Designing dendritic cell-targeted nanovaccine for combined treatment with P-selectin inhibitor for glioblastoma

Glioblastoma (GB) is an aggressive type of cancer and the most lethal type of primary tumors in the central nervous system. The conventional treatment today includes surgery followed by chemotherapy with the cytotoxic alkylating agent Temozolomide and radiotherapy. GB is commonly classified as a “cold tumor” due to its low mutation burden, leading to an insufficient anti-tumor immune response. Consequentially, the immunosuppressive microenvironment has limited the clinical outcomes of immunotherapy in GB. Moreover, we recently showed that co-culture of GB cells with microglia, resulted in a significant increase of P-Selectin expression, an adhesion molecule normally expressed on the surface of endothelial and immune cells. Interestingly, inhibition of P-Selectin resulted in anti-tumorigenic activation of microglia, enhanced infiltration of cytotoxic T-cells and reduction of T-regulatory cells in tumor microenvironment (TME). To further sensitize the GB microenvironment to immunotherapies, we combined P-Selectin inhibitor with our dendritic cell-targeted nanovaccine (NV) system. This NV platform is decorated with mannose moieties targeting CD206 on dendritic cells, and entraps GB neoantigen to induce immune mediated anti-tumor response. The NV was fully characterized by dynamic light scattering to determine its mean average size and surface charge. In addition, the GB neoantigen entrapment efficiency was measured by fluorescamine, which revealed 60% loading. We evaluated the NV’s therapeutic effect on our unique ex vivo 3D spheroid model of GB co-cultured with splenocytes. In splenocytes isolated from GB-bearing mice treated with the NV, we observed a strong and specific cytotoxic activity against the GB spheroids. To achieve the strongest anti-tumor effect, we chose to combine the P-Selectin inhibitor (SELPi) with the NV. This approach was evaluated in vivo using our established orthotopic murine model. The combined treatment showed superiority over the single therapy decreasing tumor growth, evaluated by MRI, and prolonging survival. The combination of SELPi, which polarizes resident microglia towards pro-inflammatory activation, with the NV, which activates peripheral T-cells against the tumor, may generate a strong immune response against GB, thus providing an effective synergistic approach for managing the disease progression.