Metabolic interactions between tumor cells and the immune system in GBM: A potential Achilles heel of GBM for novel therapeutics - ABSTRACT Background: We recently revealed that glioblastoma (GBM) contain cell populations with distinct metabolic requirements, with fast-cycling cells (FCCs) harnessing aerobic glycolysis, and treatment-resistant slow-cycling cells (SCCs) preferentially engaging lipid metabolism. How the different tumor cells interact with immune cells and how this metabolic heterogeneity shapes the immune landscape in GBM has yet to be understood. Objectives/Hypothesis: The objectives of this study are to understand the mechanisms of communication in the tumor microenvironment, specifically to characterize the metabolic interactions between SCCs (a therapeutically resistant population that drive disease progression and recurrence) and the immune compartment. Here, we will investigate a model of intercellular communication within GBM where SCCs shape an immunosuppressive tumor milieu, which in turn assume metabolic support to SCCs by providing them with lipids, which are essential for SCC metabolism and function. Importantly, we will test multiple genetic and clinically amenable pharmacological approaches disrupting this metabolic interplay to antagonize GBM. Specific aims: Our specific aims will be 1) Dissect the relationship of SCCs with the tumor microenvironment, 2) Delineate how recruited immune suppressive cell mediate SCC-driven tumor progression, and 3) Establish that immune infiltrates provide metabolic support to SCCs by providing lipids. Study design: The link between tumor heterogeneity and tumor immune landscape in GBM will be deciphered with specific investigations of the metabolic interplay taking place between these cellular compartments. In aim 1, we will delineate the cell lineage (SCC vs FCC) relationship with immune infiltrates by investigating their genomic profile and spatial organization, using single cell RNA sequencing technology and GeoMx Digital Spatial Profiling, respectively. We will also evaluate the role of the specific adipokine, Lipocalin-2, in shaping the immune microenvironment. In aim 2 we will employ multiple approaches disrupting the macrophage, myeloid- derived suppressor cell, and regulatory T cell compartments, and compare the effect on survival, growth and chemotherapy sensitivity of SCCs and FCCs. In aim 3 the use of fluorescently labeled lipids combined with flow cytometry and time lapse imaging will enable the comparison of lipid transfer between immune cells, FCCs and SCCs. Finally, in vivo experiments will test the hypothesis that targeting lipid trafficking (inhibition of FABP3 or ApoE) or lipogenesis (statin treatment) provide therapeutic benefits by affecting SCCs and rendering the overall tumor more responsive to chemotherapy. Based on the recently reported synergistic effect of statins with immune checkpoint inhibitors, we will also evaluate the combination of statins with anti PD-1 therapy. Impact: Successfully completed, this project will validate therapeutically amenable approaches targeting metabolic communication to improve brain tumor associated morbidity and mortality.
