PROJECT SUMMARY Patients diagnosed with glioblastoma (GBM) have a median overall survival of less than two years even after receiving multimodal therapies. Multiple factors account for this treatment resistance including: 1) Inability of therapies to cross the blood-brain barrier to reach invading cells; 2) GBM’s molecular heterogeneity and overlapping escape mechanisms that overcome targeted therapies; 3) Evasive mechanisms that render GBMs resistant to immunotherapy. Therefore, there is an unmet need for GBM treatment approaches that address multiple resistance mechanisms. The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily which was discovered as a transmembrane receptor for the products of nonenzymatic glycation and oxidation of proteins. RAGE is expressed by glioma cells and is activated by its ligands present in GBM tumor microenvironment (TME). Activation of RAGE stimulates multiple signaling pathways that promote GBM progression. Recently, we demonstrated that genetic ablation of intracellular RAGE in gliomas inhibited multiple oncogenic pathways that not only regulated glioma growth and invasion, but also, improved the efficacy of immunotherapies by promoted an immunologically “permissive” TME. We also discovered that RAGE ablation in TME enhances the efficacy of immunotherapy. Based on these observations, we propose to evaluate RAGE inhibition as a multifaceted therapy for GBM. Our central hypothesis is that RAGE inactivation will not only suppress oncogenic pathways that are important for GBM growth and invasion, but also, enhance responses to immunotherapy. Three independent aims are proposed. Aim 1 will determine the mechanism of RAGE ablation on enhancing the anti-tumor immune responses in syngeneic mouse GBM models. Findings from this Aim will uncover novel strategies that could enhance immunotherapy efficacy in these resistant tumors. Aim 2 will measure the synergistic effects of small molecule RAGE inhibitors with immunotherapy. In this Aim, we will perform the pre-clinical studies to optimize the dosing regimen of RAGE inhibitors for future GBM clinical trials. Finally, Aim 3 will Identify mechanisms of immunotherapy resistance to RAGE ablation. This Aim will identify the mechanisms by which RAGE ligands such as S100A9 attenuate tumor immune responses. Success of any of these aims, which are supported by compelling preliminary data, is expected to lead to the development of novel and critically needed GBM therapies.