In two clinical trials to eliminate the activity of breast cancer stem cells (BCSCs) with bevacizumab (VEGF inhibitor) (NCT01190345) or reparixin (CXCR1/2 inhibitor) (NCT01861054), ALDH1A1 is one of the markers to measure the effect of drugs on BCSC activity. Here, CXCR1 is linked to breast cancer.