Gut microbiota-driven hippuric acid hydrolysis promotes pancreatic tumorigenesis by suppressing NK cell activity

Abstract

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies, characterized by a lack of effective early detection, profoundly immunosuppressive microenvironment, and poor responsiveness to current therapies. Emerging evidence suggests that gut microbiota and their metabolites play important roles in pancreatic tumorigenesis. Glycoproteins shed from pancreatic precancerous lesions may influence the composition of the gut microbiota and their metabolites. We established a pancreatic precancerous lesion mouse model and performed integrated fecal metagenomic sequencing and non-targeted metabolomic profiling to characterize microbiota composition and metabolite alterations. Further we use plasma samples from patients, in vitro cytotoxicity assays and in vivo orthotopic pancreatic tumor models, fecal microbiota transplantation and pancreatic homogenate gavage to assess the effect of microbiota and metabolite alterations. And we conduct RNA sequencing, qPCR, ELISA, flow cytometry, molecular docking, and surface plasmon resonance to further explore its mechanisms. We identified hippuric acid as a key microbiota-derived metabolite that was significantly reduced during pancreatic tumorigenesis, which was associated with suppressed anti-tumor immunity and enhanced PDAC progression. This reduction was associated with enrichment of microbiota harboring hippurate hydrolase and correlated with poor prognosis in PDAC patients. Mechanistically, hippuric acid activated IL-21R–STAT3–TBX21 signaling axis, promoting the expression of cytotoxic effector molecules, including granzyme B and perforin, thus enhancing NK cell cytotoxicity. Molecular docking and surface plasmon resonance analyses further suggested a direct interaction between hippuric acid and IL-21R. Collectively, our study uncovers a previously unrecognized positive feedback regulatory loop involving the PDAC-gut microbiota–hippuric acid–NK cell-PDAC axis and highlights the critical role of gut microbiota and their metabolites in pancreatic tumorigenesis.