TanshinoneIIA enhances the chemosensitivity of breast cancer cells to doxorubicin through down-regulating the expression of MDR-related ABC transporters.

As the first-line drug for breast cancer chemotherapy, doxorubicin (Dox) has strong cardiotoxicity. Meanwhile, prolonged Dox treatment of patients with breast cancer may result in resistance of breast cancer cells to Dox and an increased number of Dox-resistant breast cancer stem cells (BCSCs), thereby easily leading to breast cancer relapse. TanshinoneIIA (Tan IIA) has anti-tumor activity in addition to its cardiovascular protective effect. By preparing Dox resistant human breast cancer MCF-7 cells, here, we wanted to assess a new use of Tan IIA in enhancing the chemosensitivity of breast cancer cells to Dox and investigated its possible mechanisms. The results showed that Tan IIA could enhance the anti-tumor effect of Dox on MCF-7 and MCF-7/dox cells in a dose-dependent manner, especially that of on MCF-7/dox cells. Even nontoxic dose of Tan IIA could also promote intracellular Dox accumulation of MCF-7 and MCF-7/dox cells through down-regulating the expression of efflux ABC transporters including P-gp, BCRP and MRP1, which can effectively eliminated cancerous cells including BCSCs, thereby enhancing the chemosensitivity of breast cancer. Therefore, Tan IIA can be used as a new potential chemotherapeutic sensitizer for the combination treatment of breast cancer.