Integrated DNA methylation and copy-number profiling identify three clinically and biologically relevant groups of anaplastic glioma
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The outcome of patients with anaplastic gliomas varies considerably. Whether a molecular classification of anaplastic gliomas based on large-scale genomic or epigenomic analyses is superior to histopathology for reflecting distinct biological groups, predicting outcomes and guiding therapy decisions has yet to be determined. Epigenome-wide DNA methylation analysis, using a platform which also allows the detection of copy-number aberrations, was performed in a cohort of 228 patients with anaplastic gliomas (astrocytomas, oligoastrocytomas, and oligodendrogliomas), including 115 patients of the NOA-04 trial. We further compared these tumors with a group of 55 glioblastomas. Unsupervised clustering of DNA methylation patterns revealed two main groups correlated with IDH status: CpG island methylator phenotype (CIMP) positive (77.5 %) or negative (22.5 %). CIMPpos (IDH mutant) tumors showed a further separation based on copy-number status of chromosome arms 1p and 19q. CIMPneg (IDH wild type) tumors showed hallmark copy-number alterations of glioblastomas, and clustered together with CIMPneg glioblastomas without forming separate groups based on WHO grade. Notably, there was no molecular evidence for a distinct biological entity representing anaplastic oligoastrocytoma. Tumor classification based on CIMP and 1p/19q status was significantly associated with survival, allowing a better prediction of outcome than the current histopathological classification: patients with CIMPpos tumors with 1p/19q codeletion (CIMP-codel) had the best prognosis, followed by patients with CIMPpos tumors but intact 1p/19q status (CIMP-non-codel). Patients with CIMPneg anaplastic gliomas (GBM-like) had the worst prognosis. Collectively, our data suggest that anaplastic gliomas can be grouped by IDH and 1p/19q status into three molecular groups that show clear links to underlying biology and a significant association with clinical outcome in a prospective trial cohort.
KeywordsAnaplastic glioma IDH G-CIMP 1p/19q 450 k
The work was supported by the German Cancer Aid (Deutsche Krebshilfe, “Molecular classification of anaplastic gliomas in the NOA-04 trial”, project 110624) to WW and MW and the Personalized Oncology Program of the NCT Heidelberg.
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