title: MiR-106b~25 cluster regulates multidrug resistance in an ABC transporter-independent manner via downregulation of EP300.
abstract: MicroRNA (miR)-106b~25 cluster regulates bypass of doxorubicin and γ-radiation induced senescence by downregulation of the E-cadherin transcriptional activator EP300. We asked whether upregulation of miR-106~25 cluster generates cells with a truly multidrug resistant (MDR) phenotype and whether this is due to upregulation of the ATP-binding cassette (ABC) transporter P-glycoprotein. We used minimally transformed mammary epithelial breast cancer cells (MTMECs) in which the miR-106b~25 cluster was experimentally upregulated by lentiviral transfection or in which hairpins targeting either EP300 or E-cadherin mRNAs have been expressed with lentiviruses. We find that overexpression of miR-106b~25 cluster led to the generation of MDR MTMECs (resistant to etoposide, colchicine and paclitaxel). Paclitaxel resistance was also studied after experimental downregulation of EP300 or E-cadherin. However none of these cells overexpressed P-glycoprotein or where able to efflux a fluorescent derivative of paclitaxel, making this phenotype drug-transporter independent. Paclitaxel treatment in MTMECs led to an increase in early apoptotic cells (Annexin V-positive), activation of caspase-9 and increase in the proportion of cells at the G2/M phase of the cell cycle. However, MTMEC overexpressing miR-106b~25 cluster, or with EP300 or E-cadherin downregulated, showed less activation of apoptosis, caspase-9 and caspase-3/-7 activities. Thus, miR-106b~25 cluster controls transporter-independent MDR by apoptosis evasion via downregulation of EP300.
authors.affiliation: The Third Department of Breast Cancer, China Tianjin Breast Cancer Prevention, Treatment and Research Center, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Tianjin 300060, P.R. China.
authors.forename: Yunhui
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Kaiyong
authors.initials: K
authors.lastname: Li
authors.affiliation: Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Asaduzzaman
authors.affiliation: Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Raquel
authors.initials: R
authors.lastname: Cuella
authors.affiliation: State Key Laboratory of Experimental Hematology, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300020, P.R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Shi
authors.affiliation: Division of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Selina
authors.initials: S
authors.lastname: Raguz
authors.affiliation: Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Raoul Charles
authors.initials: RC
authors.lastname: Coombes
authors.affiliation: State Key Laboratory of Experimental Hematology, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300020, P.R. China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Yagüe
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001940:Breast / Q000166:cytology*; D015820:Cadherins / Q000096:biosynthesis / Q000235:genetics; D002461:Cell Line, Transformed; D003078:Colchicine / Q000494:pharmacology; D015536:Down-Regulation; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D050881:E1A-Associated p300 Protein / Q000096:biosynthesis* / Q000235:genetics; D004847:Epithelial Cells / Q000187:drug effects* / Q000528:radiation effects; D005047:Etoposide / Q000494:pharmacology; D005720:Gamma Rays; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D005810:Multigene Family; D009363:Neoplasm Proteins / Q000235:genetics* / Q000502:physiology; D017239:Paclitaxel / Q000494:pharmacology; D010641:Phenotype; D012334:RNA, Neoplasm / Q000235:genetics*; D014161:Transduction, Genetic; D014410:Tumor Stem Cell Assay
chemical_list: D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D015820:Cadherins; C542541:MIRN106 microRNA, human; D035683:MicroRNAs; D009363:Neoplasm Proteins; D012334:RNA, Neoplasm; D005047:Etoposide; D004317:Doxorubicin; D050881:E1A-Associated p300 Protein; C494360:EP300 protein, human; D017239:Paclitaxel; D003078:Colchicine