Microglia/macrophages make up the largest population of
tumor-infiltrating cells. Numerous studies have demonstrated that
glioma-associated microglia/macrophages (
GAMs) could promote the malignant progression of
gliomas in various pathways. However, the primary function of
GAMs in
glioma remains inconclusive. First, by the CIBERSORT algorithm, we evaluated the content of microglia/macrophages in
glioma tissues by bioinformatic analysis of omic data from thousands of
glioma samples. Subsequently, we analyzed and confirmed the significant relationship between
GAMs and the malignant phenotype of
glioma, including survival time, IDH mutation status, and time of symptom onset. Afterward, Epithelial-Mesenchymal Transition (EMT) was identified by Gene Set Enrichment Analysis (GSEA) from numerous biological processes as the most relevant mechanism of malignant progression to
GAMs. Moreover, a series of clinical samples were detected, including normal brain and various-grade
glioma tissues. The results not only showed that
GAMs were significantly associated with
gliomas and their
malignancy but also that
GAMs were highly correlated with the degree of EMT in
gliomas. In addition, we isolated
GAMs from
glioma samples and constructed co-culture models (in vitro) to demonstrate the promotion of the EMT process in
glioma cells by
GAMs. In conclusion, our study clarified that
GAMs exert oncogenic effects with EMT in
gliomas, suggesting the possibility of
GAMs as immunotherapeutic targets.