title: Inhibition of cathepsin B activity attenuates extracellular matrix degradation and inflammatory breast cancer invasion.
abstract: BACKGROUND
  Inflammatory breast cancer (IBC) is an aggressive, metastatic and highly angiogenic form of locally advanced breast cancer with a relatively poor three-year survival rate. Breast cancer invasion has been linked to proteolytic activity at the tumor cell surface. Here we explored a role for active cathepsin B on the cell surface in the invasiveness of IBC.
  
  
  METHODS
  We examined expression of the cysteine protease cathepsin B and the serine protease urokinase plasminogen activator (uPA), its receptor uPAR and caveolin-1 in two IBC cell lines: SUM149 and SUM190. We utilized a live cell proteolysis assay to localize in real time the degradation of type IV collagen by IBC cells. IBC patient biopsies were examined for expression of cathepsin B and caveolin-1.
  
  
  RESULTS
  Both cell lines expressed comparable levels of cathepsin B and uPA. In contrast, levels of caveolin-1 and uPAR were greater in SUM149 cells. We observed that uPA, uPAR and enzymatically active cathepsin B were colocalized in caveolae fractions isolated from SUM149 cells. Using a live-cell proteolysis assay, we demonstrated that both IBC cell lines degrade type IV collagen. The SUM149 cells exhibit predominantly pericellular proteolysis, consistent with localization of proteolytic pathway constitutents to caveolar membrane microdomains. A functional role for cathepsin B was confirmed by the ability of CA074, a cell impermeable and highly selective cathepsin B inhibitor, to significantly reduce pericellular proteolysis and invasion by SUM149 cells. A statistically significant co-expression of cathepsin B and caveolin-1 was found in IBC patient biopsies, thus validating our in vitro data.
  
  
  CONCLUSIONS
  Our study is the first to show that the proteolytic activity of cathepsin B and its co-expression with caveolin-1 contributes to the aggressiveness of IBC.
authors.affiliation: Department of Pharmacology, Wayne State University, Detroit, Michigan 48201, USA.
authors.forename: Bernadette C
authors.initials: BC
authors.lastname: Victor
authors.forename: Arulselvi
authors.initials: A
authors.lastname: Anbalagan
authors.forename: Mona M
authors.initials: MM
authors.lastname: Mohamed
authors.forename: Bonnie F
authors.initials: BF
authors.lastname: Sloane
authors.forename: Dora
authors.initials: D
authors.lastname: Cavallo-Medved
mesh_terms: D002401:Cathepsin B / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D021941:Caveolae / Q000378:metabolism; D051242:Caveolin 1 / Q000378:metabolism; D045744:Cell Line, Tumor; D024141:Collagen Type IV / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D005109:Extracellular Matrix / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D058922:Inflammatory Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D039641:Integrin beta Chains / Q000378:metabolism; D009361:Neoplasm Invasiveness; D011485:Protein Binding; D021381:Protein Transport; D059748:Proteolysis; D055293:Receptors, Urokinase Plasminogen Activator / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
chemical_list: C400541:CA 074 methyl ester; D051242:Caveolin 1; D024141:Collagen Type IV; D004151:Dipeptides; D039641:Integrin beta Chains; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator; D002401:Cathepsin B
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