A Bromodomain-Containing Protein 4 (BRD4) Inhibitor Suppresses Angiogenesis by Regulating AP-1 Expression.

Zijun Zhou,Zhiqing Liu,Lijing Wang,Xiaoming Li,Rongxin Zhang,Jia Zhou,Jian Chen,Liuyou Li,Lixun Huang,Yuying Yao,Qian-Qian Zhang

doi:10.3389/fphar.2020.01043

Abstract

Angiogenesis dysregulation contributes to inflammation, infections, immune disorders, and carcinogenesis. Bromodomain-containing protein 4 (BRD4) is an epigenetic reader that recognizes histone proteins and acts as a transcriptional regulator to trigger tumor growth and the inflammatory response. The pan-bromodomain and extra-terminal domain (BET) inhibitor, (+)-JQ1 (1), was reported to inhibit angiogenesis. However, owing to the non-selectivity action of (+)-JQ1 towards all BET family members, the role of BRD4 and that of its bromodomains (BD1 and BD2) in angiogenesis remains elusive. Herein, we identified a potent BRD4 inhibitor, ZL0513 (7), which exhibited significant anti-angiogenic effects in chick embryo chorioallantoic membrane (CAM) and yolk sac membrane (YSM) models. This inhibitor also directly suppressed the viability and tube formation of human umbilical vascular endothelial cells (HUVECs). Moreover, ZL0513 (7) was found to inhibit the phosphorylation of c-jun and c-fos, important members of activating protein-1 (AP-1) transcription factor complexes that enhance angiogenesis. The findings on this novel BRD4 inhibitor indicate that, in addition to being a powerful pharmacological tool for further elucidating the roles and functions of BRD4 and its BD domains in angiogenesis, it may serve as a potential therapeutic strategy for targeting the vasculature in various angiogenesis-dysregulated human diseases.

Highlights

The family of bromodomain and extra-terminal domain (BET) proteins is composed of bromodomain-containing protein 2 (BRD2), BRD3, Bromodomain-containing protein 4 (BRD4), and bromodomain testis-specific protein (BRDT)
The preliminary results of 16 selected compounds are presented in Table 1, including the commercially available BET family member selective inhibitors (+)-JQ1 (1), ZL0454 (2), and MS436 (3), as well as other representative compounds that are selected from a primary assay used to explore anti-angiogenesis through functional studies
It has been established that the abnormal formation of blood vessels is effective as a treatment for patients with cancer, chronic liver disease, cardiovascular disease or other diseases; using anti-angiogenic agents as inhibitors has become a major therapeutic strategy (Liao et al, 2014; Chen et al, 2018; Srivastava et al, 2018)

Summary

Introduction

The family of bromodomain and extra-terminal domain (BET) proteins is composed of bromodomain-containing protein 2 (BRD2), BRD3, BRD4, and bromodomain testis-specific protein (BRDT). Similar to other BET family members, BRD4 contains two highly conserved N-terminal bromodomains (BDs), BD1 and BD2, which can recognize acetylated lysine residues and non-histone proteins to transcriptionally regulate gene expression, cell cycle progression, cell proliferation, and apoptosis (Dey et al, 2000; Kanno et al, 2004; Dey et al, 2009). BRD4 BD2 recognizes and binds to diacetylated histone H3 and recruits non-histone proteins (Filippakopoulos et al, 2012; Shi et al, 2014; Liu et al, 2017). Discovery and development of BRD4 inhibitors is urgently needed and has attracted increasing attention

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Results

Conclusion