Abstract
Breast cancer is the leading cause of death from cancer in women worldwide. Chemotherapy represents one key treatment modality for the clinical management of breast cancer. However, ATP-binding cassette (ABC) transporter mediated active efflux of structurally and mechanistically different cytotoxic compounds results in multidrug resistance (MDR), eventually leading to failure of chemotherapy. The concept of combining anti-cancer drugs and transport inhibitors has been advocated as a concept for re-sensitization of resistant breast cancer to chemotherapy. Whether inhibition of efflux transporters may have the potential to improve therapeutic outcomes is discussed controversially. In this review we discuss challenges in the treatment of breast cancer, the role of MDR in development and the potential of natural products to overcome MDR.