Protein disulfide isomerase (PDI) is overexpressed in glioblastoma, the most aggressive form of brain cancer, and folds nascent proteins responsible for the progression and spread of the disease. Herein we describe a novel nanomolar PDI inhibitor, pyrimidotriazinedione 35G8, that is toxic in a panel of human glioblastoma cell lines. We performed a medium‐throughput 20 000‐compound screen of a diverse subset of 1 000 000 compounds to identify cytotoxic small molecules. Cytotoxic compounds were screened for PDI inhibition, and, from the screen, 35G8 emerged as the most cytotoxic inhibitor of PDI. Bromouridine labeling and sequencing (Bru‐seq) of nascent RNA revealed that 35G8 induces nuclear factor‐like 2 (Nrf2) antioxidant response, endoplasmic reticulum (ER) stress response, and autophagy. Specifically, 35G8 upregulated heme oxygenase 1 and solute carrier family 7 member 11 (SLC7A11) transcription and protein expression and repressed PDI target genes such as thioredoxin‐interacting protein 1 (TXNIP) and early growth response 1 (EGR1). Interestingly, 35G8‐induced cell death did not proceed via apoptosis or necrosis, but by a mixture of autophagy and ferroptosis. Cumulatively, our data demonstrate a mechanism for a novel PDI inhibitor as a chemical probe to validate PDI as a target for brain cancer.

中文翻译：

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一类蛋白质二硫键异构酶抑制剂治疗胶质母细胞瘤的发现和机理研究

蛋白质二硫键异构酶（PDI）在胶质母细胞瘤（脑癌的最具侵略性形式）中过表达，并且折叠负责该疾病进展和传播的新生蛋白质。在这里，我们描述了一种新型的纳摩尔PDI抑制剂，嘧啶三嗪二酮35G8，在一组人胶质母细胞瘤细胞系中具有毒性。我们对1 000 000种化合物的不同子集进行了中通量20000化合物筛查，以鉴定具有细胞毒性的小分子。对细胞毒性化合物进行了PDI抑制作用的筛选，并且从筛选物中发现35G8是PDI最具细胞毒性的抑制剂。新生RNA的溴尿苷标记和测序（Bru-seq）表明35G8诱导类似核因子2（Nrf2）的抗氧化反应，内质网（ER）应激反应和自噬。具体而言，35G8上调了血红素加氧酶1和溶质载体家族7成员11（SLC7A11）的转录和蛋白质表达，并抑制了PDI靶基因，如硫氧还蛋白相互作用蛋白1（TXNIP）和早期生长反应1（EGR1）。有趣的是，35G8诱导的细胞死亡不是通过细胞凋亡或坏死进行的，而是通过自噬和肥大病的混合进行的。累积地，我们的数据证明了一种新型PDI抑制剂作为化学探针来验证PDI作为脑癌靶点的机制。