Auranofin is a gold (I)-containing compound used for the treatment of rheumatic arthritis. Auranofin has anticancer activity in animal models and is approved for clinical trials for lung and ovarian carcinomas. Both the cytosolic and mitochondrial forms of the selenoprotein thioredoxin reductase (TrxR) are well documented targets of auranofin. Auranofin was recently reported to also inhibit proteasome activity at the level of the proteasome-associated deubiquitinases (DUBs) UCHL5 and USP14. We here set out to re-examine the molecular mechanism underlying auranofin cytotoxicity towards cultured cancer cells. The effects of auranofin on the proteasome were examined in cells and in vitro, effects on DUB activity were assessed using different substrates. The cellular response to auranofin was compared to that of the 20S proteasome inhibitor bortezomib and the 19S DUB inhibitor b-AP15 using proteomics. Auranofin was found to inhibit mitochondrial activity and to an induce oxidative stress response at IC50 doses. At 2-3-fold higher doses, auranofin inhibits proteasome processing in cells. At such supra-pharmacological concentrations USP14 activity was inhibited. Analysis of protein expression profiles in drug-exposed tumor cells showed that auranofin induces a response distinct from that of the 20S proteasome inhibitor bortezomib and the DUB inhibitor b-AP15, both of which induced similar responses. Our results support the notion that the primary mechanism of action of auranofin is TrxR inhibition and suggest that proteasome DUB inhibition is an off-target effect. Whether proteasome inhibition will contribute to the antineoplastic effect of auranofin in treated patients is unclear but remains a possibility.

中文翻译：

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重用金诺芬：硫氧还蛋白还原酶仍然是该药物的主要靶标。

金诺芬是用于治疗风湿性关节炎的含金（I）的化合物。金诺芬在动物模型中具有抗癌活性，已被批准用于肺癌和卵巢癌的临床试验。硒蛋白硫氧还蛋白还原酶（TrxR）的胞质和线粒体形式都是金诺芬的靶点。最近有报道称金诺芬还可​​以在蛋白酶体相关的去泛素酶（DUBs）UCHL5和USP14的水平上抑制蛋白酶体的活性。我们在这里着手重新检查金诺芬对培养的癌细胞的细胞毒性的分子机制。在细胞和体外检查金诺芬对蛋白酶体的作用，并使用不同的底物评估对DUB活性的作用。使用蛋白质组学将对金诺芬的细胞反应与20S蛋白酶体抑制剂硼替佐米和19S DUB抑制剂b-AP15的反应进行了比较。发现金诺芬以IC50剂量抑制线粒体活性并诱导氧化应激反应。在高2到3倍的剂量下，金诺芬抑制细胞中蛋白酶体的加工。在这样的超药理浓度下，USP14活性被抑制。对暴露于药物的肿瘤细胞中蛋白质表达谱的分析表明，金诺芬诱导的反应不同于20S蛋白酶体抑制剂硼替佐米和DUB抑制剂b-AP15，两者均诱导相似的反应。我们的研究结果支持金诺芬作用的主要机制是抑制TrxR的观点，并表明蛋白酶体DUB的抑制作用是脱靶作用。