目的·检测Fas相关死亡结构域蛋白（Fas-associated protein with death domain，FADD）在头颈部鳞状细胞癌（head and neck squamous cell carcinoma，HNSCC）中的表达水平，并探究FADD促进HNSCC细胞增殖的分子机制。方法·利用GEPIA 2数据库分析肿瘤组织中FADD表达水平及其与预后的关系；通过对HNSCC组织进行免疫组织化学染色（immunohistochemistry staining，IHC），探究FADD在正常、不典型增生和肿瘤组织中的表达水平变化；构建稳定低表达FADD的人HNSCC Fadu、HSC3细胞株，并通过蛋白印迹实验和实时荧光定量PCR（quantitative real-time PCR，qRT-PCR）方法进行验证；使用LiveCyte活细胞追踪系统、克隆形成、细胞活力检测等方法探究FADD对HNSCC细胞增殖水平的调控作用；使用免疫共沉淀串联质谱（co-immunoprecipitation mass spectrum，Co-IP/MS）鉴定与FADD发生相互作用的蛋白，并应用CRISPR/Cas9技术、LiveCyte活细胞追踪系统、蛋白印迹实验等方法对与FADD相互作用的蛋白进行进一步机制研究。结果·数据库分析显示FADD在头颈鳞癌中显著高表达，并与患者不良预后相关。免疫组化染色表明FADD在HNSCC患者正常组织、不典型增生及肿瘤组织中的表达水平呈现递增趋势。在HNSCC细胞中敲低FADD后，与对照组相比，细胞的增殖能力显著降低，形成克隆数减少。Co-IP/MS结果显示，FADD与CUT样同源盒1（CUT-like homeobox 1，CUX1）蛋白存在相互作用，敲低FADD后CUX1表达水平升高。同时，在HNSCC细胞中敲除CUX1能够显著促进肿瘤细胞增殖能力。敲除CUX1可部分逆转FADD低表达引起的增殖抑制。结论·FADD在HNSCC中具有显著促癌作用，并与不良预后相关。FADD可通过与CUX1发生相互作用降低其表达水平进一步调控肿瘤细胞的增殖能力。

Objective ·To detect the expression level of Fas-associated protein with death domain (FADD) in head and neck squamous cell carcinoma (HNSCC) and to explore the molecular mechanisms by which FADD promotes the proliferation of HNSCC cells. Methods ·The GEPIA 2 database was utilized to analyze the expression level of FADD in tumor tissues and to evaluate its association with prognosis. Immunohistochemistry staining (IHC) was performed on HNSCC tissues to investigate the changes in FADDexpression levels in normal, dysplastic, and tumor tissues. Stable FADD-knockdown Fadu and HSC3 cell lines were constructed and validated using Western blotting and quantitative real-time PCR (qRT-PCR). The regulatory effect of FADD on the proliferation of HNSCC cells was explored using the LiveCyte live-cell tracking system, colony formation assay, and cell viability assay. Proteins interacting with FADD were identified by co-immunoprecipitation mass spectrometry (Co-IP/MS), and further mechanistic studies were conducted using CRISPR/Cas9 technology, LiveCyte live-cell tracking system, and Western blotting. Results ·Analysis of the GEPIA2 database indicated that FADD was significantly overexpressed in head and neck cancer and was associated with poor prognosis. IHC staining showed that FADD expression levels progressively increased from normal to dysplastic to tumor tissues in HNSCC patients. Knockdown of FADD in HNSCC cells resulted in significantly reduced proliferation and colony formation compared to the control group. Co-IP/MS results showed that FADD interacted with the CUX1 protein, and FADD knockdown led to increased CUX1 expression. Moreover, CUX1 knockdown significantly promoted HNSCC cell proliferation and reversed the anti-proliferative phenotype caused by FADD knockdown. Conclusion ·FADD plays a significant pro-carcinogenic role in HNSCC and is associated with poor prognosis. FADD can further regulate tumor cell proliferation by interacting with CUX1 and suppressing its expression level.