Oncogenic HRAS Suppresses Clusterin Expression Through Promoter Hypermethylation
Oncogene (2006) 25, 4890–4903 & 2006 Nature Publishing Group All rights reserved 0950-9232/06 $30.00 www.nature.com/onc ORIGINAL ARTICLE Oncogenic HRAS suppresses clusterin expression through promoter hypermethylation P Lund1, K Weihaupt1, T Mikeska2, D Jammas2, X Chen1, R-J Kuban3, U Ungethu¨ m3, U Krapfenbauer1, H-P Herzel4, R Scha¨ fer1,3, J Walter2 and C Sers1 1Laboratory of Molecular Tumor Pathology, Institute of Pathology, Charite´, Berlin, Germany; 2Department of Natural Sciences – Technical Faculty III FR 8.3, Biological Sciences, Institute of Genetics/Epigenetics, University of Saarland, Saarbru¨cken, Germany; 3Laboratory of Functional Genome Research, Charite´, Berlin, Germany and 4Institute for Theoretical Biology, Humboldt University Berlin, Berlin, Germany Silencing of gene expression by methylation of CpG Introduction islands in regulatory elements is frequently observed in cancer. However, an influence of the most common Activation of RAS proteins by point mutations is oncogenic signalling pathways onto DNA methylation frequently observed in cancers of the colon, pancreas, has not yet been investigated thoroughly. To address this thyroid, lung and the myeloid system (Bos, 1989). RAS issue, we identified genes suppressed in HRAS-trans- genes encode small GTP-binding proteins that act as formed rat fibroblasts but upregulated after treatment major molecular switches in signal transduction pro- with the demethylating agent 5-Aza-2-deoxycytidine and cesses, transmitting extracellular signals to cytoplasmic with the MEK1,2 inhibitor U0126. Analysis of gene signalling cascades (Campbell et al., 1998). The onco- expression by microarray and Northern blot analysis genic forms of RAS proteins are locked in their active revealed the MEK/ERK target genes clusterin, matrix state and contribute to transformation, angiogenesis, metalloproteinase 2 (Mmp2), peptidylpropyl isomerase invasion and metastasis by constitutive activation of C-associated protein, syndecan 4, Timp2 and Thbs1 to be downstream pathways.
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