Figure 5
Inhibition of DNA-repair and clonogenic survival by src siRNA or src inhibitor PP2. A549 cells were either treated with src siRNA (72 h) (A/C) or with src inhibitor PP2 (1 h) (B/D). Subsequently cells were irradiated with 2, 4 and 6 Gy and after 24 h cells were fixed. Residual damage was visualized by incubation with γH2AX antibody (A/B). Each bar represents the mean ± SE of residual repair foci positive for γH2AX per cell nucleus. For each data point 300 nuclei were evaluated. Asterisks indicate significant differences (Student's t-test * p < 0.05). For colony formation assay cells pretreated either with src siRNA (C) or PP2 (D) were irradiated and seeded at a density of 500 cells per 78 cm2 dish. After 10 days colonies were fixed and stained. Surviving fractions were calculated on the basis of colony counts and plating efficiency. Each value represents the mean of three independent experiments. Differences were considered as statistically significant for p < 0.05 (t-test) and were marked with an asterisk *.