Cells were pre-treated with 0µM (●), 2.5µM (♦) or 10µM (■) of NU7026 and then irradiated with 0, 2, 4, 6, 8 Gy. A) RPMI 8226, B) U266, C) OPM2. Only OPM2 cells showed the predicted decrease in survival after treatment with the DNA-PK inhibitor. Each point on the survival curve represents the surviving fraction ± SE from three separate experiments.