Early increases in DNA-PKcs activity in resistant B-CLL cell extracts after γ-irradiation. (A) DNA-PKcs activity in resistant B-CLL (R) nuclear protein extracts (25 μg/lane) and sensitive B-CLL (S) nuclear protein extracts (25 μg/lane) at the indicated times after treatment with 10 Gy γ-irradiation. The results shown are representative of those obtained in all extracts tested (n = 3 for resistant samples and n = 3 for sensitive samples). (B) DNA-PKcs activity in untreated nuclear protein extracts from 3 resistant B-CLL samples (R₁,R₂,R₃) and from 3 sensitive B-CLL samples (S₁,S₂,S₃). (C) Mean (± SEM) DNA-PKcs activity in 3 resistant B-CLL samples (R) and 3 sensitive B-CLL samples (S) at the indicated times after irradiation. Values are given in arbitrary units (AU). (D) DNA-PKcs activity in resistant (R) and sensitive (S) B-CLL nuclear protein extracts (25 μg/lane) from cells that were either left untreated (-) or treated with 10 Gy irradiation (+, measurements were carried out 15 minutes after irradiation), 1 μM wortmannin, or 10 μM NU7026. A representative experiment is shown. See Supplemental Figure S2 for more information.