A Computational-Based Approach to Identify Estrogen Receptor / Heterodimer Selective Ligands.

The biologic effects of estrogens are transduced by two estrogen receptors (ERs), ER and ER, which function in dimer forms. The ER/ homodimer promotes and the ER/ inhibits estrogen-dependent growth of mammary epithelial cells; the functions of ER/ heterodimers remain elusive. Using compounds that promote ER/ heterodimerization, we have previously shown that ER/ heterodimers appeared to inhibit tumor cell growth and migration in vitro. Further dissection of ER/ heterodimer functions was hampered by the lack of ER/ heterodimer-specific ligands. Herein, we report a multistep workflow to identify the selective ER/ heterodimer-inducing compound. Phytoestrogenic compounds were first screened for ER transcriptional activity using reporter assays and ER dimerization preference using a bioluminescence resonance energy transfer assay. The top hits were subjected to in silico modeling to identify the pharmacophore that confers ER/ heterodimer specificity. The pharmacophore encompassing seven features that are potentially important for the formation of the ER/ heterodimer was retrieved and subsequently used for virtual screening of large chemical libraries. Four chemical compounds were identified that selectively induce ER/ heterodimers over their respective homodimers. Such ligands will become unique tools to reveal the functional insights of ER/ heterodimers.