title: Modulation of MDR1 gene expression in multidrug resistant MCF7 cells by low concentrations of small interfering RNAs.
abstract: MDR1 overexpression is one form of the multidrug resistance (MDR) phenotype, which can be acquired by patients initially responsive to chemotherapy. Because of the high toxicity of the inhibitors of P-glycoprotein (P-gp), the protein encoded by MDR1, attention has been focused on selective modulation of the MDR1 gene. Small interfering RNAs (siRNAs) were shown to be powerful tools for such a purpose, even when used at low concentrations (< or =20 nM) in order to avoid sequence nonspecific effects. Two siRNAs used at 20 nM were shown to lead to efficient down-regulation of MDR1 at the protein level (only ca. 20% total P-gp expression remaining) in the doxorubicin selected MCF7-R human cell line. Cell surface expression of P-gp was inhibited, leading to reversal of the drug efflux phenotype (about 40% reversal with the most efficient siRNA) and enhancement of chemosensitivity (about 35%). At the mRNA level, the down-regulation of MDR1 obtained with the most efficient siRNA increased from about 50% (5 nM siRNA) to 60% (10 or 20 nM). The advantage of using a combination of siRNAs instead of a single one has been suggested.
authors.affiliation: Laboratoire de Biophysique Moléculaire, Cellulaire et Tissulaire, CNRS (UMR 7033), Université P. et M. Curie, Paris, France.
authors.forename: Vérène
authors.initials: V
authors.lastname: Stierlé
authors.forename: Alain
authors.initials: A
authors.lastname: Laigle
authors.forename: Béatrice
authors.initials: B
authors.lastname: Jollès
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D002452:Cell Count / Q000379:methods; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003630:Daunorubicin / Q000032:analysis / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D005434:Flow Cytometry / Q000379:methods; D005453:Fluorescence; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D019450:Genes, MDR / Q000187:drug effects* / Q000235:genetics*; D006801:Humans; D012333:RNA, Messenger / Q000032:analysis / Q000187:drug effects / Q000235:genetics; D034741:RNA, Small Interfering / Q000138:chemical synthesis / Q000145:classification / Q000494:pharmacology*; D013997:Time Factors; D014343:Trypan Blue; D014700:Verapamil / Q000494:pharmacology
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014700:Verapamil; D014343:Trypan Blue; D003630:Daunorubicin