Division of Surgical Oncology Department of Surgery, Faculty of Medicine Public Health and Nursing, Universitas Gadjah Mada, Yogyakarta, Indonesia.
Institute of Pathology, Medizinische Hochschule Hannover, Hannover, Germany.
PLoS One. 2019 May 6;14(5):e0216374. doi: 10.1371/journal.pone.0216374. eCollection 2019.
Reactivation of interspersed repetitive sequences due to loss of methylation is associated with genomic instability, one of the hallmarks of cancer cells. LINE-1 hypomethylation is a surrogate marker for global methylation loss and is potentially a new diagnostic and prognostic biomarker in tumors. However, the correlation of LINE-1 hypomethylation with clinicopathological parameters and the CpG island methylator phenotype (CIMP) in patients with liver tumors is not yet well defined, particularly in Caucasians who show quite low rates of HCV/HBV infection and a higher incidence of liver steatosis. Therefore, quantitative DNA methylation analysis of LINE-1, RASSF1A, and CCND2 using pyrosequencing was performed in human hepatocellular carcinomas (HCC, n = 40), hepatocellular adenoma (HCA, n = 10), focal nodular hyperplasia (FNH, n = 5), and corresponding peritumoral liver tissues as well as healthy liver tissues (n = 5) from Caucasian patients. Methylation results were correlated with histopathological findings and clinical data. We found loss of LINE-1 DNA methylation only in HCC. It correlated significantly with poor survival (log rank test, p = 0.007). An inverse correlation was found for LINE-1 and RASSF1A DNA methylation levels (r2 = -0.47, p = 0.002). LINE-1 hypomethylation correlated with concurrent RASSF1/CCND2 hypermethylation (Fisher's exact test, p = 0.02). Both LINE-1 hypomethylation and RASSF1A/CCND2 hypermethylation were not found in benign hepatocellular tumors (HCA and FNH). Our results show that LINE-1 hypomethylation and RASSF1A/CCND2 hypermethylation are epigenetic aberrations specific for the process of malignant liver transformation. In addition, LINE-1 hypomethylation might serve as a future predictive biomarker to identify HCC patients with unfavorable overall survival.
由于去甲基化导致散在重复序列的重新激活与基因组不稳定性有关，而基因组不稳定性是癌细胞的标志之一。LINE-1 低甲基化是整体甲基化丢失的替代标志物，并且在肿瘤中可能是新的诊断和预后生物标志物。然而，LINE-1 低甲基化与肝肿瘤患者的临床病理参数和 CpG 岛甲基化表型（CIMP）之间的相关性尚未明确界定，特别是在 HCV/HBV 感染率相当低且肝脂肪变性发生率较高的白种人群中。因此，使用焦磷酸测序对来自白种人患者的 40 例肝细胞癌（HCC）、10 例肝细胞腺瘤（HCA）、5 例局灶性结节性增生（FNH）和相应的肿瘤周围肝组织以及 5 例健康肝组织中的 LINE-1、RASSF1A 和 CCND2 进行了定量 DNA 甲基化分析。将甲基化结果与组织病理学发现和临床数据相关联。我们仅在 HCC 中发现 LINE-1 DNA 甲基化缺失。它与较差的生存显著相关（对数秩检验，p = 0.007）。LINE-1 和 RASSF1A DNA 甲基化水平呈负相关（r2 = -0.47，p = 0.002）。LINE-1 低甲基化与同时的 RASSF1/CCND2 高甲基化相关（Fisher 精确检验，p = 0.02）。良性肝细胞肿瘤（HCA 和 FNH）中均未发现 LINE-1 低甲基化和 RASSF1/CCND2 高甲基化。我们的结果表明，LINE-1 低甲基化和 RASSF1/CCND2 高甲基化是恶性肝转化过程中的特定表观遗传异常。此外，LINE-1 低甲基化可能成为识别总体生存不利的 HCC 患者的未来预测性生物标志物。
