DDEL-27. Nano-therapeutic modulation of lactate transport in myeloid cells potentiates anti-tumor immunity and radiotherapy for glioblastoma

Abstract Myeloid-rich microenvironment is a hallmark of glioblastoma (GBM), the most aggressive and lethal brain malignancies in adults, leading to profound immunosuppression and therapy resistance. Metabolic dysregulation in tumor-associated myeloid cells (TAMCs) has been recognized as a key player driving immune evasion and supporting their pro-tumorigenic roles. Our single-cell RNA sequencing analysis and multiplex immunofluorescence have demonstrated high overexpression of monocarboxylate transporter 4 (MCT4), a key lactate transporter, in TAMCs in both murine and human GBMs, which may greatly contribute to TAMC-mediated GBM immunosuppression. To enable a myeloid-specific targeting of MCT4 in GBM, we have developed MCT4 nano-therapeutics using our antibody-directed immune targeting (ADIT) nano-platform. Lipid nanoparticles were surface functionalized with anti-PD-L1 antibody and encapsulated with small interfering RNA (siRNA) that targets MCT4. Our data indicated a robust and durable MCT4 inhibition, achieving over 90% gene knockdown efficiency. In vitro, MCT4 nano-therapeutics effectively targeted and reprogrammed immunosuppressive TAMCs, and restored CD8+ T cell proliferation and activation. In vivo, MCT4 nano-therapeutics through intracranial administration significantly improved the anti-glioma effectiveness of radiotherapy in CT-2A glioma-bearing C57 mice, leading to enhanced brain tumor infiltration of effector CD8+ T cells and CD103+ dendritic cells as well as much prolonged animal survival. When further combined with anti-CTLA-4 immune checkpoint therapy, over 60% of mice were cured from CT-2A glioma, and the long-term survivor animals developed anti-glioma immunological memory. Besides intracranial injections, we have also demonstrated the effectiveness of MCT4 nano-therapeutics through a systemic intranasal delivery route. These findings altogether may highlight a great potential of targeting lactate transport for modulating myeloid-mediated GBM immunosuppression and create a new immunotherapeutic approach to improve the existing standard treatments and immunotherapies for GBM.