Effects of Combining Immune-Priming Sub-Lethal Low-Dose Radiation with 4-1BB Activation and Gal-3 Blockade in In Vitro and Preclinical Group-3 Medulloblastoma Models
- Cancers (Basel). 2026 Jun 10;18(12):1890. doi: 10.3390/cancers18121890.
- 1. Department of Neurosurgery, Medical University of South Carolina, Charleston, SC 29425, USA.
- 2. Department of Radiation Oncology, Medical University of South Carolina, Charleston, SC 29425, USA.
- 3. Department of Neurosurgery, Endeavor Health, Evanston, IL 60201, USA.
- 4. Pritzker School of Medicine, University of Chicago, Chicago, IL 60637, USA.
- 5. Department of Medicine/Hematology-Oncology, UMass Memorial Health, Worcester, MA 01605, USA.
- 6. Department of Pediatric Neurosurgery, Medical University of South Carolina, Charleston, SC 29406, USA.
Background/objectives: Pediatric group 3 (G3) medulloblastomas (MB) are therapy resistant and have a significantly worse prognosis than the Other MB subtypes. Aggressive radiation/chemotherapy improves survival, but potential long-term comorbidities include neurocognitive deficits. In previous work, we demonstrated that low-dose X-ray radiation (LDXR) acts as an immunological Adjuvant. Recent studies have demonstrated that Galectin-3 (Gal-3) expression in MB tumors accelerates M2 macrophage infiltration and restricts T cell receptor (TCR)-mediated signaling. Immunotherapy with an agonistic anti-4-1BB monoclonal antibody (mAb) activates CD8+ T cells, promoting their survival and acquisition of potent cytolytic properties. Building on these findings, we hypothesized that immune priming via sublethal LDXR, combined with a Gal-3 inhibitor and an anti-4-1BB mAb, would boost anti-tumor effects, resulting in survival benefits.
Methods: We tested this hypothesis in vitro in co-cultures of human MB cells and in vivo, in an immunocompetent G3MB mouse model (MP1). Treatment effects were assessed using Western blot, flow cytometry, hematoxylin and eosin (H&E) staining, immunofluorescence imaging, and analysis of cytokine and chemokine expression.
Results: Our data demonstrated higher Gal-3 expression in MB patient-derived tumor tissue than in non-tumor tissue. LDXR modulated major histocompatibility complex molecules, and, combined with a Gal-3 inhibitor and an anti-4-1BB mAb, altered T-cell/tumor-cell interactions, enhanced T-cell-mediated MB cell death, and shifted cytokine production to drive microglial polarization toward the M1 subtype. Furthermore, H&E-stained tumor sections showed a ~70% reduction in tumor size compared with untreated controls.
Conclusions: These preclinical findings suggest that combining immune priming with sublethal LDXR, Gal-3 inhibition, and 4-1BB activation may be an effective treatment strategy for G3MB.