Radioresistance is a principal culprit for the failure of radiotherapy in hepatocellular carcinoma (HCC). Insights on the regulation genes of radioresistance and underlying mechanisms in HCC are awaiting for profound investigation. In this study, the suppressor of cytokine signaling 2 (SOCS2) were screened out by RNA-seq and bioinformatics analyses as a potential prognosis predictor of HCC radiotherapy and then were determined to promote radiosensitivity in HCC both in vivo or in vitro. Meanwhile, the measurements of ferroptosis negative regulatory proteins of solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4), intracellular lipid peroxidation and Fe²⁺ concentration suggested that a high level of ferroptosis contributed to the radiosensitization of HCC. Moreover, SOCS2 and SLC7A11 were expressed oppositely in HCC clinical tissues and tumour xenografts with different radiosensitivities. Mechanistically, the N-terminal domain of SLC7A11 was specifically recognized by the SH2-structural domain of SOCS2. While the L162 and C166 of SOCS2-BOX region could bind elongin B/C compound to co-form a SOCS2/elongin B/C complex to recruit ubiquitin molecules. Herein, SOCS2 served as a bridge to transfer the attached ubiquitin to SLC7A11 and promoted K48-linked polyubiquitination degradation of SLC7A11, which ultimately led to the onset of ferroptosis and radiosensitization of HCC. In conclusion, it was demonstrated for the first time that high-expressed SOCS2 was one of the biomarkers predicting radiosensitivity of HCC by advancing the ubiquitination degradation of SLC7A11 and promoting ferroptosis, which indicates that targeting SOCS2 may enhance the efficiency of HCC radiotherapy and improve the prognosis of patients.

Extracellular miR-1246 promotes lung cancer cell proliferation and enhances radioresistance by directly targeting DR5

Background: Hypoxia-mediated radioresistance is a major reason for the adverse radiotherapy outcome of non-small cell lung cancer (NSCLC) in clinical, but the underlying molecular mechanisms are still obscure. Methods: Cellular and exosomal ANGPTL4 proteins under different oxygen status were examined. Colony survival, lipid peroxidation and hallmark proteins were employed to determine the correlation between ferroptosis and radioresistance. Gene regulations, western blot and xenograft models were used to explore the underlying mechanisms of the role of ANGPTL4 in radioresistance. Results: ANGPTL4 had a much higher level in hypoxic NSCLC cells compared to normoxic cells. Up- or down- regulation of ANGPTL4 positively interrelated to the radioresistance of NSCLC cells and xenograft tumours. GPX4-elicited ferroptosis suppression and lipid peroxidation decrease were authenticated to be involved in the hypoxia-induced radioresistance. ANGPTL4 encapsulated in the exosomes from hypoxic cells was absorbed by neighbouring normoxic cells, resulting in radioresistance of these bystander cells in a GPX4-dependent manner, which was diminished when ANGPTL4 was downregulated in the donor exosomes. Conclusion: Hypoxia-induced ANGPTL4 rendered radioresistance of NSCLC through at least two parallel pathways of intracellular ANGPTL4 and exosomal ANGPTL4, suggesting that ANGPTL4 might applicable as a therapeutic target to improve the therapeutic efficacy of NSCLC.

Glioblastoma multiforme (GBM) is the most common brain malignancy insensitive to radiotherapy (RT). Although macroautophagy/autophagy was reported to be a fundamental factor prolonging the survival of tumors under radiotherapeutic stress, the autophagic biomarkers coordinated to radioresistance of GBM are still lacking in clinical practice. Here we established radioresistant GBM cells and identified their protein profiles using tandem mass tag (TMT) quantitative proteomic analysis. It was found that SDC1 and TGM2 proteins were overexpressed in radioresistant GBM cells and tissues and they contributed to the poor prognosis of RT. Knocking down SDC1 and TGM2 inhibited the fusion of autophagosomes with lysosomes and thus enhanced the radiosensitivity of GBM cells. After irradiation, TGM2 bound with SDC1 and transported it from the cell membrane to lysosomes, and then bound to LC3 through its two LC3-interacting regions (LIRs), coordinating the encounter between autophagosomes and lysosomes, which should be a prerequisite for lysosomal EPG5 to recognize LC3 and subsequently stabilize the STX17-SNAP29-VAMP8 QabcR SNARE complex assembly. Moreover, when combined with RT, cystamine dihydrochloride (a TGM2 inhibitor) extended the lifespan of GBM-bearing mice. Overall, our findings demonstrated the EPG5 tethering mode with SDC1 and TGM2 during the fusion of autophagosomes with lysosomes, providing new insights into the molecular mechanism and therapeutic target underlying radioresistant GBM.Abbreviations: BafA₁: bafilomycin A₁; CQ: chloroquine; Cys-D: cystamine dihydrochloride; EPG5: ectopic P-granules 5 autophagy tethering factor; GBM: glioblastoma multiforme; GFP: green fluorescent protein; LAMP2: lysosomal associated membrane protein 2; LIRs: LC3-interacting regions; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; NC: negative control; RFP: red fluorescent protein; RT: radiotherapy; SDC1: syndecan 1; SNAP29: synaptosome associated protein 29; SQSTM1/p62: sequestosome 1; STX17: syntaxin 17; TGM2: transglutaminase 2; TMT: tandem mass tag; VAMP8: vesicle associated membrane protein 8; WT: wild type

Glioblastoma multiforme (GBM) remains a therapeutic challenge due to its aggressive nature and recurrence. This study establishes a radioresistant GBM cell model through repeated irradiation and observes a cellular senescence-like phenotype in these cells. Comprehensive genomic and transcriptomic analyses identify IFI16 as a central regulator of this phenotype and contributes to radioresistance. IFI16 activates HMOX1 transcription thereby attenuating ferroptosis by reducing lipid peroxidation, ROS production, and intracellular Fe²⁺ content following irradiation. Furthermore, IFI16 interacts with the transcription factors JUND and SP1 through its pyrin domain, robustly facilitating HMOX1 expression, further inhibiting ferroptosis and enhancing radioresistance in GBM. Notably, glyburide, a sulfonylurea compound, effectively disrupts IFI16 function and enhances ferroptosis and radiosensitivity. By targeting the pyrin domain of IFI16, glyburide emerges as a potential therapeutic agent against GBM radioresistance. These findings underscore the central role of IFI16 in GBM radioresistance and offer promising avenues to improve GBM treatment.

Purpose: Tumor resistance towards radiation has been a big obstacle in the poor prognosis of lung cancer. It has been reported that hypoxia and autophagy partly contribute to this resistance. However, there is controversy over whether autophagy plays a positive role in cancer therapy or not. We aim to find out the specific mechanism of radiation resistance. Materials and methods: A549 cells were treated with conditioned medium (CM) under 12 h hypoxia or normoxia before irradiation, followed by the measurement of clonogenic survival, reactive oxygen species (ROS), signal of mitochondria and autophagy flux. In some experiments, the A549 cells were respectively transfected with LC3 small interfering RNA (siRNA), or treated with Earle’s Balanced Salt Solution (EBSS). Results: We found that hypoxia enhanced cell radioresistance by increasing the induction of autophagy. And after hypoxia stress, the number of mitochondria was reduced but the cellular ROS level was enhanced. It was significant that autophagy may enhance cell radioresistance by reducing ROS during hypoxic treatment. Conclusions: We elucidated the possible mechanisms of autophagy in regulating cancer cell death or survival. These results supply a new opinion about the intrinsic factor of radioresistance of hypoxia tumors.