Aberrant DNA hypomethylation of the long interspersed nuclear elements (LINE-1 or L1) has been recognized as an early event of colorectal transformation. Simultaneous genetic and epigenetic analysis of colorectal adenomas may be an effective and rapid strategy to identify key biological features leading to accelerated colorectal tumorigenesis. In particular, global and/or intragenic LINE-1 hypomethylation of adenomas may represent a helpful tool for improving colorectal cancer (CRC) risk stratification of patients after surgical removal of polyps. To verify this hypothesis, we analyzed a cohort of 102 adenomas derived from 40 high-risk patients (who developed CRC in a post-polypectomy of at least one year) and 43 low-risk patients (who did not develop CRC in a post-polypectomy of at least 5 years) for their main pathological features, the presence of hotspot variants in driver oncogenes (KRAS, NRAS, BRAF and PIK3CA), global (LINE-1) and intragenic (L1-MET) methylation status. In addition to a significantly higher adenoma size and an older patients’ age, adenomas from high-risk patients were more hypomethylated than those from low-risk patients for both global and intragenic LINE-1 assays. DNA hypomethylation, measured by pyrosequencing, was independent from other parameters, including the presence of oncogenic hotspot variants detected by mass spectrometry. Combining LINE-1 and L1-MET analyses and profiling the samples according to the presence of at least one hypomethylated assay improved the discrimination between high and low risk lesions (p = 0.005). Remarkably, adenomas with at least one hypomethylated assay identified the patients with a significantly (p < 0.001) higher risk of developing CRC. Multivariable analysis and logistic regression evaluated by the ROC curves proved that methylation status was an independent variable improving cancer risk prediction (p = 0.02). LINE-1 and L1-MET hypomethylation in colorectal adenomas are associated with a higher risk of developing CRC. DNA global and intragenic hypomethylation are independent markers that could be used in combination to successfully improve the stratification of patients who enter a colonoscopy surveillance program.

中文翻译：

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评估结直肠腺瘤中的全局和基因内低甲基化改善了患者分层和结直肠癌风险预测

长散在的核元件（LINE-1 或 L1）的异常 DNA 低甲基化已被认为是结肠直肠转化的早期事件。结直肠腺瘤的同时遗传和表观遗传分析可能是一种有效且快速的策略，可识别导致加速结直肠肿瘤发生的关键生物学特征。特别是，腺瘤的全局和/或基因内 LINE-1 低甲基化可能是改善手术切除息肉后患者结直肠癌 (CRC) 风险分层的有用工具。为了验证这一假设，我们分析了来自 40 名高危患者（在至少一年的息肉切除术后发展为 CRC）和 43 名低危患者（在术后未发展为 CRC）的 102 个腺瘤队列。至少5年的息肉切除术）的主要病理特征，驱动癌基因（KRAS、NRAS、BRAF 和 PIK3CA）、全局（LINE-1）和基因内（L1-MET）甲基化状态中存在热点变异。除了显着更高的腺瘤大小和更高的患者年龄外，在全局和基因内 LINE-1 检测中，高风险患者的腺瘤比低风险患者的低甲基化程度更高。通过焦磷酸测序测量的 DNA 低甲基化与其他参数无关，包括通过质谱检测到的致癌热点变体的存在。结合 LINE-1 和 L1-MET 分析并根据至少一种低甲基化分析的存在对样品进行分析，提高了高风险和低风险病变之间的区分 (p = 0.005)。值得注意的是，具有至少一种低甲基化测定的腺瘤可显着识别患者（p < 0. 001) 患 CRC 的风险较高。通过 ROC 曲线评估的多变量分析和逻辑回归证明甲基化状态是提高癌症风险预测的独立变量 (p = 0.02)。结直肠腺瘤中的 LINE-1 和 L1-MET 低甲基化与发生 CRC 的较高风险相关。DNA 全局和基因内低甲基化是独立的标志物，可以联合使用以成功改善进入结肠镜检查监测计划的患者的分层。