PGP and cancer: Breast cancer resistance protein and P-gp could transport an extensive range of functionally and structurally disparate anti-cancer mediators to the extracellular space, including epipodophyllotoxins, anthracyclines, actino taxanes, bisantrene, imatinib, camptothecins, saquinavir, vinca alkaloids, thiopurines, colchicine, methotrexate, and mitoxantrone.5