N-acetylcysteine enhances multidrug resistance-associated protein 1 mediated doxorubicin resistance.
BACKGROUND
Resistance of cancer cells against anticancer agents is caused partly by multidrug resistance-associated protein 1 (MRP1). The exact mechanism of MRP1-involved multidrug resistance has not yet been clarified, although 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) inhibits GSH synthesis. The aim of our study was to investigate the effect of NAC and BSO on MRP1-mediated doxorubicin resistance in human embryonic kidney (HEK293) and its MRP1-transfected 293MRP cells.


METHODS
Human embryonic kidney cells were transfected with a plasmid encoding the whole MRP1 gene. Both cells were incubated with doxorubicin in the presence or absence of NAC and/or BSO. The viability of both cells was determined under different incubation conditions. Glutathione, 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 doxorubicin. DL-buthionine (S,R)-sulfoximine decreased NAC-enhanced MRP1-mediated doxorubicin resistance, indicating that induction of MRP1-mediated doxorubicin resistance depends on GSH synthesis. Doxorubicin decreased the cellular GSH concentration and increased GPx activity. Glutathione S-transferase activity was decreased by NAC.


CONCLUSIONS
Our results demonstrate that NAC enhances MRP1-mediated doxorubicin resistance and this effect depends on GSH synthesis. DL-buthionine (S,R)-sulfoximine seems a promising chemotherapy improving agent in MRP1 overexpressing tumour cells.
Akdeniz University, Antalya, Turkey.
I
I
Akan
S
S
Akan
H
H
Akca
B
B
Savas
T
T
Ozben
D000111:Acetylcysteine / Q000494:pharmacology*; D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D002470:Cell Survival; D004317:Doxorubicin / Q000627:therapeutic use*; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000494:pharmacology*; D014162:Transfection
D000111:Acetylcysteine; D000903:Antibiotics, Antineoplastic; D004317:Doxorubicin; D005978:Glutathione; D005979:Glutathione Peroxidase; D005982:Glutathione Transferase; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C421109:multidrug resistance-associated protein 1