Epithelial TLR4 Signaling Activates DUOX2 to Induce Microbiota-Driven Tumorigenesis

Abstract

BACKGROUND & AIMS: Chronic colonic inflammation leads to dysplasia and cancer in patients with inflammatory bowel disease. We have described the critical role of innate immune signaling via Toll-like receptor 4 (TLR4) in the pathogenesis of dysplasia and cancer. In the current study, we interrogate the intersection of TLR4 signaling, epithelial redox activity, and the microbiota in colitisassociated neoplasia. METHODS: Inflammatory bowel disease and colorectal cancer data sets were analyzed for expression of TLR4, dual oxidase 2 (DUOX2), and NADPH oxidase 1 (NOX1). Epithelial production of hydrogen peroxide (H 2 O 2 ) was analyzed in murine colonic epithelial cells and colonoid cultures. Colorectal cancer models were carried out in villin-TLR4 mice, carrying a constitutively active form of TLR4, their littermates, and villin-TLR4 mice backcrossed to DUOXA-knockout mice. The role of the TLR4-shaped microbiota in tumor development was tested in wild-type germ-free mice. RESULTS: Activation of epithelial TLR4 was associated with up-regulation of DUOX2 and NOX1 in inflammatory bowel disease and colorectal cancer. DUOX2 was exquisitely dependent on TLR4 signaling and mediated the production of epithelial H 2 O 2 . Epithelial H 2 O 2 was significantly increased in villin-TLR4 mice; TLR4-dependent tumorigenesis required the presence of DUOX2 and a microbiota. Mucosa-associated microbiota transferred from villin-TLR4 mice to wild-type germ-free mice caused increased H 2 O 2 production and tumorigenesis. CONCLUSIONS: Increased TLR4 signaling in colitis drives expression of DUOX2 and epithelial production of H 2 O 2 . The local milieu imprints the mucosal microbiota and imbues it with pathogenic properties demonstrated by enhanced epithelial reactive oxygen species and increased development of colitis-associated tumors. The interrelationship between epithelial reactive oxygen species and tumor-promoting microbiota requires a 2-pronged strategy to reduce the risk of dysplasia in colitis patients.

Roles of PRR-Mediated Signaling Pathways in the Regulation of Oxidative Stress and Inflammatory Diseases

“…Recently, a report showed the intersection of TLR4 signaling, epithelial redox activity and the microbiota in colitis-associated neoplasia. It was found that colonic epithelial cells (CECs) respond to Gram-negative bacterial challenge by inducing DUOX2-mediated release of ROS in a TLR4-dependent fashion [ 40 ]. In summary, NOX enzymes act downstream of TLRs signaling pathway, which are associated with ROS generation ( Figure 1 ).…”

Mapping Transcriptome Data to Protein–Protein Interaction Networks of Inflammatory Bowel Diseases Reveals Disease-Specific Subnetworks

“…DMBT1 gene, which is considered as a candidate tumor suppressor gene for the brain, lungs, stomach, and colorectal cancers, has shown an increased expression in inflamed tissues of IBD patients, and it has been stated that impaired DMBT1 function may be associated with the onset of Crohn's disease (Renner et al, 2007). Moreover, polymorphisms/mutations of Toll-like receptors (TLR), which are innate immune receptors, have been directly linked to IBD (Lu et al, 2018), and activation of epithelial TLR4 in IBD and colorectal cancer has been associated with upregulation of DUOX2 (Burgueño et al, 2020). It has been reported that MARK2, a master regulator of cell polarity in intestinal epithelial cells, may contribute to the initiation and progression of IBD by interfering with the protein kinase cascade (Yuan et al, 2017).…”

Modulation of the Host Cell Transcriptome and Epigenome by Fusobacterium nucleatum

“…In our data, HCE cells significantly upregulated UBD in response to F. nucleatum exposure. DUOX2 is upregulated in inflammatory bowel disease and colorectal cancers and, alongside DUOXA2 , is a primary driver of H 2 O 2 production in mucosal tissues, which may contribute to chronic inflammation and reactive oxygen species (ROS)-related DNA damage ( 74 , 75 ). DUOX2 and DUOXA2 were both strongly upregulated by HCE cells in response to F. nucleatum , suggesting that F. nucleatum may drive H 2 O 2 production in the setting of the colon.…”