Lipid-Metabolically Active TREM2high Microglia‑Derived Macrophages Predict Poor Prognosis and Represent an Immunotherapeutic Target in Glioma.

Gliomas are the most common primary brain tumors and characterized by poor prognosis and heavy infiltration of tumor-associated macrophages. Triggering receptor expressed on myeloid cells-2 (TREM2), known to modulate macrophage function, has shown conflicting roles in glioma pathology. In this study, we comprehensively investigated the expression, function, and clinical relevance of TREM2 in gliomas using public datasets, single-cell RNA sequencing (scRNA-seq) analysis, and multiplex immunofluorescence. scRNA-seq identified a distinct subset of microglia-derived macrophages with high TREM2 expression that exhibit a dual phenotype of immunosuppression and enhanced lipid metabolism. These cells show enrichment of genes involved in fatty acid metabolism and lipoprotein clearance, including significant upregulation of apolipoprotein E (APOE), a known TREM2 ligand. Clinically, high TREM2 expression in microglia-derived macrophages correlates with increased tumor grade, recurrence, and shorter overall and disease-free survival. In contrast, APOE expression was correlated with better survival in public datasets, though not significantly in our patient cohort. Our findings suggest that TREM2^high microglia-derived macrophages constitute a pro-tumorigenic subpopulation within the glioma microenvironment and may serve as a robust prognostic marker. The interplay between TREM2 and APOE further underscores the immunometabolic complexity of gliomas and points to TREM2 as a promising target for therapeutic intervention.