ABCB1 and cancer: Overexpression of many ATP-dependent efflux pumps, and especially ABCB1 (MDR1 or P-glycoprotein), is an important mechanism of resistance to a wide spectrum of chemotherapeutic drugs, including anthracyclines, taxanes, and Vinca alkaloids, in cancer cell lines and in many cancers, e.g., many solid and hematological tumors [100,101].