Angi-05. cdkn2a/b homozygous deletion in idh-mutant astrocytoma alters tumor cell invasion and vascular formation

Abstract High-grade gliomas represent the most common type of primary adult malignant brain tumor historically diagnosed and graded from histologic criteria alone. Gliomas harboring isocitrate dehydrogenase (IDH) 1 or 2 mutations are associated with lower grade tumors and portend a favorable prognosis relative to IDH-wildtype glioma. However, molecular profiling has identified additional alterations in lower grade gliomas that confer an aggressive high-grade phenotype and a worse clinical prognosis. Of these, the loss of CDKN2A/B in IDH-mutant astrocytoma is the strongest implicated alteration and is sufficient to define a grade 4 tumor regardless of histologic grade. However, there remain no effective therapies targeted at molecular subgroups in aggressive gliomas to date. Here, we sought to elucidate the biologic pathways and functional outcomes associated with the acquisition of high-grade behavior under loss of CDKN2A/B in IDH-mutant astrocytoma to inform future therapeutic strategies. We analyzed a cohort of patient IDH-mutant astrocytomas with whole exome and RNA sequencing data and found several candidate genes/pathways regulated concurrent with CDKN2A/B loss, including regulators of embryonic development, extracellular matrix organization and regulation of vascular processes. Moreover, we identified 1 tumor that displayed intratumoral heterogeneity of CDKN2A/B expression across biopsies. Using grade 4 IDH-mutant astrocytoma patient-derived (PDX) and established cell-lines harboring CDKN2A/B homozygous deletion, we then stably re-expressed cell cycle regulators p14, p15, and p16 using a Tet-inducible lentiviral system and confirmed their decreased proliferation as compared to parental lines. IDH-mutant cell lines with re-expression of p14, p15 or p16 were characterized by differential transcription factor activation and distinct vascular formation patterns as compared to parental lines. These lines also displayed an increased cell migration and invasive potential and were associated with enhanced integrin signaling through integrin beta-3. Together, our work supports a hypothesis of regional tumor evolution with distinct biologic phenotypes across IDH-mutant gliomas.