title: Regulation of MDR1 gene expression in multidrug-resistant cancer cells is independent from YB-1.
abstract: The MDR1 gene encoded transmembrane ABC-transporter MDR1/P-glycoprotein can mediate the phenotype of multidrug resistance (MDR), a major obstacle in the clinical management of cancer patients. It was hypothesized that YB-1 is a fundamental regulatory factor of the MDR1 gene in tumor cells and can therewith enhance drug resistance. To analyze the potential impact of YB-1 in MDR cancer cells, two specific anti-YB-1 small interfering RNAs (siRNAs) were designed for transient triggering the gene-silencing RNA interference (RNAi) pathway in the MDR cell lines EPG85-257RDB and EPP85-181RDB as well as in their drug-sensitive counterparts EPG85-257P and EPP85-181P. Since both siRNAs showed biological activity, for stable inhibition of YB-1 corresponding tetracycline-inducible short hairpin RNA (shRNA)-encoding expression vectors were designed. By treatment of the cancer cells with these constructs, the expression of the targeted YB-1 encoding mRNA and protein was completely inhibited following tetracycline exposure. These gene-silencing effects were not accompanied by modulation of the MDR1 expression or by reversal of the drug-resistant phenotype. In conclusion, the data demonstrate the utility of the analyzed RNAs as powerful laboratory tools and indicate that YB-1 is not involved in the regulation of the MDR1 gene or the development of the drug-resistant phenotype in MDR cancer cells.
authors.affiliation: Charité Campus Mitte, Institute of Pathology, Charitéplatz 1, D-10117 Berlin, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kaszubiak
authors.forename: Annette
authors.initials: A
authors.lastname: Kupstat
authors.forename: Ursula
authors.initials: U
authors.lastname: Müller
authors.forename: Romy
authors.initials: R
authors.lastname: Hausmann
authors.forename: Per Sonne
authors.initials: PS
authors.lastname: Holm
authors.forename: Hermann
authors.initials: H
authors.lastname: Lage
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism*; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D015398:Signal Transduction; D013274:Stomach Neoplasms / Q000378:metabolism*; D051840:Y-Box-Binding Protein 1
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human