Ligand-dependent genomic function of glucocorticoid receptor in triple-negative breast cancer

Area of Science:

• Oncology
• Pharmacology
• Genomics

Background:

• Glucocorticoids (GCs) are used as coadjuvants in solid tumor treatment.
• GC treatment can be linked to poor treatment response and prognosis.
• The genomic mechanisms of GCs in solid tumors remain largely unelucidated.

Purpose of the Study:

• To investigate the genomic actions of glucocorticoids in triple-negative breast cancer (TNBC).
• To identify GC-regulated genes associated with drug resistance and clinical outcomes in TNBC.
• To compare the genomic effects of dexamethasone (Dex) and a selective glucocorticoid receptor (GR) modulator, Compound A (CpdA).

Main Methods:

• Gene expression analysis in TNBC cells treated with dexamethasone (Dex).
• Analysis of GC-regulated gene expression in TNBC patient data.
• Chromatin immunoprecipitation followed by exonuclease digestion (ChIP-exo) to map GR binding sites.
• Comparison of genomic targets of Dex-liganded GR and CpdA-liganded GR.

Main Results:

• Dexamethasone (Dex) treatment upregulates genes in TNBC cells associated with drug resistance.
• These Dex-regulated genes are aberrantly expressed in TNBC patients, correlating with poor clinical outcomes.
• CpdA, a selective GR modulator, regulates fewer genes, none linked to carcinogenesis or therapy resistance.
• Dex-liganded GR binds to a specific glucocorticoid response element (GRE) driving pro-tumorigenic gene expression, unlike CpdA-liganded GR.

Conclusions:

• GCs, specifically Dex, can promote drug resistance and adverse outcomes in TNBC through specific genomic actions.
• Selective GR modulators like CpdA exhibit different genomic profiles, suggesting potential for safer coadjuvant therapies.
• Therapeutic strategies involving GCs in TNBC should consider the distinct genomic functions mediated by different GR ligands.