The Toll like receptor 4 ligand cold-inducible RNA-binding protein as vaccination platform against cancer
Tumor infiltrating lymphocytes have been associated with a better prognostic and with higher response rates in patients treated with checkpoint inhibiting antibodies, suggesting that strategies promoting tumor inflammation may enhance the efficacy of these currently available therapies. Our aim was thus to develop a new vaccination platform based on cold-inducible RNA binding protein (CIRP), an endogenous TLR4 ligand generated during inflammatory processes, and characterize whether it was amenable to combination with checkpoint inhibitors. In vitro, CIRP induced dendritic cell activation, migration and enhanced presentation of CIRP-bound antigens to T-cells. Accordingly, antigen conjugation to CIRP conferred immunogenicity, dependent on immunostimulatory and antigen-targeting capacities of CIRP. When applied in a therapeutic setting, vaccination led to CD8-dependent tumor rejection in several tumor models. Moreover, immunogenicity of this vaccination platform was enhanced not only by combination with additional adjuvants, but also with antibodies blocking PD-1/PD-L1, CTLA-4 and IL-10, immunosuppressive molecules usually present in the tumor environment and also induced by the vaccine. Therefore, priming with a CIRP-based vaccine combined with immune checkpoint-inhibiting antibodies rejected established B16-OVA tumors. Finally, equivalent activation and T-cell stimulatory effects were observed when using CIRP in vitro with human cells, suggesting that CIRP-based vaccination strategies could be a valuable clinical tool to include in combinatorial immunotherapeutic strategies in cancer patients.