Fig. 4.

Radiation survival is dependent on AKT, DNA-PKsc and serum concentration. Radiation sensitivity was analyzed with clonogenic assay (4 Gy) in DLD-1 AKT isoform knockout cell lines treated with mock (a) or siRNA against DNA-PKcs (b) in 10 % FBS and 0.5 % FBS. The cells treated with 0.5 % FBS were first seeded in flasks with 10 % FBS and incubated for 24 h to allow attachment before changing to 0.5 % FBS. The cells were incubated in 24 h in 0.5 % FBS before radiation and kept in the same media after treatment. The error bars represents the standard deviation from at least three experiments. Student’s t test evaluated if there were any significant differences in SF between the parental and the AKT KO cell lines with *P < 0.05, **P < 0.01, and ***P < 0.001