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Zhang X, Selvaraju K, Saei AA, D'Arcy P, Zubarev RA, Arnér ES, Linder S. Repurposing of auranofin: Thioredoxin reductase remains a primary target of the drug. Biochimie 2019; 162:46-54. [PMID: 30946948 DOI: 10.1016/j.biochi.2019.03.015] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 03/24/2019] [Indexed: 12/11/2022]
Abstract
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.
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Affiliation(s)
- Xiaonan Zhang
- Department of Oncology-Pathology, Karolinska Institutet, SE-171 76, Stockholm, Sweden
| | - Karthik Selvaraju
- Department of Medical and Health Sciences, Linköping University, SE-581 83, Linköping, Sweden
| | - Amir Ata Saei
- Department of Medical Biochemistry and Biophysics, Division of Physiological Chemistry I, Karolinska Institutet, SE-171 77, Stockholm, Sweden
| | - Padraig D'Arcy
- Department of Medical and Health Sciences, Linköping University, SE-581 83, Linköping, Sweden
| | - Roman A Zubarev
- Department of Medical Biochemistry and Biophysics, Division of Physiological Chemistry I, Karolinska Institutet, SE-171 77, Stockholm, Sweden
| | - Elias Sj Arnér
- Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institute, SE-171 77, Stockholm, Sweden
| | - Stig Linder
- Department of Oncology-Pathology, Karolinska Institutet, SE-171 76, Stockholm, Sweden; Department of Medical and Health Sciences, Linköping University, SE-581 83, Linköping, Sweden.
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