TMIC-15. GUT MICROBIOTA CONTROLS NEUROFIBROMATOSIS-1 (NF1) OPTIC GLIOMA GROWTH THROUGH IMMUNE CIRCUIT MODULATION

Abstract Changes in the gut microbiome can have profound effects on the nervous system through modulation of T cell and microglia function. Since our prior studies demonstrated that T cells and microglia positively regulate low-grade glioma growth through the establishment of T cell-microglia immune circuit, we sought to explore the impact of changes in the gut microbiota on tumor biology. For these studies, genetically engineered Neurofibromatosis type 1 (NF1) optic glioma (Nf1-OPG) mice were raised in a germ-free environment or treated with antibiotics to deplete gut bacteria. First, we demonstrated that Nf1-OPG mice raised in a germ-free (gnotobiotic) environment or treated with specific antibiotics lacked optic gliomas and had improved OPG-induced retinal pathology (increased retinal nerve fiber layer thickness). Second, germ-free and antibiotic-treated Nf1-OPG mice gavaged with fecal microbiota from Nf1-OPG mice raised in a standard barrier facility restored optic glioma growth. Third, we showed that both germ-free and antibiotic-treated Nf1-OPG mice exhibited reduced intra-tumoral CD8+ T cell content resulting from decreased microglia chemokine production. Fourth, we discovered a gut-brain paracrine axis whose interruption reduced optic glioma growth and attenuated retinal nerve fiber layer thinning. Collectively, these findings establish a mechanistic relationship between the gut microbiota and brain tumor growth relevant to potential therapeutic interventions for pediatric low-grade gliomas.