Regulatory T cell modulation of reactive astrogliosis in brain metastasis

Project Summary The main goal of this grant proposal is to investigate the interaction between regulatory T (Treg) cells and reactive astrogliosis in the context of brain metastatic disease, and their impact on the brain metastatic process. Brain metastasis represents the final stage of cancer, for which very limited treatment is available. Inevitably, patients with brain metastasis succumb to disease in a very short time. There is a strong resistance to the initial development of brain metastasis, and the activation of astrocytes represents one of the earliest events observed during the establishment of brain lesions. Their dual role first opposing and then favoring brain metastatic progression has only started to be investigated. Treg cells colonize and expand in the inflamed brain tissue, and have been shown to inhibit reactive gliosis in a model of stroke. We have demonstrated that Treg cell ablation in early and late brain metastasis results in significant reduction of the brain tumor burden, and leads to extensive expansion of reactive astrogliosis. In this research proposal, we use a combination of in vivo genetic modeling, ex vivo brain organotypic slice cultures, immunohistochemistry, flow cytometry, and single cell RNASequencing to investigate the hypothesis that Treg cells promote the establishment and progression of brain metastasis by modulating the highly heterogenous and plastic reactive astrocyte population. Results from the proposed studies will illuminate the mechanisms of brain metastatic disease, and will provide novel opportunities based on a largely unexplored therapeutic niche.