Abstract: Background Malignant pleural effusion，a critical clinical indicator of advanced-stage malignancy and metastatic progression. The existing methods for the diagnosis of the nature of pleural effusion have defects and shortcomings，and it is impossible to timely and effectively determine the nature of pleural effusion. Metastatic lung cancer constitutes the primary etiology of malignant pleural effusion.While the roles of autophagy-related proteins Beclin-1 and LC3B- Ⅱ in lung cancer pathogenesis have been well established through multiple studies，their expression patterns and potential as diagnostic biomarkers in MPE urgently require further investigation.Objective To analyze the expression of autophagy-related proteins Beclin-1 and LC3- Ⅱ in lung cancer-associated malignant pleural effusion，and to evaluate their potential value in early clinical diagnosis Methods From May 2022 to July 2023，we performed bioinformatics analysis of Beclin-1 and LC3 using GEO，GEPIA2，and GeneMANIA databases. Pleural effusion samples were classified into malignant（n=95）and benign（n=190）groups based on ThinPrep cytologic test and clinical data. mRNA and protein expression levels of Beclin-1 and LC3- Ⅱ were quantified by RT-PCR and Western blot，respectively. LC3 puncta formation was further validated by immunofluorescence assay.Results Bioinformatics analysis confirmed the inclusion of Beclin-1 and LC3 in the differentially expressed gene profile of lung cancer.RT PCR revealed significantly higher mRNA expression levels of both Beclin-1 and LC3 in benign controls versus malignant cases（P<0.05）.Western blot analysis showed elevated Beclin-1 and LC3- Ⅱ protein abundance in benign specimens compared to malignant group（P<0.05）. Immunofluorescence microscopy identified increased FITC-labeled LC3- Ⅱ puncta in benign controls. Conclusion By analyzing the expression differences of autophagy-related proteins Beclin-1 and LC3- Ⅱ in benign pleural effusion and metastatic malignant pleural effusion of lung cancer，may facilitate early diagnosis of MPE and provide novel perspectives for differential diagnosis and targeted therapeutic strategies.

Key words: Lung neoplasms, Pleural effusion, Autophgy related proteins, Beclin-1, LC3-Ⅱ

摘要： 背景 恶性胸腔积液是肿瘤晚期以及转移的重要标志之一，现有诊断胸腔积液性质的相关方法存在缺陷与不足，无法对胸腔积液的性质进行及时有效的判断。多数恶性胸腔积液是由转移性肺癌引起，自噬成核关键蛋白Beclin-1及用于监测细胞自噬水平的LC3-Ⅱ在肺癌疾病进程中有重要作用，但在转移性胸腔积液中的应用未见相关报道，仍需进一步研究。目的 分析自噬相关蛋白Beclin-1及微管相关蛋白1轻链3-Ⅱ（MAP1LC3-Ⅱ）在肺癌转移性胸腔积液中的表达情况，探讨其在临床疾病早期诊断中的价值。方法 2022年5月—2023年7月利用GEO数据库、GEPIA2及GeneMANIA数据库分析获得Beclin-1及LC3-Ⅱ的生物信息；通过液基薄层细胞涂片并结合其临床资料对收集的胸腔积液进行分组，将其分为恶性测定组（95例）及良性对照组（190例），通过RT-PCR方法及Western Blot方法分别检测Beclin-1、LC3-Ⅱ在基因及蛋白水平表达，并利用免疫荧光试验确认LC3蛋白的表达数量。结果 生物信息学分析结果显示，Beclin-1与LC3均存在于肺癌差异表达基因数据集中，在肺癌组织与正常组织中表达具有差异性；RT-PCR结果显示Beclin-1与LC3的基因表达在良性对照组中均高于恶性测定组（P<0.05）；Western-Blot结果中Beclin-1与LC3-Ⅱ的蛋白表达在良性对照组较恶性测定组高，差异均有统计学意义（P<0.05）；此外在良性对照组中异硫氰酸荧光素标记的代表自噬体数量的LC3-Ⅱ荧光斑点较恶性测定组高。结论 通过分析自噬相关蛋白Beclin-1及LC3-Ⅱ在良性胸腔积液及肺癌转移性恶性胸腔积液中的表达差异，可用于恶性胸腔积液的早期诊断，为良恶性胸腔积液的鉴别诊断与针对性治疗提供新的视角。

关键词: 肺肿瘤, 胸腔积液, 自噬, Beclin-1, LC3-Ⅱ