Physiological and pharmacological roles of ABCG2 (BCRP): recent findings in Abcg2 knockout mice

Adv Drug Deliv Rev. 2009 Jan 31;61(1):14-25. doi: 10.1016/j.addr.2008.08.007. Epub 2008 Dec 7.


The multidrug transporter ABCG2 (BCRP/MXR/ABCP) can actively extrude a broad range of endogenous and exogenous substrates across biological membranes. ABCG2 limits oral availability and mediates hepatobiliary and renal excretion of its substrates, and thus influences the pharmacokinetics of many drugs. Recent work, relying mainly on the use of Abcg2(-/-) mice, has revealed important contributions of ABCG2 to the blood-brain, blood-testis and blood-fetal barriers. Together, these functions indicate a primary biological role of ABCG2 in protecting the organism from a range of xenobiotics. In addition, several other physiological functions of ABCG2 have been observed, including extrusion of porphyrins and/or porphyrin conjugates from hematopoietic cells, liver and harderian gland, as well as secretion of vitamin B(2) (riboflavin) and possibly other vitamins (biotin, vitamin K) into breast milk. However, the physiological significance of these processes has been difficult to establish, indicating that there is still a lot to learn about this intriguing protein.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism
  • ATP-Binding Cassette Transporters / pharmacology*
  • ATP-Binding Cassette Transporters / physiology*
  • Animals
  • Biological Transport
  • Harderian Gland / metabolism
  • Humans
  • Mammary Glands, Animal / metabolism
  • Mammary Glands, Human / metabolism
  • Mice
  • Mice, Knockout
  • Milk / metabolism
  • Milk, Human / metabolism
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism
  • Neoplasm Proteins / pharmacology*
  • Neoplasm Proteins / physiology*
  • Phytoestrogens / pharmacokinetics
  • Phytoestrogens / pharmacology
  • Porphyrins / metabolism
  • Porphyrins / pharmacokinetics
  • Porphyrins / pharmacology
  • Vitamins / pharmacokinetics
  • Xenobiotics / pharmacokinetics*
  • Xenobiotics / pharmacology


  • ABCG2 protein, human
  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • ATP-Binding Cassette Transporters
  • Abcg2 protein, mouse
  • Neoplasm Proteins
  • Phytoestrogens
  • Porphyrins
  • Vitamins
  • Xenobiotics