Figure 4. Sorafenib and HDAC inhibitors radiosensitize GBM cells. (A) GBM6 cells were treated with vehicle or Sodium Valproate (1 mM). Thirty minutes later cells were treated with vehicle or sorafenib (1 μM). Thirty minutes later cells were exposed to ionizing radiation (0–6 Gy). Cells were isolated 48 h later. Viability was determined by trypan blue exclusion (n = 3, ± SEM) *p < 0.05 greater than corresponding vehicle control treated cells. (B) GBM5 cells were treated with vehicle or Sodium Valproate (1 mM). Thirty minutes later cells were treated with vehicle or sorafenib (1 μM). Thirty minutes later cells were exposed to ionizing radiation (0–6 Gy). Cells were isolated 48 h later. Viability was determined by trypan blue exclusion (n = 3, ± SEM) *p < 0.05 greater than corresponding vehicle control treated cells. (C) DAOY cells were treated with vehicle or Sodium Valproate (1 mM). Thirty minutes later cells were treated with vehicle or sorafenib (1 μM). Thirty minutes later cells were exposed to ionizing radiation (0–6 Gy). Cells were isolated 48 h later. Viability was determined by trypan blue exclusion (n = 3, ± SEM) *p < 0.05 greater than corresponding vehicle control treated cells. (D) GBM5 and GBM6 cells plated as single cells were treated with vehicle or Sodium Valproate (1 mM). Thirty minutes later cells were treated with vehicle or sorafenib (1 μM). Thirty minutes later cells were irradiated. The media was changed 48 h later to drug free media and colonies permitted to form for the next 14 d (n = 3, ± SEM). (E) DAOY and VC312 cells plated as single cells were treated with vehicle or Sodium Valproate (1 mM). Thirty minutes later cells were treated with vehicle or sorafenib (1 μM). Thirty minutes later cells were irradiated. The media was changed 48 h later to drug free media and colonies permitted to form for the next 14 d (n = 3, ± SEM).