A significant limitation of radiation therapy is its reduced efficacy in hypoxic regions; however, HSP90 inhibition by NXD30001 and NVP-AUY922 has been shown to increase radiosensitivity in hypoxic CD133-positive subpopulations glioblastoma spheroids (10, 40), likely due to HIF-1α inhibition. This evidence concerns the gene PROM1 and glioblastoma.