Abstract
Estrogen sulfotransferase (SULT1E1), a member of the sulfotransferase family (SULTs), is the enzyme with the strongest affinity for estrogen. Despite significant associations between SULT1E1 and the progression and prognosis of a range of diseases, its functional role and potential mechanisms in lung adenocarcinoma (LUAD) remain unclear. The objective of this study was to examine the potential of SULT1E1 as a biomarker for LUAD. The molecular characteristics, disease relevance and expression levels of SULT1E1 in different cancers were analysed using public databases. GEPIA 2, Starbase and other databases were employed to analyse the expression levels of SULT1E1 in LUAD tissues and normal lung tissues, and to investigate the correlation with clinical stages. A prognostic analysis was conducted using the KM database and the tumour database. The SULT1E1 protein interaction network was constructed using the STRING database. The LUAD dataset from TCGA was employed for the purposes of performing functional enrichment and immune infiltration analyses. Subsequently, the expression levels of SULT1E1 in LUAD cell lines, human LUAD tissues and normal tissues were detected by Western blot and other methods. The expression of SULT1E1 was further detected by immunohistochemical staining, and the correlation between the expression level of SULT1E1 and the clinical characteristics and prognosis of LUAD patients was verified. The expression of SULT1E1 in cytoplasm and nucleus was detected by cellular immunofluorescence. Significant reductions in SULT1E1 expression were observed across various tissues and cell lines of LUAD, as supported by both bioinformatics and Western blotting analyses. Analysis of gene ontology suggested that SULT1E1 potentially exerts anticarcinogenic effects by modulating protein serine/threonine kinase activity and its associated pathway. Additionally, KEGG and GSEA analyses indicated SULT1E1's involvement in drug metabolism, choline metabolism in cancer, hormone synthesis, and other relevant pathways. Examination of immune infiltration demonstrated a strong correlation between SULT1E1 expression and the presence of immune cells such as TAM and Treg. Furthermore, SULT1E1 expression levels in LUAD were found to correlate with TNM stage, histological stage, platelet count to lymphocyte count ratio (PLR), neutrophil count to lymphocyte count ratio (NLR), and systemic immune-inflammation index (SII). Low SULT1E1 expression levels were significantly associated with shorter overall survival (OS) in LUAD patients. The suppression of lung adenocarcinoma (LUAD) by SULT1E1 makes it a potential biomarker for diagnosing and predicting the prognosis of LUAD.