Department of Gastroenterology, Hospital Clínic, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Institut d'Investigacions Biomediques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Catalonia, Spain.
Bioinformatics Unit, CIBERehd, Barcelona, Catalonia, Spain.
PLoS One. 2014 Mar 18;9(3):e91033. doi: 10.1371/journal.pone.0091033. eCollection 2014.
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.
表观遗传学被认为在多种散发性结直肠癌（CRC）的癌变中起主要作用。先前的研究表明肿瘤对之间存在一致的 DNA 高甲基化。然而，仅分析了少数甲基化标记物。本研究旨在使用全基因组 DNA 甲基化分析描述多种 CRC 的表观遗传特征。我们分析了 EPICOLON II 队列中 12 例同步 CRC 患者和 29 例年龄、性别和肿瘤位置配对的单发肿瘤患者。使用 Illumina Infinium HM27 DNA 甲基化分析进行 DNA 甲基化分析。最显著的结果通过 Methylight 进行验证。还分析了肿瘤样本的 CpG 岛甲基化表型（CIMP）；KRAS 和 BRAF 突变和错配修复缺陷状态。进行了功能注释聚类。我们在多个肿瘤相对于单发肿瘤中发现了 102 个 CpG 位点，这些 CpG 位点的 DNA 呈现出显著的高甲基化（β 值差异≥0.1）。Methylight 测定法验证了 4 个选定基因的结果（p=0.0002）。12 个多肿瘤中有 8 个（66.6%）被分类为 CIMP-高，而 29 个单发肿瘤中有 5 个（17.2%）（p=0.004）。有趣的是，在多肿瘤中发现的 102 个（74.5%）高甲基化 CpG 位点中的 76 个也存在于 CIMP-高肿瘤中。对多肿瘤中高甲基化基因的功能分析发现，富集了参与不同肿瘤发生功能的基因。总之，多发性 CRC 与独特的甲基化表型相关，并且肿瘤多发性与 CIMP-高密切相关。我们的结果可能对揭示肿瘤多发性的潜在机制很重要。
