PGP and cancer: For example, in human cancer over-expression of PGP is linked to resistance to vinca alkaloids, anthracyclines, epipodophyllotoxins and also tubulin polymerizing drugs whereas MRP1 is responsible for resistance to vincristine and vinblastine, methothrexate, anthracyclines, etoposide, paclitaxel and irinotecan [8,9].