Streptococcus anginosus–Derived Methionine Promotes Gastric Cancer Progression: Gut | July 2026

Introduction:

Streptococcus anginosus has emerged as a microbial signature associated with gastric cancer, but the mechanism linking this bacterium to tumour progression has remained unclear. This study identifies bacterially produced methionine as a key metabolite connecting S. anginosus colonisation with gastric cancer growth.

Why was this study needed?

• S. anginosus has been associated with gastric cancer risk and proposed as a screening biomarker.
• The biological mechanism by which this bacterium promotes tumour progression was unknown.
• Microbial metabolites may directly influence tumour behaviour and host metabolism.
• Understanding these pathways could identify new diagnostic and therapeutic targets.
• Functional validation was needed beyond observational microbiome associations.

Results:

• S. anginosus promoted gastric cancer progression in cellular and animal models, while patients with high bacterial abundance showed enrichment of microbial methionine-biosynthesis pathways.
• Methionine produced by S. anginosus was identified as a major tumour-promoting metabolite, and cancer tissue–derived bacterial strains reproduced this effect.
• Deletion of the bacterial metE gene impaired methionine production and reduced the tumour-promoting activity of S. anginosus, confirming a causal role for this pathway.

Clinical Impact: The findings move S. anginosus from being only a microbial marker of gastric cancer to a potential functional driver of disease. The S. anginosus–metE–methionine axis could support future microbial risk stratification and provide a target for microbiome-directed or metabolic interventions.

Bottom Line: Streptococcus anginosus may accelerate gastric cancer through metE-dependent methionine production. Targeting this bacterium or its methionine-biosynthesis pathway may offer a new strategy for gastric cancer prevention and treatment.