title: MicroRNA-328 negatively regulates the expression of breast cancer resistance protein (BCRP/ABCG2) in human cancer cells.
abstract: Breast cancer resistance protein (BCRP/ABCG2) is a molecular determinant of pharmacokinetic properties of many drugs in humans. To understand post-transcriptional regulation of ABCG2 and the role of microRNAs (miRNAs) in drug disposition, we found that microRNA-328 (miR-328) might readily target the 3'-untranslated region (3'-UTR) of ABCG2 when considering target-site accessibility. We then noted 1) an inverse relation between the levels of miR-328 and ABCG2 in MCF-7 and MCF-7/MX100 breast cancer cells and 2) that miR-328 levels could be rescued in MCF-7/MX100 cells by transfection with miR-328 plasmid. Luciferase reporter assays showed that ABCG2 3'-UTR-luciferase activity was decreased more than 50% in MCF-7/MX100 cells after transfection with miR-328 plasmid, the activity was increased over 100% in MCF-7 cells transfected with a miR-328 antagomir, and disruption of miR-328 response element within ABCG2 3'-UTR led to a 3-fold increase in luciferase activity. Furthermore, the level of ABCG2 protein was down-regulated when miR-328 was over-expressed, and the level was up-regulated when miR-328 was inhibited by selective antagomir. Altered ABCG2 protein expression was associated with significantly declined or elevated levels of ABCG2 3'-UTR and coding sequence mRNAs, suggesting possible involvement of the mechanism of mRNA cleavage. Finally, miR-328-directed down-regulation of ABCG2 expression in MCF-7/MX100 cells resulted in an increased mitoxantrone sensitivity, as manifested by a significantly lower IC(50) value (2.46 +/- 1.64 microM) compared with the control (151 +/- 32 microM). Together, these findings suggest that miR-328 targets ABCG2 3'-UTR and, consequently, controls ABCG2 protein expression and influences drug disposition in human breast cancer cells.
authors.affiliation: Department of Pharmaceutical Sciences, University at Buffalo, The State University of New York, NY 14260-1200, USA.
authors.forename: Yu-Zhuo
authors.initials: YZ
authors.lastname: Pan
authors.forename: Marilyn E
authors.initials: ME
authors.lastname: Morris
authors.forename: Ai-Ming
authors.initials: AM
authors.lastname: Yu
mesh_terms: D020413:3' Untranslated Regions; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis* / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology; D001943:Breast Neoplasms; D045744:Cell Line, Tumor; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D035683:MicroRNAs / Q000096:biosynthesis / Q000235:genetics*; D008942:Mitoxantrone / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D035683:MicroRNAs; D009363:Neoplasm Proteins; D008942:Mitoxantrone