Abstract A013: Auranofin induces lethality driven by reactive oxygen species in high-grade serous ovarian cancer cells
Authors: Abdalbari Farah H. , Jaramillo Elvis M. , Forgie Benjamin N. , Tran Estelle , Goyeneche Alicia A. , Telleria Carlos M. 
Published: March 2024

Abstract
High-grade serous ovarian cancer (HGSOC) accounts for 70% of ovarian cancer cases in the clinical setting; the survival rate for this disease remains remarkably low due to the lack of a long-term consolidation therapy following standard platinum-based chemotherapy. There is minimal improvement in the survival rate of this disease due to the development of resistance to platinum drugs as the disease recurs. The purpose of this study was to develop a novel treatment modality against HGSOC using the gold complex auranofin (AF). AF primarily functions as a pro-oxidant agent through the inhibition of thioredoxin reductase (TrxR), an antioxidant enzyme that is overexpressed in ovarian cancer. We explored the effect of AF on TrxR activity and various mechanisms of cytotoxicity using HGSOC cells that are clinically sensitive (PEO1) or resistant (PEO4) to platinum. We treated PEO1 cells and PEO4 cells with AF for 72 hours and analyzed its short-term toxicity by assessing cell viability and DNA content by flow cytometry, and the long-term anti-proliferative capacity using colony formation assays. We also assessed the mechanisms of cell death induced by AF including the activation of mechanisms of apoptosis, activation of executor caspases -3 and -7, cleavage of poly-(ADP-ribose) polymerase (PARP), changes in the mitochondrial membrane potential (MMP), and DNA damage. In addition, we studied the interaction between AF and another pro-oxidant, L-buthionine sulfoximine (L-BSO), an anti-glutathione (GSH) agent. We demonstrate that AF potently inhibits the activity of TrxR at non-cytotoxic concentrations while reducing the viability of HGSOC cells regardless of their sensitivities to platinum. We showed that AF induces accumulation of reactive oxygen species (ROS), triggers the depolarization of the mitochondrial membrane, and kills HGSOC cells by inducing apoptosis. AF-induced cell death and morphological effects were abrogated by the ROS scavenger, N-acetyl cysteine (NAC). In addition, the lethality of AF in HGSOC was associated with the activation of caspase-3/7, cleavage of PARP, and the generation of DNA damage, effects that were prevented by the ROS scavenger NAC. Finally, when AF and L-BSO were combined, we observed a synergistic lethality against HGSOC cells, which was mediated by a further increase in ROS with a decrease in the antioxidant, GSH. In summary, our results support the concept that AF can be used alone to kill HGSOC cells by causing ROS-mediated apoptosis. Furthermore, we demonstrate that a large depletion of antioxidants caused by combining AF and L-BSO is highly efficient in synergistically killing HGSOC cells. These findings suggest that the combination of AF and L-BSO is a potential option to develop a consolidation therapy against HGSOC, which can overcome the problem of platinum resistance during recurrent stages of the disease.
Citation Format: Farah H. Abdalbari, Elvis M. Jaramillo, Benjamin N. Forgie, Estelle Tran, Alicia A. Goyeneche, Carlos M. Telleria. Auranofin induces lethality driven by reactive oxygen species in high-grade serous ovarian cancer cells [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr A013.