Inhibition of glutamine synthetase enhances hepatocellular carcinoma radiosensitivity through ROS-induced excessive mitophagy.

BACKGROUND

Glutamine' synthetase (GS) plays a central role in glutamine metabolism and has been implicated in the progression and treatment resistance of hepatocellular carcinoma (HCC). Although previous studies have explored GS in tumor metabolism, its role in modulating mitophagy and radiosensitivity in HCC cells remains unclear.

METHODS

We analyzed GS expression in HCC using data from the TCGA database, followed by treatment of HepG2, Hep3B and Huh7 cells with the GS inhibitor L-methionine sulfoximine (MSO) and exposure to ionizing radiation. Cellular responses were evaluated through CCK-8 assays, Western blotting, immunofluorescence, flow cytometry, colony formation assays, and mitochondrial membrane potential measurements.

RESULTS

Correlation analysis revealed a positive association between GS expression and mitophagy-related genes in HCC. MSO treatment enhanced the effects of radiotherapy, leading to increased ROS production, reduced antioxidant capacity, and aggravated mitochondrial damage. Mitophagy activation was confirmed by LC3-II accumulation and upregulation of the PINK1/Parkin pathway. Notably, the radiosensitizing effect of MSO was partially reversed by Mdivi-1, indicating that mitophagy contributes to MSO-mediated radiosensitization.

CONCLUSION

These findings indicate that inhibition of GS enzyme activity enhances oxidative stress and mitophagy, thereby promoting radiosensitivity in HCC cells. This study provides new insights into the role of GS in overcoming radiotherapy resistance and highlights its potential as a therapeutic target to improve radiotherapeutic outcomes in HCC.