title: DNA end binding activity and Ku70/80 heterodimer expression in human colorectal tumor.
abstract: OBJECTIVE
  To determine the DNA binding activity and protein levels of the Ku70/80 heterodimer, the functional mediator of the NHEJ activity, in human colorectal carcinogenesis.
  
  
  METHODS
  The Ku70/80 DNA-binding activity was determined by electrophoretic mobility shift assays in 20 colon adenoma and 15 colorectal cancer samples as well as matched normal colonic tissues. Nuclear and cytoplasmic protein expression was determined by immunohistochemistry and Western blot analysis.
  
  
  RESULTS
  A statistically significant difference was found in both adenomas and carcinomas as compared to matched normal colonic mucosa (P<0.00). However, changes in binding activity were not homogenous with approximately 50% of the tumors showing a clear increase in the binding activity, 30% displaying a modest increase and 15% showing a decrease of the activity. Tumors, with increased DNA-binding activity, also showed a statistically significant increase in Ku70 and Ku86 nuclear expression, as determined by Western blot and immunohistochemical analyses (P<0.001). Cytoplasmic protein expression was found in pathological samples, but not in normal tissues either from tumor patients or from healthy subjects.
  
  
  CONCLUSIONS
  Overall, our DNA-binding activity and protein level are consistent with a substantial activation of the NHEJ pathway in colorectal tumors. Since the NHEJ is an error prone mechanism, its abnormal activation can result in chromosomal instability and ultimately lead to tumorigenesis.
authors.affiliation: Laboratory of Molecular Medicine and Biotechnology, Università Campus Bio-Medico, Via Longoni, 83, Rome 00155, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Mazzarelli
authors.forename: Paola
authors.initials: P
authors.lastname: Parrella
authors.forename: Davide
authors.initials: D
authors.lastname: Seripa
authors.forename: Emanuela
authors.initials: E
authors.lastname: Signori
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Perrone
authors.forename: Carla
authors.initials: C
authors.lastname: Rabitti
authors.forename: Domenico
authors.initials: D
authors.lastname: Borzomati
authors.forename: Armando
authors.initials: A
authors.lastname: Gabbrielli
authors.forename: Maria Giovanna
authors.initials: MG
authors.lastname: Matera
authors.forename: Carolina
authors.initials: C
authors.lastname: Gravina
authors.forename: Marco
authors.initials: M
authors.lastname: Caricato
authors.forename: Maria Luana
authors.initials: ML
authors.lastname: Poeta
authors.forename: Monica
authors.initials: M
authors.lastname: Rinaldi
authors.forename: Sergio
authors.initials: S
authors.lastname: Valeri
authors.forename: Roberto
authors.initials: R
authors.lastname: Coppola
authors.forename: Vito Michele
authors.initials: VM
authors.lastname: Fazio
mesh_terms: D000236:Adenoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D034961:Antigens, Nuclear / Q000737:chemistry / Q000378:metabolism*; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004247:DNA / Q000378:metabolism*; D051747:DNA-Activated Protein Kinase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D000072200:Ku Autoantigen; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000378:metabolism
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D004247:DNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen