Development and evaluation of a novel series of Nitroxoline-derived BET inhibitors with antitumor activity in renal cell carcinoma

Wei Chen,Shijie Chen,Zhifeng Chen,Yiqian Xie,Hong Ding,Liping Liao,Jing Xing,Yiran Huang,Mingyue Zheng,Zhiyi Yao,Shijie Fan,Kaixian Chen,Cheng Luo,Hao Zhang,Yuanyuan Zhang,Hao Jiang,Hualiang Jiang

doi:10.1038/s41389-018-0093-z

Abstract

Small molecular inhibitors targeting BRD4 family proteins are emerging as promising therapies in many types of human malignancies. However, whether BRD4, as well as other BET family members, may serve as therapeutic targets in renal cell carcinoma (RCC) remains unknown. In this study, we found that both BRD2 and BRD4 were over-expressed in RCC tissues, knock-down both of which achieved potent anti-proliferative effects in RCC cells. A novel category of BET inhibitors, originated from an approved drug Nitroxoline, were synthesized and evaluated with biochemical and cellular assays, as well as the method of crystallography. The complex crystal structures of several compounds in this category with the first bromodomain of BRD4 (BRD4-BD1) were solved, revealing the binding mechanism and facilitating further structural optimizations. Among them, compound BDF-1253 showed an approximately four-fold improvement in BRD4 inhibition compared with the prototype Nitroxoline and had good selectivity for BET proteins against other bromodomain proteins or epi-enzymes in biochemical assays. Compound BDF-1253 efficiently suppressed the expression of BET downstream genes, impaired RCC cells viability via inducing cell cycle arrest and apoptosis, and decreased tumor growth in RCC xenografts. In summary, these results suggest that inhibition of BET family members has great therapeutic potentials in the treatment of RCC, and the novel series of BET inhibitors reported here are promising to become RCC drug candidates.

Highlights

Acetylation is an important and widespread form of post-translational modification, which plays crucial roles in epigenetic regulation
The role of bromodomain and extra-terminal (BET) family members in renal cell carcinoma To examine whether BRD4, as well as other BET family members, may serve as potential therapeutic targets in RCC, we first investigated their roles in RCC
Knocking down of BRD2 or BRD4 moderately inhibited the proliferation of RCC 786-O and A498 cells, while knocking down both of them resulted in more significant antiproliferative effects (Fig. 1d)

Summary

Introduction

Acetylation is an important and widespread form of post-translational modification, which plays crucial roles in epigenetic regulation. Emerging evidence shows that BRD4 and other BET family members could become novel therapeutic targets of cancers[7,8,9,10]. The efficacy of BET inhibitors in renal cell carcinoma (RCC) was poorly evaluated, and it remained to be answered whether BRD4, as well as other BET family members, can serve as therapeutic targets for the treatment of RCC. The discovery and validation of novel targets are crucial for the development of new therapeutics and agents for RCC treatment. As it was revealed that BRD4 inhibition decreased the expression and protein abundance of c-Myc and related downstream genes[14,15,16,17], we suppose inhibitors targeting BRD4 or other members in BET family might have therapeutic potentials in the treatment of RCC18–21. Several series of BET inhibitors have been reported[22,23,24], it is worthwhile to develop novel inhibitors with different chemical skeletons, which might have improved drug-like properties and could be used in specific clinical applications

Methods

Results

Conclusion