CDKN2A couples lipid metabolism to ferroptosis in glioblastoma

ABSTRACT Glioblastoma (GBM) is the most frequent and deadly primary brain tumor in adults; the median survival of patients with GBM remains a dismal 14-16 months with no improvement over standard of care since its introduction 15 years ago. Thus, identifying new therapeutic strategies for GBM is an urgent unmet medical need. Significant evidence indicates that, similar to other cancers, GBM have reprogrammed metabolism to support the requisite demands to fuel malignant growth and survival. Notably, work from our group and others has demonstrated a link between specific genetic alterations (e.g., EGFR) in GBM and rewired metabolism, consequently revealing nodes of therapeutic intervention to exploit GBM metabolism. However, comprehensive molecular profiling has shown that there is considerable molecular heterogeneity among GBM patients, and an unbiased investigation into how this molecular diversity in GBM shapes the metabolome has yet to be conducted. In preliminary studies, we have used integrated next-generation sequencing (RNA and Exome Seq) together with large-scale “shotgun” lipidomics from over 50 GBM patient and patient-derived samples to determine if molecular heterogeneity influences the lipidome of GBM. Using this cutting edge, systems-level approach we have identified a unique lipid signature enriched in GBM tumors with deletion of the tumor suppressor, CDKN2A: the most frequently altered driver gene in GBM. Importantly, as an apparent consequence of this specific lipid enrichment, CDKN2A null GBM demonstrate selective susceptibility to ferroptosis – a recently described form of lipid-peroxidation dependent cell death. These exciting preliminary results have led to the following aims both to determine the underlying mechanistic basis for these observations and to evaluate the therapeutic potential of inducing ferroptosis in CDKN2A-deleted GBM mouse models. In Aim 1, stable isotope-labeled metabolic tracing and metabolic flux analysis will be conducted to evaluate how the loss of CDKN2A elicits a shift in fatty acid composition relative to CDKN2A WT GBM. Aim 2 investigates the molecular pathways underlying enhanced sensitivity to ferroptosis in CDNK2A null GBM. Finally, Aim 3 will assess whether the exploitation of ferroptosis can selectively inhibit growth of CDKN2A null patient-derived orthotopic GBM xenografts. Together, the proposed studies will provide mechanistic insight into a previously unappreciated link between a common genetic alteration in GBM (CDKN2A deletion) and composition of the GBM lipidome, and evaluate the therapeutic potential of ferroptosis in controlling growth of this genetically-defined subset of GBM tumors.