Glioblastoma (GBM) is the most common type of primary malignant tumor in adults and contributes disproportionately to cancer morbidity and mortality. Understanding its molecular pathogenesis is crucial for improving diagnosis and treatment. Integrated analysis of genomic, proteomic, post-translational modification and metabolomics data on 99-treatment naïve GBMs provided insights to GBM biology. Multiple key findings emerged that were not known from traditional genomic analyses: (1) Analysis of protein phosphorylation identified key signaling intermediates in the RTK/RAS path-way common to multiple RTK genomic alterations (PTPN11 and PLCG1), potentially offering common therapeutic targets for different oncogenic drivers in GBM. (2) Phosphoproteomics also identified potential druggable targets based on kinase-substrate pathway analysis, as well as novel phosphoprotein targets associated with the regulation of telomere length by ATRX in IDH mutants. (3) TP53 protein abundance in GBM is regulated by protein/phosphoprotein effectors (4) Four immune GBM subtypes exist, characterized by distinct immune cell population differences – Immune High and Immune Low phenotypes in GBM were driven by tumor-associated macrophage markers, and associated with distinct epigenetic modifications and histone acetylation patterns. (5) The mesenchymal subtype displays EMT signatures specific in tumor cells, distinct from infiltrating immune cells. (6) Histone H2B acetylation and immune-low GBM was driven largely by BRDs, CREBBP, and EP300. (7) Identification of key metabolic changes in IDH mutants facilitating the accumulation of onco-metabolite 2-HG were also associated with lipidomic changes. This work identifies additional therapeutic channels for GBM and novel information useful for more accurate stratification patients for effective treatment.

Citation Format: Jill S. Barnholtz-Sloan. Gaining biologic insights into glioblastoma using proteomics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr SY07-02.