To further investigate the effect of apoptosis in CML cells, Annexin V/PI double-staining assay was conducted in K562, KU-812 cells and #1 primary CML cells treated by various concentrations of wogonin (0, 5, 10, 20, 40, 80 μM) for 48 h. This evidence concerns the gene ANXA5 and chronic myelogenous leukemia, BCR-ABL1 positive.