Identification of EXO1 as a potential biomarker associated with prognosis and tumor immune microenvironment for specific human cancers

Exonuclease 1 (EXO1) is an evolutionarily conserved exonuclease, which have function on maintaining genomic stability. Elevated expression of EXO1 has been reported in certain cancers. However, a comprehensive pan-cancer analysis of EXO1 is still lacking and its role in human cancer development remains poorly understood. This study aims to investigate the genetic alterations and expression perturbations of EXO1 and evaluate its potential clinical relevance in different cancer types. By employing powerful bioinformatics tools and utilizing data sourced from The Cancer Genome Atlas and the Genotype-Tissue Expression datasets, a comprehensive pan-cancer analysis of EXO1 was conducted, including an examination of gene expression, alterations in genetics, DNA methylation patterns, survival outcomes, clinical traits, immune features, and functional enrichment analysis. EXO1 was found to be highly expressed across 20 tumor types, including lung adenocarcinoma, lung squamous cell carcinoma, and breast invasive carcinoma. The expression levels of EXO1 are frequently associated with later clinical stages and unfavorable outcomes. Genetic alterations in EXO1 were predominantly found to be amplified in a pan-cancer context. A total of 131 missense mutations, 24 truncation mutations, 1 in-frame mutation, 6 splice site mutations, and 1 fusion mutation were identified. Interestingly, a significant co-occurrence of alterations in EXO1 with other ten gene alterations were identified. The expression of EXO1 in multiple tumors showed a significant correlation with tumor mutational burden, microsatellite instability, and genes related to immunological checkpoints. In most types of cancer, a strong correlation exists between the expression of EXO1 and the infiltration of CD4⁺ Th2 cells, memory CD4⁺ T cells, myeloid-derived suppressor cells, and common lymphoid progenitors. Analysis of 150 genes related to EXO1 demonstrate an enrichment in processes such as cell cycle regulation, DNA damage repair, and relevant signaling pathways, suggesting a possible mechanism through which EXO1 may facilitate tumor development. This study offers a deep insight into the role of EXO1 in different types of human cancers, indicating that EXO1 could act as an important prognostic biomarker and a therapeutic target for certain types of cancer.