It has been reported that CSCs exist in many kinds of tumors, including breast cancer, lung cancer, leukaemia, glioblastoma, colon cancer, live cancer and so on (Visvader and Lindeman, 2008), meanwhile, some molecular markers have been used to separate CSCs from total cancer cell population, such as ALDH (Ginestier et al., 2007) and CD24−CD44+ (Al-Hajj et al., 2003) for BCSCs, CD90 (Yang et al., 2008) and CD133 (Ma et al., 2007) for liver cancer stem cells, ABCB5 and CD271+ for melanoma cancer stem cells (Schatton et al., 2008), CD133 for brain tumor stem cells (Singh et al., 2004). This evidence concerns the gene PROM1 and breast cancer.