title: Sustained extracellular signal-regulated kinase1/2 mitogen-activated protein kinase signalling is related to increased p21 expression in cholesteatoma epithelium.
abstract: CONCLUSIONS
  These results show for the first time that the RAS/RAF/ERK1/2 MAPK signalling pathway is active and involved in p21-mediated cell cycle arrest in human cholesteatoma epithelium.
  
  
  OBJECTIVE
  In a previous report we have demonstrated that the epithelium in human cholesteatoma is characterized by high p53-dependent p21 expression. The RAS/RAF/extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein kinase (MAPK) signalling pathway can induce p21 expression and subsequent cell cycle arrest via p53-dependent or -independent mechanisms. We designed the present study to investigate whether the RAS/RAF/ERK1/2 MAPK signalling pathway is involved in p53-dependent and p21-mediated cell cycle arrest in human cholesteatoma.
  
  
  METHODS
  A total of 18 cholesteatoma samples and 18 paired control retro-auricular skin samples were immunohistochemically stained for p53, p21, phosphorylated ERK1/2 (pERK1/2) and total ERK1/2. Positive cells were counted by means of digital image analysis. Double-label fluorescence immunohistochemistry was performed to demonstrate co-expression of p21 and pERK1/2.
  
  
  RESULTS
  Protein expression of p53, p21 and pERK1/2 differed significantly between cholesteatoma epithelium and retro-auricular skin (p <0.01). In cholesteatoma, co-expression of p21 and pERK1/2 was prominent, whereas in retro-auricular skin there was hardly any co-expression. Positive correlations were found between p53 and p21 (p =0.003) and between p21 and pERK1/2 (p =0.013).
authors.affiliation: Departments of Ear, Nose & Throat, Leiden University Medical Centre, Leiden, The Netherlands. m.a.huisman@LUMC.nl
authors.forename: Margriet A
authors.initials: MA
authors.lastname: Huisman
authors.forename: Emile
authors.initials: E
authors.lastname: De Heer
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Grote
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018424:Cholesteatoma, Middle Ear / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D018816:Genes, cdc / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000276:immunology / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000276:immunology / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000276:immunology; D048490:raf Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D008562:Membrane Glycoproteins; D016159:Tumor Suppressor Protein p53; D048490:raf Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C089319:Ras-dependent mitogen-activated protein kinase kinase kinase