title: Molecular mechanism of Mitomycin C-dependent caspase-8 regulation: implications for apoptosis and synergism with interferon-alpha signalling.
abstract: Caspase-8 is frequently mutated or silenced in several tumors including hepatocellular carcinomas (HCC) thereby potentially contributing to chemoresistance. The aim of our present study was to evaluate if chemotherapeutic drugs may mediate their effects through up-regulation of caspase-8 gene transcription. Huh7 hepatoma cells were transfected with a caspase-8 promoter construct fused to a luciferase reporter gene followed by stimulation with a subset of different chemotherapeutic drugs. Several drugs slightly induced caspase-8 promoter activity. However, strong caspase-8 promoter induction was found after Mitomycin C (MMC) treatment and this correlated with an increase in endogenous caspase-8 mRNA expression. Further molecular analysis demonstrated that MMC controls caspase-8 transcription via a c-jun/AP1 site located in the promoter in close proximity to the transcription start site. Inactivation of this c-jun/AP1 site using a dominant-negative c-jun adenovirus or site-directed mutagenesis inhibited MMC-dependent promoter induction. MMC treatment resulted in higher caspase-8 enzymatic activity and apoptosis and could be synergistically enhanced by co-stimulation with interferon-alpha (IFNalpha) via independent transcriptional mechanisms. In summary MMC controls caspase-8 expression via a c-jun/AP1 element in its promoter region. MMC-induced up-regulation of caspase-8 triggers apoptosis in target cells which can be further enhanced by IFNalpha. Therefore these findings also provide a potential new therapeutic approach to treat cancer cells.
authors.affiliation: Department of Medicine III, University Hospital Aachen, RWTH Aachen University, Pauwelsstrasse 30, 52074, Aachen, Germany. cliedtke@ukaachen.de
authors.forename: Christian
authors.initials: C
authors.lastname: Liedtke
authors.forename: Daniela
authors.initials: D
authors.lastname: Lambertz
authors.forename: Nadine
authors.initials: N
authors.lastname: Schnepel
authors.forename: Christian
authors.initials: C
authors.lastname: Trautwein
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000235:genetics; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000235:genetics*; D045744:Cell Line, Tumor; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D016685:Mitomycin / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020218:Response Elements; D015398:Signal Transduction / Q000187:drug effects*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D016898:Interferon-alpha; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D016685:Mitomycin; D053148:Caspase 3; D053181:Caspase 8