TMIC-27. THE ROLE OF AQUAPORIN-4 IN GLIOBLASTOMA-ASSOCIATED VASOGENIC CEREBRAL EDEMA

Abstract Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults. Vasogenic cerebral edema is a severe complication that occurs in a majority of GBM patients, leading to a significant increase in intracranial pressure, accompanying neurological deficits, and increased mortality rates. Edema in GBM patients is almost exclusively managed by the corticosteroid dexamethasone (DEX), which has recently been found to have several drawbacks, including immunosuppression and interference with radiation therapy. Thus, there is an urgent need to better understand the mechanisms of edema resolution in GBM in order to identify alternative treatment strategies. The water channel aquaporin-4 (AQP4) is a critical player in the brain's water homeostasis, with increased levels in GBM compared to the normal brain. To gain more insight into the role of AQP4 in GBM-associated edema, we used the RCAS/tv-a system to generate de novo GBM with different driver mutations in Aqp4 knockout (KO), heterozygous (HET), and wild-type (WT) mice. Multiplex IF staining combined with RNAScope of tumors showed that AQP4 expression co-localized with GFAP-positive reactive astrocytes in perivascular areas. Our results indicated that tumor-bearing mice in an Aqp4-deficient background had increased edema content and decreased survival, suggesting that AQP4 is important for edema resolution from tumors. Loss of Aqp4 also significantly decreased astrocyte coverage in the tumor core, but not in the tumor periphery. Moreover, anti-VEGFA treatment only improved vessel leakage and reduced edema in WT tumor-bearing mice. Ongoing studies are focused on characterizing the impact of Aqp4 loss on the gene expression profile of tumor core-specific astrocytes using single-cell RNA sequencing and spatial transcriptomics. We are also studying the cellular distribution of AQP4 in GBM and the effect of DEX treatment on AQP4 levels.