CNSC-47. SENOLYTICS ERADICATE SENESCENT MICROGLIA IN THE BRAIN PARENCHYMA AND IMPROVE SURVIVAL IN OLDER ADULT MICE WITH GLIOBLASTOMA

Abstract BACKGROUND Glioblastoma (GBM) is the most common aggressive primary malignant brain tumor in adults with a poor median survival rate. Despite the aggressive standard of care treatment combining surgical resection, chemo-, and radio-therapy, the median overall survival (OS) is only ~15-18 months. Progressively increasing subject age is inversely associated with GBM patient OS such that older adults tend to have significantly worse survival outcomes compared to younger counterparts. Senescent cells accumulate in the body during progressive aging and contribute to worse outcomes in older adult mice with GBM. Senolytics are pharmacologics that cause senescent cells to undergo cell death. OBJECTIVE To comprehensively profile the treatment effect of senolytics combined with or without immunotherapy in mice with GBM across the lifespan. METHODS Young 7-9- and older adult 97-104-week-old wild-type (WT; C57BL/6) and 110-130-week-old INK-ATTAC mice with or without intracranial SB28 cells were treated with or without brain radiation (RT), PD-1 mAb, and an IDO enzyme inhibitor with the senolytics, dasatinib + quercetin, or the AP compound that induces p16INK4A+ senescent cell death in INK-ATTAC mice (n=5/group). The quantification of beta-galactosidase positive cells by flow cytometry was performed on brain-resident neurons, astrocytes, oligodendrocytes, microglia, as well as dendritic cells, macrophages, neutrophils, T cells in the tumor and non-tumor bulk mass. Overall survival was also evaluated. RESULTS Senolytics or AP compound treatment both decrease beta-galactosidase positive microglia in the older adult brain with GBM (p<0.05). Combining radio- and immuno-therapy with senolytics improves overall survival of older adult mice with intracranial GBM (p<0.05). CONCLUSIONS Our ongoing work aims to understand how senescent microglia affect neuronal health and function in the older adult brain with GBM. KEYWORDS Glioma, senescence, senolytic.