Purpose: The breast cancer resistance protein (BCRP) is involved in in vitro multidrug resistance and was first identified in the breast cancer cell line MCF7/AdrVp. The aim of this study was to investigate the role of BCRP in resistance of breast cancer to anthracycline treatment.
Experimental design: BCRP mRNA was determined with real-time reverse transcription-PCR and immunostaining in nine breast cancer cell lines and in samples of 25 primary breast carcinomas and 27 patients who received preoperative anthracycline-based therapy. Tumor response to treatment and patient survival were recorded.
Results: In cell lines, only MCF7 and BT20 had BCRP mRNA levels coinciding with membrane-bound immunostaining. In clinical samples, BCRP expression varied widely (range, 0.01-0.86). With immunohistochemistry, BCRP was detected in vessels and normal breast epithelium but not in tumor cells. There was no difference in BCRP expression between anthracycline-naïve and treated tumor samples. BCRP expression was not associated with decreased response or survival.
Conclusions: There is no indication that elevated BCRP expression in breast carcinomas confers resistance to anthracyclines. Expression was not detectable with immunohistochemistry.