title: Active matrix metalloproteinase 9 expression is associated with primary glioblastoma subtype.
abstract: OBJECTIVE
  Glioblastoma multiforme (GBM) is an aggressive cancer characterized by extensive brain invasion. Matrix metalloproteinase (MMP)-9 plays a major role in this process. GBMs can be divided into two subtypes based on distinct clinical and molecular features. Primary GBMs arise de novo and frequently overexpress the epidermal growth factor receptor (EGFR) and its ligand-independent variant, EGFR variant III (EGFRvIII); secondary GBMs progress from a lower grade glioma and commonly harbor p53 mutations. Because EGFR signaling promotes MMP-9 expression and activation in other cancer cell types, we analyzed whether MMP-9 was associated with primary GBM subtype.
  
  
  METHODS
  Autopsies were performed on 20 GBM patients, and MMP expression was assessed by gelatin zymography in the tumor and the adjacent normal brain. EGFR, EGFRvIII, p53, and activated mitogen-activated protein kinase/extracellular signal-regulated kinase were assessed by immunohistochemistry, and associations between molecular phenotype and MMP-9 expression were analyzed.
  
  
  RESULTS
  Latent MMP-9 was detected in 90% of tumors, and active MMP-9 was found in 50% of tumors. MMP-9 was not detected in any of the normal brain samples (P < 0.001). More importantly, primary GBMs were significantly more likely than secondary GBMs to contain active MMP-9 (69% of primary and 14% of secondary GBMs contained active MMP-9; P = 0.027). Active MMP-9 was observed in 73% of EGFR-overexpressing/wild-type p53-staining tumors but in only 20% of EGFR-negative/aberrant p53-staining tumors (P = 0.072). Active MMP-9 expression was even more strongly correlated with EGFRvIII expression, occurring in 83% of the EGFRvIII-immunopositive tumors but in none of the EGFRvIII-negative tumors (P = 0.0004). Extracellular signal-regulated kinase activation was also strongly correlated with EGFRvIII expression (P < 0.0001) and with MMP-9 activation (P = 0.003).
  
  
  CONCLUSIONS
  These results identify a novel association between MMP-9 activation and primary GBM subtype and suggest that primary GBM patients, especially those whose tumors express EGFRvIII, may benefit from anti-MMP therapy.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California 90095-1732, USA.
authors.forename: Gheeyoung
authors.initials: G
authors.lastname: Choe
authors.forename: Jun K
authors.initials: JK
authors.lastname: Park
authors.forename: Lisa
authors.initials: L
authors.lastname: Jouben-Steele
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Kremen
authors.forename: Linda M
authors.initials: LM
authors.lastname: Liau
authors.forename: Harry V
authors.initials: HV
authors.lastname: Vinters
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Cloughesy
authors.forename: Paul S
authors.initials: PS
authors.lastname: Mischel
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000145:classification / Q000201:enzymology* / Q000401:mortality / Q000556:secondary; D004790:Enzyme Induction; D066246:ErbB Receptors / Q000096:biosynthesis; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018773:Genes, erbB-1; D016158:Genes, p53; D005909:Glioblastoma / Q000145:classification / Q000201:enzymology* / Q000401:mortality / Q000556:secondary; D006801:Humans; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000032:analysis; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis* / Q000235:genetics; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D011379:Prognosis; D015398:Signal Transduction; D016019:Survival Analysis; D016159:Tumor Suppressor Protein p53 / Q000032:analysis
chemical_list: D009363:Neoplasm Proteins; D016159:Tumor Suppressor Protein p53; C410723:epidermal growth factor receptor VIII; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9