Abstract 1403: ROS metabolism and autophagy as potential targets to improve head and neck cancer treatment
Authors: Gurel Zafer , Luo Qianyun , Luy Michael S. , Kimple Randall J. 
Published: June 2022

Abstract
Introduction: Cancer cells exhibit a high degree of plasticity to adapt the rapidly changing tumor microenvironment (TME), in part by altering cellular metabolic pathways at a faster and more efficient pace than normal cells. Cancer cell plasticity, with genetic and epigenetic alterations, promote the diversity of cancer cells contributing to heterogeneity within the tumor. Head and neck cancer (HNC) is a notable example of this diversity; HNC tumors harbor cells with a wide genetic and metabolic heterogeneity, including cancer stem cells (CSC). Despite current treatment approaches, more than 40% of HNC patients have disease recurrence. Thus, we developed a multimodal approach to effectively prevent the development of radio/drug-resistance.
Experimental Procedures: Nuclear-localized mkate2 expressing HNC cell numbers detected for every 6 hours by using IncuCyte S3 instrument. Apoptotic cells detected via NucView 488 Caspase-3 substrate and ROS levels determined using CellROX green simultaneously with cell numbers in the IncuCyte S3 instrument. Synergy scores calculated according to viability in SynergyFinder 2.0 web-application.
Results: Our preliminary data profiling of metabolic regulators as radiosensitizer indicate that auranofin (AUR, thioredoxin reductase inhibitor) and buthionine sulfoximine (BSO, γ-glutamylcysteine synthetase inhibitor), given in combination with radiation (RT+AUR+BSO): 1) significantly inhibit proliferation in HNC cell lines, 2) increase ROS accumulation, and 3) reduce the surviving fraction of cells in colony forming assays compared to individual/dual agent applications. Furthermore, we added an autophagy inhibitor, SAR405, in our treatment regimen because of the crosstalk between ROS levels and autophagy. Human (FaDu and UM-SCC-47) and murine (MOC1 and MOC2) HNC cell were treated with +/-AUR+/-BSO+/-SAR405 and high-throughput combinatorial screening of cell numbers obtained over time. The combination of AUR+BSO+SAR405 registered a higher synergy score than the double combinations. Furthermore, as compared to single or double drug applications, the AUR+BSO+SAR405 group had a greater apoptotic cell rate and ROS levels.
Conclusion: We present here a high-throughput method to screen multi-drug synergy. Multi-modal approach is important to prevent recurrence by providing a broader effect on heterogenous cancer cells in tumor. Moreover, multi-drug combinations allow usage of lower doses of drugs effectively, hence lowers the treatment-related adverse effects. This approach indicated the possibility of HNC treatment by increasing the ROS levels beyond the containable threshold which is consistent with the recent findings about the alterations in redox metabolism, particularly upregulation in thioredoxin and glutathione pathways, in many cancer types. In vivo experiments are ongoing to evaluate the potential of this combination for clinical studies.
Citation Format: Zafer Gurel, Qianyun Luo, Michael S. Luy, Randall J. Kimple. ROS metabolism and autophagy as potential targets to improve head and neck cancer treatment [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 1403.