[Expression of FAT1 in Lung Adenocarcinoma and Its Relationship 
with Immune Cell Infiltration].

BACKGROUND: Lung cancer is a leading cause of cancer-related deaths. Non-small cell lung cancer (NSCLC) is the most common pathological subtype, with adenocarcinoma being the predominant type. FAT atypical cadherin 1 (FAT1) is a receptor-like protein with a high frequency of mutations in lung adenocarcinoma. The protein encoded by FAT1 plays a crucial role in processes such as cell adhesion, proliferation, and differentiation. This study aims to investigate the expression of FAT1 in lung adenocarcinoma and its relationship with immune infiltration. METHODS: Gene expression levels and relevant clinical information of 513 lung adenocarcinoma samples and 397 adjacent lung samples were obtained through The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) data. The mRNA expression levels of the FAT1 gene in lung adenocarcinoma tissues were analyzed, along with its association with the prognosis of lung adenocarcinoma patients. Pathway enrichment analysis was conducted to explore the signaling pathways regulated by the FAT1 gene. Immunoblotting was used to detect the differential expression of FAT1 in lung epithelial cells and various lung cancer cell lines, while immunohistochemistry was employed to assess FAT1 expression in lung cancer and adjacent tissues. RESULTS: FAT1 gene mutations were identified in 14% of lung adenocarcinoma patients. TCGA database data revealed significantly higher FAT1 mRNA expression in lung adenocarcinoma tissues compared to adjacent lung tissues. Kaplan-Meier analysis indicated lower survival rates in lung adenocarcinoma patients with higher FAT gene expression. Pathway enrichment analysis suggested the involvement of FAT1 in tumor development pathways, and its expression was closely associated with immune cell infiltration. Immunohistochemical validation demonstrated significantly higher expression of FAT1 in cancer tissues compared to adjacent lung tissues. CONCLUSIONS: FAT1 mRNA is highly expressed in lung adenocarcinoma tissues, and elevated FAT1 mRNA expression is associated with poor prognosis in lung adenocarcinoma patients. FAT1 may serve as a potential biomarker for lung cancer.