Ubiquitin-specific Peptidase 53 Suppresses Head/Neck Tumorigenesis by Stabilizing FBXW7

Background/Aim: Head and neck squamous cell carcinoma (HNSC) remains a cancer with a poor prognosis despite treatment options of surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy. Novel targets and therapeutics await identification. The aim of this study was to identify such targets and therapeutics using a prognosis-based approach and validate them experimentally. Materials and Methods: UALCAN, cBioPortal, Reactome, L2S2, and TIMER3 were used to study the prognosis, gene expression, pathways, therapeutics, and immunity of HNSC, respectively. Ubiquitin-specific peptidase 53 (USP53) was among the top prognostic factors in HNSC based on the UALCAN analysis. The FaDu human HNSC cell line, which exhibits high USP53 expression, was used in the subsequent experiments. Cell proliferation, cell cycle, sphere formation, and proximity ligation assays were performed. Results: USP53 was found to be downregulated in HNSC and predicted a better prognosis. The pathway and therapeutic analyses revealed that USP53-low HNSC was enriched in cell-cycle dysregulation and could be mimicked by a cyclin-dependent kinase inhibitor (CDKi). In vitro, USP53 knockdown increased HNSC proliferation and sensitivity to CDKi in two- and three-dimensional assays. Multiomic analyses revealed that USP53 may deubiquitinate F-box and WD repeat domain–containing 7 (FBXW7) and subsequently suppress HNSC proliferation. This was verified using a proximity ligation assay (PLA). Lastly, USP53 is negatively associated with M2 macrophages. Conclusion: USP53 functions as a critical tumor suppressor in HNSC by post-translationally stabilizing the E3 ubiquitin ligase FBXW7. This molecular mechanism establishes a targetable cell-cycle vulnerability sensitive to cyclin-dependent kinase inhibitors and uncovers a direct connection between deubiquitinase activity and tumor immune cell infiltration.