title: Modulation of breast cancer resistance protein (BCRP/ABCG2) gene expression using RNA interference.
abstract: Overexpression of the breast cancer resistance protein (BCRP/ABCG2) confers multidrug resistance (MDR) to tumor cells and often limits the efficacy of chemotherapy. To circumvent BCRP-mediated MDR, a common approach is the use of potent and specific inhibitors of BCRP transport such as fumitremorgin C, novobiocin, and GF120918. Here, we evaluated a new approach using RNA interference for the specific knockdown of BCRP. We designed and synthesized small interfering RNA (siRNA) using T7 RNA polymerase and showed that siRNAs markedly down-regulated both exogenous and endogenous expression of BCRP. As a functional consequence, knockdown of BCRP by siRNAs increased the sensitivity of human choriocarcinoma BeWo cells to mitoxantrone and topotecan by 10.5- and 8.2-fold, respectively. Using flow cytometry, we found that introduction of siRNAs also enhanced the intracellular accumulation of topotecan. We have previously identified an estrogen response element in the BCRP promoter and have shown that 17beta-estradiol increased BCRP mRNA expression. Furthermore, in the present study, we found that expression of BCRP protein was inducible by 17beta-estradiol and that this effect was ameliorated by the introduction of siRNAs. These studies indicate that siRNAs could modulate MDR in vitro and may present a new approach to overcome BCRP-mediated drug resistance.
authors.affiliation: Department of Biopharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
authors.forename: P L Rachel
authors.initials: PL
authors.lastname: Ee
authors.forename: Xiaolong
authors.initials: X
authors.lastname: He
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Ross
authors.forename: William T
authors.initials: WT
authors.lastname: Beck
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D002477:Cells; D002822:Choriocarcinoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D008942:Mitoxantrone / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D011247:Pregnancy; D034622:RNA Interference; D012333:RNA, Messenger; D019772:Topotecan / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014594:Uterine Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D004958:Estradiol; D019772:Topotecan; D008942:Mitoxantrone