The aryl hydrocarbon receptor is required for induction of p21cip1/waf1 expression and growth inhibition by SU5416 in hepatoma cells.

Edmond F O’Donnell,Nancy I Kerkvliet,Martin Pearce,Hyo Sang Jang,Siva Kumar Kolluri

doi:10.18632/oncotarget.16056

Edmond F O’Donnell, Nancy I Kerkvliet + Show 3 more

Open Access

https://doi.org/10.18632/oncotarget.16056

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Journal: Oncotarget	Publication Date: Mar 9, 2017
Citations: 15	License type: cc-by

Affiliation: Oregon State University

Abstract

The aryl hydrocarbon receptor (AhR) is a potential clinical target for cancer and autoimmune dysfunction. Identifying selective AhR modulators that produce desirable clinical outcomes represents an opportunity for developing new anti-cancer agents. Repurposing clinically-used drugs with established safety profiles that activate the AhR represents a good starting place to pursue this goal. In this study, we characterized the AhR-dependent effects of SU5416 (Semaxanib) following its identification in a small-molecule library screen. SU5416 potently activated AhR-dependent reporter genes, induced AhR nuclear localization, facilitated AhR-DNA binding, and increased, expression of its endogenous target genes. SU5416 significantly inhibited proliferation of Hepa1 hepatoma cells in an AhR-dependent manner, but did not induce apoptosis. SU5416 also inhibited the growth of human HepG2 liver cancer cells. The effects of SU5416 correlated with an increased G1 population and increased expression of cell cycle inhibitor p21cip1/waf1 at both the mRNA and protein level. Increased expression of p21cip1/waf1 by SU5416 required expression of both AhR and Arnt. In addition, evidence for long-term activation of the AhR in vivo by a single dose of SU5416 was identified by analyzing published microarray data. Our results provide support for continued investigation of the AhR as therapeutic for cancers such as hepatocellular carcinoma. In addition, our findings raise the possibility that some of the previously observed anti-proliferative effects of SU5416 may be due to activation of the AhR.

Highlights

The aryl hydrocarbon receptor (AhR) is a ligand activated transcription factor known primarily as the mediator of toxicity of dioxins and polyaromatic hydrocarbons, the most-well characterized of which is 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) [1, 2]
TCDD and other AhR ligands have been shown to upregulate expression of the cyclindependent kinase (CDK) inhibitor p27kip1 resulting in G1 arrest and growth inhibition of hepatoma cells [4]
We first wanted to characterize the ability of SU5416 to activate the AhR, and in addition determine the mechanism of this activation by asking whether SU5416 is an AhR ligand

Summary

Introduction

The aryl hydrocarbon receptor (AhR) is a ligand activated transcription factor known primarily as the mediator of toxicity of dioxins and polyaromatic hydrocarbons, the most-well characterized of which is 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) [1, 2]. TCDD and other AhR ligands have been shown to upregulate expression of the cyclindependent kinase (CDK) inhibitor p27kip resulting in G1 arrest and growth inhibition of hepatoma cells [4]. The CDK inhibitor p21cip1/waf has been shown to be a ligand-dependent AhR target gene in some cell types. Whereas TCDD does not increase expression of p21cip1/waf in human SK-N-SH neuronal cells [5], functional XREs/ AhREs in the p21waf1/cip promoter have been identified that are responsive to 3-methylcholanthrene (3-MC) [6]. The ability of the AhR to function as a tumor suppressor in the www.impactjournals.com/oncotarget absence of exogenous ligands has been demonstrated in a mouse model of prostate cancer [8], but this appears to be a context dependent effect, with some studies suggesting a proproliferative function of the AhR in cancer [9]

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