Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Department of Nuclear Medicine, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin 300070, PR China.
Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Immunology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, PR China.
Bioorg Chem. 2023 Nov;140:106793. doi: 10.1016/j.bioorg.2023.106793. Epub 2023 Sep 3.
BRD4,as a transcriptional and epigenetic regulator to mediate cellular functions, plays an important role in cancer development.Targeting BRD4 with conventional inhibitors in cancer therapy requires high doses, which often leads to off-target and adverse effects. BRD4-targeted proteolysis-targeting chimeras (PROTACs) can catalytically degrade BRD4 utilizing the endogenous proteasome system, and exhibit promising anti-tumor activity. However, most of the developed PROTACs are non-cancer specific and relatively toxic towards normal cells, limiting their practical applications in cancer treatment. By taking advantage of higher glutathione (GSH) levels in cancer cells than that in normal cells, we developed several GSH-responsive PROTAC precursors 1a-c via the attachment of a GSH-trigger unit on the hydroxyl group of the VHL (von Hippel-Lindau) ligand for the recruitment of E3 ligase. Among the precursors, 1a can be efficiently activated by the innately higher concentrations of GSH in lung cancer cells (A549 and H1299) to release active PROTAC 1, degrading intracellular BRD4 and resulting in cytotoxicity, which is confirmed by mechanistic investigation. On the other hand, 1a cannot be efficiently triggered in normal lung cells (WI38 and HULEC-5a) containing lower levels of GSH, therefore reducing the adverse effects on normal cells. This work provides an alternative proof of concept approach for developing stimuli-responsive PROTAC precursors, and affords a novel insight to improve the selectivity and minimize the adverse effects of current PROTACs, hence enhancing their clinical potential.
BRD4 作为一种转录和表观遗传调节剂，介导细胞功能，在癌症发展中发挥重要作用。在癌症治疗中用传统抑制剂靶向 BRD4 需要高剂量，这往往会导致脱靶和不良反应。BRD4 靶向蛋白水解靶向嵌合体（PROTAC）可以利用内源性蛋白酶体系统催化降解 BRD4，并表现出有希望的抗肿瘤活性。然而，大多数开发的 PROTAC 是非癌症特异性的，对正常细胞相对有毒，限制了它们在癌症治疗中的实际应用。利用癌细胞中比正常细胞更高的谷胱甘肽（GSH）水平，我们通过将 GSH 触发单元连接到 VHL（von Hippel-Lindau）配体的羟基上来开发了几种 GSH 响应性 PROTAC 前体 1a-c，用于招募 E3 连接酶。在这些前体中，1a 可以被肺癌细胞（A549 和 H1299）中固有较高浓度的 GSH 有效地激活，释放活性 PROTAC 1，降解细胞内 BRD4 并导致细胞毒性，这通过机制研究得到证实。另一方面，1a 不能被含有较低 GSH 水平的正常肺细胞（WI38 和 HULEC-5a）有效地触发，从而减少对正常细胞的不良反应。这项工作为开发刺激响应性 PROTAC 前体提供了另一种概念验证方法，并为提高现有 PROTAC 的选择性和最小化其不良反应提供了新的见解，从而增强了它们的临床潜力。
