Concentration effects of Cd1, Cd2 and Cd3 on breast negative cancer MDA-MB-231 cells. MDA-MB-231 cells were treated with DMSO (as control) or different concentrations of Cd1, Cd2 and Cd3 for 24 h, followed by the chymotrysin-like activity assay (A), Western blot analysis of polyubiquitinated proteins, PARP and IκB-α (B), and cellular morphologic changes (C). Columns, mean+/−SE of three independent experiments; bars, SD.