Fig. 8: Dietary methionine supplementation activates T cells and suppresses tumour progression in immunocompetent mice.

a, Dietary methionine supplementation reduced the abundance of circulating T cells (n = 11 mice on 1.3% diet and 9 mice on 0.4% diet, two-tailed unpaired Student’s t-test). b, Dietary methionine supplementation increased the abundance and fraction of activated CD8⁺ T cells (n = 11 mice on 1.3% diet and 9 mice on 0.4% diet, two-tailed unpaired Student’s t-test). c, Dietary methionine supplementation reduced exhaustion of circulating CD4⁺ T cells in C57BL/6J mice (n = 11 mice on 1.3% diet and 9 mice on 0.4% diet, two-tailed unpaired Student’s t-test). d, Dietary methionine supplementation increases the expression of microbial l-cysteine desulfhydrase (lcd) gene in faeces (n = 5 mice per group, box-and-whiskers plot, whiskers indicate minimum to maximum values, corrected using the Benjamini–Hochberg method for the false discovery rate). e, Dietary methionine supplementation increased the expression of key sulfur metabolic genes in faeces (n = 10 mice per group, from an independent experimental cohort, multiple Student’s t-tests). f, Dietary methionine supplementation inhibited tumour growth in Apc^min+/− mice (n = 11 mice on 1.3% diet and 28 mice on 0.4% diet, two-tailed unpaired Student’s t-test). g, Dietary methionine supplementation increased blood T cell fractions in Apc^min+/− mice (n = 5 mice per group, two-tailed unpaired Student’s t-test). h, Dietary methionine supplementation increased survival of Apc^min+/− mice (n = 9 mice on a 0.4% diet and 6 mice on a 1.3% diet. Log-rank test). i, Dietary methionine supplementation repressed tumour growth in immunocompetent mice but enhanced tumour growth in immunodeficient mice (n = 10 tumours per group, two-tailed unpaired Student’s t-test between 1.3% versus 0.4% only). j, Dietary methionine supplementation increased blood CD8⁺CD3⁺ T cells in Balb/c mice (n = 10 mice on a 1.3% diet and 9 mice on a 0.4% diet, two-tailed unpaired Student’s t-test). k, Dietary methionine supplementation dose not significantly affected tumour growth and response to anti-PD-1 treatment in germ-free Balb/c mice (n = 8 mice/16 tumour injections per group, two-way ANOVA; one outlier in the 1.3% + anti-PD-1 group was removed). l, The impact of dietary methionine supplementation on blood T cells in germ-free Balb/c mice (n = 8 mice per group, two-way ANOVA). Values are expressed as the mean ± s.e.m., except in h. Details of statistical tests are included in Methods.

Source data