| Objective: Radiotherapy is one of the important treatment for patients with liver cancer.However,due to the inherent and acquired radiation resistance of tumor cells,many patients undergo radiation resistance,recurrence and metastasis.MCU mediates the uptake of mitochondrial calcium and has important effects on maintaining mitochondrial homeostasis,regulating mitochondrial metabolism,oxidative stress and cell survival.However,the role and mechanism of MCU in regulating radiosensitivity of liver cancer are still unclear.Methods: First,we detected the effect of MCU on the radiosensitivity of liver cancer cells,and explored the effect of MCU on cell apoptosis and DNA damage repair of liver cancer cells exposed to radiation.In order to further explore the mechanism of MCUinduced radiation resistance,we detected the expression of mitochondrial calciumdependent IDH2 after knocking down MCU.Furthermore,the rescue operation of MCU-IDH2 was carried out to verify the effect of MCU-IDH2 on apoptosis,DNA damage repair and radiosensitivity of liver cancer cells.Then we tested the effects of the MCU-IDH2 on cellular oxidative stress levels and on acetyl coenzyme A/histone acetylation/DNA damage repair protein levels.Finally,injecting MCU-si RNA into nude mouse transplanted tumors in vivo to test the combined effect of silencing MCU and radiotherapy.At the same time,we used bioinformatics to analyze the expression of MCU in patients with liver cancer and its influence on prognosis.And explore the correlation between MCU-IDH2 and the efficacy of radiotherapy in clinical pathological tissues.Results: In this study,we found that knockdown of MCU can inhibit the expression of mitochondrial calcium-dependent IDH2,increase cell apoptosis,inhibit DNA damage repair under radiation,and then increase the radiosensitivity of liver cancer cells.In liver cancer cells,MCU-induced radiation resistance is mediated by mitochondrial calcium-dependent IDH2.Knocking down IDH2 in liver cancer cells can rescue the radiation resistance caused by overexpression of MCU.Further exploring the internal mechanism,we found that knocking down MCU-IDH2 disrupted dynamically balance of cellular redox homeostasis.Besides this,knocking down MCUIDH2 promoted the accumulation of acetyl coenzyme A and activated the mitochondria retrograde signaling,increased the acetyl coenzyme A-dependent histone acetylation level and inhibited the expression of DNA damage repair genes.Finally,we further confirmed that silencing MCU combined with radiotherapy significantly inhibits the growth of subcutaneous transplanted tumors in nude mice.Bioinformatics analysis and immunohistochemistry staining of clinical pathological tissues showed that the high expression of MCU was positively correlated with the poor prognosis of patients with liver cancer(HR=1.94,95%CI=1.36-2.78,P<0.001).Among patients with liver cancer received local radiotherapy,patients with low expression of MCU were more sensitive to radiotherapy.Conclusions: In this study,we found that knock down of MCU can inhibit the expression of mitochondrial calcium-dependent IDH2,increase the occurrence of apoptosis,inhibit DNA damage repair,and thereby increase the radiosensitivity of liver cancer cells.Knocking down MCU-IDH2,broke the dynamically balance of cellular redox homeostasis,activated mitochondrial reverse signaling pathways through acetyl coenzyme A,promoted histone acetylation,inhibit DNA damage repair,and ultimately increased cell radiosensitivity.Our research has enriched the important role of mitochondrial retrograde signaling in tumor cell radiation resistance,and provided a theoretical research basis on targeting MCU to improve radiosensitivity of liver cancer. |
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