CSIG-08. UNRAVEL THE ROLE OF RNA MODIFICATION IN H3K27-ALTERED DIFFUSE MIDLINE GLIOMA

Abstract BACKGROUND Recent advances in tumor biology have highlighted genetic and epigenetic alterations as key drivers of malignancy, leading to the discovery of new therapeutic targets. In addition to DNA and histone modifications, RNA modification has emerged as a critical regulatory layer in cancer. However, the epitranscriptomic role in pediatric brain tumors, particularly H3K27-altered diffuse midline glioma (DMG), remains largely unknown. METHODS We explored how RNA modifications contribute to the malignancy of DMG. We profiled RNA modifications and gene expression in pediatric high-grade glioma (pHGG) cells with or without H3K27M mutation using RNA-seq and RIP-seq. Alternative RNA processing including RNA splicing and DNA-RNA hybrid (R-loop) formation was examined by RNA-seq and S9.6 dot plot, CUT&Tag, and immunocytochemistry. DNA damage was evaluated gH2AX expression by immunoblotting and immunocytochemistry. In vivo tumor growth and animal survival will be examined by serial bioluminescence image and anima subject survival. RESULTS We identified a specific RNA-modifying enzyme (referred to as factor X) that was consistently upregulated in DMG cells. Genetic and pharmacological inhibition of factor X significantly suppressed cell proliferation in DMG relative to H3 wildtype pHGG. We also found that targeted inhibition of factor X induced R-loops accumulation and DNA damage in DMG cells, suggesting mechanistic links between RNA modifications and tumor growth. Work is underway to determine the anti-tumor activity of inhibitor treatment of factor X in orthotopic patient-derived xenograft (PDX) DMG models. CONCLUSION This study unravels the role of RNA modification in DMG and identifies new epitranscriptomic target for the treatment of DMG.