Rbio-02. novel, quiescent subpopulation emerges after low-dose irradiation of glioma stem cells

Glioblastoma (GBM) tumors contain a subset of highly radiation resistant cells referred to as glioma stem cells (GSCs). We used single-cell RNA-seq (scRNA-seq) to characterize the transcriptional states that increase in size following GSC irradiation to further our understanding of the acute responses to radiotherapy. We treated two GBM patient-derived xenograft-derived GSC lines to low-dose irradiation (4 Gy). We then conducted scRNA-seq before irradiation and three days and one-week post-irradiation. As expected, the number of GSCs undergoing division through the cell cycle was drastically reduced relative to control conditions, and a subpopulation of GSCs with DNA damage response markers emerged after irradiation. Interestingly, we observed a novel, distinct subpopulation that was common between GSC lines, expanded after irradiation, and featured marker genes related to cell cycle arrest in response to external stressors. Gene regulatory network analysis identified transcription factors (TFs) likely to regulate these marker genes and potentially the dynamics of this subpopulation. The TFs were also related to cell cycle suppression and the overall expression state of these cells was similar to the quiescent Neural G0 state, indicating that our novel subpopulation may contain quiescent GSCs. In upcoming studies, we plan to perturb these TFs and marker genes to determine the importance of these genes in the GSC response to irradiation. Further exploration of this novel quiescent subpopulation may lead to new druggable targets that sensitize GBM tumors to radiotherapy.