ABCB1 and cancer: P-glycoprotein (P-gp/ABCB1) is an ATP-binding cassette (ABC) transporter that extrudes various anticancer drugs (e.g., paclitaxel, etoposide, vincristine, and doxorubicin) from cancer cells, as well as various endogenous molecules (Kathawala et al., 2015).