P18.35.B RBFOX1 GENE INFLUENCES NEURONAL SUBTYPE PLASTICITY IN INVASIVE HIGH GRADE GLIOMA CELLS

Abstract BACKGROUND High-grade glioma (HGG) is the most common and aggressive form of primary brain cancer with poor prognosis. Standard of care surgery employs Magnetic Resonance Imaging (MRI) to identify the contrast enhancing (CE) core for resection, leaving behind an unresected non-enhancing (NE) invasive rim of tumor which borders healthy brain tissue and invariably contributes to recurrence. Recent multi-omic analyses identified predominant neuronal and immune signatures within NE tumor; understanding these signatures could provide key insights to combatting recurrence and improving patient outcomes. To this end, we utilized a novel graph database method to integrate multi-omic data from a unique dataset of multi-regional spatially-localized biopsies from the CE core and invasive NE rim from a large cohort of patients with HGG. MATERIAL AND METHODS 159 IDH-wildtype tumor biopsy samples from the NE and CE regions of 74 glioma patients were profiled by bulk RNA sequencing. Differentially expressed genes (DEG) (n=1159) across NE and CE samples were selected using EdgeR. Samples were hierarchically clustered (method = median) for each DEG and represented as nodes in a Neo4j graph network. Edges were generated between nodes sharing ≥ 1 sample. Modularity optimization was used to identify communities of densely connected nodes. Genes occurring exclusively within NE communities were localized by cell type using external single-cell RNA sequencing datasets and selected as candidate source nodes for NE network random walks. RBFOX1 was selected as a source (walk length = 5; 10,000 walks/source node). Random walks traversing samples with significantly elevated RBFOX1 expression (one-tailed test) were kept for analysis. Genes occurring at significantly high frequency (one-tailed test) within random walks were ranked by correlation with RBFOX1 expression in NE samples and analyzed by gene set enrichment analysis (GSEA) for biological processes using clusterProfiler. RESULTS RBFOX1, a neurodevelopmental regulator, was upregulated (logFC = 1.85) in NE samples and uniquely occurred in NE communities. We show RBFOX1 is differential expressed in the aggressive Neuronal glioma subtype and enriched in neuroepithelial/astrocyte subpopulations across single cell HGG datasets. NE network random walks identified 201 DEGs associated with RBFOX1. GSEA revealed upregulation of neurodevelopmental signatures and downregulation of proliferative pathways amongst RBFOX1’s network. CONCLUSION RBFOX1’s genetic network within NE tumor represents neurodevelopmental processes potentially underlying glioma invasiveness within the NE region. As such, understanding the mechanistic role of key genes within the RBFOX1 network may provide insight into novel strategies for targeting these invasive cells within an aggressive subtype of glioma in the NE rim.