Integrated analyses reveal two molecularly and clinically distinct subtypes of H3 K27M-mutant diffuse midline gliomas with prognostic significance

We identified two subgroups of diffuse midline gliomas (DMGs) with unsupervised hierarchical cluster analyses of DNA methylation data from 149 DMGs derived from different localisations: DMG-A and DMG-B. The two epigenetic DMG-subtypes have different characteristics: DMG-A are enriched for cases with MAPK-signalling-pathway associated mutations, a methylated MGMT-promoter, medullary localisation and adult age, while DMG-B are enriched for cases with TP53-mutations, PDGFRA-amplifications, pontine localisation and paediatric patients. DMG-A have a significantly better overall survival compared to DMG-B (p < 0.001). This effect on survival is larger than that of all other parameters tested, and all other parameters are dependent on the cluster attribution. Hence, the subtype attribution based on two methylation clusters is best suited to predict survival as it integrates different molecular and clinical parameters. Bisulphite converted DNA from 149 samples was hybridised to either Illumina HumanMethylation450 BeadChips or Infinium MethylationEPIC BeadChips.