CNSC-45. EXTRINSIC ELECTRICAL MODULATION IMPACTS GLIOBLASTOMA TUMOR GROWTH BY DISRUPTING ITS INTERCELLULAR COMMUNICATION

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Abstract Glioblastoma (GBM) is an incurable primary malignant neoplasm of the central nervous system. GBM as an electrically active neoplasm diffusely colonizes healthy brain tissues, disrupting the neurotransmission balance and causing glioma-related epilepsy (GRE) in up to 50% of patients. Interestingly, GRE is an independent favorable prognostic factor for survival in GBM. The therapeutic induction of seizure may have a previously unexplored oncologic value in GBM. We have previously reported in CT-2A-bearing mice subjected to daily extrinsic electrical modulation (EEM) diminished tumor progression and increased overall survival relative to sham-treated mice, but the mechanism by which EEM produces its anti-tumor effect remains uncertain. Therefore, GBM-bearing mice (CT-2A cells xenografted into 5-7 weeks old C57BL/6 female mice, n=5/group) received either a single EEM of 2.0 millicoulombs (mC) or sham treatment. The mice were terminated at 3 hours, 24 hours, 4, 7, and 10 days post-EEM, and tumors and contralateral brain cortex were analyzed using bulk RNA-sequencing and Sequential immunofluorescence (SeqIFTM). SeqIFTM revealed how EEM activates neuronal activity via cFOS expression and induces tumor-specific cell damage through cleaved caspase-3 expression, without affecting healthy brain tissue. Furthermore, RNA-seq performed post-EEM revealed gene expression changes of not only synapse organization markers but also of several tumor-tumor and tumor-neuron connectivity key markers, such as growth-associated protein 43 (GAP43), neuroligin-3 (NLGN3), and glutamate receptors such as GRIA4 and GRIN1 between others. However, the expression of these markers diminished significantly 96h after-EEM, indicating a reduction in intercellular electrical communication by the inhibition of the neoplasm cells electrical integration with neuronal circuits by downregulating glutamatergic receptor expression, blocking the synapse-forming protein NLGN3, and the network-connecting protein GAP43. Taken together, our findings reveal how by the disruption of these critical interactions within the tumor microenvironment though EEM impacts on GBM growth making it more susceptible to therapeutic interventions.