TMIC-05. Unraveling transcriptomic and phosphokinomic dynamics of the tumor microenvironment during glioma progression

Abstract BACKGROUND BRAF gene alterations play a significant role in driving disease in pediatric low-grade glioma (LGG), the most prevalent brain tumor in children. Tumors with BRAFV600E mutation, especially with CDKN2A deletion, are prone to progression to high-grade glioma (HGG), which has poor outcomes and limited therapeutic options. The mechanisms underlying this progression, particularly within the tumor microenvironment (TME), remain poorly understood. OBJECTIVES To elucidate mechanisms of progression in BRAFV600E-mutated/CDKN2A-deleted gliomas, with a focus on the evolving TME and phosphokinome activity. We aim to identify critical mediators, including kinases and specific cell populations such as glioma-associated oligodendroglia (GA-Olig), as potential therapeutic targets. METHODS We developed a novel transgenic mouse model allowing conditional BRAFV600E activation and CDKN2A deletion via adenovirus-Cre injection into the mouse brain, generating tumors that recapitulate LGG-to-HGG progression. We analyzed TME dynamics across progression stages using magnetic resonance imaging, histology, single-cell RNA sequencing, immunofluorescence, and phosphoproteomics of patient samples with BRAFV600E-mutated LGG and HGG. Pediatric glioma datasets were used for cross-species validation of our mouse data. RESULTS We identified dynamic TME remodeling across glioma progression stages. Notably, GA-Oligo, including both oligodendrocytes (OLs) and oligodendrocyte precursor cells (OPCs), exhibited grade-dependent functional heterogeneity related to phagocytosis, immunomodulation, metabolism, neuronal regulation, and myelination. Key GA-Oligo-mediated molecular candidates were identified from mouse and human datasets for further ongoing investigation. Phosphokinome profiling of patient samples revealed activation of kinase signaling pathways associated with tumor-TME interactions. Several kinases involved in PI3K-Akt, ErbB, and immune-related signaling (phagocytosis) were differentially expressed. Validation of kinase expression in our glioma progression mouse model is ongoing. CONCLUSIONS Our study reveals coordinated transcriptomic and phosphokinomic remodeling of the TME during glioma progression, with previously underappreciated contributions from GA-Oligo within the TME. These findings support developing therapies targeting both the TME and oncogenic signaling to prevent malignant transformation in high-risk pediatric gliomas.