The phenomenon of multidrug resistance (MDR) in cancer is associated with the overexpression of the ATP-binding cassette (ABC) transporter proteins, including multidrug resistance-associated protein 1 (MRP1) and P-glycoprotein. MRP1 plays an active role in protecting cells by its ability to efflux a vast array of drugs to sub-lethal levels[[1].

[1] JF Lu et al. MRP1 and its role in anticancer drug resistance. Drug Metab Rev. 2015;47(4):406-19.