Objective We aimed to elucidate the mutual regulation mechanism of ubiquitin-specific protease 22 (USP22) and hypoxia inducible factor-1α (HIF1α), and the mechanism they promote the stemness of hepatocellular carcinoma (HCC) cells under hypoxic conditions.
Design Cell counting, migration, self-renewal ability, chemoresistance and expression of stemness genes were established to detect the stemness of HCC cells. Immunoprecipitation, ubiquitination assay and chromatin immunoprecipitation assay were used to elucidate the mutual regulation mechanism of USP22 and HIF1α. HCC patient samples and The Cancer Genome Atlas data were used to demonstrate the clinical significance. In vivo USP22-targeting experiment was performed in mice bearing HCC.
Results USP22 promotes hypoxia-induced HCC stemness and glycolysis by deubiquitinating and stabilising HIF1α. As direct target genes of HIF1α, USP22 and TP53 can be transcriptionally upregulated by HIF1α under hypoxic conditions. In TP53 wild-type HCC cells, HIF1α induced TP53-mediated inhibition of HIF1α-induced USP22 upregulation. In TP53-mutant HCC cells, USP22 and HIF1α formed a positive feedback loop and promote the stemness of HCC. HCC patients with a loss-of-function mutation at TP53 and high USP22 and/or HIF1α expression tend to have a worse prognosis. The USP22-targeting lipopolyplexes caused high tumour inhibition and high sorafenib sensitivity in mice bearing HCC.
Conclusion USP22 promotes hypoxia-induced HCC stemness by a HIF1α/USP22 positive feedback loop on TP53 inactivation. USP22 is a promising target for the HCC therapy.
- hepatocellular carcinoma
- cancer stemness
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SL, QS and QZ contributed equally.
Contributors XX, SL, QS, SZ, HX and PS designed the research. SL, QS, QZ, QY, PL, SX, JX, XW, TF, LX, KC, BC, GJ and XZ performed experiments and acquisition of data. SL, QS, QZ, XH, JM, ZF, YW and JL analyzed and interpreted data. SL, QS, QZ. QY, RW, CZ and XX wrote the paper and critically reviewed the manuscript. All authors read and approved the final version of the manuscript.
Funding This work was supported in part by funding from the National Science and Technology Major Project of China (2017ZX10203205), the National Natural Science Funds for Distinguished Young Scholar of China (81625003) and the Cheung Kong Scholars Program of China to XX, the National Natural Science Foundation of China (81902407) to SL; the Zhejiang Science and Technology Key Research and Development Project (2018C04010) to SL; the Zhejiang Public Welfare Technology Research Program (LGF18H160015) to TF.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The Medical Ethics Committee of the First Affiliated Hospital of Zhejiang University.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available in a public, open access repository.
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