NR4A1 Ligands as Potent Inhibitors of Breast Cancer Cell and Tumor Growth.

Keshav Karki,Abigail Schoeller,Kumaravel Mohankumar,Rupesh Shrestha,Stephen Safe,Gregory Martin

doi:10.3390/cancers13112682

Abstract

Simple SummaryBis-indole derived (CDIMs) bind the orphan nuclear receptor 4A1 (NR4A1) and inhibit NR4A1-regulated cancer cell and tumor growth. In this study a subset of 3,5-disubstituted phenyl CDIM compounds that bound NR4A1 were investigated in a breast cancer model. All of these analogs were potent inhibitors of breast tumor growth in a xenograft model using MDA-MB-231 cells at doses ≤ 1 mg/kg/d.Nuclear receptor 4A1 (NR4A1, Nur77, TR3) is more highly expressed in breast and solid tumors compared to non-tumor tissues and is a pro-oncogenic factor in solid tumor-derived cancers. NR4A1 regulates cancer cell growth, survival, migration, and invasion, and bis-indole-derived compounds (CDIMs) that bind NR4A1 act as antagonists and inhibit tumor growth. Preliminary structure-binding studies identified 1,1-bis(3′-indolyl)-1-(3,5-disubstitutedphenyl)methane analogs as NR4A1 ligands with low KD values; we further investigated the anticancer activity of the four most active analogs (KD’s ≤ 3.1 µM) in breast cancer cells and in athymic mouse xenograft models. The treatment of MDA-MB-231 and SKBR3 breast cancer cells with the 3-bromo-5-methoxy, 3-chloro-5-trifluoromethoxy, 3-chloro-5-trifluoromethyl, and 3-bromo-5-trifluoromethoxy phenyl-substituted analogs decreased cell growth and the expression of epidermal of growth factor receptor (EGFR), hepatocyte growth factor receptor (cMET), and PD-L1 as well as inhibited mTOR phosphorylation. In addition, all four compounds inhibited tumor growth in athymic nude mice bearing MDA-MB-231 cells (orthotopic) at a dose of 1 mg/kg/d, which was not accompanied by changes in body weight. These 3,5-disubstituted analogs were the most potent CDIM/NR4A1 ligands reported and are being further developed for clinical applications.

Highlights

It is estimated that in 2020, there will be 279,100 new cases of breast cancer in the United States and 42,690 deaths from this disease [1]
The interactions of bis-indole-derived CDIM compounds containing a 3,5-disubstituted phenyl group with the ligand-binding domain of NR4A1 were investigated by determining the fluorescence quenching of Trp in the ligand-binding pocket
The 3,5-disubstituted phenyl ring was oriented toward the solvent-exposed outer portion of the binding pocket

Summary

Introduction

It is estimated that in 2020, there will be 279,100 new cases of breast cancer in the United States and 42,690 deaths from this disease [1]. Most early-stage breast cancers are estrogen receptor α—positive and epidermal growth factor receptor 2 (EGFR2, HER2) negative [3], and are treated with antiestrogens such as tamoxifen and/or aromatase inhibitors (e.g., anastrozole), which block the ERα-mediated function and inhibit 17β-estradiol synthesis, respectively [4]. Breast cancer patients with tumors that overexpress the epidermal growth factor receptor 2 (EGFR2, HER2) are successfully treated with the antibody Herceptin that targets and inactivates HER2 [5]. Patients with triple negative breast tumors that do not express HER2, ERα, or the progesterone receptor are more aggressive and highly invasive, and are treated with drug cocktails that include cytotoxic drugs, which cause serious toxic side effects [6].

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