Figure 6.

Cell line-dependent induction of radioresistance through nucleoside supplementation. Exponentially growing cells were treated with or without the combination of olaparib and adavosertib and with or without external nucleosides as indicated. (A) Example of gating for γH2AX intensity measurement in G1 and mid-S phase cells as assessed by DAPI co-staining. The cells were fixed after 4 h of treatment and analyzed for γH2AX induction by flow cytometry. (B) Bars depict the average median γH2AX staining intensity of cells in G1 and mid-S phase. Values were normalized to the intensity of DMSO-treated mid-S phase cells of the respective experiments. Asterisks mark statistically significant differences upon nucleoside supplementation. (C) Two hours after addition of inhibitors ± nucleosides the cells were irradiated and after further 24 h seeded for colony formation without addition of inhibitors. Asterisks mark statistically significant differences in survival upon nucleoside supplementation, color indicates solvent controls or inhibitor treatment. Differences between DMSO treatment and dual inhibition without nucleoside supplementation (solid lines) were significant for all cell lines (not indicated). Significant changes are indicated with * and **indicating p ≤ 0.05 and p ≤ 0.01, respectively (two-tailed Student’s t-test).