Potent Anti-Glioblastoma Effects of Next-Generation MNK Inhibitors

Background/Objectives: Glioblastoma (GBM) remains one of the most aggressive and treatment-resistant malignancies, driven in part by heterogeneous, therapy-resistant glioma stem cells (GSCs). Improving clinical outcomes will require innovative therapeutic approaches that target unique molecular vulnerabilities. The mitogen-activated protein kinase (MAPK) pathway drives tumor progression across multiple cancers, including GBM. MAPK-interacting kinases (MNK1/2) represent MAPK downstream effectors that phosphorylate eukaryotic translation initiation factor 4E (eIF4E), a regulator of oncogenic and anti-apoptotic mRNA translation. We previously identified pharmacological MNK inhibition as a promising therapeutic strategy for GBM, but most available MNK inhibitors lack specificity. Methods: Novel MNK inhibitor compounds were developed using medicinal chemistry optimization and evaluated through molecular docking and kinome profiling analyses. Antineoplastic activity was assessed in established GBM cell lines and patient-derived glioma stem cell models cultured as 3-D neurospheres under stem cell-permissive conditions. Effects on MNK signaling, cell viability, neurosphere growth, migration, invasion, and apoptosis were analyzed using immunoblotting, flow cytometry, viability assays, wound healing assays, and 3-D invasion assays. In addition, a compound screen was performed to identify therapeutic agents that enhance MNK-targeted therapy, followed by validation using pharmacological inhibition and siRNA-mediated knockdown approaches. Results: Our next-generation MNK inhibitor NUCC-201893 exhibited high target specificity and greater potency than the lead compound NU808, effectively suppressing eIF4E phosphorylation, GBM cell viability, neurosphere growth, migration, and invasion. Compound screening identified DNA methyltransferase (DNMT) inhibition as a potent enhancer of MNK blockade. Pharmacological DNMT inhibition enhanced the cytotoxic effects of siRNA-mediated MNK1 knockdown, while concurrent pharmacological inhibition of MNKs and DNMT resulted in greater suppression of neurosphere growth and robust induction of apoptotic responses in GSCs. Conclusions: These findings identify dual MNK and DNMT inhibition as a promising combinatorial strategy that effectively triggers antineoplastic effects in GBM cells and GSCs.