Jac-A caused K562 cell apoptosis. 106 of K562 cells were treated with different concentrations of Jac-A for 48 h. Cells were then stained with Annexin V-FITC and propidium iodide, and analysed using flow cytometry. Four different cell populations marked as the following: live cell population (PI - AV-), early apoptosis (PI - AV+), late apoptosis (PI + AV+) and dead cells (PI + AV-). Cells were treated with no Jac-A (A), 0.5% DMSO (B), or 0.1, 1, 5, 10 μM/L Jac-A (C, D, E and F). The results are one representative of three independent experiments.