Abstract B148: Novel low-atomic cluster Ag5 induced oxidative stress and antiproliferation in Esophageal Squamous Cell Carcinoma Cells
Authors: Kamata Ryo , Yamauchi Toyohiro , Sakae Yuta , Breckenridge Ross , Treder Martin , Ohashi Akihiro 
Published: December 2023

Abstract
Background: Accumulation of reactive oxygen species (ROS) intensively activates cellular stress responses leading to cell death, thus ROS levels are strictly controlled by various antioxidants in normal cells. Esophageal cancer (ESCA), the sixth most common cause of cancer deaths, highly accumulates ROS under uncontrolled redox balances to activate oxidative-stress response pathways. Arjuna Therapeutics has developed a novel low-atomic cluster Ag5 as a ROS inducer, which strongly inhibits antioxidant pathways of glutathione and thioredoxin. In this study, we pharmacologically evaluate Ag5 on its therapeutic potential in preclinical ESCA models.
Materials and Methods: Gene enrichment analyses were performed with 6,327 RNA-seq data of 14 cancer types in TCGA database. Cell panel studies of ATP-based cell viability was performed in vehicle control, Ag5 (3 uM), N-acetylcysteine (NAC, 5mM), and combination treatments in 31 esophageal squamous cell carcinoma (ESCC) cell lines and 5 non-ESCC cell lines. NAC) treatment was used as a rescue control of an antioxidant. We also conducted time-lapse imaging analysis with DCFDA (ROS indicator) and SYTOX (cell death marker). The morphology of mitochondria and ER were determined by electron microscope (EM).
Results: Gene enrichment analyses revealed ROS-related genes were upregulated in ESCA compared to other cancer types. In the cell panel studies, Ag5 also exhibited potent antiproliferation in large numbers of ESCC cell lines, and NAC profoundly attenuated its antiproliferative activity. Time-lapse microscopy in ESCC cell line KYSE190　demonstrated that Ag5 increased DCFDA in 20 min and SYTOX in 60 min after the treatment, respectively, while combination treatment with NAC less detected these markers. Ag5-treated KYSE190 also exhibited necrosis-like morphology of swollen- and round-shape cells. In EM, damaged mitochondria and expanded endoplasmic reticulum were frequently observed in Ag5-treated KYSE190 cells. These data indicated that Ag5 induced ROS-mediated antiproliferation in ESCC cell lines.
Conclusions: Ag5 exhibited ROS-mediated antiproliferative activities in large numbers of ESCC cell lines. Our preclinical results suggest the therapeutic potential of Ag5 as a novel cancer drug candidate for ESCC.
Conflict of interest disclosure: AO is a part-time employee of Astellas Pharma Inc. from 2023 as a cross-appointment system. AO was an employee of Takeda Pharmaceutical Company, Ltd. AO reported paid consulting or advisory roles for Ono Pharmaceutical Company Ltd., Craif Inc., and GEXVal Inc. out of this study. AO receives research fundings from Astellas Pharma Inc., Astellas Pharma Global Development Inc., and Daiichi Sankyo Company, Ltd. out of this study. RB and MT are board members of Arjuna Therapeutics.
Citation Format: Ryo Kamata, Toyohiro Yamauchi, Yuta Sakae, Ross Breckenridge, Martin Treder, Akihiro Ohashi. Novel low-atomic cluster Ag5 induced oxidative stress and antiproliferation in Esophageal Squamous Cell Carcinoma Cells [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B148.