Sarcosine promotes trafficking of dendritic cells and improves efficacy of anti-tumor dendritic cell vaccines via CXC chemokine family signaling

BACKGROUND: Dendritic cell (DC) vaccine efficacy is directly related to the efficiency of DC migration to the lymph node after delivery to the patient. We discovered that a naturally occurring metabolite, sarcosine, increases DC migration in human and murine cells resulting in significantly improved anti-tumor efficacy. We hypothesized that sarcosine induced cell migration was due to chemokine signaling. METHODS: DCs were harvested from the bone marrow of wild type C57BL/6 mice and electroporated with tumor messenger RNA (mRNA). Human DCs were isolated from peripheral blood mononuclear cells (PBMCs). DCs were treated with 20 mM of sarcosine. Antigen specific T cells were isolated from transgenic mice and injected intravenously into tumor bearing mice. DC vaccines were delivered via intradermal injection. In vivo migration was evaluated by flow cytometry and immunofluorescence microscopy. Gene expression in RNA was investigated in DCs via RT-PCR and Nanostring. RESULTS: Sarcosine significantly increased human and murine DC migration in vitro. In vivo sarcosine-treated DCs had significantly increased migration to both the lymph nodes and spleens after intradermal delivery in mice. Sarcosine-treated DC vaccines resulted in significantly improved tumor control in a B16F10-OVA tumor flank model and improved survival in an intracranial GL261-gp100 glioma model. Gene expression demonstrated an upregulation of CXCR2, CXCL3 and CXCL1 in sarcosine- treated DCs. Further metabolic analysis demonstrated the up-regulation of cyclooxygenase-1 and Pik3cg. Sarcosine induced migration was abrogated by adding the CXCR2 neutralizing antibody in both human and murine DCs. CXCR2 neutralizing antibody also removed the survival benefit of sarcosine-treated DCs in the tumor models. CONCLUSION: Sarcosine increases the migration of murine and human DCs via the CXC chemokine pathway. This platform can be utilized to improve existing DC vaccine strategies.