Liquiritigenin

MF101 promoted ERbeta, but not ERalpha, activation of an estrogen response element (ERE) upstream of the luciferase reporter gene. MF101 also selectively regulates transcription of endogenous genes through ERbeta. The ERbeta-selectivity was not due to differential binding, since MF101 binds equally to ERalpha and ERbeta. Fluorescence resonance energy transfer and protease digestion studies showed that MF101 produces a different conformation in ERalpha from ERbeta, when compared with the conformations produced by estradiol. The specific conformational change induced by MF101 allows ERbeta to bind to an ERE and recruit coregulatory proteins that are required for gene activation. MF101 did not activate the ERalpha-regulated proliferative genes, c-myc and cyclin D1, or stimulate MCF-7 breast cancer cell proliferation or tumor formation in a mouse xenograft model.