title: Activator protein 1 (AP-1) contributes to EpCAM-dependent breast cancer invasion.
abstract: BACKGROUND
  EpCAM is a cell-surface glycoprotein that is overexpressed in the majority of epithelial carcinomas. However, the functional role of EpCAM in regulating cancer invasion remains controversial, and the mechanism(s) underlying EpCAM-mediated regulation of breast cancer invasion remain to be defined.
  
  
  METHODS
  EpCAM expression was manipulated in breast cancer cell lines using RNA interference and cDNA expression constructs. Recombinant EpCAM was used to rescue EpCAM signaling following specific ablation of EpCAM. Protein and gene expression, invasion, transcription factor activity, and protein phosphorylation were measured using standard molecular biology techniques.
  
  
  RESULTS
  In loss-of-function, and gain-of-function experiments we demonstrate that EpCAM expression is associated with increased breast cancer invasion in vitro and in vivo. We demonstrate further that specific ablation of EpCAM expression is associated with decreased activator protein-1 (AP-1) transcription factor activity. Phosphoprotein analyses confirm that specific ablation of EpCAM is associated with decreased phosphorylation of the AP-1 subunit c-Jun. Recombinant soluble extracellular EpCAM (rEpCAM) is able to rescue invasion, AP-1 transcription factor activity, and c-Jun phosphorylation in a dose-dependent fashion. Pharmacologic inhibitors, and constitutively active constructs of the c-Jun N-terminal kinase (JNK) signal transduction pathway, suggest that the impact of EpCAM expression on AP-1 transcription factor activity is mediated through the JNK pathway. In functional rescue experiments, forced expression of c-Jun rescues invasion in breast cancer cells following specific ablation of EpCAM.
  
  
  CONCLUSIONS
  These data demonstrate for the first time that EpCAM expression can influence the JNK/AP-1 signal transduction pathway, and suggest that modulation of AP-1 transcription factor activity contributes to EpCAM-dependent breast cancer invasion. These data have important implications for the design and application of molecular therapies targeting EpCAM.
authors: Department of Surgery, Washington University School of Medicine, Campus Box 8109, 660 South Euclid Avenue, St, Louis, Missouri 63110, USA.
authors: Narendra V
authors: NV
authors: Sankpal
authors: John D
authors: JD
authors: Mayfield
authors: Mike W
authors: MW
authors: Willman
authors: Timothy P
authors: TP
authors: Fleming
authors: William E
authors: WE
authors: Gillanders
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism*; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D000071858:Epithelial Cell Adhesion Molecule; D005260:Female; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020935:MAP Kinase Signaling System; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness; D010766:Phosphorylation; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1