Targeting the FOSL1/IKKα positive feedback loop attenuates glioblastoma malignancy via suppression of NF-κB signaling

Rationale: Glioblastoma (GBM), the most aggressive primary tumor of the central nervous system, remains clinically intractable because of marked molecular heterogeneity and persistent therapeutic resistance, underscoring the need for novel targeted interventions. Methods: Gene expression profiles from the TCGA and CGGA datasets were analyzed to identify prognostic transcription factors. Functional validation was performed using lentiviral-mediated knockdown and overexpression in GBM cell lines, followed by assays for proliferation, migration, invasion and apoptosis. Underlying molecular mechanisms were investigated using chromatin immunoprecipitation (ChIP), co-immunoprecipitation (co-IP), ubiquitination assays, and in vitro kinase assays. A nanocapsule-based siRNA delivery system was engineered and evaluated for its stability, cellular uptake, and blood-brain barrier penetration. Therapeutic efficacy was assessed in orthotopic GBM models using bioluminescence imaging, survival analysis, and histopathological examination. Results: This study identified FOS-like antigen 1 (FOSL1) as a key oncogenic driver that facilitates GBM progression through a positive feedback loop with inhibitor of nuclear factor kappa-B kinase subunit alpha (IKKα). Mechanistic studies revealed that FOSL1 enhances transcriptional upregulation of IKKα, while IKKα reciprocally stabilizes FOSL1 by suppressing its phosphorylation and subsequent ubiquitin-proteasomal degradation. Ubiquitination assays further identified ubiquitin C-terminal hydrolase L3 (UCHL3) as the principal de-ubiquitinase mediating FOSL1 stabilization through selective removal of K48-linked polyubiquitin chains. This FOSL1-driven positive feedback loop ultimately activated NF-κB signaling, resulting in enhanced invasion and malignancy of GBM. From a therapeutic standpoint, targeting the FOSL1/IKKα/UCHL3 feedback axis yielded significant attenuation of multiple malignant phenotypes of GBM using a novel nanoparticle-based siRNA delivery system (plofsome@siFOSL1), which effectively suppressed FOSL1 expression. Conclusions: The findings of this study establish a previously unrecognized FOSL1/IKKα/UCHL3 positive feedback loop as a central driver of GBM pathogenesis through activation of NF-κB signaling, providing a promising molecular target for future GBM therapeutic strategies.