T4302 CD133+ cells were infected with control lentivirus or lentivirus directing expression of NICD2. Cells were pre-treated with 2 μM DPAT for 4 hours and exposed to 3-Gy radiation. Irradiated cells were collected at 24 or 48 hours after radiation, and unirradiated cells were collected at 48 hours after radiation. (A C, D) Protein levels of phospho-Akt (S473), total Akt, PTEN, Bcl-2, Bcl-xL, Mcl-1, phospho-p53 (S15), total p53 and PUMA were assessed by immunoblotting. Actin was used as the loading control. (B) Control cells or NICD2-expressing cells were pre-treated with 10 μM PI3K inhibitor, LY294002, or 50 μM Akt inhibitor III (SH-6), for 4 hours prior to radiation exposure. Relative caspase 3/7 activities were determined at 48 hours after radiation exposure.