way-169916 and Breast-Neoplasms

Cellular homeostasis in higher organisms is maintained by balancing cell growth, differentiation, and death. Two important systems that transmit extracellular signals into the machinery of the cell nucleus are the signaling pathways that activate nuclear factor kappaB (NF-kappaB) and estrogen receptor (ER). These two transcription factors induce expression of genes that control cell fates, including proliferation and cell death (apoptosis). However, ER has anti-inflammatory effects, whereas activated NF-kappaB initiates and maintains cellular inflammatory responses. Recent investigations elucidated a nonclassical and nongenomic effect of ER: inhibition of NF-kappaB activation and the inflammatory response. In breast cancer, antiestrogen therapy might cause reactivation of NF-kappaB, potentially rerouting a proliferative signal to breast cancer cells and contributing to hormone resistance. Thus, ER ligands that selectively block NF-kappaB activation could provide specific potential therapy for hormone-resistant ER-positive breast cancers.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Breast Neoplasms; Cell Division; Cells, Cultured; Cyclin D1; Estrogens; Female; Gene Expression Regulation; Humans; I-kappa B Proteins; Ligands; Mice; Mice, Knockout; Models, Biological; Neoplasms, Hormone-Dependent; NF-kappa B; Pyrazoles; Receptors, Estrogen; Selective Estrogen Receptor Modulators; Signal Transduction; Transcriptional Activation

Small molecules stabilize specific protein conformations from a larger ensemble, enabling molecular switches that control diverse cellular functions. We show here that the converse also holds true: the conformational state of the estrogen receptor can direct distinct orientations of the bound ligand. 'Gain-of-allostery' mutations that mimic the effects of ligand in driving protein conformation allowed crystallization of the partial agonist ligand WAY-169916 with both the canonical active and inactive conformations of the estrogen receptor. The intermediate transcriptional activity induced by WAY-169916 is associated with the ligand binding differently to the active and inactive conformations of the receptor. Analyses of a series of chemical derivatives demonstrated that altering the ensemble of ligand binding orientations changes signaling output. The coupling of different ligand binding orientations to distinct active and inactive protein conformations defines a new mechanism for titrating allosteric signaling activity.

Topics: Allosteric Regulation; Binding Sites; Breast Neoplasms; Cell Line, Tumor; Dose-Response Relationship, Drug; Humans; Ligands; Mutation; Protein Conformation; Pyrazoles; Receptors, Estrogen; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Time Factors