作为转录和表观遗传调节因子，在细胞功能调节中，BRD4在癌症发展中发挥重要作用。使用常规抑制剂靶向BRD4进行癌症治疗需要高剂量，往往导致非靶标和不良反应。BRD4靶向的蛋白酶解靶向融合物（PROTACs）可以催化降解利用内源性蛋白酶体系统的BRD4，并展现出有希望的抗肿瘤活性。然而，大多数已开发的PROTACs非特异性肿瘤，相对对正常细胞有毒，限制了它们在癌症治疗中的实际应用。通过利用癌细胞中较正常细胞更高的谷胱甘肽（GSH）水平的优势，我们通过在VHL（von Hippel-Lindau）配体的羟基上连接GSH触发单元，开发出几种GSH响应性的PROTAC前体1a-c，以招募E3连接酶。在这些前体中，1a可以通过肺癌细胞（A549和H1299）中内在更高浓度的GSH有效激活，释放出活性的PROTAC 1，降解细胞内的BRD4并导致细胞毒性，这一机制研究结果证实。另一方面，1a在含有较低GSH水平的正常肺细胞（WI38和HULEC-5a）中不能高效激活，从而减少对正常细胞的不良影响。本研究提供了开发刺激响应性PROTAC前体的替代概念方法，并为改善目前PROTACs的特异性和减少不良反应提供了新的见解，从而增强了其临床潜力。版权所有© 2023 Elsevier Inc. 保留所有权利。

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.Copyright © 2023 Elsevier Inc. All rights reserved.