ABCB1 and cancer: Pgp1 is the gene product of MDR1(ABCB1), a member of the ABC (ATP binding cassette) superfamily of transporter proteins, and it acts as an energy-dependent cancer drug efflux pump, preventing adequate intracellular accumulation of a large number of cytotoxic drugs including anthracyclines (doxorubicin,daunorubicin), vinca alkaloids (vinblastine), taxanes (paclitaxel, docetaxel) and many others.