Background: Ferroptosis is a regulated cell death mode triggered by iron-dependent toxic membrane lipid peroxidation. As a novel cell death modality that is morphologically and mechanistically different from other forms of cell death, such as apoptosis and necrosis, ferroptosis has attracted extensive attention due to its association with various diseases. Evidence on ferroptosis as a potential therapeutic strategy has accumulated with the rapid growth of research on targeting ferroptosis for tumor suppression in recent years. Methods: We summarize the currently known characteristics and major regulatory mechanisms of ferroptosis and present the role of ferroptosis in cellular stress responses, including ER stress and autophagy. Furthermore, we elucidate the potential applications of ferroptosis in radiotherapy and immunotherapy, which will be beneficial in exploring new strategies for clinical tumor treatment. Result and conclusion: Based on specific biomarkers and precise patient-specific assessment, targeting ferroptosis has great potential to be translated into practical new approaches for clinical cancer therapy, significantly contributing to the prevention, diagnosis, prognosis, and treatment of cancer.

The aim of the present study was to investigate the radiosensitizing effect of genistein, and the corresponding mechanisms of action on breast cancer cells with different estrogen receptor (ER) status. Human breast cancer cell lines such as MCF-7 (ER-positive, harboring wild-type p53) and MDA-MB-231 (ER-negative, harboring mutant p53) were irradiated with X-rays in the presence or absence of genistein. Cell survival, DNA damage and repair, cell cycle distribution, cell apoptosis, expression of proteins related to G₂/M cell cycle checkpoint and apoptosis were measured with colony formation assays, immunohistochemistry, flow cytometry and western blot analysis, respectively. Genistein showed relatively weak toxicity to both cell lines at concentrations in the range of 5–20 μM. Using the dosage of 10 μM genistein, the sensitizer enhancement ratios after exposure to X-rays at a 10% cell survival (IC₁₀) were 1.43 for MCF-7 and 1.36 for MDA-MB-231 cells, respectively. Significantly increased DNA damages, arrested cells at G₂/M phase, decreased homologous recombination repair protein Rad51 foci formation and enhanced apoptotic rates were observed in both cell lines treated by genistein combined with X-rays compared with the irradiation alone. The combined treatment obviously up-regulated the phosphorylation of ATM, Chk2, Cdc25c and Cdc2, leading to permanent G₂/M phase arrest, and up-regulated Bax and p73, down-regulated Bcl-2, finally induced mitochondria-mediated apoptosis in both cell lines. These results suggest that genistein induces G₂/M arrest by the activation of the ATM/Chk2/Cdc25C/Cdc2 checkpoint pathway and ultimately enhances the radiosensitivity of both ER+ and ER- breast cancer cells through a mitochondria-mediated apoptosis pathway.

Radiotherapy (RT) is considered an important therapeutic strategy in the fight against colorectal cancer (CRC). However, the existence of some radioresistance factors becomes the main challenge for the RT. Recently, non-coding RNAs (ncRNAs) have shown an important role in modulating cancer cell responses to ionizing radiation (IR). It is therefore of great significance to elucidate the exact mechanisms of ncRNAs in IR-mediated responses to CRC. Microarrays were used to identify specific miRNAs that may be altered in response to IR. Bioinformatics, luciferase reporter analyses were used to explore the targets of miR-6778-5p. CircRNA CBL.11 was identified to bind with miR-6778-5p by bioinformatic analysis, AGO2 immunoprecipitation and biotinylated RNA pull-down assay. Functional experiments, including CCK-8 assay, cell colony formation assay and EdU incorporation were conducted to investigate the biological roles of miR-6778-5p and circular RNA CBL.11. MiR-6778-5p was suppressed in CRC cells after irradiation. Results of functional experiments indicated that miR-6778-5p promoted the proliferation of CRC cells. Luciferase reporter analyses showed that YWHAE was a target of miR-6778-5p, which mediated the function of miR-6778-5p in the proliferation of CRC cells via the p53 pathway. Furthermore, we have noticed that after carbon ion irradiation, circRNA CBL.11 was increased in CRC cells and could function as a competing endogenous RNA (ceRNA) to regulate YWHAE expression by sponging miR-6778-5p, resulting in regulation the proliferation of CRC cells. CircRNA CBL.11 may play an important role in improving the efficacy of carbon ion RT against CRC.

PERK is one of the transmembrane sensors of unfolded protein response (UPR) triggered by ER stress. In this study, we evaluated the role of PERK in the sensitivity of hepatocellular carcinoma (HCC) cells to high linear energy transfer (LET) carbon ions (CI). We found that CI irradiation could induce ER stress in HCC cells. On the one hand, PERK promoted autophagy via regulating ATF4 expression; on the other hand, PERK regulated p53 expression, and the latter either induced autophagy through up-regulating DRAM, or directly promoting apoptosis through the mitochondrial pathway or facilitating ferroptosis via down-regulating SLC7A11 (the extrinsic pathway), but independent of GPX4 (the intrinsic pathway). These factors jointly determined the sensitivity of HCC cells to high-LET CI radiation. Inhibiting TP53 directly increased cellular radioresistance definitely. Moreover, the death of HepG2 (TP53 wild type) cells induced by high-LET CI irradiation combined with sorafenib treatment might be caused by a mixed-type regulated cell death (RCD) including both apoptosis and ferroptosis, suggesting that apoptosis and ferroptosis are synergetic cell death modes regulated by TP53, which is one of the reasons why the sensitivity of HepG2 cells is higher than that of Hep3B (TP53 null type) and PLC/PRF5 (TP53 mutated type) cells. Therefore, our work might shed light on the potential therapeutic implication of CI radiotherapy combined with PERK targeted clinical drugs to implement personalized and precise treatment of HCCs.