2354 - MTA3-Driven Glutamine Synthetase Upregulation as a Mechanism for Radiosensitivity Regulation in Non-Small Cell Lung Cancer
Presenter(s)
L. Du1, M. Wang1, Y. Tan1, Y. Jiang1, D. Yang1, D. Tao1, and W. Zhou2; 1Radiation Oncology Center, Chongqing University Cancer Hospital, Chongqing, China, 2Department of Radiation Oncology, Chongqing University Cancer Hospital, Chongqing, China, China
Purpose/Objective(s): Metastasis-associated protein 3 (MTA3) functions variably across cancer types as either an oncogene or tumor suppressor. However, its role in regulating radiosensitivity in non-small cell lung cancer (NSCLC) remains poorly understood. The study aims to explore how MTA3 affects the radiosensitivity of NSCLC cells and tumors.
Materials/Methods: We assessed MTA3's impact on NSCLC radiosensitivity using colony formation assays and xenograft tumor models in nude mice. Glutaminolysis was investigated by measuring glutamine consumption and glutamate production, along with assessing the activity of key metabolic enzymes, Glutaminase (GLS) and Glutamine Synthetase (GS), using specialized activity assay kits. Chromatin Immunoprecipitation (ChIP) and Gaussia luciferase assays confirmed MTA3's regulatory role in glutaminolysis. Immunohistochemistry was used to assess the expression of MTA3 and GS in primary NSCLC tissue samples. Survival analysis was conducted using Kaplan-Meier curves, and statistical significance was determined by log-rank tests.
Results: The colony formation assay revealed that MTA3 depletion decreased clonogenic survival while its overexpression increased survival following irradiation. Xenograft tumors from MTA3 knockdown and overexpressing cells were markedly smaller and larger, respectively, following IR. These findings suggest that MTA3 influences radiosensitivity both in vitro and in vivo. Additionally, MTA3 knockdown and overexpression led to a reduction and acceleration in glutamine consumption and glutamate production, respectively. To investigate the underlying mechanism, we assessed the activity of two key enzymes involved in glutaminolysis, GS and GLS. MTA3 knockdown predominantly inhibited GS activity, while overexpression enhanced GS activity, with minimal effects on GLS. Notably, the radiosensitivity reduction induced by MTA3 overexpression was significantly reversed by GS inhibition, underscoring the pivotal role of GS in MTA3-mediated regulation of radiosensitivity. Mechanistically, Chromatin Immunoprecipitation (ChIP) and Gaussia luciferase assays demonstrated that MTA3 is recruited to the promoter region of GS, where it enhances GS transcription. However, knockdown of EBF1 abolished MTA3's ability to promote GS expression and interfered with MTA3’s binding to the GS promoter. These findings collectively suggest that MTA3, in collaboration with EBF1, upregulates GS expression in NSCLC cells, thereby stimulating glutaminolysis and reducing radiosensitivity. Finally, clinical analysis revealed that NSCLC patients in the MTA3high/GShigh group exhibited significantly shorter overall survival, highlighting the clinical relevance of this regulatory axis.
Conclusion: MTA3 mediates the suppression of radiosensitivity through the upregulation of GS, and the MTA3high/GShigh expression signature could potentially serve as a prognostic indicator for NSCLC patients.