SYN1 is associated with immune infiltrates and might be a prognostic biomarker for glioma

Background: Conventional treatments for glioma patients are not curative, and patient survival remains limited. Therefore, it is crucial to explore additional potent prognostic biomarkers for gliomas. SYN1, a member of the synapsin gene family, has been implicated in various neuropsychiatric illnesses. However, its role in glioma progression remains unclear. Methods: Clinical and gene expression profile data of primary tumors were obtained from TCGA database. GEPIA was used to investigate SYN1 expression and plot survival curves of the involved patients. TIMER and CIBERSORT were used to analyze the immune infiltrates and responses of 22 TIICs, respectively. Gene set enrichment analysis (GSEA) was performed to identify the potential function of SYN1 in glioma. Furthermore, we collected tissue samples from 25 glioma patients for validation analysis using quantitative real-time PCR, western blot, and immunohistochemistry. Results: 457 eligible glioma samples downloaded from TCGA (including grade II 229 cases and III 228 cases) were involved in the current study. We found SYN1 was poorly expressed in tumor tissue and higher SYN1 expression could significantly improve the survival of glioma patients. Besides, we found that age, grade, and SYN1 were independent prognostic factors for glioma patients. In addition, macrophages M2, macrophages M0, T cells CD4 memory resting, T cells follicular helper, and plasma cells are the main immune cells affected by SYN1 expression. And the expression of SYN1 was negatively correlated with infiltrating levels of B cell, CD4 + T cell, Macrophages, Neutrophil, and Dendritic cell. SYN1 could also significantly influence the cumulative survival of B cell, CD8 + T cell, CD4 + T cell, Macrophages, Neutrophil, and Dendritic cell. The GSEA results indicated that ADIPOGENESIS, G2M_CHECKPOINT, GLYCOLYSIS, KRAS_SIGNALING_DN, KRAS_SIGNALING_UP, MYC_TARGETS_V1, NOTCH_SIGNALING, P53_PATHWAY, PANCREAS_BETA_CELLS, and SPERMATOGENESIS are mainly enriched pathways between the high and low expression groups of SYN1. Further clinical validation found that the expression of SYN1 mRNA and protein was significantly downregulated in glioma tissues. Conclusion: SYN1 is found to be associated with immune infiltrates and might be a prognostic biomarker for glioma.