Abstract 128: SIRT3 supports anchorage-independent survival of ovarian cancer cells
Authors: Tang Priscilla , Kim Yeon Soo , Gupta-Vallur Piyushi , Elhaw Amal T. , Javed Zaineb , Pan Weihua , Hempel Nadine 
Published: June 2022

Abstract
Metabolic changes during tumor progression have numerous consequences on cancer cells, including an increased risk of cell death due to production of reactive oxygen species (ROS). Antioxidant defense adaptations thus accompany metabolic alterations as essential survival mechanisms during metastasis. We observe that oxidative phosphorylation is increased when ovarian cancer (OC) cells transition to anchorage independence (a-i), an important step during metastasis in the peritoneal cavity. To combat the rise in oxidative stress resulting from this metabolic shift, a rapid increase in the sirtuin 3 (SIRT3)/superoxide dismutase 2 (SOD2) axis occurs to reduce the mitochondrial superoxide anion surge and to maintain cellular viability. We demonstrate that this upregulation occurs in transcription, translation, and SIRT3-mediated regulation of SOD2 activity. However, the fate of the hydrogen peroxide (H2O2) resulting from superoxide dismutation through SIRT3/SOD2 remains unknown. RNAseq analysis of attached versus a-i conditions revealed a significant downregulation of peroxiredoxin 3, a major scavenger of H2O2 in the mitochondria, suggesting that OCs have a net increase in mitochondrial H2O2 in a-i. At sub-lethal levels, H2O2 serves as a second messenger of redox signaling, primarily via protein cysteine oxidation, which has been implicated with metastasis. We thus hypothesize that increases in SIRT3/SOD2/H2O2 play a role as mediators of redox signaling during OC anchorage-independent survival, spheroid formation and metastasis. Using the HyPer7 redox probe and manipulation of SIRT3 and SOD2 expression, H2O2 generation and localization in a-i are being assessed using 3D fluorescence microscopy. Moreover, siRNA mediated knock-down of SIRT3 in a-i leads to the downregulation of genes involved in specific signaling pathways, including NF-kB signaling, the inflammatory response, and metabolism. Mass-spec studies are underway to identify specific SIRT3 target proteins upstream of these transcriptional changes, by assessing global cysteine oxidation and the cellular acetylome to determine the role of H2O2-dependent redox signaling and SIRT3-dependent protein de-acetylation, respectively. Given the increase in SIRT3-dependent inflammatory signaling in a-i, we are exploring how the SIRT3/SOD2/H2O2 axis influences OC interaction with tumor associated macrophages and mesenchymal stem cells, commonly found in the ascites tumor environment. This work demonstrates a multi-faceted role for the SIRT3/SOD2/H2O2 axis in a-i survival, a key step during OC metastasis.
Citation Format: Priscilla Tang, Yeon Soo Kim, Piyushi Gupta-Vallur, Amal T. Elhaw, Zaineb Javed, Weihua Pan, Nadine Hempel. SIRT3 supports anchorage-independent survival of ovarian cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 128.