TAMI-51. HORIZONTAL MITOCHONDRIAL TRANSFER FROM THE TUMOR MICROENVIRONMENT TO GLIOBLASTOMA INCREASES TUMORIGENICITY

Abstract

Abstract Communication between glioblastoma (GBM) and its microenvironment facilitates tumor growth and therapeutic resistance, and is facilitated through a variety of mechanisms. Organelle transfer between cells was recently observed, including mitochondria transfer from astrocytes to neurons after ischemic stroke. Given the dependence of GBM on microenvironmental interactions, we hypothesized that mitochondria transfer from tumor microenvironment to GBM cells could occur and affect metabolism and tumorigenicity. We interrogated this in vivo by establishing intracranial GBM tumors in mito::mKate2 mice (with trackable fluorescent mitochondria) using syngeneic GFP-expressing tumor cells (SB28 and GL261 models). We also cultured stromal cell types from mito::mKate2 mice with tumor cells, enabling sorting of tumor cells with and without exogenous mitochondria. Confocal microscopy revealed horizontal transfer of mKate2+ mitochondria from mouse cells to implanted GBM cells in vivo and was confirmed by flow cytometry where 20-40% of GBM cells acquired exogenous mitochondria. Transfer was negligible in wildtype mice transplanted with mito::mKate2 bone marrow cells, suggesting that brain-resident cells were the main donors. In vitro, astrocytes and microglia exhibited 5 to 10-fold higher mitochondrial transfer rate than bone-marrow derived macrophages. Seahorse metabolic profiling revealed that GBM cells with mKate2+ mitochondria had 40% lower respiratory reserve compared to cells without exogenous mitochondria. Median survival of mice implanted with SB28 that acquired mitochondria was significantly shorter and in vivo limiting dilution confirmed the frequency of tumor-initiating cells was 3-fold higher in SB28 cells with exogenous mitochondria. Our data indicate that horizontal mitochondrial transfer from brain-resident glia to mouse GBM tumors alters tumor cell metabolism and increases their tumorigenicity. Ongoing studies are assessing gene expression in GBM cells acquiring exogenous mitochondria; validating findings in human specimens; and screening for transfer inhibitor drugs. Horizontal mitochondrial transfer represents a foundational tumor microenvironment interaction contributing to glioblastoma plasticity, and is likely to inform next-generation treatment strategies.