Systemic Delivery of an Adjuvant CXCR4-CXCL12 Signaling Inhibitor Encapsulated in Synthetic Protein Nanoparticles for Glioma Immunotherapy.

Glioblastoma (GBM) is an aggressive primary brain cancer, with a 5 year survival of ∼5%. Challenges that hamper GBM therapeutic efficacy include (i) tumor heterogeneity, (ii) treatment resistance, (iii) immunosuppressive tumor microenvironment (TME), and (iv) the blood-brain barrier (BBB). The C-X-C motif chemokine ligand-12/C-X-C motif chemokine receptor-4 (CXCL12/CXCR4) signaling pathway is activated in GBM and is associated with tumor progression. Although the CXCR4 antagonist (AMD3100) has been proposed as an attractive anti-GBM therapeutic target, it has poor pharmacokinetic properties, and unfavorable bioavailability has hampered its clinical implementation. Thus, we developed synthetic protein nanoparticles (SPNPs) coated with the transcytotic peptide iRGD (AMD3100-SPNPs) to target the CXCL2/CXCR4 pathway in GBM via systemic delivery. We showed that AMD3100-SPNPs block CXCL12/CXCR4 signaling in three mouse and human GBM cell cultures in vitro and in a GBM mouse model in vivo. This results in (i) inhibition of GBM proliferation, (ii) reduced infiltration of CXCR4+ monocytic myeloid-derived suppressor cells (M-MDSCs) into the TME, (iii) restoration of BBB integrity, and (iv) induction of immunogenic cell death (ICD), sensitizing the tumor to radiotherapy and leading to anti-GBM immunity. Additionally, we showed that combining AMD3100-SPNPs with radiation led to long-term survival, with ∼60% of GBM tumor-bearing mice remaining tumor free after rechallenging with a second GBM in the contralateral hemisphere. This was due to a sustained anti-GBM immunological memory response that prevented tumor recurrence without additional treatment. In view of the potent ICD induction and reprogrammed tumor microenvironment, this SPNP-mediated strategy has a significant clinical translation applicability.

Tumor cell membrane enveloped aluminum phosphate nanoparticles for enhanced cancer vaccination.

An ideal cancer vaccine should contain both strongly immunogenic cancer-specific antigen and potent adjuvant for stimulating robust cellular immunity which are pivotal for clearance of cancer cells. However, most of commercially available adjuvants such as aluminum phosphate gel cannot stimulate robust cellular immune response. In the current study, we reformed microscale aluminum phosphate gel adjuvant into nanoscale and fabricated CpG loaded and B16F10 tumor cell membrane coated aluminum phosphate nanoparticles (APMC). The resultant nano-vaccines showed a size of around 60 nm and a negative surface charge of -40 mV. Tumor cell membrane not only served as tumor antigens but also effectively improved the colloidal dispersion of aluminum phosphate nanoparticles. Subcutaneously injected APMC were efficiently drained to mouse lymph nodes, significantly increased co-uptake of tumor antigen and CpG by lymph node resident antigen presenting cells, promoted maturation of these cells and enhanced lysosomal antigen escape. After immunizing mice, they triggered robust cellular immunity, including potent IFN-γ+CD4+ T cells, IFN-γ+CD8+ T cells, cytotoxic T lymphocytes and cytokine excretion in spleen and lymph node cells. The elicited responses significantly suppressed tumor growth and prolonged survival of mice in both prophylactic and therapeutic melanoma models. This promising vaccine delivery system shows great potential to clinical transformation and can be further developed for personalized cancer vaccines.