ERBB2 and breast cancer: In general, there is some evidence that the limitation of chemotherapy and radiation treatment may be associated with the inability to target breast cancer stem cells (Phillips et al, 2006; Fillmore and Kuperwasser, 2008; Li et al, 2008; Tanei et al, 2009), and the efficacy of HER2 inhibitors may relate to their influence on stem cell populations in HER2-positive tumours (Korkaya et al, 2008).