title: Expression of the cyclin-dependent kinase inhibitor p27 in keratoacanthoma.
abstract: BACKGROUND
  Keratoacanthomas are characterized by initial rapid enlargement followed by clinical regression. A series of cyclin and cyclin-dependent kinase complexes regulate cell cycle progression. p27(kip) inhibits a variety of cyclin-cyclin-dependent kinase complexes in vitro and may act to hold eukaryotic cells in a quiescent state (G0).
  
  
  OBJECTIVE
  We examined expanding and regressing keratoacanthomas for expression of p27(kip).
  
  
  METHODS
  An immunohistochemical method was used to visualize and count p27(kip)-labeled cells in 5 expanding and 15 regressing keratoacanthomas.
  
  
  RESULTS
  In normal epidermis p27(kip) was found overlying the nuclei of suprabasilar keratinocytes. In expanding keratoacanthoma there was little expression of p27(kip) in nuclei of atypical keratinocytes composing the tumor (1.25 +/- 2.1 labeled cells per high-power field); in regressing keratoacanthoma the nuclei of most suprabasilar keratinocytes in atypical tumor aggregates contained p27(kip) (55.1 +/- 28.6 labeled cells per high-power field). The difference was significant at P values of less than.001.
  
  
  CONCLUSIONS
  The identification of p27(kip) in regressing keratoacanthoma but not in expanding keratoacanthoma suggests that p27(kip) may be playing a role in promoting regression of keratoacanthoma and is a potential target for pharmacologic intervention.
authors.affiliation: Department of Dermatology, St Louis University Health Science Center, Missouri, USA.
authors.forename: W
authors.initials: W
authors.lastname: Hu
authors.forename: T
authors.initials: T
authors.lastname: Cook
authors.forename: C W
authors.initials: CW
authors.lastname: Oh
authors.forename: N S
authors.initials: NS
authors.lastname: Penneys
mesh_terms: D018797:Cell Cycle Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D007636:Keratoacanthoma / Q000201:enzymology* / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D012871:Skin Diseases / Q000201:enzymology* / Q000235:genetics; D025521:Tumor Suppressor Proteins
chemical_list: D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases