TMIC-36. Intercellular mitochondria transfer drives immunosuppressive astrocyte reprogramming in glioblastoma

Abstract Glioblastoma (GBM) is the most aggressive brain tumor, characterized by its ability to manipulate the tumor microenvironment (TME) for sustained tumor growth and recurrence. Astrocytes, the most abundant glial cells, adopt reactive phenotypes upon interacting with glioma cells. While tumor-associated astrocytes drive GBM proliferation, immunosuppression, and treatment resistance, the mechanisms by which cancer cells reprogram astrocytes remain poorly defined. Our previous studies showed that mitochondria transfer from astrocytes to GBM cells enhances tumorigenicity, but the role of this communication pathway in astrocyte biology remains unclear. Utilizing co-cultures of patient-derived GBM cells (PDCs) expressing mito-GFP and hTERT-immortalized human astrocytes, we identified mitochondria transfer to astrocytes in a GBM cell type-dependent manner, with rates as high as ~40% in some models. Targeted sequencing of unique mtDNA variants additionally revealed transfer of PDC mtDNA to co-cultured astrocytes. Initial in-vivo experiments demonstrated that co-implantation of astrocytes with PDCs accelerated tumorigenesis in immunocompromised mice. To assess the relevance of mitochondria transfer in the tumor microenvironment, we subsequently implanted mitochondria-labelled PDCs and demonstrated that tumor-associated astrocytes contained GBM-derived mitochondria. Functionally, acquisition of GBM mitochondria promoted astrocyte proliferation, increased cellular reactive oxygen species (ROS), and enhanced secretion of the chemokine CCL2, which is implicated in the recruitment of immunosuppressive myeloid cells in GBM. Astrocyte proliferation and increased CCL2 were orthogonally validated in vitro through addition of cell-free PDC mitochondria. Mechanistic investigations further revealed that tumor necrosis factor (TNF) enhanced GBM-to-astrocyte mitochondria transfer. These findings elucidate a poorly understood, fundamental process by which mitochondria transfer promotes astrocyte reactivity and supports an immunosuppressive tumor microenvironment. Future studies will explore the molecular drivers of GBM mitochondria transfer and astrocyte reprogramming to identify potential therapeutic vulnerabilities.