Tumor-suppressive role of miR-216b impacts cell cycle regulation in high-grade glioma

High-grade gliomas (HGGs) are the most aggressive adult brain tumors, with a dismal median survival of approximately 15 months, highlighting the need for novel therapeutic strategies. In a prior immunotherapy trial using dendritic cells against glioblastoma, miR-216b emerged as a potential predictive biomarker. Thus, we hypothesize that miR-216b impacts glioma aggressiveness and thereby therapeutic success. Here, we demonstrate that miR-216b is significantly downregulated in the majority of Isocitrate dehydrogenase 1/2 (IDH) wild-type HGG tissue samples (n = 42) and cell models (n = 18). Functional assays revealed that miR-216b overexpression impairs glioma cell proliferation, migration, and stemness characteristics. Transcriptomic and target prediction analyses identified CDK4, a key cell cycle regulator, as a direct target of miR-216b, confirmed via luciferase reporter assays. Correspondingly, upregulating miR-216b (mimic) via transfection decreased CDK4 mRNA and protein levels accompanied by a p21-dependent increase of cells in G0/G1 phase. In addition, miR-216b expression correlated with increased sensitivity to the CDK4/6 inhibitor Abemaciclib. Notably, miR-216b levels were significantly higher in less aggressive IDH-mutant gliomas (n = 21), linking its downregulation to malignancy grade. Collectively, our findings discovered miR-216b as a tumor suppressor in HGGs, modulating CDK4 expression and affecting the responsiveness to CDK4/6 inhibitors. The observed results support the potential of miR-216b as both a prognostic and predictive indicator in HGGs.