title: Endogenous and radiation-induced expression of gammaH2AX in biopsies from patients treated for carcinoma of the uterine cervix.
abstract: OBJECTIVE
  The possibility of using gammaH2AX foci as a marker of DNA damage and as a potential predictor of tumour response to treatment was examined using biopsies from 3 sets of patients with advanced carcinoma of the cervix. The relation between endogenous gammaH2AX expression and hypoxia was also examined.
  
  
  METHODS
  Set 1 consisted of 26 biopsies that included pre-treatment and 24h post-radiation treatment samples. Pre-treatment biopsies from 12 patients in Set 2 were used to develop image analysis software while pre-treatment biopsies from 33 patients in Set 3 were examined for the relation between staining for the hypoxia marker pimonidazole and endogenous gammaH2AX expression. Formalin-fixed paraffin-embedded sections were analyzed after antigen retrieval and fluorescence antibody labeling for the hypoxia markers CAIX or pimonidazole in combination with gammaH2AX staining.
  
  
  RESULTS
  Before treatment, 24+/-19% of cells contained gammaH2AX foci, with most positive cells containing fewer than 5 foci per nucleus. Twenty-four hours after exposure to the first fraction of 1.8-2.5Gy, 38+/-19% contained foci. CAIX positive cells were 1.4 times more likely to exhibit endogenous gammaH2AX foci, and pimonidazole-positive cells were 2.8 times more likely to contain gammaH2AX foci. For 18 patients for whom both pre-treatment and 24h post-irradiation biopsies were available, local control was unrelated to the fraction of cells that retained gammaH2AX foci. However, 24h after irradiation, tumours that had received 2.5Gy showed a significantly higher fraction of cells with residual gammaH2AX foci than tumours given 1.8Gy.
  
  
  CONCLUSIONS
  Endogenous gammaH2AX foci are enriched in hypoxic tumour regions. Small differences in delivered dose can produce quantifiable differences in residual DNA damage that can overshadow inter-tumour differences in response.
authors.affiliation: Medical Biophysics Department, British Columbia Cancer Agency Research Centre, 675 W. 10th Ave., Vancouver, BC V5Z 1L3, Canada. polive@bccrc.ca
authors.forename: Peggy L
authors.initials: PL
authors.lastname: Olive
authors.forename: C Adriana
authors.initials: CA
authors.lastname: Banuelos
authors.forename: Ralph E
authors.initials: RE
authors.lastname: Durand
authors.forename: Joo-Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Christina
authors.initials: C
authors.lastname: Aquino-Parsons
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor; D001707:Biopsy, Needle; D002584:Cervix Uteri / Q000473:pathology*; D005260:Female; D015870:Gene Expression / Q000528:radiation effects; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects*; D006657:Histones / Q000235:genetics*; D006801:Humans; D008875:Middle Aged; D002583:Uterine Cervical Neoplasms / Q000235:genetics* / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor; C468783:H2AX protein, human; D006657:Histones