Background: There is a growing recognition that tumor-associated macrophages (TAMs) are recruited to the glioma environment, facilitating tumor proliferation and migration by creating an immunosuppressive microenvironment. CD68 has been widely reported as a specific marker of TAMs in cancer. 
Purpose: To clarify the role of CD68 in glioma, we investigated its function at the transcriptome level and relationship with clinical practice. 
Patients and methods: In total, 325 RNA-seq data from Chinese Glioma Genome Atlas (CGGA) and 697 RNA-seq data from The Cancer Genome Atlas (TCGA) network were enrolled in this study. CD68-specific findings were further analyzed with R language, and the prognostic impacts were validated through analyzing the overall survival (OS). 
Results: CD68 showed a positive correlation with the WHO grade of malignancy in glioma. Meanwhile, CD68 was predominantly expressed in IDH wide type and mesenchymal subtype. Gene ontology (GO) analysis revealed that CD68-related genes were closely related to inflammatory response and immune response. Moreover, seven cultures of metagenes further confirmed that CD68 was a specific marker for macrophages in inflammatory response and played an important role in suppressing T-cell-mediated immunity. The Pearson correlation test suggested that CD68 showed robust correlation with other markers of macrophages and immune checkpoints, including PD-1 and TIM-3. Clinically, a high expression level of CD68 in tumors exhibited a poor survival in glioma patients. 
Conclusion: Our results demonstrated that CD68 acted as an immune suppressor and contributed to glioma progression in the tumor microenvironment. These findings may expand our understanding of CD68-specific clinical and immune features in glioma.
Keywords: CD68, tumor-associated macrophage, glioma, immunotherapy