The wnt–b-Catenin–IL-10 signaling axis in intestinal APCs protects mice from colitis-Associated colon cancer in response to gut microbiota

Loss of immune tolerance to gut microflora is inextricably linked to chronic intestinal inflammation and colitis-associated colorectal cancer (CAC). The LRP5/6 signaling cascade in APCs contributes to immune homeostasis in the gut, but whether this pathway in APCs protects against CAC is not known. In the current study, using a mouse model of CAC, we show that the LRP5/6–b-catenin–IL-10 signaling axis in intestinal CD11c⁺ APCs protects mice from CAC by regulating the expression of tumor-promoting inflammatory factors in response to commensal flora. Genetic deletion of LRP5/6 in CD11c⁺ APCs in mice (LRP5/6^DCD11c) resulted in enhanced susceptibility to CAC. This is due to a microbiota-dependent increased expression of proinflammatory factors and decreased expression of the immunosuppressive cytokine IL-10. This condition could be improved in LRP5/6^DCD11c mice by depleting the gut flora, indicating the importance of LRP5/6 in mediating immune tolerance to the gut flora. Moreover, mechanistic studies show that LRP5/6 suppresses the expression of tumor-promoting inflammatory factors in CD11c⁺ APCs via the b-catenin–IL-10 axis. Accordingly, conditional activation of b-catenin specifically in CD11c⁺ APCs or in vivo administration of IL-10 protected LRP5/6^DCD11c mice from CAC by suppressing the expression of inflammatory factors. In summary, in this study, we identify a key role for the LRP5/6–b-catenin–IL-10 signaling pathway in intestinal APCs in resolving chronic intestinal inflammation and protecting against CAC in response to the commensal flora. The Journal of Immunology, 2020, 205: 2265–2275.