Genistein decreases breast cancer stem cells in vitro . (A), (B) Genistein decreased the size (A) (×200, scale bar = 100 μm) and number (B) of mammospheres. MCF-7 cells were treated with different concentrations of genistein, and then were cultured in ultra-low-attachment plates with serum-free medium for 7 days. Mammospheres were collected and evaluated. (C), (D) The percentage of CD44+/CD24– breast cancer stem-like cells was reduced by genistein treatment. The phenotype of CD44+/CD24– cells was measured by flow cytometry. Similar results were obtained in three independent experiments, and the representative microscopic picture and flow cytometry pattern are shown. *P <0.05, **P <0.01, Student’s t test. FITC, fluorescein isothiocyanate; PE, phycoerythrin.