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A multidrug resistance transporter from human MCF-7 breast cancer cells
L A Doyle1, W Yang, L V Abruzzo
1Greenebaum Cancer Center of the University of Maryland, Baltimore MD 21201, USA.
Abstract:
MCF-7/AdrVp is a multidrug-resistant human breast cancer subline that displays an ATP-dependent reduction in the intracellular accumulation of anthracycline anticancer drugs in the absence of overexpression of known multidrug resistance transporters such as P glycoprotein or the multidrug resistance protein. RNA fingerprinting led to the identification of a 2.4-kb mRNA that is overexpressed in MCF-7/AdrVp cells relative to parental MCF-7 cells. The mRNA encodes a 655-aa [corrected] member of the ATP-binding cassette superfamily of transporters that we term breast cancer resistance protein (BCRP). Enforced expression of the full-length BCRP cDNA in MCF-7 breast cancer cells confers resistance to mitoxantrone, doxorubicin, and daunorubicin, reduces daunorubicin accumulation and retention, and causes an ATP-dependent enhancement of the efflux of rhodamine 123 in the cloned transfected cells. BCRP is a xenobiotic transporter that appears to play a major role in the multidrug resistance phenotype of MCF-7/AdrVp human breast cancer cells.
Insights
A novel transporter, breast cancer resistance protein (BCRP), was identified in multidrug-resistant breast cancer cells. BCRP confers resistance to common chemotherapy drugs by actively exporting them from cells.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- MCF-7/AdrVp cells exhibit multidrug resistance (MDR) to anthracyclines.
- This resistance occurs without P-glycoprotein or MRP overexpression.
- The underlying molecular mechanism of MDR in these cells was unknown.
Purpose of the Study:
- To identify the molecular basis for the observed MDR phenotype in MCF-7/AdrVp breast cancer cells.
- To characterize the function of the newly identified transporter involved in drug resistance.
Main Methods:
- RNA fingerprinting was employed to identify differentially expressed genes.
- Full-length cDNA of the identified gene was cloned and expressed in MCF-7 cells.
- Drug accumulation, retention, and efflux assays were performed using various anticancer agents and rhodamine 123.
Main Results:
- A 2.4-kb mRNA encoding a 655-amino acid protein, termed breast cancer resistance protein (BCRP), was overexpressed in MCF-7/AdrVp cells.
- Enforced BCRP expression in MCF-7 cells conferred resistance to mitoxantrone, doxorubicin, and daunorubicin.
- BCRP overexpression led to reduced daunorubicin accumulation and retention, and enhanced ATP-dependent efflux of rhodamine 123.
Conclusions:
- Breast cancer resistance protein (BCRP) is a novel ATP-binding cassette transporter.
- BCRP plays a significant role in the multidrug resistance phenotype of MCF-7/AdrVp human breast cancer cells.
- BCRP functions as a xenobiotic transporter responsible for drug efflux.