MRP8, a new member of ABC transporter superfamily, identified by EST database mining and gene prediction program, is highly expressed in breast cancer.
Identification of breast cancer resistant protein/mitoxantrone resistance/placenta-specific, ATP-binding cassette transporter as a transporter of NB-506 and J-107088, topoisomerase I inhibitors with an indolocarbazole structure.
Promoter activity was characterized by a luciferase reporter assay using transient transfection of the human breast cancer cell line MCF7, and the human choriocarcinoma cell lines JAR, BeWo and JEG-3, which we find to have high endogenous expression of BCRP.
Recently, the breast cancer-resistant protein (BCRP), the equivalent of mitoxantrone-resistant protein (MXR) or placental ABC transporter (ABCP), was described in AML.
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.
A role of BCRP in the transverse distribution of lipids in the plasma membrane is supported by the increased outward transport of the lipid analogue C6- N -(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-PS in BCRP -overexpressing EPG85-257 cells and MCF-7 human breast cancer cells.
In the present study, we show that at physiologic levels, estrogens markedly decrease endogenous BCRP expression in the estrogen-responsive and estrogen receptor alpha (ERalpha)-positive human breast cancer MCF-7 cells, but not in estrogen-nonresponsive human cancer cells.
Previously, a MDR cell line MCF7/AdVp3000 was selected from breast cancer cell line MCF7 against Adriamycin, and overexpression of ABCG2 was thought to cause MDR in this derivative cell line.
Using oligonucleotide microarrays (HG-U133 Plus 2.0; Affymetrix), we analyzed the ABC transporter gene expression profiles in breast cancer patients who underwent sequential weekly paclitaxel/FEC (5-fluorouracil, epirubicin and cyclophosphamide) neoadjuvant chemotherapy.
Genetic polymorphisms of glutathione S-transferase (GST) genes including GSTT1 positive/null, GSTM1 positive/null, and GSTP1 A313G, and genes for reduced folate carrier 1 G80A (RFC1 G80A), methylenetetrahydrofolate reductase C677T (MTHFR C677T), and breast cancer resistant protein C421A (BCRPC421A) were determined for 26 patients by the polymerase chain reaction (PCR) method or by direct sequencing.
Western blot analysis with anti-ABCG2 monoclonal BXP-21 antibody detected a robust band at approximately 72 kDa in the ABCG2-overexpressing MCF-MX100 cell line, whereas low expression was found in human and rat brain cell systems.
Major role of some members of the ATP-binding cassette (ABC) family of membrane transporters including MDR1 (ABCB1, P-glycoprotein) and breast cancer resistant protein (BCRP, ABCG2) is protection against environmental toxins.
We report that dephosphorylation of extracellular signal-regulated kinase (ERK) by treatment with mitogen-activated protein kinase/ERK kinase (MEK) inhibitors causes two opposing effects, transcriptional upregulation and prompted protein degradation of endogenous BCRP in breast cancer MCF-7 cells.
Dexamethasone showed a dose-independent and a time-dependent effect on decreasing the mRNA level of BCRP gene in comparison with control in MCF-7 and MCF-7/MX breast cancer cell lines, whereas no changes were noted in the presence of indomethacin.
Besides overexpression of MDR1, the member of the ABC transporter family, glucosylceramide synthase (GCS) which allows cellular escape from ceramide-induced cellular apoptosis by mediating ceramide glycosylation was considered to be related with multidrug resistance (MDR) in breast cancer.