Mitochondria-mediated human leukemic cell apoptosis. Reduction of mitochondrial transmembrane potential of HL-60 (A) and U937 (B) cells treated with ZEA. Cells were stained with 40 nM DiOC6 for 15 min and then subjected to flow cytometry. Cells with decreased mitochondrial transmembrane potential are less stained with DiOC6. (C) Release of cytochrome c from mitochondria. HL-60 cells were treated with ZEA (10, 50 μg/ml) for 4 h and cytosolic cytochrome c was detected by Western blotting. Representative data from three independent experiments are shown.