ABCB1 and breast carcinoma: The increase in expression of MDR1 gene is responsible for doxorubicin resistance in human hepatocellular carcinoma cell lines (Park et al., 1994[32]); the increase in expression of MDR1 in human breast cancer has been shown to correlate with resistance to taxol and doxorubicin (Mechetner et al., 1998[23]).