New biomarkers are urgently needed to improve personalized treatment approaches for head and neck squamous cell carcinoma (HNSCC). Global DNA hypomethylation has wide-ranging functions in multistep carcinogenesis, and the hypomethylation of long interspersed nucleotide element-1 (LINE-1) is related to increased retrotransposon activity and induced genome instability. However, little information is available regarding LINE-1 hypomethylation and its prognostic implications in HNSCC. In this study, we analyzed LINE-1 hypomethylation levels in a well-characterized dataset of 317 primary HNSCC tissues and 225 matched pairs of normal mucosa tissues, along with five oral cavity cancer (OCC) circulating tumor DNA (ctDNA) samples using quantitative real-time methylation and unmethylation PCR. The analysis was performed according to various clinical characteristics and prognostic implications. The results demonstrated that LINE-1 hypomethylation levels were significantly higher in the HNSCC tissues than in corresponding normal tissues from the same individuals (P < 0.001). Univariate analysis revealed that high levels of LINE-1 hypomethylation were correlated with poor disease-free survival (DFS; log-rank test, P = 0.038), whereas multivariate analysis demonstrated that they were significant independent prognostic factor for DFS (hazard ratio: 2.10, 95% confidence interval: 1.02–4.36; P = 0.045). Moreover, samples with high LINE-1 hypomethylation levels exhibited the greatest decrease in 5-hydroxymethylcytosine (5-hmC) levels and increase in tumor-suppressor gene methylation index (P = 0.006 and P < 0.001, respectively). Further, ctDNA studies also showed that LINE-1 hypomethylation had high predictive ability in OCC. LINE-1 hypomethylation is associated with a higher risk of early OCC relapse, and is hence, a potential predictive biomarker for OCC. Furthermore, 5-hmC levels also exhibited predictive potential in OCC, based on their inverse correlation with LINE-1 hypomethylation levels. LINE-1 hypomethylation analysis, therefore, has applications in determining patient prognosis and real-time surveillance of disease recurrence, and could serve as an alternative method for OCC screening.

中文翻译：

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长散在的核元素 1 低甲基化在口腔癌液体活检中具有新的预后价值和潜在用途

迫切需要新的生物标志物来改进头颈部鳞状细胞癌 (HNSCC) 的个性化治疗方法。全局 DNA 低甲基化在多步骤致癌作用中具有广泛的作用，长散在核苷酸元件 1 (LINE-1) 的低甲基化与反转录转座子活性增加和诱导的基因组不稳定性有关。然而，关于 LINE-1 低甲基化及其在 HNSCC 中的预后意义的信息很少。在这项研究中，我们分析了 317 个原发性 HNSCC 组织和 225 个匹配的正常粘膜组织对以及五个口腔癌 (OCC) 循环肿瘤 DNA (ctDNA) 样本的充分表征的数据集中的 LINE-1 低甲基化水平。时间甲基化和非甲基化 PCR。该分析是根据各种临床特征和预后意义进行的。结果表明，HNSCC 组织中的 LINE-1 低甲基化水平显着高于来自同一个体的相应正常组织（P < 0.001）。单变量分析显示，高水平的 LINE-1 低甲基化与较差的无病生存期相关（DFS；对数秩检验，P = 0.038），而多变量分析表明它们是 DFS 的重要独立预后因素（风险比：2.10 , 95% 置信区间：1.02–4.36；P = 0.045)。此外，具有高 LINE-1 低甲基化水平的样本表现出 5-羟甲基胞嘧啶 (5-hmC) 水平的最大下降和肿瘤抑制基因甲基化指数的增加（分别为 P = 0.006 和 P < 0.001）。更远，ctDNA 研究还表明 LINE-1 低甲基化在 OCC 中具有很高的预测能力。LINE-1 低甲基化与早期 OCC 复发的较高风险相关，因此是 OCC 的潜在预测生物标志物。此外，基于 5-hmC 水平与 LINE-1 低甲基化水平的负相关，5-hmC 水平在 OCC 中也表现出预测潜力。因此，LINE-1 低甲基化分析可用于确定患者预后和实时监测疾病复发，并可作为 OCC 筛查的替代方法。基于它们与 LINE-1 低甲基化水平的负相关，5-hmC 水平在 OCC 中也表现出预测潜力。因此，LINE-1 低甲基化分析可用于确定患者预后和实时监测疾病复发，并可作为 OCC 筛查的替代方法。基于它们与 LINE-1 低甲基化水平的负相关，5-hmC 水平在 OCC 中也表现出预测潜力。因此，LINE-1 低甲基化分析可用于确定患者预后和实时监测疾病复发，并可作为 OCC 筛查的替代方法。