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RASSF1Apromoter methylation and expression analysis in normal and neoplastic kidney indicates a role in early tumorigenesis

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9 pages
Epigenetic silencing of the RAS association domain family 1A ( RASSF1A ) tumor suppressor gene promoter has been demonstrated in renal cell carcinoma (RCC) as a result of promoter hypermethylation. Contradictory results have been reported for RASSF1A methylation in normal kidney, thus it is not clear whether a significant difference between RASSF1A methylation in normal and tumor cells of the kidney exists. Moreover, RASSF1A expression has not been characterized in tumors or normal tissue as yet. Results Using combined bisulfite restriction analysis (COBRA) we compared RASSF1A methylation in 90 paired tissue samples obtained from primary kidney tumors and corresponding normal tissue. Bisulfite sequence analysis was carried out using both pooled amplicons from the tumor and normal tissue groups and subclones obtained from a single tissue pair. Expression of RASSF1A was analyzed by the use of tissue arrays and immunohistochemistry. We found significantly increased methylation in tumor samples (mean methylation, 20%) compared to corresponding normal tissues (mean methylation, 11%; P < 0.001). Densely methylated sequences were found both in pooled and individual sequences of normal tissue. Immunohistochemical analysis revealed a significant reduced expression of RASSF1A in most of the tumor samples. Heterogeneous expression patterns of RASSF1A were detected in a subgroup of histologically normal tubular epithelia. Conclusion Our methylation and expression data support the hypothesis that RASSF1A is involved in early tumorigenesis of renal cell carcinoma.
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Molecular Cancer
BioMedCentral
Open Access Research RASSF1Apromoter methylation and expression analysis in normal and neoplastic kidney indicates a role in early tumorigenesis 1 1 2 3 Inga Peters , Kristina Rehmet , Nadine Wilke , Markus A Kuczyk , 3 1 1 1 Jörg Hennenlotter , Tyark Eilers , Stefan Machtens , Udo Jonas and 1 Jürgen Serth*
1 2 Address: Department of Urology, Medizinische Hochschule Hannover, Hannover, Germany, Department of Forensic Medicine, Medizinische 3 Hochschule Hannover, Germany and Department of Urology, EberhardKarls University, Tübingen, Germany Email: Inga Peters  ingapeters@gmx.de; Kristina Rehmet  kristina.rehmet@nuigalway.ie; Nadine Wilke  wilke.nadine@mhhannover.de; Markus A Kuczyk  markus.kuczyk@med.unituebingen.de; Jörg Hennenlotter  joerg.hennenlotter@med.unituebingen.de; Tyark Eilers  Eilers.tyark@mhhannover.de; Stefan Machtens  stefan.machtens@mkhbgl.de; Udo Jonas  jonas.udo@mhhannover.de; Jürgen Serth*  serth.juergen@mhhannover.de * Corresponding author
Published: 16 July 2007 Received: 5 March 2007 Accepted: 16 July 2007 Molecular Cancer2007,6:49 doi:10.1186/1476-4598-6-49 This article is available from: http://www.molecular-cancer.com/content/6/1/49 © 2007 Peters et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background:Epigenetic silencing of the RAS association domain family 1A (RASSF1A) tumor suppressor gene promoter has been demonstrated in renal cell carcinoma (RCC) as a result of promoter hypermethylation. Contradictory results have been reported forRASSF1Amethylation in normal kidney, thus it is not clear whether a significant difference betweenRASSF1Amethylation in normal and tumor cells of the kidney exists. Moreover, RASSF1A expression has not been characterized in tumors or normal tissue as yet. Results:Using combined bisulfite restriction analysis (COBRA) we compared RASSF1A methylation in 90 paired tissue samples obtained from primary kidney tumors and corresponding normal tissue. Bisulfite sequence analysis was carried out using both pooled amplicons from the tumor and normal tissue groups and subclones obtained from a single tissue pair. Expression of RASSF1A was analyzed by the use of tissue arrays and immunohistochemistry. We found significantly increased methylation in tumor samples (mean methylation, 20%) compared to corresponding normal tissues (mean methylation, 11%;P< 0.001). Densely methylated sequences were found both in pooled and individual sequences of normal tissue. Immunohistochemical analysis revealed a significant reduced expression of RASSF1A in most of the tumor samples. Heterogeneous expression patterns of RASSF1A were detected in a subgroup of histologically normal tubular epithelia. Conclusion:Our methylation and expression data support the hypothesis thatRASSF1Ais involved in early tumorigenesis of renal cell carcinoma.
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