Honokiol induces apoptosis in the presence of IL-4. PBMCs from B-CLL patients were pretreated with 25 ng/mL IL-4 for 24 hours and then treated with 40 μM honokiol and examined for apoptosis using annexin V-FITC double staining. The numbers in each quadrant indicate the percentage of cells labeled with annexin V-FITC (bottom right), PI (top left), or annexin V-FITC and PI (top left), or the percentage unlabeled (bottom left). A representative example is shown in panel A, and data from 7 patients are shown in panel B. Apoptotic cells were defined as the percentage of cells that were annexin-V positive, and data are shown as mean ± standard deviation. ^*P < .005 when cells incubated with either honokiol or honokiol and IL-4 were compared with cells incubated in medium alone.