Dendritic cell progenitors engineered to express extracellular-vesicle–internalizing receptors enhance cancer immunotherapy in mouse models

Abstract

Cancer immunotherapy using dendritic cells (DC) pulsed ex vivo with tumour antigens is considered safe, but its clinical efficacy is generally modest. Here we engineer DC progenitors (DCP), which can replenish conventional type 1 DCs (cDC1) in mice, to constitutively express IL-12 together with a non-signalling chimeric receptor, termed extracellular vesicle-internalizing receptor (EVIR). By binding to a bait molecule (GD2 disialoganglioside) expressed on cancer cells and their EVs, the EVIR enforces EV internalization by cDC1 to promote their cross-dressing with preformed, tumour-derived MHCI-peptide complexes. Upon systemic deployment to mice, the engineered DCPs cause only mild and transient elevation of liver enzymes, acquire tumour-derived material, engage tumour-specific T cells, and enhance the efficacy of PD-1 blockade in an immunotherapy-resistant melanoma model comprising both GD2-positive and -negative cancer cells, without the need for ex vivo antigen pulsing. These results indicate that EVIR-engineered DCPs may avert the positive selection of antigen-negative cancer cells, potentially addressing a critical limitation of immunotherapies targeting defined tumour antigens. Tumour-antigen-pulsed mature dendritic cells (DC) have not been as efficient for cancer therapy as hoped to be, due to their sub-optimal antigen-presentation and migration capacities. Here the authors utilise DC progenitors, constitutively expressing IL-12 and an engineered extracellular vesicle-internalizing receptor (EVIR), which give rise to mature conventional type 1 DCs with improved antigen presenting capacities, resulting in improved anti-tumour immunity in a mouse model of melanoma.