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Small Molecule Liver X Receptor Modulator GAC0001E5 Targets Mechanisms of Endocrine Resistance in Estrogen

Shinjini Basu1, Asitha Premaratne1, Scott Widmann2,3

  • 1Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, TX 77004, USA.

Biomolecules
|June 26, 2026
PubMed

Insights

A novel Liver X receptor (LXR) ligand, GAC0001E5 (1E5), shows antiproliferative effects in estrogen receptor-positive breast cancer. It downregulates key proteins and pathways, offering potential for endocrine-resistant tumors.

Area of Science:

  • Oncology
  • Molecular Biology
  • Endocrinology

Background:

  • Endocrine therapy is standard for ER-positive breast cancer, but resistance develops in ~40% of patients.
  • Liver X receptors (LXRs) regulate lipid metabolism and are implicated in cancer metabolic reprogramming.
  • A novel LXR ligand, GAC0001E5 (1E5), demonstrated antiproliferative activity in breast cancer cells.

Purpose of the Study:

  • To investigate the mechanisms of action of LXR ligand 1E5 in ER-positive breast cancer cells.
  • To explore 1E5's effects on endocrine-responsive (MCF-7) and endocrine-resistant (MCF-7-TamR) cell lines.
  • To elucidate potential crosstalk between LXR and endocrine resistance pathways.

Main Methods:

  • Treatment of MCF-7 and MCF-7-TamR cells with LXR ligand 1E5.
  • Analysis of LXR, ERα, AR, and HER2 expression levels.
  • siRNA-mediated knockdown of LXR to assess LXR-dependent mechanisms.

Main Results:

  • 1E5 treatment downregulated LXR and its target genes.
  • Significant reduction in ERα and ER-responsive gene expression observed.
  • Aberrant AR and HER2 expression, linked to resistance, were downregulated by 1E5.
  • LXR knockdown partially mimicked 1E5 effects, indicating LXR-dependent and independent actions.

Conclusions:

  • 1E5 exhibits potent effects on ER-positive breast cancer cells, including endocrine-resistant types.
  • Findings suggest crosstalk between LXR and pathways regulating endocrine response and resistance.
  • 1E5 and LXR represent potential therapeutic targets for endocrine-resistant breast cancer.
Keywords:
breast cancerendocrine resistanceestrogen receptorliver X receptor

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