Expressional and prognostic value of TREM1 in ovarian cancer: A comprehensive study based on bioinformatics and clinical analysis validation

<b>Background:</b> Triggering receptor expressed in myeloid cells-1 (TREM1) is an important regulator of innate and adaptive immunity, which can directly amplify an inflammatory response. Current studies have found the immunomodulatory role of TREM1 in tumor microenvironment. However, the role of TREM1 in ovarian cancer (OV) remains unclear. <b>Methods:</b> Based on TCGA and GEO database, we performed bioinformatics analysis to evaluate the expression profile of TREM1. Then, the prognostic value of TREM1 was determined through Kaplan-Meier survival analyses. GO and KEGG enrichment along with GSEA analyses were performed to identify potential biological functions of TREM1 based on the gene co-expression network. IHC and RT-qPCR on clinical samples were performed to validate our database-derived results. Additionally, ESTIMATE and CIBERSORT analyses were used to assess the correlation between TREM1 and tumor microenvironment. Finally, the expression, prognosis and immune regulation patterns of TREM1 in pan-cancer were further explored to validate the role of TREM1 as a biomarker. <b>Results:</b> The expression of TREM1 is abnormally high in OV than in normal tissues. Patients with high TREM1 expression were linked with poor overall survival (OS) and disease-free survival (DFS). Then, cox regression analysis and a nomogram indicated that TREM1 was an independent prognostic factor and proved the effective predictive performance in OV. Enrichment analysis showed that TREM1 was highly enriched in cancer-and immune-related pathways. Additionally, immune analysis revealed that TREM1 was robustly positively associated with tumor-associated macrophages (TAMs) and regulatory T cells (Tregs) infiltrating. Moreover, pan-cancer analysis showed TREM1 was closely associated with prognosis and immune-related genes expression in various types of cancer. <b>Conclusions:</b> Through a systematic and comprehensive analysis, our study revealed that TREM1 could serve as a prognostic and immunological biomarker in ovarian cancer.