title: Telomerase activity in gastrointestinal stromal tumors.
abstract: BACKGROUND
  Telomerase activity has been observed in 80-90% of carcinomas derived from various organs. However, to the authors' knowledge this report is the first assessment of telomerase activity in gastrointestinal stromal tumors (GISTs).
  
  
  METHODS
  Telomerase activity was analyzed by the telomerase repeat amplification protocol assay in 29 tumors from 26 patients (23 primary tumors from 22 patients, 1 pair of primary and metastatic tumors from 1 patient, and 4 metastatic tumors from 3 patients). Phenotypes, tumor cell proliferation, and overexpression of p53 protein were evaluated immunohistochemically.
  
  
  RESULTS
  Seven of 24 primary tumors (29%) and 5 of 5 metastatic tumors (100%) showed telomerase activity. Telomerase activity positive (+) GISTs were significantly larger (P < 0.05) and showed a significantly higher rate of proliferation than telomerase activity negative (-) tumors (P < 0.0001). All telomerase activity (+) GISTs were classified histologically as high risk tumors. Conversely, 15 of the 17 telomerase (-) GISTs were classified histologically as low risk tumors (P < 0.0001). With regard to p53 immunoreactivity, two and seven telomerase activity (+) tumors showed diffuse and sporadic positivity, respectively, whereas only five telomerase activity (-) tumors showed only focal or sporadic positivity. Telomerase activity was correlated significantly with poor prognosis (P < 0.05) in the patients in whom the primary GISTs were evaluated (n = 23).
  
  
  CONCLUSIONS
  Telomerase activity may be a useful marker for evaluating the malignant potential of GIST. A distinct subgroup of GISTs is a target for therapy with a telomerase inhibitor.
authors.affiliation: Department of Pathology, Jichi Medical School, Minamikawachigunn, Tochigi, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Sakurai
authors.forename: M
authors.initials: M
authors.lastname: Fukayama
authors.forename: Y
authors.initials: Y
authors.lastname: Kaizaki
authors.forename: K
authors.initials: K
authors.lastname: Saito
authors.forename: K
authors.initials: K
authors.lastname: Kanazawa
authors.forename: M
authors.initials: M
authors.lastname: Kitamura
authors.forename: Y
authors.initials: Y
authors.lastname: Iwasaki
authors.forename: T
authors.initials: T
authors.lastname: Hishima
authors.forename: Y
authors.initials: Y
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Koike
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000032:analysis*; D011379:Prognosis; D011933:Reagent Kits, Diagnostic; D017154:Stromal Cells / Q000473:pathology; D019098:Telomerase / Q000032:analysis*
chemical_list: D009363:Neoplasm Proteins; D011933:Reagent Kits, Diagnostic; D019098:Telomerase