EXTH-36. PI3K INHIBITION IN CONJUNCTION WITH THE KETOGENIC DIET REDUCES GROWTH AND NEUROINFLAMMATION IN PEDIATRIC HIGH-GRADE GLIOMA

Abstract

Abstract Pediatric high-grade glioma remains a poorly treatable disease with high mortality. Targeted therapies have gained interest in this disease, but efficacy is limited by therapeutic resistance, often because of tumor heterogeneity. Phosphoinositide 3-kinase (PI3K) inhibitors represent a strong drug class for pediatric glioma, but their use is associated with insulin feedback that reactivates the PI3K pathway and drives therapeutic resistance. Here, we target insulin feedback that is the primary mechanism of PI3K inhibitor-related therapeutic resistance in pediatric high-grade glioma using the ketogenic diet. We treated patient-derived pediatric high-grade glioma stem cells with vehicle or the pan-PI3K inhibitor, BKM-120, in conjunction with phenformin to decrease glucose utilization. These cells exhibited 65% less proliferation when exposed to BKM-120 and phenformin. We treated NOD scid gamma (NSG) mice containing patient-derived pediatric high-grade glioma xenografts with vehicle or BKM-120 on a regular or ketogenic diet to determine whether reducing insulin feedback increases BKM-120 efficacy. Mice with intracranial glioma xenografts survived longer when treated with BKM-120 on the ketogenic diet than with BKM-120 or the ketogenic diet alone. We measured pro-inflammatory cytokines in glioma cells treated with BKM-120 and phenformin in comparison to vehicle-treated cells to determine their effect on neuro-inflammation. We also applied conditioned medium from glioma cells treated with BKM-120 and phenformin to cortical neurons to measure oxidative stress. We found that phenformin reduced the production of pro-inflammatory cytokines, including TNF-alpha, IFN-gamma, IL-1beta, and IL-6, by BKM-120-treated glioma cells. Cortical neurons treated with conditioned medium from BKM-120- and phenformin-treated glioma cells exhibited less oxidative stress than those treated with BKM-120 alone. Our results demonstrate that lowering glucose utilization and insulin feedback increases efficacy of PI3K inhibition and decreases neuro-inflammation. By using the ketogenic diet to reduce systemic glucose levels, this strategy may enhance efficacy and reduce morbidity of PI3K inhibitors in this population.