title: Role of FoxO1 activation in MDR1 expression in adriamycin-resistant breast cancer cells.
abstract: The development of multidrug resistance 1 (MDR1) can be mediated by a number of different mechanisms but elevated gene expression of MDR1 (P-glycoprotein) has often been a major cause of chemoresistance in many cancer cells. Therefore, the present study aimed to investigate the role of forkhead box-containing protein, O subfamily (FoxO), transcription factors in regulating the MDR1 gene expression. The proximal promoter region of the human MDR1 contained a putative FoxO-binding site, which partially overlapped with the enhancer/enhancer-binding protein beta-binding region. Gel shift and immunoblot analysis of subcellular fractions revealed that nuclear levels of FoxO1 and its DNA-binding activity were selectively enhanced in MCF-7/ADR cells, which was reversed by a FoxO1 antibody. Reporter gene assays showed that the transcription of MDR1 gene is stimulated by FoxO1 overexpression. Moreover, both MDR1 expression and doxorubicin resistance in MCF-7/ADR cells were reversed by FoxO1 small interfering RNA (siRNA). The MDR1 expression in MCF-7/ADR cells was also inhibited by insulin, a functional FoxO1 inactivator. In conclusion, FoxO1 is a novel transcriptional activator of MDR1 and is crucial for MDR1 induction in MCF-7/ADR cells.
authors.affiliation: BK21 Project Team, College of Pharmacy, Chosun University, Gwangju 501-759, South Korea.
authors.forename: Chang-Yeob
authors.initials: CY
authors.lastname: Han
authors.forename: Kyoung-Bin
authors.initials: KB
authors.lastname: Cho
authors.forename: Hong-Seok
authors.initials: HS
authors.lastname: Choi
authors.forename: Hyo-Kyung
authors.initials: HK
authors.lastname: Han
authors.forename: Keon-Wook
authors.initials: KW
authors.lastname: Kang
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology*; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D024202:Electrophoretic Mobility Shift Assay; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology; D010957:Plasmids; D000077297:Pregnane X Receptor; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D022782:CCAAT-Enhancer-Binding Protein-beta; C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D007328:Insulin; D000077297:Pregnane X Receptor; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011987:Receptors, Steroid; D004317:Doxorubicin