INSP-13. Malignant networks in brain tumors: from basic discoveries to clinical implications

Abstract Integration into communicating tumor cell networks is a way how the entire brain tumor organism can progress in the brain, and resist therapies. It started with our discovery of ultra-long membrane protrusions, tumor microtube (TM), in tumor cells from glioblastomas and other incurable adult and pediatric glioma entities (Osswald et al., Nature 2015). These TMs are used for early brain invasion, and later interconnect single tumor cells to communicating and resistant multicellular networks, but also glioma cells to neurons in the brain, with neuron-glioma synapses stimulating glioma progression (Venkataramani et al., Nature 2019). Increasing formation of these homotypic and heterotypic networks is seen with increasing glioma malignancy: lowest in low-grade oligodendrogliomas, and highest in glioblastomas and K27M mutated gliomas. The genetic reduction of GAP-43, a crucial neurodevelopmental factor that drives TM formation and function, not only deprived glioblastoma cells from the ability to form functional tumor networks, but also made radiotherapy much more effective, by and large eradicating experimental tumors from the mouse brain, which is typically not possible with radiotherapy alone. Consistent with the concept of tumor cell resilience by network integration, radiotherapy and also chemotherapy (Weil et al., Neuro-Oncology 2017) preferentially killed the unconnected glioblastoma cells, leaving the tumor cell networks largely intact. Damage to the tumor network by surgical measures induced a self-healing response. Taken together, integration into multicellular, highly functional, communicating and resilient networks is not only a feature of the nervous system, but also of incurable, most aggressive brain tumors. In this talk, clinical concepts that originate from these discoveries are presented, including a network disconnection strategy currently tested in the German MecMeth trial (EudraCT2021-000708-39), and the AMPAR inhibitor perampanel as a potential inhibitor of neuron-glioma synapses. Furthermore, new basic and translational developments in the field of brain tumor networks are presented and discussed.