Characteristic methylation profile in CpG island methylator phenotype-negative distal colorectal cancers

Byonggu An, Yutaka Kondo, Yasuyuki Okamoto, Keiko Shinjo, Yukihide Kanemitsu, Koji Komori, Takashi Hirai, Akira Sawaki, Masahiro Tajika, Tsuneya Nakamura, Kenji Yamao, Yasushi Yatabe, Makiko Fujii, Hideki Murakami, Hirotaka Osada, Tohru Tani, Keitaro Matsuo, Lanlan Shen, Jean Pierre J. Issa, Yoshitaka Sekido

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)

Abstract

Aberrant DNA methylation is involved in colon carcinogenesis. Although the CpG island methylator phenotype (CIMP) is defined as a subset of colorectal cancers (CRCs) with remarkably high levels of DNA methylation, it is not known whether epigenetic processes are also involved in CIMP-negative tumors. We analyzed the DNA methylation profiles of 94 CRCs and their corresponding normal-appearing colonic mucosa with 11 different markers, including the five classical CIMP markers. The CIMP markers were frequently methylated in proximal CRCs (p < 0.01); however, RASSF1A methylation levels were significantly higher in distal CRCs, the majority of which are CIMP-negative (p < 0.05). Similarly, methylation levels of RASSF1A and SFRP1 in the normal-appearing mucosae of distal CRC cases were significantly higher than those in the proximal CRC cases (p < 0.05). They were also positively correlated with age (RASSF1A, p < 0.01; SFRP1, p < 0.01). Microarray-based genome-wide DNA methylation analysis of 18 CRCs revealed that 168 genes and 720 genes were preferentially methylated in CIMP-negative distal CRCs and CIMP-positive CRCs, respectively. Interestingly, more than half of the hypermethylated genes in CIMP-negative distal CRCs were also methylated in the normal-appearing mucosae, indicating that hypermethylation in CIMP-negative distal CRCs is more closely associated with age-related methylation. By contrast, more than 60% of the hypermethylated genes in CIMP-positive proximal CRCs were cancer specific (p < 0.01). These data altogether suggest that CpG island promoters appear to be methylated in different ways depending on location, a finding which may imply the presence of different mechanisms for the acquisition of epigenetic changes during colon tumorigenesis.

Original languageEnglish
Pages (from-to)2095-2105
Number of pages11
JournalInternational Journal of Cancer
Volume127
Issue number9
DOIs
Publication statusPublished - 01-11-2010
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Oncology
  • Cancer Research

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