This study reveals a novel mechanism by which osteopontin-positive macrophages in the hypoxic microenvironment promote malignant progression of glioma, and proposes a combination strategy in which targeting OPN enhances the therapeutic efficacy of temozolomide.
Literature Overview
The article titled 'Hypoxia-Induced Osteopontin-Positive Glioma-Associated Macrophages Facilitate Glioma Mesenchymal Transition via NF-κB Pathway Activation,' published in the journal Cancer Communications, reviews and summarizes how hypoxic conditions in the glioblastoma (GBM) microenvironment induce glioma-associated macrophages (GAMs) to express osteopontin (OPN), thereby promoting the molecular mechanisms underlying tumor cell transition toward a mesenchymal phenotype. Through integrated multi-omics analysis, functional experiments, and animal model validation, the study systematically elucidates the pro-tumorigenic role of OPN+ GAMs and their potential therapeutic value. The entire paragraph is coherent and logically structured, ending with a Chinese period.Background Knowledge
Glioblastoma (GBM) is the most common primary malignant brain tumor in adults, characterized by high heterogeneity and invasiveness, with a very poor prognosis and a median survival of approximately 15 months. Its tumor microenvironment (TME) is immunosuppressive, a major contributor to treatment resistance. Glioma-associated macrophages (GAMs) are the predominant non-tumor component in the TME and typically exhibit an M2-like phenotype, promoting tumor progression and establishing an immunosuppressive environment. Hypoxia is a hallmark of GBM and widely participates in tumor metabolic reprogramming, stem cell maintenance, angiogenesis, and therapy resistance. Previous studies have shown that hypoxia can regulate immune cell function, but its specific impact on GAMs remains incompletely understood. The mesenchymal subtype of GBM is more aggressive, associated with poorer prognosis, and often accompanied by NF-κB pathway activation. Osteopontin (OPN/SPP1) is a secreted phosphorylated glycoprotein involved in inflammation, tissue remodeling, and tumor progression, frequently overexpressed in various cancers and linked to adverse outcomes. However, whether hypoxia regulates OPN expression in GAMs and its role in GBM mesenchymal transition remains unclear. This study focuses on phenotypic changes in GAMs under hypoxic conditions, revealing an H3K4me3-WDR5-OPN-NF-κB-PD-L1 signaling axis, offering a novel intervention strategy for targeting the tumor microenvironment.
Research Methods and Experiments
The research team employed transcriptomic sequencing, single-cell RNA sequencing (scRNA-seq), and spatial transcriptomic analysis to systematically evaluate the relationship between hypoxia and GAMs. Survival analyses were performed using the TCGA and CGGA databases, calculating scores for hypoxia, GAM infiltration, and mesenchymal features. In vitro experiments utilized THP-1 and U937 monocytic cell lines, differentiated into macrophages under hypoxic (1% O₂) or normoxic conditions, and conditioned media (CM) were collected to treat glioma cells. Molecular mechanisms were validated using chromatin immunoprecipitation (ChIP), qRT-PCR, Western blot, and immunofluorescence. In vivo, orthotopic glioma models were established using GL261 and human U87-MG cells to assess the therapeutic efficacy of combining an OPN inhibitor with temozolomide (TMZ). Multiplex immunohistochemistry (mIHC) and H&E staining were used for clinical sample validation.Key Conclusions and Perspectives
Research Significance and Prospects
This study systematically reveals how the hypoxic microenvironment reprograms GAMs via epigenetic mechanisms to acquire pro-tumorigenic functions, thereby driving malignant progression of GBM. As a key effector molecule, OPN links hypoxia signaling with mesenchymal transition and immune checkpoint expression, making it a promising therapeutic target.
Targeting OPN or its upstream regulator WDR5 may reverse the immunosuppressive microenvironment and enhance chemosensitivity. Future studies could explore the potential of combining OPN inhibitors with other immunotherapies (e.g., PD-1/PD-L1 blockade). Furthermore, OPN+ GAMs may serve as biomarkers for patient stratification and treatment response prediction.
Conclusion
This study elucidates a novel mechanism by which hypoxia-induced OPN-positive glioma-associated macrophages promote glioma mesenchymal transition through NF-κB pathway activation. Hypoxia upregulates OPN expression in GAMs via WDR5-mediated H3K4me3 modification; secreted OPN acts on the CD44 receptor of tumor cells, activating NF-κB signaling, inducing PD-L1 expression, and promoting mesenchymal phenotypic transition. Functional experiments and animal models confirm that targeting OPN enhances the therapeutic efficacy of temozolomide. This study not only deepens our understanding of the interaction mechanisms between immune and tumor cells within the tumor microenvironment but also provides new theoretical foundations and potential therapeutic strategies for immune-metabolic intervention in glioblastoma. Clinical data support the association between high SPP1 expression and poor patient prognosis, highlighting its potential as a prognostic biomarker and therapeutic target. Future efforts should further explore the feasibility of targeting the OPN pathway in clinical translation, offering new insights for overcoming therapy resistance in GBM.
