[Multidrug resistance protein (MRP)]

Two different integral glycoproteins, the 170 kD P-glycoprotein(P-gp) and the 190 kD multidrug resistance protein (MRP), are involved in the acquisition of multidrug resistance phenotypes in cancer cells. These two proteins belong to the ATP-binding cassette (ABC) superfamily but their primary structures are quite dissimilar, sharing only approximately 15% amino acid identity. Nevertheless, MRP and P-gp confer resistance to a similar profile of chemotherapeutic agents. These two proteins seem to play a similar role in the acquirement of multidrug resistance. However, it has recently been demonstrated that MRP can specifically transport the cysteinyl leukotriene, LTC4, and some other glutathione conjugates, suggesting that MRP had a function different from P-gp. This review summarizes the current data on the structural and functional characteristics of MRP, its ability to confer multidrug resistance and its clinical relevance in drug resistant malignant disease.