Pharmacologic Induction of ERα SUMOylation Disrupts Its Chromatin Binding

Area of Science:

• Endocrinology
• Molecular Biology
• Oncology

Background:

• Estrogen receptor α (ERα)-positive breast cancer is treated with ERα inhibitors, such as selective estrogen receptor modulators (SERMs) and selective estrogen receptor degraders (SERDs).
• The precise pharmacological mechanisms of different ERα inhibitors are not fully understood.

Purpose of the Study:

• To investigate the molecular mechanisms underlying the action of ERα inhibitors.
• To identify how specific ERα inhibitors like fulvestrant, raloxifene, and elacestrant affect ERα function.

Main Methods:

• Utilized formaldehyde cross-linking, ERα immunoprecipitation, and mass spectrometry to identify protein interactions.
• Performed biochemical and genomic assays to confirm ERα SUMOylation and chromatin binding inhibition.

Main Results:

• Fulvestrant, a SERD, was found to induce interactions between ERα and SUMO E3 ligases PIAS1 and PIAS2.
• Confirmed that fulvestrant triggers ERα SUMOylation, subsequently inhibiting ERα's DNA-binding capacity.
• Identified raloxifene (SERM) and elacestrant (oral SERD) as additional compounds that induce ERα SUMOylation and impair chromatin interaction.

Conclusions:

• Discovered a novel mechanism where specific ERα inhibitors disrupt ERα activity via SUMOylation.
• Findings provide crucial insights for designing advanced ERα-targeted breast cancer therapies.