Analysis of DNA methylation profiles confirms a high proportion of immune cells in glioblastoma samples

Glioblastomas are malignant tumors that belong to the central nervous system and are challenging to diagnose due to their significant intratumoral heterogeneity, which makes molecular testing and diagnosis confirmation particularly difficult. In addition to identifying typical genetic mutations such as IDH, H3F3A G34 and K27, WHO recommendations emphasize the importance of analyzing the tumor epigenome to define its class based on DNA methylation patterns and methylation status of specific genomic regions, particularly the MGMT promoter region. Based on our clinical experience, molecular genetic studies sometimes yield contradictory results due to the heterogeneous cellular composition of glioblastomas. In this study, we present a series of observations made on 35 glioblastoma samples in which we compare the morphological features and the results of cell type detection by deconvolution method based on total DNA methylation profiles. Our results suggest that samples of mesenchymal class glioblastomas may contain over 50 % non-tumor immune cells, which should be considered in genetic testing of these tumors.