| 1. |
- Geli, Janos
(författare)
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Further delineation of molecular alterations in adreno-medullary tumors
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pheochromocytomas, abdominal paragangliomas and neuroblastomas are tumors of the sympathetic nervous system. Anatomically pheochromocytomas and abdominal paragangliomas arise from sympathoadrenal paraganglia, within and outside the adrenal medulla, respectively. On the other hand, neuroblastomas may present both in the adrenal medulla and along the sympathetic trunk. While pheochromocytomas and abdominal paragangliomas are mostly adult cancers originating from chromaffin cells, neuroblastoma is a pediatric tumor, deriving from immature sympathetic nerve cells. During cancer development, neoplastic cells accumulate a perplexing variety of genetic and epigenetic changes, enabling them to escape control mechanisms of proliferation and cell death. The overall objective of this thesis is to shed further light on the genetic and epigenetic pathways that contribute to the molecular pathogenesis of these tumors. In Paper I promoter specific and genome wide methylation changes were quantitatively assessed in relation to clinical features in a panel pheochromocytomas / abdominal paragangliomas. Based on methylation levels in the tumor suppressor genes, p16INK4A, CDH1, DCR2, RARB, RASSF1A, NORE1A, TP73, APC, DAPK1, p14ARF and PTEN, a CpG island methylator phenotype (CIMP) was defined as concerted hypermethylation in three or more genes. A subset of abdominal paragangliomas displayed CIMP phenotype, which was associated with malignant behavior and young age at presentation. This observation raises a prospective for potential benefits of epigenetically acting drugs for a subgroup of young abdominal paraganglioma patients with adverse prognosis. In addition genome wide hypomethylation was seen in tumors as compared to normal adrenal samples providing further support for the general significance of global hypomethylation in neuroendocrine cancers. In Paper II the RIZ1 tumor suppressor in 1p36.2 was assessed as a candidate target for the distal 1p deletions in these tumors. Intragenic LOH and suppressed mRNA expression was detected in a substantial proportion of the tumors. This was not associated, however with RIZ1 promoter methylation. The recurrent inactivation RIZ1 suggests that this event may be a significant contributing factor to tumorigenesis in pheochromocytomas and abdominal paragangliomas. NORE1A and RASSF1A are proapoptotic RAS effectors with tumor suppressor functions. In paper III their role was explored in pheochromocytomas and abdominal paraganliomas. Suppressed NORE1A and RASSF1A mRNA levels were detected in tumors compared to normal adrenal medulla. Methylation of the RASSF1A promoter was significantly associated with malignant behavior, while NORE1A methylation was uncommon. The anti-tumorigenic role of NORE1A was functionally investigated in Nore1A transfected PC12 pheochromocytoma cells. Ectopic expression of Nore1a resulted in enhanced apoptosis and impaired colony formation in soft agar suggesting that suppression of NORE1A contributes to the transformed phenotype in these tumors. In paper IV the role of NORE1A was investigated in neuroblastoma tumors and cell lines. Supression of NORE1A mRNA expression was evident in cell lines and tumors, particularly in cases without MYCN amplification. Methylation of the NORE1A promoter was not a characteristic event contrasting RASSF1A, which showed frequent hypermethylation. Transient expression of Nore1a in SK-N-BE(2) cells resulted in enhanced apoptosis and delayed cell cycle progression, suggesting that suppression of NORE1A may contribute to tumorigenesis. In Paper V, to further substantiate the general role of NORE1A and RASSF1A in cancer, we extended the analysis of these molecules to follicular thyroid tumors. Substantially reduced NORE1A mRNA expression was seen in all PAX8-PPARγ positive tumors while RAS mutation and PAX8-PPARγ fusions were mutually exclusive. RASSF1A expression was reduced in the majority of tumors analyzed. Studies in knock-out models indicate that inactivation of products of the CDKN2A locus, p16INK4A and p14ARF, promotes pheochromocytoma development. In Paper VI, the involvement of CDKN2A in human pheochromocytomas and abdominal paragangliomas was studied, with regard to promoter methylation, expression and sequence alterations. The p16INK4A promoter was heavily methylated in a subset of paragangliomas, and it was associated with malignant disease. Frequent suppression of p16INK4A mRNA and protein expression was seen in tumors. By contrast no significant methylation or reduced mRNA expression was evident for p14ARF. Sequence variations were observed in four tumors including a missense mutation. These results suggest that p16INK4A, and not p14ARF is a frequent target of inactivating events in human pheochromocytoma and abdominal paraganglioma.
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| 2. |
- Jarbo, Caroline, et al.
(författare)
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Detailed assessment of chromosome 22 aberrations in sporadic pheochromocytoma using array-CGH.
- 2006
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Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 118:5, s. 1159-64
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Tidskriftsartikel (refereegranskat)abstract
- Pheochromocytoma is a predominantly sporadic neuroendocrine tumor derived from the adrenal medulla. Previous low resolution LOH and metaphase-CGH studies reported the loss of chromosomes 1p, 3q, 17p and 22q at various frequencies. However, the molecular mechanism(s) behind development of sporadic pheochromocytoma remains largely unknown. We have applied high-resolution tiling-path microarray-CGH with the primary aim to characterize copy number imbalances affecting chromosome 22 in 66 sporadic pheochromocytomas. We detected copy number alterations on 22q at a frequency of 44%. The predominant finding was monosomy 22 (30%), followed by terminal deletions in 8 samples (12%) and a single interstitial deletion. We further applied a chromosome 1 tiling-path array in 7 tumors with terminal deletions of 22q and found deletions of 1p in all cases. Our overall results suggest that at least 2 distinct regions on both 22q and 1p are important in the tumorigenesis of sporadic pheochromocytoma. A large proportion of pheochromocytomas also displayed indications of cellular heterogeneity. Our study is to our knowledge the first array-CGH study of sporadic pheochromocytoma. Future analysis of this tumor type should preferably be performed in the context of the entire human genome using genome-wide array-CGH, which is a superior methodological approach. Supplemental material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.htm
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| 3. |
- Laurell, Cecilia, et al.
(författare)
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Transcriptional profiling enables molecular classification of adrenocortical tumours
- 2009
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Ingår i: European Journal of Endocrinology. - 0804-4643 .- 1479-683X. ; 161:1, s. 141-152
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Tumours in the adrenocortex are common human tumours. Malignancy is however, rare, the yearly incidence being 0.5-2 per million inhabitants, but associated with a very aggressive behaviour. Adrenocortical tumours are often associated with altered hormone production with a variety of clinical symptoms. The aggressiveness of carcinomas together with the high frequency of adenomas calls for a deeper understanding of the underlying biological mechanisms and an improvement of the diagnostic possibilities. Methods: Microarray gene expression analysis was performed in tumours of adrenocortex with emphasis on malignancy as well as hormonal activity. The sample set consisted of 17 adenomas, 11 carcinomas and 4 histological normal adrenocortexes. RNA from these was hybridised according to a reference design on microarrays harbouring 29 760 human cDNA clones. Confirmation was performed with quantitative real time-PCR and western blot analysis. Results: Unsupervised clustering to reveal relationships between samples based on the entire gene expression profile resulted in two subclusters; carcinomas and non-cancer specimens. A large number of genes were accordingly found to be differentially expressed comparing carcinomas to adenomas. Among these were IGF2, FGFR1 and FGFR4 in growth factor signalling the most predominant and also the USP4, UBE2C and UFD1L in the ubiquitin-proteasome pathway. Moreover, two subgroups of carcinomas were identified with different survival outcome, suggesting that survival prediction can be made on the basis of gene expression profiles. Regarding adenomas with aldosterone overproduction, OSBP and VEGFB were among the most up-regulated genes compared with the other samples. Conclusions: Adrenocortical carcinomas are associated with a distinct molecular signature apparent in their gene expression profiles. Differentially expressed genes were identified associated with malignancy, survival as well as hormonal activity providing a resource of candidate genes for an exploration of possible drug targets and diagnostic and prognostic markers.
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| 4. |
- Velazquez-Fernandez, David, et al.
(författare)
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Expression profiling of adrenocortical neoplasms suggests a molecular signature of malignancy.
- 2005
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Ingår i: Surgery. - : Elsevier BV. - 0039-6060 .- 1532-7361. ; 138:6, s. 1087-1094
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Tidskriftsartikel (refereegranskat)abstract
- Background. Distinguishing between adrenocortical adenomas and carcinomas is often difficult. Our aim was to investigate the differences in transcriptional profiles between benign and malignant adrenocortical neoplasms using complementary DNA microarray techniques. Methods. We studied 7 patients with adrenocortical carcinomas and 13 with adenomas. Histopathology was reviewed in all patients, clinical follow-up was at least 1 year. Hybridizations were Performed in duplicate against RNA reference. Expression levels were analyzed in the R environment for statistical computing with the use of aroma, limma, statistics, and class packages. Results. Transcriptional profiles were homogeneous among adenomas, while carcinomas were much more heterogeneous. Hierarchical clustering and self-organizing maps could separate clearly carcinomas from adenomas. Among genes that were most significantly upregulated in carcinomas were 2 ubiquilin-related genes (USP4 and UFD1L) and several insulinlike growth factor-related genes (IGF2, IGF2R, IGFBP3 and IGFBP6). Among genes that were most significantly downregulated in carcinomas were a cylokine gene (CXCL10), several genes related to cell metabolism (RARRES2, ALDH1A1, CYBRD1 and GSTA4), and the cadherin 2 gene (CDH2). Conclusions. Through the use of cDNA arrays, adrenocortical adenomas and carcinomas appear to be clearly distinguishable on the basis of their specific molecular signature. The biologic importance of the up- and downregulated genes is yet to be determined.
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