Targeting Ferroptosis to Enhance Radiosensitivity of Glioblastoma

Glioblastoma (GBM), one of the most common malignant tumors in the central nervous system (CNS), is characterized by diffuse and invasive growth as well as resistance to various combination therapies.GBM is the most prevalent type with the highest degree of malignancy and the worst prognosis. While current clinical treatments include surgical resection, radiotherapy, temozolomide chemotherapy, novel molecular targeted therapy, and immunotherapy, the median survival time of GBM patients is only about one year. Radiotherapy is one of the important treatment modalities for GBM, which relies on ionizing radiation to eradicate tumor cells.Approximately 60% to 70% of patients need to receive radiotherapy as postoperative radiotherapy or neoadjuvant radiotherapy during the treatment process. However, during radiotherapy, the radioresistant effect caused by DNA repair activation and cell apoptosis inhibition impedes the therapeutic effect of malignant glioblastoma.Ferroptosis was first proposed by Dr. Brent R. Stockwell in 2012. It is an iron-dependent mode of cell death induced by excessive lipid peroxidation. Although the application of ferroptosis in tumor therapy is still in the exploratory stage, it provides a completely new idea for tumor therapy as a novel form of cell death. Ferroptosis has played a significant role in the treatment of GBM. Specifically, research has revealed the key processes of ferroptosis occurrence, including intracellular iron accumulation, reactive oxygen species (ROS) generation, lipid peroxidation, and a decrease in the activity of the antioxidant system. Among them, glutathione peroxidase 4(GPX4) in the cytoplasm and mitochondria, ferroptosis suppressor protein 1(FSP1) on the plasma membrane, and dihydroorotate dehydrogenase (DHODH) in the mitochondria constitute an antioxidant protection system against ferroptosis. In iron metabolism, nuclear receptor coactivator 4(NCOA4) can mediate ferritin autophagy to regulate intracellular iron balance based on intracellular iron content. Heme oxygenase1(HMOX1) catalyzes heme degradation to release iron and regulate ferroptosis. Radiation can trigger ferroptosis by generating ROS,inhibiting the signaling axis of the antioxidant system, depleting glutathione, upregulating acyl-CoA synthase long chain family member 4(ACSL4), and inducing autophagy. Interestingly, some articles has documented that exposure to low doses of radiation (6 Gy for 24 h or 8 Gy for 4-12 h) can induce the expression of SLC7A11 and GPX4 in breast cancer and lung cancer cells, leading to radiation resistance, while radiation-induced ferroptosis occurs after 48 h. In contrast, high doses of ionizing radiation (20 Gy and 50 Gy) increase lipid peroxidation after 24 h. This suggests that radiation-induced oxidative stress is a double-edged sword that can regulate ferroptosis in both directions, and the ultimate fate of cells after radiation exposure--developing resistance and achieving homeostasis or undergoing ferroptosis--depends on the degree and duration of membrane lipid damage caused by the radiation dose. In addition,during the process of radiotherapy,methods such as inducing iron overload,damaging the antioxidant system,and disrupting mitochondrial function are used to target ferroptosis,thereby enhancing the radiosensitivity of glioblastoma. By promoting the occurrence of ferroptosis in tumor cells as a strategy to improve radiotherapy sensitivity, we can enhance the killing effect of ionizing radiation on tumor cells,thus providing more treatment options for patients with glioblastoma. In this paper, we reviewed ferroptosis and its mechanism, analyzed the molecular mechanism of radiation-induced ferroptosis, and discussed the effective strategies to regulate ferroptosis in enhancing the sensitivity of radiotherapy, with a view to providing an important reference value for improving the current status of glioblastoma treatment