Fig. 1: NaCl is highly enriched in solid tumors.

a, Schematic presentation of intratumoral and peritumoral tissue biopsies from patients with breast cancer. b,c, Quantification of Na⁺ (b) and K⁺ (c) concentrations with ICP–OES in intratumoral and peritumoral biopsies from patients with breast cancer (n = 9; mean ± s.e.m., two-tailed, paired Student’s t-test). d, Preranked GSEA of patients with breast cancer from TCGA. Running enrichment scores and sorted positions of the 1,956 significantly upregulated genes from the NaCl signature are shown. The NaCl signature was generated by transcriptomic comparison of CD8⁺ memory T cells cultured under high versus low NaCl conditions (top 60 significantly upregulated DEGs). P, significance of the enrichment (one-tailed test for positive enrichment); n₁ and n₂, number of patients providing either solid tumor samples or healthy breast tissue samples, respectively. e, ScRNA-seq of intra- and peritumoral CD8⁺ T cells from patients with breast cancer (n = 3) (GEO accession no. GSE114727)¹¹. The module score for the transcriptomic NaCl signature obtained from DEGs on direct transcriptomic comparison of CD8⁺CD45RA⁻ T cells from high compared with low NaCl conditions, as described in d, was tested in intra- and peritumoral CD8⁺ T cells. CD8⁺ T cells were identified using marker gene expression.