ANGI-05. CDKN2A/B HOMOZYGOUS DELETION PROMOTES ANGIOGENESIS VIA WT1 IN IDH-MUTANT ASTROCYTOMA

Abstract High-grade gliomas represent the most common type of primary adult malignant brain tumor. IDH1/2 mutations are linked to lower-grade gliomas and better patient outcomes; however, molecular profiling has revealed additional alterations that drive aggression. CDKN2A/B loss in IDH-mutant astrocytoma is recognized as a key marker of grade 4 tumor biology, yet there remain no effective targeted therapies in aggressive gliomas. Here, we analyzed a cohort of patient-derived IDH-mutant astrocytoma with whole-exome and RNA sequencing data and identified several candidate genes and pathways concurrently regulated with CDKN2A/B loss, revealing an enhanced signature related to vascular processes. We sought to elucidate the angiogenic mechanisms and functional outcomes associated with high-grade behavior following CDKN2A/B loss in IDH-mutant astrocytoma to inform future therapeutic strategies. We used grade 4 IDH-mutant astrocytoma patient-derived xenograft (PDX) and established cell lines harboring homozygous CDKN2A/B deletion. We re-expressed the cell cycle regulators p14, p15, and p16 using a Tet-inducible lentiviral system and confirmed reduced proliferation compared to parental lines. Re-expression of p14, p15, or p16 also resulted in decreased glioma cell migration and invasion. Intriguingly, re-expressing these regulators reduced VEGF secretion. HUVEC cells cultured with conditioned media (CM) from the re-expression glioma lines decreased canonical activation of PI3K/Akt and Stat3 signaling and a diminished capacity to promote endothelial migration, invasion, and tube formation. Furthermore, in vivo Matrigel plug assays using CM from the re-expression lines showed a decreased ability to recruit endothelial cells, pericytes, and form vascular organized structures. We identified the WT1 transcription factor as an upstream regulator of angiogenesis. WT1 expression was inversely correlated with CDKN2A/B expression in patient data, and knockdown of WT1 in astrocytoma cells reduced VEGF secretion and impaired ability to promote endothelial migration. Taken together, our findings reveal a novel role for WT1 in VEGF-driven angiogenesis in IDH-mutant astrocytoma with CDKN2A/B homozygous deletion.