MCF-7aro/ERE, a Novel Cell Line for Rapid Screening of Aromatase Inhibitors, ERalpha Ligands and ERRalpha Ligands

We have previously generated a breast cancer cell line, MCF-7aro, which over-expresses aromatase and is also ER positive. Recently, this MCF-7aro cell line was stably transfected with a promoter reporter plasmid, pGL3-Luc, containing three repeats of estrogen responsive element (ERE). Experiments using MCF-7aro/ERE have demonstrated that it is a novel, non-radioactive screening system for aromatase inhibitors (AIs), ERalpha ligands and ERRalpha ligands. The screening is carried out in a 96-well plate format. To evaluate this system, the cells were cultured overnight in charcoal-dextran stripped FBS medium supplemented with 0.1 nM testosterone or 17beta-estradiol, and various concentrations of antiestrogens or AIs. We found that the luciferase activity was induced when the cells were cultured either in the presence of testosterone or 17beta-estradiol. Furthermore, a 50% decrease in luciferase activity could be achieved when the cells were cultured in the presence of testosterone together with letrozole, anastrozole, tamoxifen or fulvestrant (concentrations being 75 nM, 290 nM, 100 nM, and 5 nM, respectively), compared to the testosterone-only cultured cells. Using this assay system, we confirmed that 3(2'-chlorophenyl)-7-methoxy-4-phenylcoumarin is an agonist of ER. Furthermore, genestein has been shown to be a ligand of ERRalpha because its binding could be blocked by an ERRalpha inverse agonist, XCT790. These results indicate that MCF-7aro/ERE is a novel cell line for rapid screening of AIs, ERalpha ligands and ERRalpha ligands.