Embryonic tumors share few recurrent mutations, suggesting that other mechanisms, such as aberrant DNA methylation, play a prominent role in their development. The loss of imprinting (LOI) at the chromosome region 11p15 is the germline alteration behind Beckwith–Wiedemann syndrome that results in an increased risk of developing several embryonic tumors. This study analyzed the methylome, using EPIC Beadchip arrays from 99 sporadic embryonic tumors. Among these tumors, 46.5% and 14.6% presented alterations at imprinted control regions (ICRs) 1 and 2, respectively. Based on the methylation levels of ICR1 and ICR2, four clusters formed with distinct methylation patterns, mostly for medulloblastomas (ICR1 loss of methylation (LOM)), Wilms tumors, and hepatoblastomas (ICR1 gain of methylation (GOM), with or without ICR2 LOM). To validate the results, the methylation status of 29 cases was assessed with MS-MLPA, and a high level of agreement was found between both methodologies: 93% for ICR1 and 79% for ICR2. The MS-MLPA results indicate that 15 (51.7%) had ICR1 GOM and 11 (37.9%) had ICR2 LOM. To further validate our findings, the ICR1 methylation status was characterized via digital PCR (dPCR) in cell-free DNA (cfDNA) extracted from peripheral blood. At diagnosis, we detected alterations in the methylation levels of ICR1 in 62% of the cases, with an agreement of 76% between the tumor tissue (MS-MLPA) and cfDNA methods. Among the disagreements, the dPCR was able to detect ICR1 methylation level changes presented at heterogeneous levels in the tumor tissue, which were detected only in the methylome analysis. This study highlights the prevalence of 11p15 methylation status in sporadic embryonic tumors, with differences relating to methylation levels (gain or loss), location (ICR1 or ICR2), and tumor types (medulloblastomas, Wilms tumors, and hepatoblastomas).
胚胎肿瘤中复发性突变较少，这表明其他机制（如异常的DNA甲基化）在其发生发展中起重要作用。染色体区域11p15的印记丢失（LOI）是Beckwith-Wiedemann综合征的种系改变，导致多种胚胎肿瘤的发病风险增加。本研究使用EPIC Beadchip芯片对99例散发性胚胎肿瘤进行了甲基化组分析。在这些肿瘤中，分别有46.5%和14.6%的病例在印记控制区（ICR）1和2出现异常。根据ICR1和ICR2的甲基化水平，形成了四个具有不同甲基化模式的聚类，主要对应于髓母细胞瘤（ICR1低甲基化）、肾母细胞瘤和肝母细胞瘤（ICR1高甲基化，伴或不伴ICR2低甲基化）。为验证结果，采用MS-MLPA技术对29例样本的甲基化状态进行评估，两种方法显示出高度一致性：ICR1为93%，ICR2为79%。MS-MLPA结果显示15例（51.7%）存在ICR1高甲基化，11例（37.9%）存在ICR2低甲基化。为进一步验证发现，通过数字PCR（dPCR）对从外周血提取的游离DNA（cfDNA）进行ICR1甲基化状态表征。在诊断时，我们在62%的病例中检测到ICR1甲基化水平异常，肿瘤组织（MS-MLPA）与cfDNA检测方法的一致性达76%。在不一致的病例中，dPCR能够检测到肿瘤组织中呈现异质性水平的ICR1甲基化改变，而这些改变仅在甲基化组分析中被发现。本研究揭示了11p15甲基化状态在散发性胚胎肿瘤中的普遍性，其差异涉及甲基化水平（增高或降低）、位置（ICR1或ICR2）以及肿瘤类型（髓母细胞瘤、肾母细胞瘤和肝母细胞瘤）。
11p15 Epimutations in Pediatric Embryonic Tumors: Insights from a Methylome Analysis
肿瘤(癌症)患者之家