Genistein decreased breast cancer stem cells in vivo . (A) Genistein remarkably reduced the tumor volume and weight: 1 × 106 MCF-7 cells were inoculated into the mouse mammary fat pad for 2 weeks, and then were treated daily with 20 and 50 mg/kg genistein. After 2 weeks of treatment, mice were sacrificed. Error bars represent standard deviations, n = 5. (B) Immunohistochemistry staining with aldehyde dehydrogenase isoform 1 (ALDH1) antibodies (brown in cytoplasm), ×200. (C) Real-time polymerase chain reaction analyses of ALDH1 in the mouse tumor tissues. (D) ALDH1 protein level before and after treatment with genistein. * P <0.05, **P <0.01, Student’s t test. GAPDH, glyceraldehyde 3-phosphate dehydrogenase.