ABCG2 and breast cancer: Studies on the biological function of 59 reported this alkaloid as a potent antiproliferative and cytotoxic agent, with MDR reversal activity by inhibiting BCRP in a BCRP overexpressing breast cancer cell line (MDA-MB-123) and by reducing the resistance of mitoxantrone and camptothecin mediated by BCRP, but did not inhibit MDR-1 overexpressing cells growth [135].