Bufalin induced M-phase cell cycle arrest and apoptosis in SW620 cells. Cells were exposed to 20 and 80 nmol/L bufalin for 24 h and then the cell morphological changes were determined by light microscopy (magnification×200) after Wright-Giemsa staining. (a) Cell cycle was analyzed by flow cytometry after staining with propidium iodide. (b) The expression of PARP, BAX, BCL-2, caspase-3 and livin proteins were analyzed by western blot. Actin was used as the internal control (c). Data shown are representative of one of three independent experiments.