title: Chemosensitization by diverging modulation by short-term and long-term TNF-α action on ABCB1 expression and NF-κB signaling in colon cancer.
abstract: Multidrug resistance (MDR) is a major cause for cancer chemotherapy failure. Among the numerous strategies to overcome persistent action of proinflammatory cytokines, such as tumor necrosis factor α (TNF-α) permits downregulation of MDR-associated genes, including ATP-binding cassette, subfamily B 1 gene (ABCB1). A key regulator of ABCB1 expression is the transcription factor nuclear factor κ light chain enhancer (NF-κB)/p65. We analyzed diverging short- and long-term effects of TNF-α regarding modulation of NF-κB/p65 signaling and ABCB1 expression in colon cancer cells. Highly resistant ABCB1 overexpressing human HCT15 colorectal carcinoma cells were subjected to short- (30-120 min) or long-term (24-96 h) TNF-α treatment. TNF-α mediated modulation of ABCB1 expression was analyzed by real-time RT-PCR and western blot analysis. The TNF-mediated chemosensitization was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay. The involvement of TNF receptors and of NF-κB/p65 signaling was analyzed by western blot analysis, ABCB1 promoter analysis and electrophoretic mobility shift assay (EMSA). The study revealed, that long-term, but not short-term TNF-α treatment leads to TNF-receptor 1 (TNFR1) mediated downregulation of ABCB1 resulting in sensitization towards drug treatment. It dampens NF-κB/p65 activation and nuclear factor of κ light polypeptide gene enhancer in B-cells inhibitor α (IκBα) resynthesis, associated with reduced nuclear accumulation of NF-κB/p65 and reduced binding to its consensus sequence in the ABCB1 promoter. The study reveals the diverging effects of short- or long-term TNF-α action and provides novel insights on downregulation of ABCB1 expression by TNF-mediated repression of NF-κB signaling.
authors.affiliation: Experimental and Clinical Research Center, Charité, University Medicine Berlin and the Max-Delbrück-Center for Molecular Medicine, D-13125 Berlin, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Walther
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, D-13125 Berlin, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Kobelt
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, D-13125 Berlin, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Bauer
authors.affiliation: Experimental and Clinical Research Center, Charité, University Medicine Berlin and the Max-Delbrück-Center for Molecular Medicine, D-13125 Berlin, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Aumann
authors.affiliation: Experimental and Clinical Research Center, Charité, University Medicine Berlin and the Max-Delbrück-Center for Molecular Medicine, D-13125 Berlin, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Stein
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism; D015153:Blotting, Western; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism*; D015536:Down-Regulation; D018432:Drug Resistance, Multiple / Q000502:physiology; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D024202:Electrophoretic Mobility Shift Assay; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D051996:Transcription Factor RelA / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha