Neutrophils for Cancer Immunotherapy

Abstract

Neutrophils are the most abundant leukocytes in human blood circulation and are the first responders to the site of inflammation including tumors. Tumor-Associated Neutrophils (TANs) assume a pro-tumor phenotype in the immunosuppressive tumor microenvironment, thus contributing to a worsening prognosis. However, when correctly polarized, activated neutrophils possess the ability to exert anti-tumor effector function in a variety of ways. The traditional ways of activating neutrophils include biochemical stimuli such as pathogen or damage assisted molecular patterns, proinflammatory cytokines and antibodies. Such biochemically activated neutrophils may assume a pro-tumor phenotype due their phenotypic plasticity upon encountering the immunosuppressive tumor microenvironment without continuous stimulation.

In my dissertation research, I report a material-based approach for activating neutrophils and thereby polarizing them towards the antitumor phenotype ex vivo and maintain this phenotype in vivo via continuous stimulation. I designed polymer micro-patches, termed ‘Cyto-Adhesive Micro-Platforms (CAMPs),’ that adhere to the surface of neutrophils without internalization due to their discoidal geometry. Attachment of CAMPs activated the anti-tumor phenotype of neutrophils as indicated by increased expression of N1 neutrophil-related genes, upregulation of N1 biomarkers (CD95 and CD54) and the release of TNF⍺ and myeloperoxidase (MPO). Intravenously administered neutrophil-CAMPs accumulated in the spleen and tumor-draining lymph nodes and activated splenic Natural Killer (NK) and T cells and subsequently increased accumulation of dendritic cells and NK cells in the lymph nodes. Intravenous injection of CAMPloaded neutrophils in 4T1-Luc and B16F10 tumor-bearing mice resulted in a robust systemic immune response, leading to a reduction in tumor burden, and subsequent improvement in survival rate. The combination of CAMP-activated neutrophils with anti-CTLA-4 checkpoint inhibitor antibody led to strong tumor-growth inhibition of B16F10 tumors, with complete regression achieved in 33.3% of treated mice. CAMP-loaded neutrophils represent a potent, scalable, and drug-free approach for neutrophil-based solid tumor immunotherapy.