Treatment dependent changes in ATM kinase. (a) 293-ATMR cells were treated for 1hr with either vehicle, caffeine (3 mM), or CGK-733 (1 μM, 10 μM), bioluminescent activity was measured and normalized to vehicle-treated cells and expressed as fold activation. (b) 293-ATMR cells were irradiated (2 Gy) and bioluminescent activity was monitored at 5, 10, 15, 30, 60, and 120 min post- irradiation. (c) D54-ATMR cells were treated with vehicle or CGK-733 (10 μM). (d) D54-ATMR cells were irradiated (2 Gy) and reporter activity was monitored at 5, 10, 15, 30, 60, and 120 min after radiation. (e) Western blotting of phospho-ATM (Ser1981), phospho-Chk2 (Thr68), and ATM in 293-ATMR cells after irradiation (2 Gy) at various times. Asterisks indicate p-value < 0.05 compared to control cells. Error bars are s.e.m. Quantification of western blot intensities was performed using ImageJ.