Interplay of Glioblastoma Cells with Microglia Shapes Invasive Phenotypes during Long-distance Invasion.

Glioblastoma (GBM) infiltration poses a formidable therapeutic challenge, but the mechanisms enabling long-distance tumor invasion remain poorly defined. In a recent study, Nebeling and colleagues have leveraged longitudinal three-photon intravital microscopy to visualize the migratory behavior of invading GBM cells and their interactions with microglia. Using an immunocompetent autochthonous murine GBM model for live imaging of the contralateral cortex and corpus callosum (CC), the team demonstrated that the migration velocity of GBM cells varied by anatomic location, with tumor cells moving faster in the CC than in the cortex. Furthermore, GBM cells with less tumor microtubes (TM) exhibited higher motility and traveled longer distances than TM-rich cells. Interestingly, the authors also uncovered a stage-dependent, biphasic microglial response to invading GBM cells: enhanced surveillance during sparse infiltration, followed by suppressed surveillance as tumor burden increases. Functional analyses identified chemokine receptor CX3CR1 as a key regulator of microglial reactivity and a requirement of microglia to drive GBM invasiveness. These findings align with earlier evidence that spatial constraints and microglial organization influence GBM invasion. Together, these works highlight a critical role of microglia and the tumor microenvironment in shaping invasive GBM phenotypes and offer new avenues for therapeutic strategies to limit GBM invasion.