The effects and mechanisms of mefloquine on radiation sensitivity and radiation-induced immunogenic cell death in glioma cells

• 1、School of Radiation medicine and Protection,Soochow University,Suzhou,Jiangsu,215123

Abstract：To investigate the effect of mefloquine on the radiosensitivity of glioma cells under normoxic and hypoxic conditions, and to elucidate its influence on radiation-induced immunogenic cell death (ICD) as well as the underlying mechanism.Methods: Human glioma cell lines U251 and T98G were used in this study. Cells were pretreated with 30 μM mefloquine for 24 h prior to X-ray irradiation using an X-ray irradiator. Cells were cultured in a standard incubator (normoxia) and a hypoxic incubator with 1% O2 to mimic the tumor microenvironment. The radiosensitization ratio was calculated via colony formation assay. Cell viability was detected by the CCK-8 assay. The extracellular ATP level in cell supernatant was measured by chemiluminescence assay. The surface exposure of calreticulin (CRT) was determined using immunofluorescence staining and flow cytometry.Conclusion: This study confirms that the antimalarial drug mefloquine can significantly enhance the radiosensitivity of human glioma U251 and T98G cells under both normoxic and hypoxic conditions. This effect is synergistically achieved through multiple pathways, including exacerbating DNA damage and blocking its repair, upregulating intracellular reactive oxygen species (ROS) levels, and promoting tumor cell apoptosis. The combined treatment of mefloquine and radiation can synergistically amplify the immunogenic cell death (ICD) effect, markedly increase the release of extracellular ATP and the exposure level of calreticulin (CRT) on the cell membrane surface. Ultimately, by activating the endoplasmic reticulum stress pathway, it not only enhances the killing effect of radiotherapy but also triggers the adaptive anti-tumor immune response, providing an experimental basis with both fundamental value and translational potential for overcoming glioma radioresistance and developing novel radiotherapy sensitization combined with immunotherapy strategies.

Keywords： Mefloquine Glioma of the brain Radiosensitivity Endoplasmic Reticulum Stress Immunogenic cell death.