FIGURE 2.

Effect of CD30 stimulation on DNA double‐strand breaks (DSBs) through increased intracellular reactive oxygen species (ROS) in adult T‐cell leukemia/lymphoma (ATL) cell lines. (A) HUT102 cells were treated with hydrogen peroxide at the indicated concentration for 30 min, and DNA damage was analyzed by comet assay (alkaline comet: n = 31, 19, 26, 41; neutral comet: n = 27, 21, 23, 29 at each concentration, respectively). Representative comet assay images of treated cells are shown to the right of the box plots. Statistical significance was determined using the Kruskal–Wallis test. **p < 0.01, ***p < 0.001. (B) HUT102, TL‐Om1, Jurkat, CEM, and Ramos cells were stimulated by mock‐CHO or CD30L‐CHO cells for 24 h, and DNA damage was analyzed by comet assay (alkaline comet: n = 48, 27, 33, 41, 36, 41, 47, 41, 19, 29; neutral comet: n = 57, 40, 47, 38, 48, 56, 73, 62, 38, 46, respectively). Representative comet assay images of stimulated cells are shown below the boxplots plots. Statistical significance was determined by the Mann–Whitney U‐test. *p < 0.05, **p < 0.01, ***p < 0.001. (C) HUT102 cells were stimulated by CD30L‐CHO or mock‐CHO cells and treated with glutathione (GSH) (1 mM) for neutralization of intracellular ROS for 24 h. The MFI of each treatment condition is shown as a bar graph. Data are shown as mean ± SD of three independent experiments. Asterisks indicate statistical significance (*p < 0.05, **p < 0.01). (D) HUT102 cells were stimulated by mock‐CHO or CD30L‐CHO cells in the absence and presence of GSH (1 mM) for 24 h, and DNA damage was analyzed by comet assay (alkaline comet: n = 35, 56, 50; neutral comet: n = 46, 88, 55, respectively). Statistical significance was determined using the Kruskal–Wallis test. *p < 0.05, **p < 0.01. n.s., not significant