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CircRNA-ST6GALNAC6 increases the sensitivity of bladder cancer cells to erastin-induced ferroptosis by regulating the HSPB1/P38 axis

Abstract

Previous studies have demonstrated that circST6GALNAC6 is a tumor suppressor in bladder cancer. However, the role of circST6GALNAC6 in ferroptosis remains unclear. In the current study, ferroptosis was induced in bladder cancer cells by erastin. Functional experiments showed that overexpression of circST6GALNAC6 promoted ferroptosis of bladder cancer cells in vitro and in vivo. Mechanistic studies revealed that circST6GALNAC6 bound to the N-terminus of small heat shock protein 1 (HSPB1) and thus blocked the erastin-induced phosphorylation of HSPB1 at the Ser-15 site, a phosphorylation site in the protective response to ferroptosis stress. In addition, protein kinase C inhibited circST6GALNAC6-induced ferroptosis by increasing the overall phosphorylation level of HSPB1, further demonstrating the role of phosphorylation activation of HSPB1 in resistance to ferroptosis. Finally, the involvement of the HSPB1/p38 MAPK pathway in the downstream signal transduction of circST6GALNAC6 in bladder cancer ferroptosis regulation was determined. The regulatory mechanism of ferroptosis sensitivity dependent on circST6GALNAC6 expression levels in bladder cancer was revealed as circRNA regulation of various protein functions. CircST6GALNAC6 inhibits HSPB1 and promotes cell ferroptosis by occupying the phosphorylation site (Ser-15) of HSBP1 and activating the P38 MAPK signaling pathway. Therefore, enhancing the expression of circST6GALNAC6 to promote ferroptosis or using circST6GALNAC6 as a biomarker of ferroptosis sensitivity is of considerable importance to the development and application of ferroptosis intervention methods in bladder cancer.

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Fig. 1: CircST6GALNAC6 increased the sensitivity of bladder cancer cells to ferroptosis.
Fig. 2: Identification of circST6GALNA6-binding proteins.
Fig. 3: Erastin promoted the binding of circST6GALNAC6 and HSPB1 in bladder cancer.
Fig. 4: CircST6GALNAC6 increased the sensitivity of bladder cancer cells to ferroptosis by binding HSPB1.
Fig. 5: HSPB1 N-terminal interacted with circST6GALNAC6 and mediated its effects on bladder cancer cell ferroptosis.
Fig. 6: CircST6GALNAC6/HSPB1 axis regulated bladder cancer cell ferroptosis sensitivity through the p38 MAPK pathway.
Fig. 7: Role of the circST6GALNA6/HSPB1 axis in regulating bladder cancer cell ferroptosis was validated in vivo.

Data availability

All data generated or analyzed during this study are included in this published article.

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Funding

This work was supported by Hunan Provincial Natural Science Foundation of China (No. 2019JJ40442), National Natural Science Foundation of China (Grant no. 81972195), Hunan Provincial Key Area R&D Program (Grant no. 2019SK2253), Scientific Research Program of Hunan Provincial Health Commission (Grant no. 20201047) and Clinical Medical Technology Innovation Guide Project of Hunan Province (grant number S2020SFYLJS0311).

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L.W.: Conceptualization, Methodology, Writing- Original draft preparation, Investigation, Validation. S.W.: Methodology, Visualization. H.H.: Software, Data curation. K.A.: Data curation, Validation. R.X.: Methodology, Validation. L.Z.: Software, Visualization. X.Z.: Conceptualization, Writing- Original draft preparation, Supervision, Writing- Reviewing and Editing.

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Correspondence to Xuan Zhu.

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Nude mice (male, 7–8 weeks old) were provided by Hunan SJA Laboratory Animal Co., Ltd, animal experiments were performed in accordance with the guidelines of the Committee on the Ethics of Animal Experiments of Central South University.

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Wang, L., Wu, S., He, H. et al. CircRNA-ST6GALNAC6 increases the sensitivity of bladder cancer cells to erastin-induced ferroptosis by regulating the HSPB1/P38 axis. Lab Invest (2022). https://doi.org/10.1038/s41374-022-00826-3

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