A dendritic cell autophagy-neutrophil axis limits intratumoral STING immunotherapy.

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway promotes tumor immunogenicity, but intratumoral STING agonists, despite strong preclinical efficacy, have shown limited clinical efficacy. The mechanisms restricting therapeutic STING activation remain unclear. In mice, intratumoral delivery of the endogenous STING ligand cyclic guanosine monophosphate-adenosine monophosphate (GMP-AMP) (cGAMP) using viruslike particles (VLPs) preferentially activates STING in dendritic cells and primes circulating tumor-specific T cells. Using this system, we investigated mechanisms limiting effective STING-based immunotherapy. STING-induced type I interferon signaling was dispensable for cGAMP-VLP-mediated tumor control. In contrast, dendritic cell autophagy was required for generating circulating antitumor CD8 T cells and for regulating baseline neutrophil levels in lymph nodes. cGAMP-VLP overrode this regulation, inducing neutrophil accumulation in tumors and draining lymph nodes that limited efficacy. Neutrophil depletion enhanced tumor control through mechanisms involving neutrophil elastase and programmed cell death 1 ligand 1. These findings reveal that defective dendritic cell autophagy and neutrophil-mediated immunosuppression, rather than insufficient interferon signaling, hinder the effectiveness of intratumoral STING immunotherapy in preclinical mouse models.