PTEN and glioblastoma: Inhibition of the PI3K-Akt pathway has been shown to impair DNA repair after IR [23,24], and result in radiosensitization in a variety of different cell types including human GBMs [22,25] For example, inhibition of PI3K-Akt pathway via treatment with PI3K inhibitors or PTEN expression has been shown to increase radiosensitivity in human GBM cells [26,27].