title: Bridge-1 is expressed in human breast carcinomas: silencing of Bridge-1 decreases Smad2, Smad3 and Smad4 expression in MCF-7 cells, a human breast cancer cell line.
abstract: OBJECTIVE
  The aim of the study was to investigate the expression of Bridge-1 in human breast carcinomas, and to determine the in vitro regulation of Bridge-1 by activin A and the influence of Bridge-1 on activin A signaling in the human breast cancer cell line MCF-7.
  
  
  METHODS
  Bridge-1 expression in human breast carcinomas was shown after staining paraffin slides with a specific antibody against Bridge-1. To gain insight into Bridge-1 function, immortalized, human breast cancer cells (MCF-7 cell line) were stimulated with activin A and the expression of Bridge-1 was analyzed by real-time PCR and Western blot. Next, Bridge-1 was downregulated via siRNA treatment in MCF-7 cells and the expression of Bridge-1, Smad2, 3 and 4 was investigated by real-time PCR and Western blot.
  
  
  RESULTS
  Human breast carcinoma cells showed nuclear and cytoplasmic localization of Bridge-1. Activin A stimulation of the immortalized human breast adenocarcinoma cell line MCF-7 showed an increase in Bridge-1 expression by real-time PCR and Western blot. Downregulation of Bridge-1 by Bridge-1-siRNA resulted in a decreased expression of Smad2, 3 and 4 of up to 50% compared to the treatment with non-targeting siRNA.
  
  
  CONCLUSIONS
  This study is the first to demonstrate the expression of Bridge-1 in human breast carcinomas. Bridge-1 expression is increased by activin A stimulation and itself seems to influence activin A signaling by affecting the expression of Smad2, 3 and 4.
authors: Department for Gynecology and Obstetrics, University of Schleswig-Holstein, Campus Luebeck, Ratzeburgerallee 160, 23538 Lübeck, Germany. banzcon@hotmail.com
authors: Constanze
authors: C
authors: Banz-Jansen
authors: Birte
authors: B
authors: Münchow
authors: Klaus
authors: K
authors: Diedrich
authors: Dominique
authors: D
authors: Finas
mesh_terms: D028341:Activins / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D020868:Gene Silencing / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D046988:Proteasome Endopeptidase Complex / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000502:physiology; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D051899:Smad2 Protein / Q000235:genetics* / Q000378:metabolism; D051900:Smad3 Protein / Q000235:genetics* / Q000378:metabolism; D051901:Smad4 Protein / Q000235:genetics* / Q000378:metabolism
chemical_list: C114476:PSMD9 protein, human; D034741:RNA, Small Interfering; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; C422405:activin A; D028341:Activins; D046988:Proteasome Endopeptidase Complex