title: The apoptosis promoting Bcl-2 homologues Bak and Nbk/Bik overcome drug resistance in Mdr-1-negative and Mdr-1-overexpressing breast cancer cell lines.
abstract: We previously demonstrated that the forced expression of pro-caspase-3 can revert acquired chemoresistance in MT1-Adr breast cancer cells which show a defective activation of the mitochondrial pathway of apoptosis. We now asked whether the manipulation of mitochondrial apoptosis signaling can revert different types of drug resistance, i.e. the resistance due to impaired mitochondrial activation in the MT1-Adr cells and the resistance in MT3-Adr cells which is caused by increased expression of the Mdr-1/p-glycoprotein ABC transporter. Here we show that Bcl-2 overexpression is the underlying cause for the resistant phenotype in the MT1-Adr cells. Overexpression of the apoptosis-promoting Bax homologue Bak or the BH3 only protein Nbk/Bik reverts, as expected, acquired drug resistance in the MT1-Adr cells as recently demonstrated for pro-caspase-3. Moreover, we show that both apoptosis-promoters, Nbk/Bik and Bak, antagonize acquired chemoresistance for epirubicin-mediated apoptosis in MT3-Adr breast cancer cells. Neither drug uptake nor drug efflux were influenced by Bak or Nbk/Bik. Thus, our data show that manipulation of the downstream apoptosis signaling cascade by Bak and Nbk/Bik can overcome not only drug resistance due to mitochondrial apoptosis deficiency (in the MT1-Adr cells) but also classical, i.e. efflux-mediated, resistance for drug-induced cell death in the MT3-Adr cell line. Nbk/Bik and Bak could therefore be target genes to increase chemosensitivity and overcome different types of drug resistance.
authors.affiliation: Department of Hematology, Oncology, and Tumor Immunology, Charité - Campus Berlin-Buch, Humboldt University, 13125 Berlin-Buch, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Radetzki
authors.forename: Claus-Henning
authors.initials: CH
authors.lastname: Köhne
authors.forename: Clarissa
authors.initials: C
authors.lastname: von Haefen
authors.forename: Bernhard
authors.initials: B
authors.lastname: Gillissen
authors.forename: Isrid
authors.initials: I
authors.lastname: Sturm
authors.forename: Bernd
authors.initials: B
authors.lastname: Dörken
authors.forename: Peter T
authors.initials: PT
authors.lastname: Daniel
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics; D051017:Apoptosis Regulatory Proteins; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D018432:Drug Resistance, Multiple; D015251:Epirubicin / Q000633:toxicity; D005260:Female; D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014407:Tumor Cells, Cultured; D050998:bcl-2 Homologous Antagonist-Killer Protein
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D051017:Apoptosis Regulatory Proteins; C494772:BAK1 protein, human; C096820:BIK protein, human; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D050998:bcl-2 Homologous Antagonist-Killer Protein; D015251:Epirubicin