title: Multidrug resistance-associated protein 1 (MRP1) mediated vincristine resistance: effects of N-acetylcysteine and Buthionine sulfoximine.
abstract: BACKGROUND
  Multidrug resistance mediated by the multidrug resistance-associated protein 1 (MRP1) decreases cellular drug accumulation. The exact mechanism of MRP1 involved multidrug resistance has not been clarified yet, though glutathione (GSH) is likely to have a role for the resistance to occur. N-acetylcysteine (NAC) is a pro-glutathione drug. DL-Buthionine (S,R)-sulfoximine (BSO) is an inhibitor of GSH synthesis. The aim of our study was to investigate the effect of NAC and BSO on MRP1-mediated vincristine resistance in Human Embryonic Kidney (HEK293) and its MRP1 transfected 293MRP cells. Human Embryonic Kidney (HEK293) cells were transfected with a plasmid encoding whole MRP1 gene. Both cells were incubated with vincristine in the presence or absence of NAC and/or BSO. The viability of both cells was determined under different incubation conditions. GSH, Glutathione S-Transferase (GST) and glutathione peroxidase (GPx) levels were measured in the cell extracts obtained from both cells incubated with different drugs.
  
  
  RESULTS
  N-acetylcysteine increased the resistance of both cells against vincristine and BSO decreased NAC-enhanced MRP1-mediated vincristine resistance, indicating that induction of MRP1-mediated vincristine resistance depends on GSH. Vincristine decreased cellular GSH concentration and increased GPx activity. Glutathione S-Transferase activity was decreased by NAC.
  
  
  CONCLUSIONS
  Our results demonstrate that NAC and BSO have opposite effects in MRP1 mediated vincristine resistance and BSO seems a promising chemotherapy improving agent in MRP1 overexpressing tumor cells.
authors.affiliation: Department of Biochemistry, Akdeniz University, Faculty of Medicine, 07070 Antalya, Turkey. ilhan@temple.edu
authors.forename: Ilhan
authors.initials: I
authors.lastname: Akan
authors.forename: Selma
authors.initials: S
authors.lastname: Akan
authors.forename: Hakan
authors.initials: H
authors.lastname: Akca
authors.forename: Burhan
authors.initials: B
authors.lastname: Savas
authors.forename: Tomris
authors.initials: T
authors.lastname: Ozben