Ee Pui Lai Rachel, Kamalakaran Sitharthan, Tonetti Debra, He Xiaolong, Ross Douglas D, Beck William T
Department of Biopharmaceutical Sciences, University of Illinois at Chicago, 833 South Wood, Chicago, IL 60612, USA.
Cancer Res. 2004 Feb 15;64(4):1247-51. doi: 10.1158/0008-5472.can-03-3583.
The breast cancer resistance protein (BCRP) is an ATP-binding cassette half transporter that confers resistance to anticancer drugs such as mitoxantrone, anthracyclines, topotecan, and SN-38. Initial characterization of the BCRP promoter revealed that it is TATA-less with 5 putative Sp1 sites downstream from a putative CpG island and several AP1 sites (K. J. Bailey-Dell et al., Biochim. Biophys. Acta, 1520: 234-241, 2001). Here, we examined the sequence of the 5'-flanking region of the BCRP gene and found a putative estrogen response element (ERE). We showed that estrogen enhanced the expression of BCRP mRNA in the estrogen receptor (ER)-positive T47D:A18 cells and PA-1 cells stably expressing ERalpha. In BCRP promoter-luciferase assays, sequential deletions of the BCRP promoter showed that the region between -243 and -115 is essential for the ER effect. Mutation of the ERE found within this region attenuated the estrogen response, whereas deletion of the site completely abrogated the estrogen effect. Furthermore, electrophoretic mobility shift assays revealed specific binding of ERalpha to the BCRP promoter through the identified ERE. Taken together, we provide evidence herein for a novel ERE in the BCRP promoter.
乳腺癌耐药蛋白（BCRP）是一种ATP结合盒半转运蛋白，可赋予对诸如米托蒽醌、蒽环类药物、拓扑替康和SN - 38等抗癌药物的耐药性。BCRP启动子的初步特征表明，它没有TATA盒，在一个假定的CpG岛下游有5个假定的Sp1位点和几个AP1位点（K. J. Bailey - Dell等人，《生物化学与生物物理学学报》，1520: 234 - 241，2001）。在此，我们研究了BCRP基因5'侧翼区域的序列，发现了一个假定的雌激素反应元件（ERE）。我们表明，雌激素可增强雌激素受体（ER）阳性的T47D:A18细胞和稳定表达ERα的PA - 1细胞中BCRP mRNA的表达。在BCRP启动子 - 荧光素酶测定中，BCRP启动子的连续缺失表明，-243至-115之间的区域对于ER效应至关重要。在该区域内发现的ERE突变减弱了雌激素反应，而该位点的缺失则完全消除了雌激素效应。此外，电泳迁移率变动分析揭示了ERα通过鉴定出的ERE与BCRP启动子的特异性结合。综上所述，我们在此为BCRP启动子中的一个新型ERE提供了证据。
