Here we also demonstrated that the combination of PBI-05204 and RT significantly reduced the colony formation capacity of GSCs as evidenced by a reduction in the amount and size of the newly formed neurospheres and the level of neural stem cell markers including SOX2, Oct3/4, CD44 and Stro-1 in PBI-05204 and RT co-treated GBM cells, which was consistent with previously published reports (Colapietro et al., 2020a). Here, SOX2 is linked to glioblastoma.