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Discovery of a potent BRD4 PROTAC and evaluation of its bioactivity in breast cancer cell lines
Junjie Hu1, Jincui Yang2, Runxuan Zhou3
1Department of Clinical Research, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat- Sen University Cancer Center, Guangzhou, China.
Abstract:
Proteolysis targeting chimeras (PROTACs) targeting bromodomain-containing protein 4 (BRD4) proved to be powerful BRD4 degraders, which showed superiority in vitro and in vivo anti-tumor activity in many cancer models. Referring to the design of ARV-825, ARV-771 and MZ1, two novel BRD4 PROTACs were rationally designed and prepared via connecting the pan-BET selective bromodomain inhibitor JQ1 and two universal E3 ligase ligands targeting Von Hippel-Lindau (VHL) and cereblon (CRBN), namely VHL-JQ1 and CRBN-JQ1. Comparable to the degradation potency of ARV-825, ARV-771, and MZ1, both BRD4 PROTACs demonstrated potent BRD4 degradation efficacy. VHL-JQ1 showed superior antitumor activity against triple-negative breast cancer (TNBC) cell lines across multiple cellular processes, including cell proliferation suppression, migration and invasion inhibition, cell cycle arrest, and apoptosis induction. In addition, RNA-seq analysis revealed both shared and distinct gene expression profiles between BRD4 PROTAC-treated and JQ1-treated cells. Notably, VHL-JQ1 induced more pronounced mRNA expression changes compared to CRBN-JQ1 and JQ1. KRAS and NOTCH signaling pathways might be involved in the transcriptomic differences induced by BRD4 PROTACs and JQ1 treatment. Furthermore, combination therapy studies revealed that VHL-Q1 exhibited antagonistic effects when combined with paclitaxel, while demonstrating synergistic effects with cisplatin in TNBC treatment. Overall, our findings highlight VHL-JQ1 as a promising chemical probe for investigating BRD4 biological functions and a potential therapeutic candidate for TNBC treatment.
Insights
Two novel proteolysis targeting chimeras (PROTACs) targeting bromodomain-containing protein 4 (BRD4) were developed. VHL-JQ1 demonstrated potent BRD4 degradation and superior anti-triple-negative breast cancer activity, showing promise for therapeutic development.
Area of Science:
- Oncology
- Molecular Biology
- Drug Discovery
Background:
- Proteolysis targeting chimeras (PROTACs) offer a novel therapeutic strategy by inducing targeted protein degradation.
- Bromodomain-containing protein 4 (BRD4) is a key epigenetic regulator implicated in various cancers.
- Existing BRD4 inhibitors and PROTACs show anti-tumor potential, necessitating further exploration of novel agents.
Purpose of the Study:
- To design and synthesize novel BRD4-targeting PROTACs utilizing established E3 ligase ligands.
- To evaluate the BRD4 degradation efficacy and anti-cancer activity of these novel PROTACs, particularly VHL-JQ1.
- To investigate the molecular mechanisms and therapeutic potential of VHL-JQ1 in triple-negative breast cancer (TNBC).
Main Methods:
- Rational design and synthesis of VHL-JQ1 and CRBN-JQ1 PROTACs based on the JQ1 bromodomain inhibitor.
- Assessment of BRD4 degradation efficacy in cancer cell lines.
- In vitro evaluation of anti-tumor effects, including proliferation, migration, invasion, cell cycle, and apoptosis assays.
- RNA-sequencing (RNA-seq) analysis to profile gene expression changes.
- Combination therapy studies with standard chemotherapeutic agents.
Main Results:
- Both VHL-JQ1 and CRBN-JQ1 effectively degraded BRD4, comparable to existing PROTACs.
- VHL-JQ1 exhibited superior anti-TNBC activity, suppressing proliferation, migration, invasion, arresting cell cycle, and inducing apoptosis.
- RNA-seq revealed distinct gene expression profiles, with VHL-JQ1 inducing more significant changes than CRBN-JQ1 and JQ1, potentially involving KRAS and NOTCH pathways.
- VHL-JQ1 showed synergistic effects with cisplatin and antagonistic effects with paclitaxel in TNBC treatment.
Conclusions:
- VHL-JQ1 is a potent BRD4 degrader with significant anti-TNBC activity.
- VHL-JQ1 serves as a valuable chemical probe for studying BRD4 functions.
- VHL-JQ1 represents a promising therapeutic candidate for TNBC, with potential for combination therapies.
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