Accurate grading of IDH-mutant gliomas defines patient prognosis and guides the treatment path. Histological grading is challenging, and aside from CDKN2A/B homozygous deletions in IDH-mutant astrocytomas, there are no other objective molecular markers used for grading. RNA-sequencing was conducted on primary IDH-mutant astrocytomas (n = 138) included in the prospective CATNON trial, which was performed to assess the prognostic effect of adjuvant and concurrent temozolomide. We integrated the RNA-sequencing data with matched DNA-methylation and NGS data. We also used multi-omics data from IDH-mutant astrocytomas included in the TCGA dataset and validated results on matched primary and recurrent samples from the GLASS-NL study. Since discrete classes do not adequately capture grading of these tumours, we utilised DNA-methylation profiles to generate a Continuous Grading Coefficient (CGC) based on classification scores from a CNS-tumour classifier. CGC was an independent predictor of survival outperforming current WHO-CNS5 and methylation-based classification. Our RNA-sequencing analysis revealed four distinct transcription clusters that were associated with (i) upregulation of cell cycling genes; (ii) downregulation of glial differentiation genes; (iii) upregulation of embryonic development genes (e.g. HOX, PAX, and TBX) and (iv) upregulation of extracellular matrix genes. The upregulation of embryonic development genes was associated with a specific increase of CpG island methylation near these genes. Higher grade IDH-mutant astrocytomas have DNA-methylation signatures that, on the RNA level, are associated with increased cell cycling, tumour cell de-differentiation and extracellular matrix remodelling. These combined molecular signatures can serve as an objective marker for grading of IDH-mutant astrocytomas.

IDH 突变神经胶质瘤的准确分级可定义患者预后并指导治疗路径。组织学分级具有挑战性，除了 IDH 突变星形细胞瘤中的 CDKN2A/B 纯合缺失外，没有其他客观分子标志物用于分级。对前瞻性 CATNON 试验中包括的原发性 IDH 突变星形细胞瘤 （n = 138） 进行 RNA 测序，以评估辅助和同步替莫唑胺的预后影响。我们将 RNA 测序数据与匹配的 DNA 甲基化和 NGS 数据进行了整合。我们还使用了 TCGA 数据集中包含的 IDH 突变星形细胞瘤的多组学数据，并验证了 GLASS-NL 研究中匹配的原发和复发样本的结果。由于离散类别不能充分捕捉这些肿瘤的分级，我们利用 DNA 甲基化谱根据 CNS-肿瘤分类器的分类分数生成连续分级系数 （CGC）。CGC 是优于当前 WHO-CNS5 和基于甲基化的分类的生存率的独立预测因子。我们的 RNA 测序分析揭示了四个不同的转录簇，它们与 （i） 细胞循环基因的上调有关;（ii） 神经胶质分化基因的下调;（iii） 胚胎发育基因（例如 HOX、PAX 和 TBX）的上调和 （iv） 细胞外基质基因的上调。胚胎发育基因的上调与这些基因附近 CpG 岛甲基化的特异性增加有关。更高级别 IDH 突变的星形细胞瘤具有 DNA 甲基化特征，在 RNA 水平上，这与细胞周期增加、肿瘤细胞去分化和细胞外基质重塑有关。 这些组合的分子特征可以作为 IDH 突变星形细胞瘤分级的客观标志物。