Abstract
Intratumoral microbiota can affect the development and progression of many types of cancer, including gastric cancer. A better understanding of the precise mechanisms by which microbiota support gastric cancer could lead to improved therapeutic approaches. In this study, we investigated the effect of intratumoral microbiota on the tumor immune microenvironment during gastric cancer malignant progression. Analysis of human gastric cancer tissues with 16S rRNA amplicon sequencing revealed that Fusobacterium nucleatum was significantly enriched in gastric cancer tissues with lymph node metastasis and correlated with a poor prognosis. F. nucleatum infection spontaneously induced chronic gastritis and promoted gastric mucosa dysplasia in mice. Furthermore, gastric cancer cells infected with F. nucleatum showed accelerated growth in immunocompetent mice compared with immunodeficient mice. Single-cell RNA sequencing uncovered that F. nucleatum recruited tumor-associated neutrophils (TAN) to reshape the tumor immune microenvironment. Mechanistically, F. nucleatum invaded gastric cancer cells and activated IL17/NF-κB/RelB signaling, inducing TAN recruitment. F. nucleatum also stimulated TAN differentiation into the protumoral subtype and subsequent promotion of PD-L1 expression, further facilitating gastric cancer immune evasion while also enhancing the efficacy of anti-PD-L1 antibody therapy. Together, these data uncover mechanisms by which F. nucleatum affects gastric cancer immune evasion and immunotherapy efficacy, providing insights for developing effective treatment strategies. Significance: Intratumoral F. nucleatum activates NF-κB signaling to facilitate gastric cancer immune evasion by promoting tumor-associated neutrophil recruitment that sensitizes tumors to immune checkpoint blockade therapy.