Simultaneous blocking of CD47 and PD-L1 increases innate and adaptive cancer immune responses and cytokine release

Background: Treatment multiple tumors by immune therapy can be achieved by mobilizing both innate and adaptive immunity. The programmed death ligand 1 (PD-L1; or CD274, B7-H1)is a critical “don't find me” signal to the adaptive immune system. Equally CD47 is a critical “don't eat me” signal to the innate immune system and a regulator of the adaptive immune response. Method: Both of CD47 and PD-L1 are overexpressed on the surface of cancer cells to enable to escape immune-surveillance. We designed EpCAM (epithelial cell adhesion molecule)-targeted cationic liposome (LPP-P4-Ep)containing si-CD47 and si-PD-L1 could target high-EpCAM cancer cells and knockdown both CD47 and PD-L1 proteins. Findings: Efficient silencing of CD47 and PD-L1 versus single gene silencing in vivo by systemic administration of LPP-P4-Ep could significantly inhibited the growth of solid tumors in subcutaneous and reduced lung metastasis in lung metastasis model. Target delivery of the complexes LPP-P4-Ep increased anti-tumor T cell and NK cell response, and release various cytokines including IFN-γ and IL-6 in vivo and in vitro. Interpretation: This multi-nanoparticles showed significantly high-EpCAM tumor targeting and lower toxicity, and enhanced immune therapeutic efficacy. Our data indicated that dual-blockade tumor cell-specific innate and adaptive checkpoints represents an improved strategy for tumor immunotherapy. Fund: This research supported by the Ministry of Science and Technology of the People's Republic of China (grant number 2015CB931804); the National Natural Science Foundation of China (NSFC, grant numbers 81703555, U1505225 and 81773063), and the China Postdoctoral Science Foundation (grant number 2017 M620268).