ABCG2 and cancer: Because the ATP-binding cassette (ABC) transporters including P-glycoprotein (P-gp/ABCB1), multi-drug resistance-associated protein 1 (MRP1/ABCC1), lung resistance protein (LRP), and breast cancer resistance protein (BCRP/ABCG2), are membrane proteins that couple the energy derived from ATP hydrolysis to extrude a variety of chemotherapeutic drugs out of the cancer cells [18], we examined the effect of COX-2 on expression of these proteins by Western blot.