Neoadjuvant tamoxifen synchronizes ERα binding and gene expression profiles related to outcome and proliferation

Area of Science:

• Oncology
• Molecular Biology
• Genomics

Background:

• Estrogen receptor alpha (ERα)-positive breast cancers often develop resistance to tamoxifen therapy.
• Predictive biomarkers for tamoxifen treatment outcomes are needed.
• Previous studies often analyze pre-treatment samples, missing direct drug effects on tumors.

Purpose of the Study:

• To investigate the in vivo effects of neoadjuvant tamoxifen on ERα activity and gene expression in breast tumors.
• To identify potential biomarkers for tamoxifen response by analyzing molecular changes post-treatment.

Main Methods:

• Assessed DNA copy number, gene expression, and ERα/chromatin binding in tumor specimens before and after neoadjuvant tamoxifen treatment.
• Analyzed synchronized ERα/chromatin interactions and downstream gene expression patterns.
• Investigated the role of FOXA1 and growth factor signaling in ERα dynamics.

Main Results:

• Neoadjuvant tamoxifen synchronized ERα/chromatin interactions and gene expression, reducing inter-tumor variability.
• ERα-synchronized sites showed dynamic FOXA1 action, influenced by growth factor signaling.
• Genes linked to tamoxifen-synchronized sites could differentiate patient response to tamoxifen.

Conclusions:

• Tamoxifen therapy directly impacts ERα behavior and gene expression in vivo.
• Post-treatment biomarker discovery offers added value for predicting tamoxifen efficacy.
• Understanding drug-induced molecular changes is crucial for improving breast cancer treatment.