NaCl enhances CD8 T cell effector functions in cancer immunotherapy.

CD8 T cells control tumors but inevitably become dysfunctional in the tumor microenvironment. Here, we show that sodium chloride (NaCl) counteracts T cell dysfunction to promote cancer regression. NaCl supplementation during CD8 T cell culture induced effector differentiation, IFN-γ production and cytotoxicity while maintaining the gene networks responsible for stem-like plasticity. Accordingly, adoptive transfer of tumor-specific T cells resulted in superior anti-tumor immunity in a humanized mouse model. In mice, a high-salt diet reduced the growth of experimental tumors in a CD8 T cell-dependent manner by inhibiting terminal differentiation and enhancing the effector potency of CD8 T cells. Mechanistically, NaCl enhanced glutamine consumption, which was critical for transcriptional, epigenetic and functional reprogramming. In humans, CD8 T cells undergoing antigen recognition in tumors and predicting favorable responses to checkpoint blockade immunotherapy resembled those induced by NaCl. Thus, NaCl metabolism is a regulator of CD8 T cell effector function, with potential implications for cancer immunotherapy.