Progesterone receptor downregulates breast cancer resistance protein expression via binding to the progesterone response element in breast cancer

Abstract

Breast cancer resistance protein (BCRP) plays a major role in multidrug resistance (MDR). Sequence analysis reveals there is a novel progesterone response element (PRE) in the BCRP promoter, suggesting progesterone receptor (PR) may have a function in the regulation of BCRP expression. We examined the expressions of BCRP, PR, estrogen receptor a (ERa), androgen receptor (AR) and Her-2 in 95 breast cancer samples by immunohistochemistry. Then, to identify the role of PR in the regulation of BCRP expression, two constructs encoding full length BCRP cDNA driven by putative PRE promoter or constitutive CMV promoter were transfected into MCF-7 and MDA-MB-231, respectively. Reverse transcription-polymerase chain reaction (RT-PCR) and western blotting were used to detect the expression of BCRP. Further electrophoretic mobility shift assay (EMSA) was used to verify the nuclear protein-DNA specific binding. We innovatively found that the expression of BCRP negatively related with that of PR and ERa in breast cancer by immunohistochemistry. While at a cellular level, after being treated by progesterone and 17b-estradiol, BCRP mRNA and protein levels were significantly reduced in a concentration-dependent manner in MCF-7/ P-BCRP cells with PR bound to the identified PRE in BCRP promoter. Our results demonstrated that active PR inactived BCRP expression via progesterone-PR complexes binding to PRE in BCRP promoter in breast cancer cells. (Cancer Sci 2012; 103: 959-967) T o date, breast cancer is the most prevalent type of malignant tumor in women, and the multidrug resistance (MDR) is a major obstacle in successful chemotherapy. Breast cancer resistance protein (BCRP) is identified first from drug selected human breast cancer cells (MCF-7/AdrVp).(1) It overexpresses in many cancer cell lines and belongs to the subfamily of G of the ATP-binding cassette (ABC) transporter superfamily.(2-4) It can efflux a variety of chemotheraputic agents including mitoxantrone, topotecan and anthracyclines out of the cell.(5) Therefore, the investigation of mechanism of BCRP expression may bring out better treatment measures for cancer therapy.Recent reports suggest that the BCRP expression may be adjusted at the promoter level by steroid hormones, such as estrogen, progesterone and testosterone via classical pathways, but the data have some conflicts. (6)(7)(8) Hormone-receptor (HR) status has a major role in the prognosis and treatment of breast cancer patients. Estrogen plays an important role in the regulation of progesterone receptor (PR) in both mammary gland and breast cancer. However, there are still 2.00-8.12% of breast cancer patients immunohistochemically with ER-/PR+ and it often occurs in young or middle-aged women. The ER-/PR+ tumors are larger in size and appear more aggressive compared with the group of ER+/ PR+.(9) Therefore, in those ER negative breast cancer cells, the PR expression level should be greatly compromised, which implies that the role of PR remains an enigma.Our group has firstly revealed that toremifen can ...

TRPS1 Confers Multidrug Resistance of Breast Cancer Cells by Regulating BCRP Expression

“…It has been found that peroxisome proliferator-activated receptor γ (PPARγ) directly regulates the transcription of ABCG2 through binding to the PPAR response elements (PPARE) in the promoter ( 41 ). In BCa, BCRP expression was regulated by estrogen though directly binding of steroid receptors to ERE/PRE in the promoter region ( 22 , 42 – 44 ). Our findings add significantly to the understanding of how BCRP upregulated during cancer development.…”

“…BCRP expression was scored for intensity (0 = negative; 1 = weak; 2 = moderate; 3 = strong) and the percentage of positive cells (0 = 0-10%; 1 = 10-40%; 2 = 40-70%; 3 = 70-100%). The optimal cut-off value for high and low expression level was identified: 0 for negative, 1-3 for low BCRP expression, and 4-9 for high expression (22,23).…”

Harmful effect of ERβ on BCRP‐mediated drug resistance and cell proliferation in ERα/PR‐negative breast cancer

“…After the genomic structure and characterization of the BCRP promoter were demonstrated, a novel estrogen/progesterone response element (ERE/PRE) was also revealed in the promoter region of BCRP . It has also been reported that E2–ERα complex upregulated, while progesterone–PR complex downregulated, BCRP expression through binding to ERE/PRE in breast cancer cells . Nevertheless, the correlation of ERβ and BCRP has not previously been reported in breast cancer.…”

“…A dual semi‐quantitative scale combining staining intensity and percentage of positive cells was used to evaluate the protein staining. Briefly, staining of BCRP was scored semi‐quantitatively for intensity (0, no expression; 1, weak; 2, moderate; 3, strong) and for the percentage of positive cells (0, < 10%; 1, 10–40%; 2, 40–70%; 3, (70%) . The staining of ERβ was scored semi‐quantitatively for intensity (0, no expression; 1, weak; 2, moderate; 3, strong) and for the percentage of positive cells (1, 0–1/100; 2, 1/100–1/10; 3, 1/10–1/3; 4, 1/3–2/3; 5, 2/3–1), according to a previously published scoring standard of ERα .…”

Progesterone Negatively Regulates BCRP in Progesterone Receptor-Positive Human Breast Cancer Cells

“…We have reported that the PROG/PR complex binds to the PRE in the BCRP promoter and regulates BCRP expression in PR-positive breast cancer cells [40]. In the current study we sought to clarify the molecular mechanisms by which PR regulates BCRP expression.…”