USP22 Contributes to Chemoresistance, Stemness, and EMT Phenotype of Triple-Negative Breast Cancer Cells by egulating the Warburg Effect via c-Myc Deubiquitination

Abstract

BackgroundUbiquitin-specific protease 22 (USP22) has been implicated in the progression of breast cancer, while its regulatory functions in triple-negative breast cancer (TNBC) have been rarely reported. This study aimed to elucidate the effect and mechanism of USP22 on the malignant phenotype of TNBC cells. Materials and MethodsThe expression of USP22, stemness genes, and EMT-related markers were analyzed by RT-qPCR and/or Western blotting. Cell stemness was determined by cell spheroid formation, flow cytometry for CD44+/CD24-, and extreme limiting dilution analysis. Cell proliferation and cisplatin (DDP) chemoresistance of TNBC cells were assessed by CCK-8 assay and xenograft model. Glycolysis was measured by Seahorse assay. The mechanism underlying the role of USP22 was explored by Co-immunoprecipitation, ubiquitination assay, and cycloheximide-chase analysis. ResultsUSP22 expression was positively correlated with DDP resistance in TNBC patients and cells. The proliferation, spheroid number, CD44+/CD24- cells, the expression of stemness genes and EMT-related markers in TNBC cells were significantly elevated after USP22 was overexpressed; however, these parameters in DDP-resistant TNBC (TNBC/DDP) cells were significantly reduced after silencing USP22. USP22 overexpression enhanced the extracellular acidification rate, proliferation, spheroid number, CD44+/CD24- cell number, and the expression of stemness genes and EMT-related markers in TNBC/DDP cells, while these effects were restrained by glycolysis inhibitors. Mechanically, USP22 interacted with c-Myc to promote its stabilization by deubiquitination in TNBC cells. Silencing of USP22 increased DDP sensitivity and survival of mice bearing TNBC. ConclusionUSP22 contributes to chemoresistance, stemness, and EMT phenotype of TNBC cells by suppressing the glycolysis via c-Myc deubiquitination.