High Regnase-1 Expression Is Associated with an Immunosuppressive Tumor Microenvironment and Aggressive Features in Glioma Patients.

Background/Objectives: Gliomas are among the most aggressive primary brain tumors in adults, characterized by profound molecular heterogeneity and poor response to conventional therapies. Immunotherapy has transformed outcomes in several cancers, yet glioma remains largely refractory, due in part to an immunosuppressive tumor microenvironment. Post-transcriptional regulation of gene expression is increasingly recognized as a key mechanism controlling immune cell function in tumors. Regnase-1, an endoribonuclease regulating the stability of inflammation- and immunity-related mRNAs, is a central modulator of immune responses; however, its role in glioma progression and immune modulation remains poorly understood. This study aimed to evaluate Regnase-1 expression in glioma and investigate its association with tumor grade, prognosis, and immune microenvironment characteristics. Methods: Regnase-1 transcript levels were evaluated by RT-PCR in tumor samples from 40 Moroccan glioma patients and validated using transcriptomic data from The Cancer Genome Atlas (TCGA, n = 672) and the Chinese Glioma Genome Atlas (CGGA, n = 959). Bioinformatic analyses and statistical assessments were performed using established pipelines. Results: Regnase-1 expression was significantly elevated in glioblastoma, IDH-wildtype tumors, and higher tumor grades, correlating with poorer overall survival, and emerging as an independent prognostic factor in the CGGA cohort. High Regnase-1 expression was associated with enrichment of pathways related to angiogenesis, hypoxia, invasion, and immune evasion. Tumors with elevated Regnase-1 showed reduced infiltration of effector immune cells (CD8+ T cells, Th1 cells) and increased presence of immunosuppressive populations, including regulatory T cells, myeloid-derived suppressor cells, and M2 macrophages. Single-cell analyses further highlighted exhausted CD8+ T cells and regulatory T cells as major populations linked to Regnase-1 expression. Notably, Regnase-1 expression also exhibited strong positive correlations with multiple inhibitory immune checkpoint pathways. Conclusions: Elevated Regnase-1 expression defines an aggressive, immunosuppressive glioma phenotype and is associated with poor prognosis, supporting its potential as a prognostic biomarker and a target for immunomodulatory strategies.