Hopp-Children's Cancer Center at the NCT Heidelberg (KiTZ), 69120, Heidelberg, Germany.
Division of Pediatric Neurooncology, German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany.
Acta Neuropathol. 2018 Aug;136(2):211-226. doi: 10.1007/s00401-018-1877-0. Epub 2018 Jun 16.
Of nine ependymoma molecular groups detected by DNA methylation profiling, the posterior fossa type A (PFA) is most prevalent. We used DNA methylation profiling to look for further molecular heterogeneity among 675 PFA ependymomas. Two major subgroups, PFA-1 and PFA-2, and nine minor subtypes were discovered. Transcriptome profiling suggested a distinct histogenesis for PFA-1 and PFA-2, but their clinical parameters were similar. In contrast, PFA subtypes differed with respect to age at diagnosis, gender ratio, outcome, and frequencies of genetic alterations. One subtype, PFA-1c, was enriched for 1q gain and had a relatively poor outcome, while patients with PFA-2c ependymomas showed an overall survival at 5 years of > 90%. Unlike other ependymomas, PFA-2c tumors express high levels of OTX2, a potential biomarker for this ependymoma subtype with a good prognosis. We also discovered recurrent mutations among PFA ependymomas. H3 K27M mutations were present in 4.2%, occurring only in PFA-1 tumors, and missense mutations in an uncharacterized gene, CXorf67, were found in 9.4% of PFA ependymomas, but not in other groups. We detected high levels of wildtype or mutant CXorf67 expression in all PFA subtypes except PFA-1f, which is enriched for H3 K27M mutations. PFA ependymomas are characterized by lack of H3 K27 trimethylation (H3 K27-me3), and we tested the hypothesis that CXorf67 binds to PRC2 and can modulate levels of H3 K27-me3. Immunoprecipitation/mass spectrometry detected EZH2, SUZ12, and EED, core components of the PRC2 complex, bound to CXorf67 in the Daoy cell line, which shows high levels of CXorf67 and no expression of H3 K27-me3. Enforced reduction of CXorf67 in Daoy cells restored H3 K27-me3 levels, while enforced expression of CXorf67 in HEK293T and neural stem cells reduced H3 K27-me3 levels. Our data suggest that heterogeneity among PFA ependymomas could have clinicopathologic utility and that CXorf67 may have a functional role in these tumors.
在通过 DNA 甲基化分析检测到的 9 个室管膜瘤分子群中，后颅窝型 A（PFA）最为常见。我们使用 DNA 甲基化分析来寻找 675 例 PFA 室管膜瘤中进一步的分子异质性。发现了两个主要亚群，PFA-1 和 PFA-2，以及 9 个次要亚型。转录组分析表明 PFA-1 和 PFA-2 具有明显不同的组织发生，但它们的临床参数相似。相比之下，PFA 亚型在诊断时的年龄、性别比例、预后以及遗传改变的频率上存在差异。一个亚型 PFA-1c 富含 1q 增益，预后相对较差，而 PFA-2c 室管膜瘤患者的 5 年总生存率>90%。与其他室管膜瘤不同，PFA-2c 肿瘤表达高水平的 OTX2，这是一种预后良好的这种室管膜瘤亚型的潜在生物标志物。我们还在 PFA 室管膜瘤中发现了复发性突变。H3 K27M 突变存在于 4.2%，仅发生在 PFA-1 肿瘤中，而未表征基因 CXorf67 的错义突变存在于 9.4%的 PFA 室管膜瘤中，但不存在于其他组中。我们在除 PFA-1f 以外的所有 PFA 亚型中均检测到高水平的野生型或突变型 CXorf67 表达，而 PFA-1f 富含 H3 K27M 突变。PFA 室管膜瘤的特征是缺乏 H3 K27 三甲基化（H3 K27-me3），我们测试了 CXorf67 结合 PRC2 并调节 H3 K27-me3 水平的假设。免疫沉淀/质谱检测到 EZH2、SUZ12 和 EED，PRC2 复合物的核心成分，与表达高水平 CXorf67 且不表达 H3 K27-me3 的 Daoy 细胞系中的 CXorf67 结合。在 Daoy 细胞中强制降低 CXorf67 水平可恢复 H3 K27-me3 水平，而在 HEK293T 和神经干细胞中强制表达 CXorf67 可降低 H3 K27-me3 水平。我们的数据表明，PFA 室管膜瘤的异质性可能具有临床病理效用，而 CXorf67 可能在这些肿瘤中具有功能作用。
