Estrone and 17β‐Estradiol Reverse Breast Cancer Resistance Protein‐mediated Multidrug Resistance

Abstract

Breast cancer resistance protein (BCRP), an adenosine triphosphate-binding cassette transporter, confers resistance to a series of anticancer reagents, including mitoxantrone, SN-38 and topotecan. In the present study, we found that estrone and 17β β β β-estradiol potentiated the cytotoxicity of mitoxantrone, SN-38 and topotecan in BCRP-transduced K562 cells (K562/BCRP). These estrogens showed only a marginal effect, or none, in parental K562 cells. Estrone and 17β β β β-estradiol increased the cellular accumulation of topotecan in K562/BCRP cells, but not in K562 cells, suggesting that these estrogens inhibit the BCRP-mediated drug efflux and overcome drug resistance.Key words: BCRP -Estrone -17β-Estradiol -MDR -Reversal of drug resistanceMultidrug drug resistance (MDR) is a common phenomenon in cancer cells. Cancer cells selected for resistance to a certain chemotherapeutic agent often reveal cross-resistance to structurally unrelated antitumor agents.1) Family members of adenosine triphosphate-binding cassette (ABC) transporters, such as MDR1 gene product P-glycoprotein and multidrug resistance-associated protein (MRP) 1, are involved in multidrug resistance by pumping out a variety of structurally and functionally diverse antitumor drugs from cells.2, 3) Breast cancer resistance protein (BCRP), also called ABCP or MXR, is a newly discovered ABC transporter. It mediates resistance to such chemotherapeutic agents as mitoxantrone, SN-38 (an active metabolite of CPT-11) and topotecan, presumably by pumping these reagents out of the cell to lower the cytotoxic effects.4-8) Overcoming MDR is a major problem in the clinical management of cancer. In order to identify agents which reverse BCRP-mediated drug resistance, we examined the effect of various organic compounds on the toxicity of mitoxantrone, SN-38 and topotecan in BCRPexpressing K562 cells. Among the compounds tested, estrone and 17β-estradiol were found to reverse BCRPmediated drug resistance.BCRP retrovirus-producing PA/MycBCRP cells were grown in high-glucose Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum at 37°C with 5% CO 2 . K562 human leukemic cells were grown in RPMI-1640 medium supplemented with 10% fetal bovine serum at 37°C with 5% CO 2 . K562 cells were transduced with the retrovirus supernatant for one day and cultured further for 2 days in the same medium without the retrovirus supernatant. Cells were then treated with SN-38 (20 ng/ml) for 5 days to enrich the transduced cells. The expression of BCRP in BCRP-transduced K562 (K562/BCRP) cells was detected with the anti-BCRP polyclonal antibody 3488. 9)The effects of chemical compounds on the sensitivity of cells to mitoxantrone, SN-38 and topotecan were evaluated by measuring cell growth inhibition after incubation at 37°C for 5 days in the absence or presence of various concentrations of anticancer drugs in combination with the chemicals examined. Cell numbers were determined with a Coulter counter. IC 50 values (drug dose causing 50% inhibition of cell growth) we...

Complex interaction of BCRP/ABCG2 and imatinib in BCR-ABL–expressing cells: BCRP-mediated resistance to imatinib is attenuated by imatinib-induced reduction of BCRP expression

“…8 In the original description, K562/BCRP cells did not have high P-gp expression. 16 During the course of selection we did not observe any induction of MDR1 mRNA or P-gp as shown in Figure 1B-C. Furthermore, we did not observe an increase in BCR-ABL mRNA or c-Kit protein as the result of mitoxantrone selection.…”

“…K562/BCRP cells were 5.5-fold resistant to mitoxantrone compared with wild-type K562 cells (Table 1), in agreement with the original report. 16 Selection with mitoxantrone (K562/BCRP-MX10) increased mitoxantrone resistance to 7.2-fold by the FDA/PI assay ( Figure 2A; Table 1), with comparable relative levels of resistance (11.8-fold) detected by the XTT assay ( Figure 2C; Table 2). Similarly, K562/BCRP-MX10 cells were more resistant to imatinib than K562 wild-type cells determined by both cytotoxicity assays ( To determine whether the resistance to imatinib is due to only BCRP overexpression, the effect of a specific inhibitor of BCRP, FTC, on resistance was studied in K562/BCRP-MX10 cells, with cellular viability assessed by the XTT assay (Figure 2C-D; Table 2).…”

“…K562 and K562/BCRP cells were kindly obtained from Dr Yoshikazu Sugimoto of the Japanese Foundation for Cancer Research 16 and were maintained in RPMI 1640 medium (Biofluids, Camarillo, CA) supplemented with 10% heat-inactivated fetal bovine serum (Gemini Bioproducts, Woodland, CA). In order to increase BCRP-mediated drug resistance, BCRP-transduced K562/BCRP cells were treated with 10 nM mitoxantrone for 1 hour prior to weekly passage (designated after mitoxantrone treatment as K562/BCRP-MX10).…”

Multidrug resistance mediated by the breast cancer resistance protein BCRP (ABCG2)

“…Estrone and 17b-estradiol have been found to potentiate the cytotoxicity of SN-38, mitoxantrone, and topotecan in BCRP-transfected cells but not in a parental K562 line (Imai et al, 2002b). Estrone and 17b-estradiol also increased the cellular accumulation of topotecan in K562/BCRP cells.…”

BCRP expression does not result in resistance to STX140 in vivo, despite the increased expression of BCRP in A2780 cells in vitro after long-term STX140 exposure

“…However, the sulphamates studied in this paper are derivatives of oestradiol, and many steroids, both unconjugated and conjugated to sulphate or glucuronide, including oestrogens, phytoestrogens and androgens, are substrates of BCRP Velamakanni et al, 2007). Studies have also shown that steroids and cholesterol, and steroid agonists and antagonists such as tamoxifen and diethylstilboestrol, can modulate the expression of BCRP without themselves being substrates (Imai et al, 2002;Janvilisri et al, 2003;Sugimoto et al, 2003;Morita et al, 2005;Pavek et al, 2005). A novel oestrogen response element (ERE) has been found in the human BCRP promoter (Ee et al, 2004a, b), although it has also been suggested that oestradiol post-transcriptionally downregulates BCRP (Imai et al, 2005).…”