Multidrug resistance mediated by the breast cancer resistance protein BCRP (ABCG2)

• Published in: Oncogene Vol. 22; no. 47; pp. 7340 - 7358
• Main Authors: Doyle, L Austin, Ross, Douglas D
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 20.10.2003
• Subjects: Animals; Anthracycline; Antineoplastic Agents - pharmacology; Antineoplastic drugs; Antitumor agents; ATP; ATP Binding Cassette Transporter, Sub-Family G, Member 2; ATP-Binding Cassette Transporters - chemistry; ATP-Binding Cassette Transporters - genetics; ATP-Binding Cassette Transporters - metabolism; BCRP protein; Breast cancer; Breast carcinoma; Breast Neoplasms - drug therapy; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Camptothecin; Chromosome 4; DNA topoisomerase; Drug resistance; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Endothelium; ErbB-1 protein; Flavopiridol; Gene Expression Regulation, Neoplastic; Gene mapping; Humans; Localization; Methotrexate; Mitoxantrone; mRNA; Multidrug resistance; Multidrug resistant organisms; Neoplasm Proteins - chemistry; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; P-Glycoprotein; Phenotypes; Proteins; Stem cells; Substrate Specificity; Transfection; Tumor cell lines
• DOI: 10.1038/sj.onc.1206938
• ISSN: 0950-9232

Observations of functional adenosine triphosphate (ATP)-dependent drug efflux in certain multidrug-resistant cancer cell lines without overexpression of P-glycoprotein or multidrug resistance protein (MRP) family members suggested the existence of another ATP-binding cassette (ABC) transporter capable of causing cancer drug resistance. In one such cell line (MCF-7/AdrVp), the overexpression of a novel member of the G subfamily of ABC transporters was found. The new transporter was termed the breast cancer resistance protein (BCRP), because of its identification in MCF-7 human breast carcinoma cells. BCRP is a 655 amino-acid polypeptide, formally designated as ABCG2. Like all members of the ABC G (white) subfamily, BCRP is a half transporter. Transfection and enforced overexpression of BCRP in drug-sensitive MCF-7 or MDA-MB-231 cells recapitulates the drug-resistance phenotype of MCF-7/AdrVp cells, consistent with current evidence suggesting that functional BCRP is a homodimer. BCRP maps to chromosome 4q22, downstream from a TATA-less promoter. The spectrum of anticancer drugs effluxed by BCRP includes mitoxantrone, camptothecin-derived and indolocarbazole topoisomerase I inhibitors, methotrexate, flavopiridol, and quinazoline ErbB1 inhibitors. Transport of anthracyclines is variable and appears to depend on the presence of a BCRP mutation at codon 482. Potent and specific inhibitors of BCRP are now being developed, opening the door to clinical applications of BCRP inhibition. Owing to tissue localization in the placenta, bile canaliculi, colon, small bowel, and brain microvessel endothelium, BCRP may play a role in protecting the organism from potentially harmful xenobiotics. BCRP expression has also been demonstrated in pluripotential "side population" stem cells, responsible for the characteristic ability of these cells to exclude Hoechst 33342 dye, and possibly for the maintenance of the stem cell phenotype. Studies are emerging on the role of BCRP expression in drug resistance in clinical cancers. More prospective studies are needed, preferably combining BCRP protein or mRNA quantification with functional assays, in order to determine the contribution of BCRP to drug resistance in human cancers.