Methylation-based noninvasive molecular diagnostics are easy and feasible tools for the early detection of colorectal cancer (CRC). However, many of them have the limitation of low sensitivity with some CRCs detection failed in clinical practice. In this study, the clinical and pathological characteristics, as well as molecular features of three methylator-groups, defined by the promoter methylation status of SDC2 and TFPI2, were investigated in order to improve the performance of CRC detection. The Illumina Infinium 450k Human DNA methylation data and clinical information of CRCs were collected from The Cancer Genome Atlas (TCGA) project and Gene Expression Omnibus (GEO) database. CRC samples were divided into three groups, HH (dual-positive), HL (single positive) and LL (dual-negative) according to the methylation status of SDC2 and TFPI2 promoters. Differences in age, tumor location, microsatellite instable status and differentially expressed genes (DEGs) were evaluated among the three groups and these findings were then confirmed in our inner CRC dataset. The combination of methylated SDC2 and TFPI2 showed a superior performance of distinguishing CRCs from normal controls than each alone. Samples of HL group were more often originated from left-side CRCs whereas very few of them were from right-side (P < 0.05). HH grouped CRCs showed a higher level of microsatellite instability and mutation load than other two groups (mean nonsynonymous mutations for HH/HL/LL: 10.55/3.91/7.02, P = 0.0055). All mutations of BRAF, one of the five typical CpG island methylator phenotype (CIMP) related genes, were found in HH group (HH/HL/LL: 51/0/0, P = 0.018). Also there was a significantly older patient age at the diagnosis in HH group. Gene expression analysis identified 37, 84 and 22 group-specific DEGs for HH, HL and LL, respectively. Functional enrichment analysis suggested that HH specific DEGs were mainly related to the regulation of transcription and other processes, while LL specific DEGs were enriched in the biological processes of extracellular matrix interaction and cell migration. The three defined mathylator groups showed great difference in tumor location, patient age, MSI and ECM biological process, which could facilitate the development of more effective biomarkers for CRC detection.

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SDC2和TFPI2的甲基化定义了大肠癌的三种甲基化表型

基于甲基化的非侵入性分子诊断是大肠癌（CRC）早期检测的简便可行的工具。但是，它们中的许多具有灵敏度低的局限性，在临床实践中某些CRC的检测失败。在这项研究中，研究了由SDC2和TFPI2的启动子甲基化状态定义的三个甲基化基团的临床和病理学特征以及分子特征，以提高CRC检测的性能。Illumina Infinium 450k人类DNA甲基化数据和CRC的临床信息来自癌症基因组图谱（TCGA）项目和基因表达综合（GEO）数据库。CRC样本分为三组，HH（双阳性），HL（单阳性）和LL（双阴性）根据SDC2和TFPI2启动子的甲基化状态而定。在三组之间评估年龄，肿瘤位置，微卫星不稳定状态和差异表达基因（DEG）的差异，然后在我们的内部CRC数据集中确认这些发现。甲基化的SDC2和TFPI2的组合显示出比普通对照更好的区分CRC与正常对照的性能。HL组的样本通常来自左侧的CRC，而很少来自右侧的（P <0.05）。与其他两组相比，HH组CRC显示出更高水平的微卫星不稳定性和突变负荷（HH / HL / LL的平均非同义突变：10.55 / 3.91 / 7.02，P = 0.0055）。所有BRAF的突变，在HH组中发现了五个典型的CpG岛甲基化子表型（CIMP）相关基因之一（HH / HL / LL：51/0/0，P = 0.018）。在HH组的诊断中，患者年龄也明显更高。基因表达分析分别确定了HH，HL和LL的37个，84个和22个组特异性DEG。功能富集分析表明，HH特异性DEGs主要与转录和其他过程的调节有关，而LL特异性DEGs则丰富了细胞外基质相互作用和细胞迁移的生物学过程。定义的三个数学组在肿瘤位置，患者年龄，MSI和ECM生物学过程方面显示出巨大差异，这可以促进开发更有效的CRC检测生物标志物。在HH组的诊断中，患者年龄也明显更高。基因表达分析分别确定了HH，HL和LL的37个，84个和22个组特异性DEG。功能富集分析表明，HH特异性DEGs主要与转录和其他过程的调节有关，而LL特异性DEGs则丰富了细胞外基质相互作用和细胞迁移的生物学过程。定义的三个数学组在肿瘤位置，患者年龄，MSI和ECM生物学过程方面显示出巨大差异，这可以促进开发更有效的CRC检测生物标志物。在HH组的诊断中，患者年龄也明显更高。基因表达分析分别确定了HH，HL和LL的37个，84个和22个组特异性DEG。功能富集分析表明，HH特异性DEGs主要与转录和其他过程的调节有关，而LL特异性DEGs则丰富了细胞外基质相互作用和细胞迁移的生物学过程。三个定义的数学组显示出在肿瘤位置，患者年龄，MSI和ECM生物学过程方面的巨大差异，这可能有助于开发更有效的CRC检测生物标志物。功能富集分析表明，HH特异性DEGs主要与转录和其他过程的调节有关，而LL特异性DEGs则丰富了细胞外基质相互作用和细胞迁移的生物学过程。定义的三个数学组在肿瘤位置，患者年龄，MSI和ECM生物学过程方面显示出巨大差异，这可以促进开发更有效的CRC检测生物标志物。功能富集分析表明，HH特异性DEGs主要与转录和其他过程的调节有关，而LL特异性DEGs则丰富了细胞外基质相互作用和细胞迁移的生物学过程。定义的三个数学组在肿瘤位置，患者年龄，MSI和ECM生物学过程方面显示出巨大差异，这可以促进开发更有效的CRC检测生物标志物。