Therapeutic Ligands Antagonize Estrogen Receptor Function by Impairing Its Mobility

Area of Science:

• Oncology
• Molecular Biology
• Endocrinology

Background:

• Estrogen receptor-positive (ER+) breast cancers often remain ER-dependent despite endocrine therapy resistance.
• Fulvestrant, a full ER antagonist, is thought to work via ER degradation but has poor physicochemical properties.
• Developing ER degraders with improved properties is a key therapeutic goal.

Purpose of the Study:

• To investigate the relationship between ER degradation and ER antagonism.
• To explore the mechanisms by which ER antagonists suppress ER activity.
• To assess the therapeutic potential of targeting transcription factor mobility.

Main Methods:

• Evaluating ER degraders for transcriptional activity and anti-proliferative effects in breast cancer cells.
• Analyzing the impact of antagonists on ER nuclear mobility and turnover.
• Investigating the link between ER immobilization and transcriptional suppression.

Main Results:

• ER degraders display a spectrum of transcriptional activities and anti-proliferative potential, not solely dependent on degradation.
• Fulvestrant-like antagonists suppress ER activity by significantly reducing ER intra-nuclear mobility.
• ER immobilization leads to increased ER turnover, contributing to antagonism.

Conclusions:

• Optimized ER degradation does not equate to full ER antagonism.
• Perturbing transcription factor mobility, specifically ER nuclear mobility, is a viable mechanism for ER antagonism.
• Targeting transcription factor mobility offers a novel therapeutic strategy for ER-dependent cancers.