BRAF mutation-specific promoter methylation of FOX genes in colorectal cancer
Open Access
- 16 January 2013
- journal article
- Published by Springer Science and Business Media LLC in Clinical Epigenetics
- Vol. 5 (1), 2
- https://doi.org/10.1186/1868-7083-5-2
Abstract
Cancer-specific hypermethylation of (promoter) CpG islands is common during the tumorigenesis of colon cancer. Although associations between certain genetic aberrations, such as BRAF mutation and microsatellite instability, and the CpG island methylator phenotype (CIMP), have been found, the mechanisms by which these associations are established are still unclear. We studied genome-wide DNA methylation differences between colorectal tumors carrying a BRAF mutation and BRAF wildtype tumors. Using differential methylation hybridization on oligonucleotide microarrays representing 32,171 CpG-rich regions, we identified 1,770 regions with differential methylation between colorectal tumor and paired normal colon. Next, we compared the tumor/normal methylation ratios between different groups of patients. Related to CIMP, we identified 749 differentially methylated regions, of which 86% had a higher tumor/normal methylation ratio in the CIMP-positive group. We identified 758 regions with a BRAF mutation-specific methylation change, of which 96% had a higher tumor/normal methylation ratio in the BRAF mutant group. Among the genes affected by BRAF mutation-specific methylation changes, we found enrichment of several cancer-related pathways, including the PI3 kinase and Wnt signaling pathways. To focus on genes that are silenced in a tumor-specific rather than a lineage-specific manner, we used information on the epigenetic silencing mark H3K27me3 in embryonic stem (ES) cells. Among the genes showing BRAF mutation-specific promoter methylation but no H3K27me3 mark in ES cells were forkhead box (FOX) transcription factors associated with the PI3 kinase pathway, as well as MLH1 and SMO. Repression of FOXD3 gene expression in tumors could be related to its promoter hypermethylation. We identified new BRAF mutation-specific methylation changes in colorectal cancer. Epigenetic downregulation of these targets may contribute to mutationally active BRAF-driven tumorigenesis, explaining its association with aberrant DNA methylation.Keywords
This publication has 45 references indexed in Scilit:
- A predicted hairpin cluster correlates with barriers to PCR, sequencing and possibly BAC recombineeringScientific Reports, 2011
- Unlocking the secrets of the genomeNature, 2009
- The human colon cancer methylome shows similar hypo- and hypermethylation at conserved tissue-specific CpG island shoresNature Genetics, 2009
- Adaptable gene‐specific dye bias correction for two‐channel DNA microarraysMolecular Systems Biology, 2009
- Mutations in Both KRAS and BRAF May Contribute to the Methylator Phenotype in Colon CancerGastroenterology, 2008
- Integrated genetic and epigenetic analysis identifies three different subclasses of colon cancerProceedings of the National Academy of Sciences, 2007
- Methylation patterns of IGFBP7 in colon cancer cell lines are associated with levels of gene expressionThe Journal of Pathology, 2007
- A stem cell–like chromatin pattern may predispose tumor suppressor genes to DNA hypermethylation and heritable silencingNature Genetics, 2007
- CpG island methylator phenotype underlies sporadic microsatellite instability and is tightly associated with BRAF mutation in colorectal cancerNature Genetics, 2006
- Control of Developmental Regulators by Polycomb in Human Embryonic Stem CellsCell, 2006