NOD2 Promotes Glioblastoma Progression Through Effects on Epithelial-Mesenchymal Transition and Cancer Stemness

Background: Glioblastoma multiforme (GBM) represents one of the most aggressive and lethal primary brain malignancies, characterized by rapid proliferation, extensive invasiveness, and a dismal prognosis. Emerging evidence implicates nucleotide-binding oligomerization domain-containing protein 2 (NOD2), an intracellular pattern recognition receptor, as a potential driver of GBM progression. This study investigates NOD2's role in promoting glioblastoma through its effects on the epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) markers. Methods: NOD2 expression levels and survival outcomes were assessed using TCGA data from GBM tumor samples (n = 153) and normal brain tissues (n = 5). NOD2 protein expression was validated in glioma cell lines using Western blot and immunofluorescence analyses. Functional studies employed siRNA-mediated NOD2 knockdown to evaluate effects on cellular proliferation, migration, invasion, and colony formation, while correlations between NOD2 and EMT/CSC markers were assessed. Results: The analysis of TCGA data revealed a significantly elevated NOD2 expression in GBM tumors compared to normal brain tissue, with a high NOD2 expression correlating with a reduced disease-free survival in GBM patients. All tested glioma cell lines demonstrated robust NOD2 expression. Functional analyses demonstrated that NOD2 depletion substantially impaired cellular proliferation, migration, invasion, and the colony-forming capacity. Mechanistically, siRNA-mediated NOD2 knockdown significantly decreased the expression of EMT (Snail, SLUG, Vimentin) and CSC markers (CD44, CD133) at both protein and mRNA levels. Conclusions: Our results indicate that NOD2 contributes to GBM progression by influencing EMT and CSC pathways. These findings suggest NOD2's potential as a therapeutic target in glioblastoma, highlighting the need for further mechanistic studies and therapeutic exploration.