Department of Neurosurgery, Technical University Munich, Munich, Germany.
Department of Neuroradiology, Klinikum rechts der Isar, School of Medicine, Technical University Munich, Munich, Germany.
ESMO Open. 2022 Oct;7(5):100566. doi: 10.1016/j.esmoop.2022.100566. Epub 2022 Aug 30.
Intratumoral heterogeneity at the cellular and molecular level is a hallmark of glioblastoma (GB) that contributes to treatment resistance and poor clinical outcome. Little is known regarding epigenetic heterogeneity and intratumoral phylogeny and their implication for molecular classification and targeted therapies.
Multiple tissue biopsies (238 in total) were sampled from 56 newly-diagnosed, treatment-naive GB patients from a prospective in-house cohort and publicly available data and profiled for DNA methylation using the Illumina MethylationEPIC array. Methylation-based classification using the glioma classifier developed by Ceccarelli et al. and estimation of the MGMT promoter methylation status via the MGMT-STP27 model were carried out. In addition, copy number variations (CNVs) and phylogeny were analyzed.
Almost half of the patients (22/56, 39%) harbored tumors composed of heterogeneous methylation subtypes. We found two predominant subtype combinations: classic-/mesenchymal-like, and mesenchymal-/pilocytic astrocytoma-like. Nine patients (16%) had tumors composed of subvolumes with and without MGMT promoter methylation, whereas 20 patients (36%) were homogeneously methylated, and 27 patients (48%) were homogeneously unmethylated. CNV analysis revealed high variations in many genes, including CDKN2A/B, EGFR, and PTEN. Phylogenetic analysis correspondingly showed a general pattern of CDKN2A/B loss and gain of EGFR, PDGFRA, and CDK4 during early stages of tumor development.
(Epi)genetic intratumoral heterogeneity is a hallmark of GB, both at DNA methylation and CNV level. This intratumoral heterogeneity is of utmost importance for molecular classification as well as for defining therapeutic targets in this disease, as single biopsies might underestimate the true molecular diversity in a tumor.
肿瘤内的细胞和分子水平异质性是胶质母细胞瘤（GB）的一个标志，导致治疗耐药和临床预后不良。关于表观遗传异质性和肿瘤内系统发育及其对分子分类和靶向治疗的意义，人们知之甚少。
从一个前瞻性内部队列和公开可用的数据中，对 56 名新诊断、未经治疗的 GB 患者的 238 个组织活检样本进行了采样，并使用 Illumina MethylationEPIC 芯片进行了 DNA 甲基化分析。使用 Ceccarelli 等人开发的神经胶质瘤分类器进行基于甲基化的分类，并通过 MGMT-STP27 模型估计 MGMT 启动子甲基化状态。此外，还分析了拷贝数变异（CNVs）和系统发育。
近一半的患者（22/56，39%）的肿瘤由异质性甲基化亚型组成。我们发现了两种主要的亚型组合：经典/间充质样和间充质/毛细胞型星形细胞瘤样。9 名患者（16%）的肿瘤由有和没有 MGMT 启动子甲基化的亚体积组成，而 20 名患者（36%）是完全甲基化的，27 名患者（48%）是完全非甲基化的。CNV 分析显示，包括 CDKN2A/B、EGFR 和 PTEN 在内的许多基因都存在高度变异。系统发育分析相应地显示了在肿瘤发生的早期阶段，CDKN2A/B 缺失和 EGFR、PDGFRA 和 CDK4 获得的一般模式。
（表观遗传）肿瘤内异质性是 GB 的一个标志，无论是在 DNA 甲基化还是 CNV 水平上。这种肿瘤内异质性对于分子分类以及在这种疾病中定义治疗靶点非常重要，因为单次活检可能低估了肿瘤的真实分子多样性。
