Multiple sporadic colorectal cancers display a unique methylation phenotype

PLoS One. 2014 Mar 18;9(3):e91033. doi: 10.1371/journal.pone.0091033. eCollection 2014.

Abstract

Epigenetics are thought to play a major role in the carcinogenesis of multiple sporadic colorectal cancers (CRC). Previous studies have suggested concordant DNA hypermethylation between tumor pairs. However, only a few methylation markers have been analyzed. This study was aimed at describing the epigenetic signature of multiple CRC using a genome-scale DNA methylation profiling. We analyzed 12 patients with synchronous CRC and 29 age-, sex-, and tumor location-paired patients with solitary tumors from the EPICOLON II cohort. DNA methylation profiling was performed using the Illumina Infinium HM27 DNA methylation assay. The most significant results were validated by Methylight. Tumors samples were also analyzed for the CpG Island Methylator Phenotype (CIMP); KRAS and BRAF mutations and mismatch repair deficiency status. Functional annotation clustering was performed. We identified 102 CpG sites that showed significant DNA hypermethylation in multiple tumors with respect to the solitary counterparts (difference in β value ≥0.1). Methylight assays validated the results for 4 selected genes (p = 0.0002). Eight out of 12(66.6%) multiple tumors were classified as CIMP-high, as compared to 5 out of 29(17.2%) solitary tumors (p = 0.004). Interestingly, 76 out of the 102 (74.5%) hypermethylated CpG sites found in multiple tumors were also seen in CIMP-high tumors. Functional analysis of hypermethylated genes found in multiple tumors showed enrichment of genes involved in different tumorigenic functions. In conclusion, multiple CRC are associated with a distinct methylation phenotype, with a close association between tumor multiplicity and CIMP-high. Our results may be important to unravel the underlying mechanism of tumor multiplicity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / metabolism
  • Colorectal Neoplasms / pathology
  • CpG Islands
  • DNA Methylation*
  • Epigenesis, Genetic
  • Female
  • Gene Expression Regulation, Neoplastic*
  • Genome-Wide Association Study
  • Genotype
  • Humans
  • Male
  • Middle Aged
  • Neoplasms, Multiple Primary / genetics*
  • Neoplasms, Multiple Primary / metabolism
  • Neoplasms, Multiple Primary / pathology
  • Phenotype
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins p21(ras)
  • ras Proteins / genetics

Substances

  • KRAS protein, human
  • Proto-Oncogene Proteins
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins p21(ras)
  • ras Proteins

Grants and funding

This work was supported by grants from the Hospital Clínic of Barcelona (Josep Font grant), Ministerio de Economí­a y Competitividad (SAF 2007-64873 and SAF2010-19273), Fundación Científica de la Asociación Española contra el Cáncer, and Instituto de Salud Carlos III (PI10/00384). “Cofinanciado por el Fondo Europeo de Desarrollo Regional (FEDER). Unión Europea. Una manera de hacer Europa”. CIBEREHD is funded by the Instituto de Salud Carlos III. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.