The Function And Molecular Mechanism Of USP4in Apoptosis Of Head And Neck Squamous Cell Carcinoma

BackgroundHead and neck squamous cell carcinoma (HNSCC) is the most common type of cancer in the otolaryngology head and neck surgery with higher morbidity and mortality, and clarifying the mechanism of tumorigenesis and proliferation with early diagnosing and treatment is crucial for improving the therapeutic efficacy. Better understanding of molecular aberrations associated with HNSCC might identify new diagnostic and therapeutic strategies for this disease.As we all know, the tumorigenesis and proliferation of malignancy are closely related to the inhibition of apoptosis, in which the activation, ubiquitination or deubiquitination regulation of cell signaling pathway NF-κB play an important role.Apoptosis is a crucial cellular response that plays a crucial role in shaping our body during development and in regulating tissue homeostasis by eliminating unwanted cells. Tumor necrosis factor (TNF) has been known as a major mediator of apoptosis as well as inflammation and tumorigenesis and has been implicated in the pathogenesis of a wide spectrum of human diseases. Upon binding to its TNF receptor type1(TNF-R1), TNF-α can activate NF-κB signaling pathway and promote cell survival, or induce death signaling and promote apoptosis. The balance between apoptotic and proliferative outcomes could be regulated by receptor-interacting protein1(RIP1) ubiquitylation state.Ubiquitination and deubiquitination are the important protein modification system in eukaryotic cells, involved in the regulation of antigen presentation, signal transduction and other physiological processes. The change of ubiquitination and deubiquitination is closely related to the tumorigenesis and proliferation of many malignancies. Deubiquitination is catalyzed by deubiquitinating enzymes (DUBs), which are proteases that cleave ubiquitin or ubiquitin-like proteins from target proteins. As a member of USP family, ubiquitin specific protease4(USP4) has been identified to deubiquitinate K63-linked ubiquitin conjugates from TRAF2(TNF receptor-associated factor2), TRAF6(TNF receptor-associated factor6) and TAK1(transforming growth factor-β-activated kinase1) and stabilizes molecules by deubiquitinating K48-linked ubiquitination.ObjectiveThis project intend to use various cells including FaDu and HEK293cells combining with varieties of molecular techniques such as co-immunoprecipitation, Dual-Luciferase Reporter Assay, in vitro deubiquitination to analyze the USP4expression differences between HNSCC tissue and adjacent normal control tissue, to clarify whether USP4involved in TNF-α-induced apoptosis and to reveal the molecular mechanism.Methods1. Analyze the USP4expression differences between HNSCC tissues and the matched adjacent non-tumor control tissues2. Research the effect of USP4in TNF-α-induced FaDu cell line apoptosis3. Reveal the molecular mechanism of USP4regulation in TNF-α-induced apoptosisResults1. Compared with the adjacent normal control tissue, USP4expression was significantly upregulated in HNSCC tissue.2. USP4negatively regulates NF-κB activation and promote TNF-α-induced apoptosis in FaDu cells.3. USP4interacts with RIP1, deubiquitinates K63-linked ubiquitination from RIP1, and then promotes TNF-α-induced apoptosis.ConclusionsUSP4is overexpressed in head and neck squamous cell carcinoma. USP4negatively regulates RIP1-mediated NF-κB activation. USP4promotes TNF-α-induced apoptosis. USP4interacts with RIP1and deubiquitinates K63-linked ubiquitination from RIP1. USP4plays a tumor suppressor role in HNSCC and may be a potential therapeutic target for HNSCC.