To investigate the effect of quercetin on glioma stem/progenitor cells (GSPCs) sensitivity to radiation, GSPCs were exposed to quercetin and IR. The changes in protein levels of LC3 in GSPCs with various treatments were confirmed by the immunoblotting analysis and immunofluorescence analysis. Growth inhibition of GSPCs was assessed with methylthiazolyl tetrazolium (MTT) and cell viability assay. Annexin V-FITC/PI staining was used to study the treatment effects on apoptosis. The results show that cells previously treated with quercetin and IR generated a decreased number of colonies as compared to untreated cells, and apoptosis level in GSPCs was significantly increased by the combined treatment with quercetin and IR. These suggest that activating autophagy may abrogate the resistance of GSPCs to radiation and could lead to the development of novel therapeutic approaches for the treatment of glioblastomas.Cited