Glioblastoma Cells Induce Neuron Loss In Vivo and In Vitro

<b>Background</b>: The vast majority of GBMs recur within 2 years following standard treatment, including radiotherapy. Seizures and epilepsy are common in GBM patients, suggesting tumor-cell-induced neuron toxicity. Additionally, the tumor cells and neurons interact during tumor development; however, the effects of tumor cells on the neurons remain unclear. <b>Methods</b>: Orthotopic xenografts initiated from GSCs expressing GFP implanted into the right striatum of nude mice were irradiated (10 Gy) 35 days after implantation, followed by immunohistochemistry (IHC) to investigate the tumor cell-neuron interactions. Moreover, we established a direct coculture of human GSCs and neurons differentiated from human iPSC-derived neural progenitor cells (NPCs) to investigate the impact of the tumor cells on the neurons. Neuronal cell counts were monitored to assess neurotoxicity. Culture CM were analyzed through cytokine profiling. <b>Results:</b> In untreated mice, tumors invaded across the right hemisphere (RH), with increased cell contact with the mouse neurons. In irradiated mice, the tumor regrowth was less invasive and had fewer neurons. In vitro, the GSCs induced neuronal death in the direct coculture. Similarly, the CM from the direct cocultures caused significant neuronal death. The cytokine analysis revealed that the cocultures uniquely secreted IL-8 into the CM. Furthermore, treatment with recombinant (r) human IL-8 caused significant neuron death, while IL-8 blocking antibodies prevented this neurotoxicity in the coculture. <b>Conclusions:</b> This study demonstrates that GBM tumors regrown after radiation lack neurons, and direct interaction between GSCs and the neurons is necessary for GSC-mediated neurotoxicity, likely involving IL-8 in neuronal death.