Modulation of GABA Neurotransmitter Signalling Impacts Glioblastoma Spheroid Growth and Response to Standard Treatment

Abstract AIMS We have identified two subtypes within glioblastoma (GBM), defined by whether a specific subset of genes is upregulated (Up responders) or downregulated (Down responders) in response the standard treatment. The biology of therapy-driven transcriptional reprogramming in the two subtypes suggests the differential involvement of GABA neurotransmitter signalling in the underlying treatment resistance mechanisms. Our aim was to address our hypothesis that modulating GABA signalling will impact treatment response in GBM, in different ways for different responder subtypes. METHOD We identified two cell lines representing the different responder subtypes: established GBM cell line A172 is an Up responder; GBM63 is a patient derived Down responder. We have grown these cells as spheroids and inspected the response to standard treatment (2 Gy radiation and 30 mM temozolomide), via growth and cell viability assays, versus untreated controls in the presence and absence of a GABAA receptor (GABAAR) modulators. We have performed RNAseq to investigate the pathways affected by inhibition and treatment. RESULTS In all cases, modulation of GABAAR activity significantly alters both growth and response to standard treatment. However, this is most commonly in different directions in the Up vs Down responders. Furthermore, the majority of genes that are differentially expressed through treatment and inhibition are dysregulated in different directions. CONCLUSION Modulation of GABA neurotransmitter signalling impacts GBM spheroid growth and response to standard treatment. Identifying the key pathways affected in different responder subtypes may indicate how this can be used in the development of more effective combination treatments for GBM.