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The human multidrug resistance-associated protein MRP is a plasma membrane drug-efflux pump
G J Zaman1, M J Flens, M R van Leusden
1Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam.
Abstract:
The multidrug-resistance associated protein MRP is a 180- to 195-kDa membrane protein associated with resistance of human tumor cells to cytotoxic drugs. We have investigated how MRP confers drug resistance in SW-1573 human lung carcinoma cells by generating a subline stably transfected with an expression vector containing MRP cDNA. MRP-overexpressing SW-1573 cells are resistant to doxorubicin, daunorubicin, vincristine, VP-16, colchicine, and rhodamine 123, but not to 4'-(9-acridinylamino)methanesulfon-m-anisidide or taxol. The intracellular accumulation of drug (daunorubicin, vincristine, and VP-16) is decreased and the efflux of drug (daunorubicin) is increased in the transfectant. The decreased accumulation of daunorubicin is abolished by permeabilization of the plasma membrane with digitonin, showing that MRP can lower the intracellular daunorubicin level against a concentration gradient. Anti-MRP antisera predominantly stain the plasma membrane of MRP-overexpressing cells. We conclude that MRP is a plasma membrane drug-efflux pump.
Insights
The multidrug-resistance associated protein (MRP) acts as a drug-efflux pump in human lung cancer cells. Overexpressing MRP reduces intracellular drug accumulation, conferring resistance to several chemotherapy agents.
Area of Science:
- Molecular Biology
- Cell Biology
- Pharmacology
Background:
- Multidrug-resistance associated protein (MRP) is a membrane protein linked to drug resistance in human tumors.
- Understanding MRP's role is crucial for overcoming chemotherapy resistance in cancer.
Purpose of the Study:
- To investigate the mechanism by which MRP confers drug resistance in SW-1573 human lung carcinoma cells.
- To determine if MRP functions as a drug-efflux pump.
Main Methods:
- Generated a SW-1573 cell subline stably transfected with an MRP cDNA expression vector.
- Assessed drug resistance profiles, intracellular drug accumulation, and drug efflux in MRP-overexpressing cells.
- Utilized anti-MRP antisera and digitonin permeabilization to localize MRP and confirm its function.
Main Results:
- MRP-overexpressing cells exhibited resistance to doxorubicin, daunorubicin, vincristine, VP-16, colchicine, and rhodamine 123.
- Intracellular accumulation of daunorubicin, vincristine, and VP-16 decreased, while daunorubicin efflux increased in transfectants.
- Digitonin treatment abolished decreased daunorubicin accumulation, indicating MRP pumps drugs against a concentration gradient.
- Anti-MRP antisera localized MRP to the plasma membrane.
Conclusions:
- MRP functions as a plasma membrane drug-efflux pump.
- MRP overexpression contributes to multidrug resistance by actively removing cytotoxic drugs from cancer cells.