胚胎肿瘤很少有复发突变,这表明其他机制,如异常的DNA甲基化,在他们的发展中发挥着突出的作用。染色体区域11p15的印记(LOI)丢失是Beckwith-Wiedemann综合征背后的种系改变,导致发展几种胚胎肿瘤的风险增加。这项研究分析了甲基化,使用EPICBeadchip阵列从99个散发性胚胎肿瘤。在这些肿瘤中,46.5%和14.6%分别在印迹控制区(ICRs)1和2出现改变。基于ICR1和ICR2的甲基化水平,形成了四个具有不同甲基化模式的簇,主要用于髓母细胞瘤(ICR1甲基化缺失(LOM)),肾母细胞瘤,和肝母细胞瘤(ICR1甲基化增加(GOM),有或没有ICR2LOM)。为了验证结果,使用MS-MLPA评估29例患者的甲基化状态,两种方法之间的一致性很高:ICR1为93%,ICR2为79%。MS-MLPA结果表明15(51.7%)具有ICR1GOM,11(37.9%)具有ICR2LOM。为了进一步验证我们的发现,通过数字PCR(dPCR)在从外周血中提取的无细胞DNA(cfDNA)中表征ICR1甲基化状态.诊断时,我们在62%的病例中检测到ICR1甲基化水平的改变,肿瘤组织(MS-MLPA)和cfDNA方法之间的一致性为76%。在分歧中,dPCR能够检测肿瘤组织中异质水平的ICR1甲基化水平变化,仅在甲基化分析中检测到。这项研究强调了11p15甲基化状态在散发性胚胎肿瘤中的患病率,与甲基化水平(增益或损失)有关的差异,位置(ICR1或ICR2),和肿瘤类型(髓母细胞瘤,肾母细胞瘤,和肝母细胞瘤)。
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).