Transcriptionally repressed genes become aberrantly methylated and distinguish tumors of different lineages in breast cancer

Duncan Sproul, Colm Nestor, Jayne Culley, Jacqueline H. Dickson, J. Michael Dixon, David James Harrison, Richard R. Meehan, Andrew H. Sims, Bernard H. Ramsahoye

Research output: Contribution to journalArticlepeer-review

120 Citations (Scopus)


Aberrant promoter hypermethylation is frequently observed in cancer. The potential for this mechanism to contribute to tumor development depends on whether the genes affected are repressed because of their methylation. Many aberrantly methylated genes play important roles in development and are bivalently marked in ES cells, suggesting that their aberrant methylation may reflect developmental processes. We investigated this possibility by analyzing promoter methylation in 19 breast cancer cell lines and 47 primary breast tumors. In cell lines, we defined 120 genes that were significantly repressed in association with methylation (SRAM). These genes allowed the unsupervised segregation of cell lines into epithelial (EPCAM+ve) and mesenchymal (EPCAM-ve) lineages. However, the methylated genes were already repressed in normal cells of the same lineage, and > 90% could not be derepressed by treatment with 5-aza-2'-deoxycytidine. The tumor suppressor genes APC and CDH1 were among those methylated in a lineage-specific fashion. As predicted by the epithelial nature of most breast tumors, SRAM genes that were methylated in epithelial cell lines were frequently aberrantly methylated in primary tumors, as were genes specifically repressed in normal epithelial cells. An SRAM gene expression signature also correctly identified the rare claudin-low and metaplastic tumors as having mesenchymal characteristics. Our findings implicate aberrant DNA methylation as a marker of cell lineage rather than tumor progression and suggest that, in most cases, it does not cause the repression with which it is associated.

Original languageEnglish
Pages (from-to)4364-4369
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number11
Early online date28 Feb 2011
Publication statusPublished - 15 Mar 2011


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