Evodiamine (EVO) binds to topoisomerase I (TopI) and causes DNA damage. (A) Molecular modeling of camptothecin (green) and EVO (yellow). (B) EVO-induced DNA damage in A2780 cells. Magnification, ×200. Cells were untreated, treated with DMSO, and EVO (25 μM) for 1 h, and were then analyzed by a neutral comet assay as described in "Materials and Methods." Upper panel, representative images. Lower panel, histogram of the tail moment plotted against each treatment condition. p values for comparisons (marked with *) were 0.005 as determined by two-tailed Student's t-test. (C) γ-H2AX levels after EVO treatment in A2780 cells. Cells were treated with 0~20 μM EVO for 6 h. Cell lysates were immunoblotted with antibody against γ-H2AX. β-Actin with constant expression was used as the internal control.