Molecular and clinical characterization of Galectin-9 in glioma through 1,027 samples

In recent years, research on glioma immunotherapy have grown rapidly. However, the autoimmune-like side effects that are caused by blocking immunological checkpoints hinder their clinical application in gliomas currently. Galectin-9, a ligand for T-cell immunoglobulin mucin 3, has shed a new light on the treatment of malignant glioma. However, the potential mechanism of Galectin-9 is still under discussion. In this study, first, we methodically gathered 1,027 glioma patients with RNA-seq and 986 patients with survival data to explore the role and mechanism of Galectin-9 in gliomas. Second, we analyzed glioma samples from 50 patients in the Department of Neurosurgery, Tianjin Medical University General Hospital. Finally, we found that Galectin-9 was strongly upregulated in glioblastoma multiforme compared with normal brain tissues and lower-grade glioma. Patients with Galectin-9 overexpression had a significantly shorter overall survival. Moreover, the tissue microarray data displayed that the expression of Galectin-9 in the core of tumor is higher than that in the border and was correlated with the shorter survival in glioma patients. Galectin-9 is more highly expressed in the mesenchymal subtype of glioblastoma multiforme than in the other subtypes. Simultaneously, Galectin-9 was closely associated with the immune response and lymphocyte activation, especially T-cell activation. To further determine the underlying role of Galectin-9 in the immune response, we selected seven immune metagenes. Through cluster analysis and correlation analysis, we discovered that Galectin-9 was highly correlated with immune checkpoint molecules and M2 tumor-associated macrophages. In summary, Galectin-9 serves as a potential therapeutic target to treat glioblastoma multiforme.