title: ABCG2 expression, function, and promoter methylation in human multiple myeloma.
abstract: We investigated the role of the breast cancer resistance protein (BCRP/ABCG2) in drug resistance in multiple myeloma (MM). Human MM cell lines, and MM patient plasma cells isolated from bone marrow, were evaluated for ABCG2 mRNA expression by quantitative polymerase chain reaction (PCR) and ABCG2 protein, by Western blot analysis, immunofluorescence microscopy, and flow cytometry. ABCG2 function was determined by measuring topotecan and doxorubicin efflux using flow cytometry, in the presence and absence of the specific ABCG2 inhibitor, tryprostatin A. The methylation of the ABCG2 promoter was determined using bisulfite sequencing. We found that ABCG2 expression in myeloma cell lines increased after exposure to topotecan and doxorubicin, and was greater in logphase cells when compared with quiescent cells. Myeloma patients treated with topotecan had an increase in ABCG2 mRNA and protein expression after treatment with topotecan, and at relapse. Expression of ABCG2 is regulated, at least in part, by promoter methylation both in cell lines and in patient plasma cells. Demethylation of the promoter increased ABCG2 mRNA and protein expression. These findings suggest that ABCG2 is expressed and functional in human myeloma cells, regulated by promoter methylation, affected by cell density, up-regulated in response to chemotherapy, and may contribute to intrinsic drug resistance.
authors.affiliation: H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Dr, Tampa, FL 33612, USA.
authors.forename: Joel G
authors.initials: JG
authors.lastname: Turner
authors.forename: Jana L
authors.initials: JL
authors.lastname: Gump
authors.forename: Chunchun
authors.initials: C
authors.lastname: Zhang
authors.forename: James M
authors.initials: JM
authors.lastname: Cook
authors.forename: Douglas
authors.initials: D
authors.lastname: Marchion
authors.forename: Lori
authors.initials: L
authors.lastname: Hazlehurst
authors.forename: Pamela
authors.initials: P
authors.lastname: Munster
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Schell
authors.forename: William S
authors.initials: WS
authors.lastname: Dalton
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Sullivan
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D015153:Blotting, Western / Q000379:methods; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D008297:Male; D008856:Microscopy, Fluorescence / Q000379:methods; D009101:Multiple Myeloma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D019772:Topotecan / Q000494:pharmacology / Q000627:therapeutic use; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000903:Antibiotics, Antineoplastic; D004791:Enzyme Inhibitors; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D019772:Topotecan; D004317:Doxorubicin