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BRCA1-mimetic compound NSC35446.HCl inhibits IKKB expression by reducing estrogen receptor-? occupancy in the IKKB promoter and inhibits NF-?B activity in antiestrogen-resistant human breast cancer cells.

ABSTRACT: PURPOSE:We previously identified small molecules that fit into a BRCA1-binding pocket within estrogen receptor-alpha (ER?), mimic the ability of BRCA1 to inhibit ER? activity ("BRCA1-mimetics"), and overcome antiestrogen resistance. One such compound, the hydrochloride salt of NSC35446 ("NSC35446.HCl"), also inhibited the growth of antiestrogen-resistant LCC9 tumor xenografts. The purpose of this study was to investigate the down-stream effects of NSC35446.HCl and its mechanism of action. METHODS:Here, we studied antiestrogen-resistant (LCC9, T47DCO, MCF-7/RR, LY2), ER?-negative (MDA-MB-231, HCC1806, MDA-MB-468), and antiestrogen-sensitive (MCF-7) cell lines. Techniques utilized include RNA-seq, qRT-PCR, cell growth analysis, cell-cycle analysis, Western blotting, luciferase reporter assays, TUNEL assays, in silico analysis of the IKKB gene, and ChIP assays. RESULTS:SC35446.HCl inhibited proliferation and induced apoptosis in antiestrogen-resistant LCC9, T47DCO, MCF-7/RR, and LY2 cells but not in ER?-negative breast cancer cell lines. IKKB (IKK?, IKBKB), an upstream activator of NF-?B, was identified as a BRCA1-mimetic-regulated gene based on an RNA-seq analysis. NSC35446.HCl inhibited IKKB, IKKA, and IKKG/NEMO mRNA and protein expression in LCC9 cells. NSC35446.HCl also inhibited NF-?B activity and expression of NF-?B target genes. In silico analysis of the IKKB promoter identified nine estrogen response element (ERE) half-sites and one ERE-like full-site. ChIP assays revealed that ER? was recruited to the ERE-like full-site and five of the nine half-sites and that ER? recruitment was inhibited by NSC35446.HCl in LCC9 and T47DCO cells. CONCLUSIONS:These studies identify functional EREs in the IKKB promoter and identify IKKB as an ER? and NSC35446.HCl-regulated gene, and they suggest that NF-?B and IKKB, which were previously linked to antiestrogen resistance, are targets for NSC35446.HCl in reversing antiestrogen resistance.

SUBMITTER: Nathan S

PROVIDER: S-EPMC5681404 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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BRCA1-mimetic compound NSC35446.HCl inhibits IKKB expression by reducing estrogen receptor-α occupancy in the IKKB promoter and inhibits NF-κB activity in antiestrogen-resistant human breast cancer cells.

Nathan Shyam S Ma Yongxian Y Tomita York A YA De Oliveira Eliseu E Brown Milton L ML Rosen Eliot M EM

Breast cancer research and treatment 20170814 3

<h4>Purpose</h4>We previously identified small molecules that fit into a BRCA1-binding pocket within estrogen receptor-alpha (ERα), mimic the ability of BRCA1 to inhibit ERα activity ("BRCA1-mimetics"), and overcome antiestrogen resistance. One such compound, the hydrochloride salt of NSC35446 ("NSC35446.HCl"), also inhibited the growth of antiestrogen-resistant LCC9 tumor xenografts. The purpose of this study was to investigate the down-stream effects of NSC35446.HCl and its mechanism of action ...[more]

PMID: 28808806

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Project description:Breast cancer resistance to the antiestrogens tamoxifen (OHT) and fulvestrant is accompanied by alterations in both estrogen-dependent and estrogen-independent signaling pathways. Consequently, effective inhibition of both pathways may be necessary to block proliferation of antiestrogen-resistant breast cancer cells. In this study, we examined the effects of apigenin, a dietary plant flavonoid with potential anticancer properties, on estrogen-responsive, antiestrogen-sensitive MCF7 breast cancer cells and two MCF7 sublines with acquired resistance to either OHT or fulvestrant. We found that apigenin can function as both an estrogen and an antiestrogen in a dose-dependent manner. At low concentrations (1 mumol/L), apigenin stimulated MCF7 cell growth but had no effect on the antiestrogen-resistant MCF7 sublines. In contrast, at high concentrations (>10 mumol/L), the drug inhibited growth of MCF7 cells and the antiestrogen-resistant sublines, and the combination of apigenin with either OHT or fulvestrant showed synergistic, growth-inhibitory effects on both antiestrogen-sensitive and antiestrogen-resistant breast cancer cells. To further elucidate the molecular mechanism of apigenin as either an estrogen or an antiestrogen, effects of the drug on estrogen receptor-alpha (ERalpha); transactivation activity, mobility, stability, and ERalpha-coactivator interactions were investigated. Low-dose apigenin enhanced receptor transcriptional activity by promoting interaction between ERalpha and its coactivator amplified in breast cancer-1. However, higher doses (>10 mumol/L) of apigenin inhibited ERalpha mobility (as determined by fluorescence recovery after photobleaching assays), down-regulated ERalpha and amplified in breast cancer-1 expression levels, and inhibited multiple protein kinases, including p38, protein kinase A, mitogen-activated protein kinase, and AKT. Collectively, these results show that apigenin can function as both an antiestrogen and a protein kinase inhibitor with activity against breast cancer cells with acquired resistance to OHT or fulvestrant. We conclude that apigenin, through its ability to target both ERalpha-dependent and ERalpha-independent pathways, holds promise as a new therapeutic agent against antiestrogen-resistant breast cancer.

Dataset Information

BRCA1-mimetic compound NSC35446.HCl inhibits IKKB expression by reducing estrogen receptor-? occupancy in the IKKB promoter and inhibits NF-?B activity in antiestrogen-resistant human breast cancer cells.

Publications

BRCA1-mimetic compound NSC35446.HCl inhibits IKKB expression by reducing estrogen receptor-α occupancy in the IKKB promoter and inhibits NF-κB activity in antiestrogen-resistant human breast cancer cells.

Similar Datasets

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