title: The effect of Topotecan on oxidative stress in MCF-7 human breast cancer cell line.
abstract: OBJECTIVE
  Topotecan, a semisynthetic water-soluble derivative of camptothecin exerts its cytotoxic effect by inhibiting topoisomerase I and causes double-strand DNA breaks which inhibit DNA function and ultimately lead to cell death. In previous studies it was shown that camptothecin causes ROS formation. The aim of this study was to investigate if Topotecan like camptotecin causes oxidative stress in MCF-7 human breast cancer cell line. Determining the oxidant effect of Topotecan may elucidate a possible alternative mechanism for its cytotoxicity.
  
  
  METHODS
  MCF-7 cells were cultured and exposed to Topotecan for 24 h at 37 degrees C. The viability of the cells (% of control) was measured using the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Lipid peroxidation (TBARS), protein oxidation (carbonyl content), sulfhydryl, glutathione (GSH) levels, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities were determined in MCF-7 cells with and without Topotecan incubation.
  
  
  RESULTS
  We found the IC(50) concentration of Topotecan as 0.218 microM in MCF-7 cells. This concentration of Topotecan was used in the incubations of the cells. Our data indicated increased oxidative status, as revealed by increased lipid peroxidation and protein oxidation, and decreased GSH and sulfhydryl levels in MCF-7 cells exposed to Topotecan compared to control cells. In contrast, there was a slight increase in SOD and a significant increase in GPx and catalase activity in MCF-7 cells incubated with Topotecan compared to the control.
  
  
  CONCLUSIONS
  These results support our hypothesis that Topotecan increases oxidative stress in MCF-7 cells.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Akdeniz University, Antalya, Turkey.
authors.forename: Mujgan
authors.initials: M
authors.lastname: Timur
authors.forename: S Halide
authors.initials: SH
authors.lastname: Akbas
authors.forename: Tomris
authors.initials: T
authors.lastname: Ozben
mesh_terms: D001943:Breast Neoplasms; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects*; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D019772:Topotecan / Q000494:pharmacology*
chemical_list: D004273:DNA, Neoplasm; D017392:Thiobarbituric Acid Reactive Substances; D019772:Topotecan