Mrp1 is a multispecific organic anion transporter that extrudes glutathione-, glucouronide- or sulfate-conjugated substrates (steroids, leukotrienes, etc.), as well as xenobiotic drugs out of cells. Mrp1 can confer multiple drug resistance to tumor cells. Absence of Mrp1 creates a functional deficiency in the cellular transport of some substrates and results in compromised inflammatory response, making this model useful for studying drug transport in inflammatory stimulus response and chemotherapeutic agents.