title: Variations in systemic biomarkers of oxidative/nitrosative stress and DNA damage before and during the consequent two cycles of chemotherapy in breast cancer patients.
abstract: BACKGROUND
  Previous studies have suggested the importance of redox regulation in carcinogenesis. The aim of this study was to evaluate the prognostic role of altered redox homeostasis and oxidative DNA damage in patients with breast carcinoma before and during two cycles of chemotherapy.
  
  
  METHODS
  This study included 30 patients whose serum samples were obtained on admission before treatment, and after the first and second cycles of chemotherapy, and 20 controls. We investigated serum total antioxidant status (TAS), thiobarbituric acid reacting substances (TBARS), total nitrite/nitrate (NOx), nitrotyrosine (NT), and 8-hydroxydeoxy-guanosine (8-OHdG), as well as antioxidant enzyme activities, such as glutathione peroxidase (GPx), glutathione reductase (GRx).
  
  
  RESULTS
  TBARS, NOx, NT and 8-OHdG concentrations were significantly increased, while antioxidant enzyme activities and TAS were significantly decreased in patients when compared to controls. A concurrent increase in TBARS, NOx, NT, and 8-OHdG and a decrease in antioxidant enzyme activities and TAS were also seen after chemotherapy. No difference was observed in the second cycle of chemotherapy when compared with the first course.
  
  
  CONCLUSIONS
  In conclusion, decreased activities of these antioxidant enzymes and low TAS concentrations observed in our study might be due to the depletion of the antioxidant defense system to combat the free radical storm produced by chemotherapy. We suggest that the increased 8-OHdG and other oxidative/nitrosative stress products that we have measured in breast cancer patients may be prognostic risk factors for the magnitude of oxidation in serum.
authors.affiliation: Cerrahpasa Medical Faculty, Department of Biochemistry, Istanbul University, Istanbul, Turkey. p_atukeren@yahoo.com
authors.forename: Pinar
authors.initials: P
authors.lastname: Atukeren
authors.forename: Berna
authors.initials: B
authors.lastname: Yavuz
authors.forename: Hilal Oguz
authors.initials: HO
authors.lastname: Soydinc
authors.forename: Sevim
authors.initials: S
authors.lastname: Purisa
authors.forename: Hakan
authors.initials: H
authors.lastname: Camlica
authors.forename: M Koray
authors.initials: MK
authors.lastname: Gumustas
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Balcioglu
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000328:Adult; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D000975:Antioxidants / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000097:blood*; D001943:Breast Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy*; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000097:blood; D005260:Female; D006801:Humans; D008875:Middle Aged; D009566:Nitrates / Q000097:blood; D009573:Nitrites / Q000097:blood; D015538:Nitrosation; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011379:Prognosis; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D014443:Tyrosine / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D000975:Antioxidants; D014408:Biomarkers, Tumor; D009566:Nitrates; D009573:Nitrites; D017392:Thiobarbituric Acid Reactive Substances; C002744:3-nitrotyrosine; D014443:Tyrosine; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine