Selective ligands of estrogen receptor β discovered using pharmacophore mapping and structure-based virtual screening

To discover novel ligands of estrogen receptor (ER) β using pharmacophore mapping and structure-based screening.

A computer-aided strategy combining pharmacophore mapping and structure-based screening was used to screen the Maybridge and Enamine databases. Yeast two-hybrid (Y2H) assay was used to detect the activity and selectivity of the chosen compounds. The transcriptional activities of the chosen compounds were demonstrated with luciferase reporter assays. The anti-proliferative effects of ER antagonists against MCF-7 and MDA-MB-231 breast cancer cells were examined using MTT assay, and the mechanisms of action were analyzed with flow cytometry analysis and Western blotting.

Through in silico screen, 95 compounds were chosen for testing in Y2H assay, which led to 20 potent ligands, including 10 agonists, 8 antagonists and 2 partial agonists with EC50 or IC50 values at μmol/L. Furthermore, 6 agonists exhibited absolute selectivity for ERβ, and 3 agonists showed higher selectivity for ERβ. The agonists 1g and 1h (10, 25, and 50 μmol/L) dose-dependently increased ER transcriptional activities, whereas the antagonists 2a and 2d (10, 25, and 50 μmol/L) caused dose-dependent inhibition on the activities. The antagonists and partial agonists at 100 μmol/L suppressed the proliferation of ERα positive MCF-7 cells and ERβ positive MDA-MB-231 cells, but were more effective against MDA-MB-231 cells. Treatment of MDA-MB-231 cells with antagonists 2a and 2d (25 and 50 μmol/L) dose-dependently increased the population of cells in the S phase. Both 2a and 2d treatment dose-dependently decreased the expression levels of cyclin A and CDK2. Meanwhile, the downregulation of cyclin E was only caused by 2d, while 2a treatment did not cause significant changes in the protein levels of cyclin E.

The selective ligands discovered in this study are promising drug candidates to be used as molecular probes to explore the differences between ERα and ERβ.