Epithelial TLR4 Signaling Activates DUOX2 to Induce Microbiota-Driven Tumorigenesis

Area of Science:

• Gastroenterology and Immunology
• Oncology
• Microbiome Research

Background:

• Chronic colonic inflammation in inflammatory bowel disease (IBD) is a precursor to dysplasia and cancer.
• Innate immune signaling via Toll-like receptor 4 (TLR4) plays a critical role in the pathogenesis of IBD-associated neoplasia.
• The interplay between TLR4 signaling, epithelial redox activity, and the gut microbiota in colitis-associated tumors remains to be fully elucidated.

Purpose of the Study:

• To investigate the intersection of TLR4 signaling, epithelial redox activity, and the gut microbiota in the development of colitis-associated neoplasia.
• To determine the role of DUOX2 and NADPH oxidase 1 (NOX1) in TLR4-mediated epithelial reactive oxygen species production.
• To assess the impact of TLR4-shaped microbiota on tumor development in a colitis model.

Main Methods:

• Analysis of IBD and colorectal cancer datasets for TLR4, DUOX2, and NOX1 expression.
• Measurement of epithelial hydrogen peroxide (H2O2) production in murine colonic epithelial cells and colonoid cultures.
• Utilized genetically modified mouse models, including villin-TLR4 and villin-TLR4/DUOXA-knockout mice, and germ-free mice to study tumor development and microbiota influence.

Main Results:

• Epithelial TLR4 activation correlated with increased DUOX2 and NOX1 expression in IBD and colorectal cancer.
• DUOX2, dependent on TLR4 signaling, mediated epithelial H2O2 production, which was significantly elevated in villin-TLR4 mice.
• TLR4-dependent tumorigenesis necessitated the presence of DUOX2 and a specific microbiota, as demonstrated by microbiota transfer experiments.

Conclusions:

• TLR4 signaling in colitis upregulates DUOX2, leading to increased epithelial H2O2 production and promoting colitis-associated tumors.
• The gut microbiota is imprinted by the local inflammatory milieu, acquiring pathogenic properties that enhance reactive oxygen species and tumor development.
• A two-pronged therapeutic approach targeting both epithelial reactive oxygen species and the tumor-promoting microbiota is necessary to mitigate dysplasia risk in colitis patients.