In addition, the previous study has shown that Tanshinone IIA enhances doxorubicin sensitivity of breast cancer by decreasing the expression of MDR-related ABC transporters [51], as CSCs hold the higher expression levels of MDR-related ABC transporters compared to that in cancer cells [52], this effect further supports our results that Tanshinone IIA could attenuate breast cancer stemness. Here, ABCG2 is linked to cancer.