ABCB1 and breast cancer: MDR1 induces multidrug resistance utilising the energy of ATP hydrolysis to pump various chemotherapeutics drugs out of cancer cells.7MDR1 transcript levels have been indicated to be generally high in some intrinsically drug-resistant tumours, including colon cancer, renal carcinoma, hepatocellular carcinoma, pancreatic cancer and breast cancer.8 Moreover, MDR1 expression in breast cancer is suggestive of a more malignant phenotype.9 Hence, MDR1 may be a key switch molecule for the effectiveness of chemotherapeutic agents in the treatment of breast cancer.