Interaction of Isoflavones with the BCRP/ABCG2 Drug Transporter

This review will provide a comprehensive overview of the interactions between dietary isoflavones and the ATP-binding cassette (ABC) G2 efflux transporter, which is also named the breast cancer resistance protein (BCRP). Expressed in a variety of organs including the liver, kidneys, intestine, and placenta, BCRP mediates the disposition and excretion of numerous endogenous chemicals and xenobiotics. Isoflavones are a class of naturally-occurring compounds that are found at high concentrations in commonly consumed foods and dietary supplements. A number of isoflavones, including genistein and daidzein and their metabolites, interact with BCRP as substrates, inhibitors, and/or modulators of gene expression. To date, a variety of model systems have been employed to study the ability of isoflavones to serve as substrates and inhibitors of BCRP; these include whole cells, inverted plasma membrane vesicles, in situ organ perfusion, as well as in vivo rodent and sheep models. Evidence suggests that BCRP plays a role in mediating the disposition of isoflavones and in particular, their conjugated forms. Furthermore, as inhibitors, these compounds may aid in reversing multidrug resistance and sensitizing cancer cells to chemotherapeutic drugs. This review will also highlight the consequences of altered BCRP expression and/or function on the pharmacokinetics and toxicity of chemicals following isoflavone exposure.