RESEARCH ARTICLE Comprehensive DNA Methylation Analysis Reveals a Common Ten-Gene Methylation Signature in Colorectal Adenomas and

Microarray analysis of promoter hypermethylation provides insight into the role and extent of DNA methylation in the development of colorectal cancer (CRC) and may be co-moni-tored with the appearance of driver mutations. Colonic biopsy samples were obtained endoscopically from 10 normal, 23 adenoma (17 low-grade (LGD) and 6 high-grade dys-plasia (HGD)), and 8 ulcerative colitis (UC) patients (4 active and 4 inactive). CRC sam-ples were obtained from 24 patients (17 primary, 7 metastatic (MCRC)), 7 of them with synchronous LGD. Field effects were analyzed in tissues 1 cm (n = 5) and 10 cm (n = 5) from the margin of CRC. Tissue materials were studied for DNA methylation status using a 96 gene panel and for KRAS and BRAFmutations. Expression levels were assayed using whole genomic mRNA arrays. SFRP1 was further examined by immunohistochem-istry. HT29 cells were treated with 5-aza-2 ’ deoxycytidine to analyze the reversal possibil-ity of DNA methylation. More than 85 % of tumor samples showed hypermethylation in 10 genes (SFRP1, SST, BNC1,MAL, SLIT2, SFRP2, SLIT3, ALDH1A3, TMEFF2,WIF1), whereas the frequency of examined mutations were below 25%. These genes distin