Activation of ERβ hijacks the splicing machinery to trigger R-loop formation in triple-negative breast cancer

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Triple-negative breast cancer (TNBC) presents aggressive behavior and limited therapeutic options, primarily chemotherapy.
• Estrogen receptor beta (ERβ) plays a crucial role in TNBC, but its downstream molecular mechanisms remain unclear.
• Novel targeted therapies are emerging for TNBC, highlighting the need for deeper mechanistic understanding.

Purpose of the Study:

• To elucidate the molecular mechanisms of ERβ activation in triple-negative breast cancer.
• To investigate the role of ERβ agonist LY500307 in inducing DNA damage and R-loop formation in TNBC cells.
• To identify key molecular players and pathways involved in ERβ-mediated therapeutic effects in TNBC.

Main Methods:

• Treatment of TNBC cells with ERβ agonist LY500307.
• Interactome studies to identify binding partners of ERβ.
• RNA sequencing and ribosome sequencing to analyze downstream gene expression and splicing.
• Analysis of clinical samples from The Cancer Genome Atlas (TCGA) and an in-house cohort.

Main Results:

• ERβ agonist LY500307 induces R-loop formation and DNA damage in TNBC cells.
• Specific residues in U2 small nuclear RNA auxiliary factor 1 (U2AF1) and ERβ are critical for their interaction.
• U2AF1 regulates the splicing of 5-oxoprolinase (OPLAH), impacting its enzymatic activity and ERβ-induced DNA damage.
• A significant correlation between ESR2 and U2AF1 expression was observed in TNBC patient samples.

Conclusions:

• ERβ activation induces R-loop formation and DNA damage in TNBC via the U2AF1-OPLAH axis.
• The study uncovers novel molecular mechanisms underlying ERβ's therapeutic potential in TNBC.
• These findings provide a strong rationale for developing ERβ activation-based therapies for TNBC patients.