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

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 nonsignalling 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. Dendritic cells (DC) are myeloid cells that can be grouped, based on their ontogeny and phenotypes, into distinct subsets: conventional dendritic cells (cDC) and plasmacytoid dendritic cells, which largely arise from rare bone marrow (BM) progenitors, as well as monocytederived dendritic cells (moDC), which derive from circulating monocytes 1-4. DCs serve as primary antigen-presenting cells that capture, process, and present tumour antigens to T cells, thereby initiating and regulating adaptive immune responses essential for effective antitumour activity 4-7. Due to their critical role in modulating the adaptive immune response against tumours, DC therapies have been extensively tested in clinical trials 8-11. In the traditional DC therapy workflow, moDCs are generated from circulating monocytes, exposed to defined tumour antigens or tumour lysates ex vivo, and activated by means of adjuvants or