The human breast cancer resistance protein (BCRP, gene symbol ABCG2) is a medically important ABC drug transporter. Overexpression of BCRP in cancer cells is associated with resistance to multiple anticancer drugs, including mitoxantrone, topotecan, and flavopiridol. Correlation between BCRP expression and drug resistance or patient survival has been observed with some hematological and solid tumors. In addition, BCRP is highly expressed in the placental syncytiotrophoblasts, in the apical membrane of the epithelium in the small intestine, and in the liver canalicular membrane. The tissue localization patterns, and results from recent studies, strongly suggest that BCRP functions as a protective efflux pump, and has the potential to limit oral absorption and increase biliary elimination of drugs that are BCRP substrates. At present, the molecular mechanism by which BCRP acts to transport drugs is unknown. Thus, the long-term goal of this proposal is to explore the molecular mechanism of BCRP. To achieve this goal, we propose one main specific aim, namely specific aim 1: structure and function analysis of BCRP. Site-directed mutagenesis and functional characterization of BCRP mutants, protein purification, and structure determination will be employed.
The specific aim 1 a is to purify BCRP overexpressed in the methylotrophic yeast Pichia pastoris. Purified protein will be functionally characterized and used for structural determination by electron microscopy.
The specific aim 1 b is mutational analyses to identify amino acid residues important for transport function and substrate selectivity of BCRP.
The specific aim 1 c is to analyze membrane topology of the transporter. Such studies will lead to a greater understanding of the molecular mechanism by which BCRP acts to transport drugs and provide the molecular basis for developing new ways to circumvent drug resistance in diseases such as cancers. Knowledge gained from the above studies will also aid in predicting potential drug-drug interactions and changes of pharmacokinetic properties of BCRP substrate drugs.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
Program Officer
Okita, Richard T
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Washington
Schools of Pharmacy
United States
Zip Code
Rosenberg, Mark F; Bikadi, Zsolt; Hazai, Eszter et al. (2015) Three-dimensional structure of the human breast cancer resistance protein (BCRP/ABCG2) in an inward-facing conformation. Acta Crystallogr D Biol Crystallogr 71:1725-35
Hazai, Eszter; Hazai, Istvan; Ragueneau-Majlessi, Isabelle et al. (2013) Predicting substrates of the human breast cancer resistance protein using a support vector machine method. BMC Bioinformatics 14:130
Ni, Zhanglin; Bikadi, Zsolt; Shuster, Diana L et al. (2011) Identification of proline residues in or near the transmembrane helices of the human breast cancer resistance protein (BCRP/ABCG2) that are important for transport activity and substrate specificity. Biochemistry 50:8057-66
Ni, Zhanglin; Mao, Qingcheng (2011) ATP-binding cassette efflux transporters in human placenta. Curr Pharm Biotechnol 12:674-85
Bikadi, Zsolt; Hazai, Istvan; Malik, David et al. (2011) Predicting P-glycoprotein-mediated drug transport based on support vector machine and three-dimensional crystal structure of P-glycoprotein. PLoS One 6:e25815
Rosenberg, Mark F; Bikadi, Zsolt; Chan, Janice et al. (2010) The human breast cancer resistance protein (BCRP/ABCG2) shows conformational changes with mitoxantrone. Structure 18:482-93
Ni, Zhanglin; Bikadi, Zsolt; Rosenberg, Mark F et al. (2010) Structure and function of the human breast cancer resistance protein (BCRP/ABCG2). Curr Drug Metab 11:603-17
Ni, Zhanglin; Bikadi, Zsolt; Cai, Xiaokun et al. (2010) Transmembrane helices 1 and 6 of the human breast cancer resistance protein (BCRP/ABCG2): identification of polar residues important for drug transport. Am J Physiol Cell Physiol 299:C1100-9
Rosenberg, Mark F; Oleschuk, Curtis J; Wu, Peng et al. (2010) Structure of a human multidrug transporter in an inward-facing conformation. J Struct Biol 170:540-7
Ni, Zhanglin; Mark, Michelle E; Cai, Xiaokun et al. (2010) Fluorescence resonance energy transfer (FRET) analysis demonstrates dimer/oligomer formation of the human breast cancer resistance protein (BCRP/ABCG2) in intact cells. Int J Biochem Mol Biol 1:1-11

Showing the most recent 10 out of 13 publications