Breast cancer progression and resistance to therapy are believed to be primarily caused by BCSCs.38,39 We observed that, besides the expansion of PMN-MDSCs, ALDH+ BCSCs, not CD24+CD29+ BCSCs,5 were increased significantly in CCL20-overexpressing tumors (Fig. 3a, b and Supplementary Fig. S10). Here, CD24 is linked to breast cancer.