T cell cancer therapy requires CD40-CD40L activation of TNF-iNOS-producing dendritic cells

The effectiveness of new cancer therapies such as checkpoint blockade and adoptive cell transfer of activated anti-tumor T cells requires overcoming immunosuppressive tumor microenvironments. We found that the activation of tumor-infiltrating myeloid cells to produce local nitric oxide is a prerequisite for adoptively transferred CD8+ cytotoxic T cells to destroy tumors. These myeloid cells are phenotypically similar to Tip-DCs or nitric oxide- and TNF-producing dendritic cells. The nitric oxide-dependent killing was tempered by coincident arginase 1 expression, which competes with iNOS for arginine, the substrate for nitric oxide production. Depletion of immunosuppressive CSF-1R-dependent arginase 1+ myeloid cells enhanced nitric oxide-dependent tumor killing. Tumor killing via iNOS was independent of the microbiota but dependent on the CD40-CD40L pathway and, in part, lymphotoxin alpha. We extended our findings in mice to uncover a strong correlation between iNOS, CD40 and TNF expression and survival in colorectal cancer patients. Our results identify a network of anti-tumor targets to boost the efficacy of cancer immunotherapies.

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Marigo I, Zilio S, Desantis G, Mlecnik B, Agnellini AHR, Ugel S, Sasso MS, Qualls JE, Kratochvill F, Zanovello P, Molon B, Ries CH, Runza V, Hoves S, Bilocq AM, Bindea G, Mazza EMC, Bicciato S, Galon J, Murray PJ, Bronte V