Fig. 4. Induction of apoptosis and necrosis by codeinone. HL-60 cells were incubated for 6 h without (control) or with 17 μm codeinone. The percent of apoptotic cells (bottom right ) was determined by FACS after Annexin staining. Cells that have bound Annexin V, but do not take up PI (bottom right quadrant of dot plot) are early apoptotic. Annexin V positive cells that also take up PI are late apoptotic (top right ). Cells that take up PI but not stained by Annexin V are necrotic cells (top left ). Cells that are negative for both Annexin V and PI (bottom left ) are nonapoptotic and nonnecrotic viable cells. Similar results were reproducibly obtained in another 3–6 independent experiments. The percent of the apoptotic cells was increased from 5.0 ± 2.2% (control, n = 7) to 41.5 ± 5.7% (codeinone-treated;P < 0.001, n = 4). HL-60 = human promyelocytic leukemic cells; FACS = fluorescence activated cell sorter; PI = propidium iodide.