Transcription factor-based gene therapy to treat glioblastoma through direct neuronal conversion

Objective: Glioblastoma (GBM) is the most prevalent and aggressive adult primary cancer in the central nervous system. Therapeuticapproaches for GBM treatment are under intense investigation, including the use of emerging immunotherapies. Here, we proposean alternative approach to treat GBM through reprogramming proliferative GBM cells into non-proliferative neurons. Methods: Retroviruses were used to target highly proliferative human GBM cells through overexpression of neural transcriptionfactors. Immunostaining, electrophysiological recording, and bulk RNA-seq were performed to investigate the mechanismsunderlying the neuronal conversion of human GBM cells. An in vivo intracranial xenograft mouse model was used to examine theneuronal conversion of human GBM cells. Results: We report efficient neuronal conversion from human GBM cells by overexpressing single neural transcription factorNeurogenic differentiation 1 (NeuroD1), Neurogenin-2 (Neurog2), or Achaete-scute homolog 1 (Ascl1). Subtype characterizationshowed that the majority of Neurog2- and NeuroD1-converted neurons were glutamatergic, while Ascl1 favored GABAergicneuron generation. The GBM cell-converted neurons not only showed pan-neuronal markers but also exhibited neuron-specificelectrophysiological activities. Transcriptome analyses revealed that neuronal genes were activated in glioma cells after overexpressionof neural transcription factors, and different signaling pathways were activated by different neural transcription factors. Importantly,the neuronal conversion of GBM cells was accompanied by significant inhibition of GBM cell proliferation in both in vitro andin vivo models. Conclusions: These results suggest that GBM cells can be reprogrammed into different subtypes of neurons, leading to a potentialalternative approach to treat brain tumors using in vivo cell conversion technology.