Bioinformatics analysis of C3 in brain low-grade gliomas as potential therapeutic target and promoting immune cell infiltration.

Low-grade gliomas is the malignant nervous tumor with distinct biological and clinical characteristics. Despite advances in diagnostic and therapeutic methods, how to significantly elongate the survival of low-grade gliomas is still challengeable. Complement 3, as the critical component in the innate immune system, plays an essential role in local immune response and participating into regulation of the epithelial-mesenchymal transition and tumor microenvironment. In this study, we systematically determined the expression levels and immunological roles of C3 in low-grade gliomas using various public databases. Then, we further identified the impact of C3 expression on immune cell infiltration compared to normal tissue, indicating the effect of cellular microenvironment on overall survival of LGG patients. We obtained clinical characteristics, transcriptome, and survival of C3 in LGG from the TCGA, GEPIA2.0, and cBioportal databases. Two differentially expressed genes (DEGs) were obtained, DEGs compared to normal tissue (DEG_G1) and DEGs between C3 high expression and C3 low expression in LGG patients (DEG_G2). By performing the GO analysis and protein-protein interaction (PPI) network of DEG_G1, we have identified the top-ranked 10 hub genes, which are highly associated with regulation of cell cycle. The gene set enrichment analysis demonstrated that overexpression of C3 in LGG patient is positively correlated with regulation of cell cycle. The relative PPI analysis and GSEA of DEG_G2 were performed and analysis results indicated that higher expression of C3 in the LGG can activate immune-related pathways. Finally, immune cell infiltration analysis of C3 in the LGG patients was employed and clearly indicated that higher neutrophil infiltration can worsen the survival of the LGG patients with higher expression of C3. These results were confirmed by the Human Protein Atlas database, in which expression level of C3 protein in gliomas patients always higher. This investigation implied that C3 can be as diagnostic biomarker and potential targets of precise therapy for the LGG patients.