title: Direct gene transfer of adenoviral-mediated interferon α into human bladder cancer cells but not the bystander factors produced induces endoplasmic reticulum stress-related cytotoxicity.
abstract: We have previously shown that adenoviral-mediated interferon α (Ad-IFNα) is cytotoxic both to cells that are sensitive to recombinant interferon α (IFNα) and to cells which are resistant to IFNα. The cancer cell-specific cytotoxic effects of Ad-IFNα involve three different mechanisms: 1. The direct effect of IFNα production causing cancer cell death in IFNα sensitive cells (1); 2. The direct effect of Ad-IFNα infection and high levels of IFNα expression in IFNα resistant cancer cells (2); and 3. The indirect effect of the Ad-IFNα bystander factors produced (2-4). After Ad-IFNα infection, the cells produce a large amount of perinuclear localized IFN protein. This protein over-load could be a major factor in the direct cancer cell death of those cells infected with Ad-IFNα compared with the indirect cytotoxic effects of the bystander factors produced. Here, we investigated whether a component of Ad-IFN-induced cell death involves protein overload-induced endoplasmic reticulum (ER) stress, using an IFNα-resistant human bladder cancer cell line (KU7), and the normal human urothelial cell line, TERT-NHUC, as preclinical models. We found that the two ER stress response pathways examined were activated in KU7 cells. In contrast, following treatment of the normal TERT-NHUC cells with Ad-IFNα, no ER stress signals were observed. In addition, no ER stress related changes were seen, when KU7 cells were exposed to conditioned medium from Ad-IFNα-treated KU7 cells, indicating that bystander produced cytotoxicity did not involve ER stress. After 24 h of Ad-IFNα infection, the KU7 cancer cells produced spliced X-box binding protein 1 and activating transcription factor 6 protein (ATF6), evoking an ER stress response that could contribute to Ad-IFNα induced apoptosis in these cancer cells. In addition, GADD153/CHOP, GADD34 and BAX were also subsequently modified following activation of the ER stress pathways, thereby signaling downstream effectors in a pro-apoptotic manner.
authors.affiliation: Department of Genitourinary Medical Oncology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: X-Q
authors.initials: XQ
authors.lastname: Zhang
authors.forename: Z
authors.initials: Z
authors.lastname: Yang
authors.forename: W F
authors.initials: WF
authors.lastname: Benedict
mesh_terms: D051702:Activating Transcription Factor 6 / Q000235:genetics / Q000378:metabolism; D000256:Adenoviridae / Q000235:genetics*; D017209:Apoptosis; D024201:Bystander Effect; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000473:pathology; D018014:Gene Transfer Techniques; D006801:Humans; D016898:Interferon-alpha / Q000008:administration & dosage / Q000235:genetics*; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000473:pathology / Q000628:therapy*
chemical_list: C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; D004268:DNA-Binding Proteins; D016898:Interferon-alpha; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors