title: Terminal differentiation and mitogen-activated protein kinase signaling in human cholesteatoma epithelium.
abstract: OBJECTIVE
  To investigate whether--in cholesteatoma epithelium--terminal differentiation, resulting in high involucrin expression, is associated with mitogen-activated protein kinase (MAPK) signaling.
  
  
  BACKGROUND
  Alterations in specific signal transduction pathways may explain abnormal differentiation of the keratinocytes in cholesteatoma. Signaling pathways used by eukaryotic cells to transduce extracellular signals into cellular responses converge on activated mitogen-activated protein kinases, mainly extracellular signal-regulated kinase, c-Jun NH2-terminal kinase, and p38.
  
  
  METHODS
  Tissue samples were taken from 16 patients with acquired cholesteatoma. Histologic examination showed that 12 of the 16 cholesteatomas were inflamed. Immunohistochemical methods were used to determine expressions of involucrin and the activated form of p38, extracellular signal-regulated kinase, and c-Jun NH2-terminal kinase proteins. The results obtained from cholesteatoma tissue were compared with paired control samples from retroauricular skin.
  
  
  RESULTS
  We demonstrated increased levels of involucrin and increased levels of the activated forms of p38 and ERK1/2 in cholesteatoma epithelium when compared with control samples. No abnormality was found in the activation and expression of JNK1/2. A positive correlation was found between p38, pERK1/2, and involucrin expression (p<0.05).
  
  
  CONCLUSIONS
  Our results demonstrate that signaling via the mitogen-activated protein kinases ERK1/2 and p38 is increased in cholesteatoma epithelium when compared with control skin. The correlations between involucrin-and phosphorylated pERK1/2 expression and between involucrin-and phosphorylated p38 expression indicates that terminal differentiation in cholesteatoma epithelium proceeds via activation of these mitogen-activated protein kinase signaling pathways. We discussed whether this increased mitogen-activated protein kinase-driven terminal differentiation is probably part of a keratinocyte survival program or caused by an inflammation-induced cellular stress response.
authors.affiliation: Department of Otorhinolaryngology, Leiden University Medical Center, 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: D016022:Case-Control Studies; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D018424:Cholesteatoma, Middle Ear / Q000378:metabolism* / Q000473:pathology; D004848:Epithelium / Q000201:enzymology; D006801:Humans; D007150:Immunohistochemistry; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011498:Protein Precursors / Q000096:biosynthesis*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D011498:Protein Precursors; C032253:involucrin; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4