomas to narrow down candidate regions as well as to identify chromosomal alterations more specific to malignant tumours. Minimal overlapping regions (MORs) were identified on 16 chromosomes, with the most frequent MORs of deletion (> or = 32%) occurring on chromosome arms 1p, 3q, 11p/q, 17p and 22q, while the chromosome arms 1q, 7p, 12q and 19p harboured the most common MORs of gain (> or = 14%). The most frequent MORs (61-75%) in the pheochromocytomas were identified at 1p, and the four regions of common losses encompassed 1p36, 1p32-31, 1p22-21 and 1p13. Tumours that did not show 1p loss generally demonstrated aberrations on chromosome 11. Gain of chromosomal material was significantly more frequent among the malignant cases. Moreover, gain at 19q, trisomy 12 and loss at 11q were positively associated with malignant pheochromocytomas, while 1q gain was commonly observed in the malignant paragangliomas. Our study revealed novel and narrow recurrent chromosomal regions of loss and gain at several autosomes, a prerequisite for identifying candidate tumour suppressor genes and oncogenes involved in the development of adrenal and extra-adrenal catecholamine-producing tumours.
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