EXTH-03. A VEGF+ SUBPOPULATION OF SCHWANN CELLS DRIVES VESTIBULAR SCHWANNOMA TUMORIGENESIS

Abstract INTRODUCTION Up to 95% of vestibular schwannomas (VS) are sporadic, however their molecular underpinnings remain obscure. OBJECTIVE To perform transcriptomic profiling of VS and investigate novel tumorigenic mechanisms. METHODS We analyzed 19 VS samples (7 sporadic, 12 NF2), and performed single-cell RNA sequencing (scRNAseq, n = 4) or single-nucleus (snRNAseq, n = 15), assays for transposase-accessible chromatin (snATACseq, n = 15) and bulk DNA methylation (n = 14). CellChat was used to predict cell-cell interactions. We characterized transcription factor binding using ChIPseq. We validated our key findings at the mRNA and protein levels using RNAscope (n = 5) and multiplex immunocytochemistry (mIHC; n = 5). Mechanistic studies were conducted using NF2-null Periostin-Cre+ mice versus their Cre- control littermates. RESULTS We profiled the VS transcriptome and identified markers for Schwann cells, macrophages, T cells and endothelial cells. We identified eight Schwann cell subclusters which were enriched for known markers for myelinating, immature, repair and non-myelinating subtypes. We also unexpectedly identified a subset of VS Schwann cells with high expression of VEFGA, and these cells were enriched for signaling via laminin, NCAM, NRXN and NEGR pathways. Using RNAscope and mIHC, we verified VEGFA expression in S100B+ Schwann cells. snRNAseq and snATACseq demonstrated increased TEAD1 expression in Schwann cells, as well as increased chromatin accessibility for TEAD family transcription factor motifs. We used ChIPseq to confirm increased TEAD1 binding at the promoters of 714 genes including VEGFA. NF2-null Periostin-Cre+ mice developed spontaneous schwannomas within their dorsal root ganglia which showed increased vegfa expression, and this was partly reversible using a novel pharmacological TEAD inhibitor in-vivo. CONCLUSIONS We performed detailed epigenetic and transcriptomic profiling of sporadic and NF2-associated VS and uncovered TEAD1-mediated overexpression of VEGFA in a subset of VS Schwann cells. TEAD inhibition may constitute a novel therapeutic target for VS.