We have previously identified the natural product obtusaquinone (OBT) as a potent antineoplastic agent with promising in vivo activity in glioblastoma and breast cancer through the activation of oxidative stress; however, the molecular properties of this compound remained elusive. We used a multidisciplinary approach comprising medicinal chemistry, quantitative mass spectrometry-based proteomics, functional studies in cancer cells, and pharmacokinetic analysis, as well as mouse xenograft models to develop and validate novel OBT analogs and characterize the molecular mechanism of action of OBT. We show here that OBT binds to cysteine residues with a particular affinity to cysteine-rich Keap1, a member of the CUL3 ubiquitin ligase complex. This binding promotes an overall stress response and results in ubiquitination and proteasomal degradation of Keap1 and downstream activation of the Nrf2 pathway. Using positron emission tomography (PET) imaging with the PET-tracer 2-[¹⁸F]fluoro-2-deoxy-d-glucose (FDG), we confirm that OBT is able to penetrate the brain and functionally target brain tumors. Finally, we show that an OBT analog with improved pharmacological properties, including enhanced potency, stability, and solubility, retains the antineoplastic properties in a xenograft mouse model.

中文翻译：

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Obtusaquinone：半胱氨酸修饰化合物，靶向Keap1降解。

我们之前已经确定了天然产物obtusaquinone（OBT）是有效的抗肿瘤药，在体内具有广阔的前景通过激活氧化应激在胶质母细胞瘤和乳腺癌中的活性；然而，该化合物的分子性质仍然难以捉摸。我们使用了多学科方法，包括药物化学，基于定量质谱的蛋白质组学，癌细胞功能研究和药代动力学分析，以及小鼠异种移植模型，以开发和验证新型OBT类似物并表征OBT作用的分子机制。我们在这里显示，OBT以对富含半胱氨酸的Keap1（一种CUL3泛素连接酶复合体的成员）具有特定的亲和力与半胱氨酸残基结合。这种结合促进了整体应激反应，并导致Keap1的泛素化和蛋白酶体降解以及Nrf2途径的下游激活。使用PET示踪剂2- [正电子发射断层扫描（PET）成像¹⁸ F]氟-2-脱氧d -葡萄糖（FDG），我们确认OBT能够穿透脑和功能上靶向脑肿瘤。最后，我们表明具有改进的药理特性（包括增强的效力，稳定性和溶解性）的OBT类似物在异种移植小鼠模型中保留抗肿瘤特性。