Objective This study aimed to explore the expression pattern of transmembrane protein 33(TMEM33)in lung adenocarcinoma and its correlation with clinical pathological features.Methods Bioinformatics tools and public databases(e.g.,TCGA and GEO)were used to analyze TMEM33 expression data in lung cancer.Then,immunoblotting and real-time quantitative PCR were performed to detect TMEM33 protein and mRNA levels in four cell lines.Immunofluorescence and immunohistochemistry were also used to assess TMEM33 expression and localization in lung adenocarcinoma and normal lung tissue samples.Results Bioinformatics analysis revealed higher TMEM33 expression in lung adenocarcinoma than in normal lung tissue(P＜0.05)and a significant correlation between TMEM33 and SLC30A9 expression(P＜0.0001).Logistic regression analysis indicated an association between TMEM33 expression and tumor T stage(OR=0.48,P=0.044).Experimental results showed higher TMEM33 protein(P＜0.01)and mRNA(P＜0.001)levels in lung adenocarcinoma cell lines than in normal lung epithelial cells.Similarly,TMEM33 protein(P＜0.05)and mRNA(P＜0.01)levels were higher in lung adenocarcinoma tissues than in adjacent tissues.Immunohistochemistry confirmed high TMEM33 expression in lung adenocarcinoma tissues.Conclusion TMEM33 is highly expressed in lung adenocarcinoma,associated with malignancy and T stage,and may be a potential prognostic and therapeutic target.