H3122 (4A), H460 (4B), and H2228 (4C) cells were treated with 0.4 µM PF02341066 or DMSO for 2 hours followed by irradiation with the indicated doses. Forty-eight hours after radiation, drug-containing media was replaced with fresh media. After 8 days, surviving colonies were stained and scored. Shown are survival curves containing the mean ± standard deviation of three separate, repeated experiments.