Dose-dependent influence of doxorubicin on cell cycle arrest, apoptosis and activation of the DNA damage response (DDR).

<p><b>A.</b> DNA content, analyzed by flow cytometry, 24 h after treatment with different concentrations of doxorubicin (0–250 nM). Representative histograms from one of three independent experiments. <b>B.</b> Concentration-dependent apoptosis measured 24 h after treatment with doxorubicin (0–250 nM). The percentage of apoptotic cells was estimated by the Annexin V/7-AAD flow cytometry assay in three independent experiments. The bars show means ± SD values. Data was analyzed using the CellQuest software. Statistical significance was estimated using the Student’s T test. <b>C.</b> Expression of the DDR proteins analyzed by Western blotting in control (C) and treated with doxorubicin (D) S3R, S4 and L5 cells. Whole cell extracts were prepared 24 h after cell treatment with the following cytostatic concentrations of dox: 50 nM (L5), 10 nM (S3R), 100 nM (S4) and β-actin was used as a loading control.