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Objective: To investigate the underlying mechanism of hyperthermia-induced inhibition of breast cancer cells, we analyzed the influence of hyperthermia on the stimulator of interferon genes (STING) signaling pathway in 4T1 cells. Method: 4T1 cells were heated in the water bath at 37°C, 40°C, 42°C, 45°C, 47°C and 50°C for 30 minutes respectively. Additionally, 4T1 cells were randomly divided into four groups and cultured under the conventional condition for 0h, 2h, 4h, 8h after treated with water bath at 42°C and 45°C. Western blot was used to detect the expression level of STING, interferon regulatory factor 3 (IRF3) protein expression and their phosphorylation, and ELISA was used to detect IFN-β secreted by 4T1 cells at different temperatures. Results: Under 37°C to 50°C, with the increase of temperature, the phosphorylation ratio of STING and IRF3 decreased (P<0.05, P<0.0001), and there is no significant change of IFN-β. After treated in the water bath at 42°C and 45°C, with the extension of following conventional culture time, the expression of STING protein in 4T1 cells did not change significantly while the expression of IRF3 protein raised (P<0.05). Conclusion: From 37°C to 50 °C, the anti-tumor immune effect of breast cancer during hyperthermia is not achieved by STING signaling pathway in 4T1 cells, but the uncomplete STING signaling pathway in 4T1 cells might improve heat tolerance by its decreased phosphorylation level.
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