Coordinate tumor-antigen uptake and dendritic cell activation by chimeric antigen receptors. [RNA-seq]

Effective anti-tumor immunity requires dendritic cells (DCs) to internalize, process and present tumor antigens to T cells. Adoptive transfer of DCs loaded ex vivo with tumor antigens has been shown to stimulate anti-tumor immunity in patients with cancer, but clinical responses have been mixed. To address limitations of traditional DC-based therapies, we constructed and functionally screened a panel of chimeric antigen receptors (CARs) optimized for expression and activity in DCs. Through this screening, we identified key functional components that informed the design of an inducible platform centered on an instructive chimeric antigen receptor (iCAR). This platform enables the DCs to (i) recognize a surface molecule present on cancer cells or their extracellular vesicles (EVs), such as GD2 and HER2, thereby promoting the acquisition of tumor-derived material that contains putative tumor antigens; (ii) undergo immunostimulatory activation to prime antigen-specific T cells via both cross-dressing and cross-presentation; and (iii) transactivate the expression of a therapeutic gene (IL-12) in response to antigen uptake. The iCAR converted melanoma-derived EVs from immune-suppressive to stimulatory cues for DCs. Moreover, systemic administration of iCAR-DCs enhanced antigen-specific T cells, expanded low-frequency T cell clonotypes, and delayed tumor growth in immunotherapy-resistant melanoma models without the need for ex vivo antigen loading or cell maturation. iCAR-DCs provide a platform for antigen-agnostic cancer immunotherapy that integrates antigen uptake with programmable DC activation.