Banxia Xiexin Decoction delays colitis-to-cancer transition by inhibiting E-cadherin/β-catenin pathway via Fusobacterium nucleatum FadA

Colitis is an important risk factor for the occurrence of colorectal cancer (CRC), and the colonization of Fusobacterium nucleatum (Fn) in the intestines accelerates this transformation process. Banxia Xiexin Decoction (BXD), originating from Shanghanlun, is a classic prescription for treating gastrointestinal diseases. Current researches indicate that BXD can effectively delay the colitis-to-cancer transition, but it is still unclear whether it can inhibit Fn colonization to achieve this delaying effect. This study explored the effect and mechanism of BXD in inhibiting Fn intestinal colonization to delay colitis-to-cancer transition. We constructed a mouse model of colitis-to-cancer transition by regularly gavaging Fn combined with azoxymethane (AOM)/dextran sodium sulfate (DSS), and administered BXD by gavage. We monitored the body weight of mice, measured the length and weight of their colons, and calculated the disease activity index (DAI) score. The growth status of colon tumors was observed by hematoxylin and eosin (H&E) staining, and the changes in gut microbiota in each group of mice were detected by 16S rDNA analysis. Immunohistochemistry was used to detect the expression of E-cadherin and β-catenin in colon tissues, and immunofluorescence was used to observe the infiltration of M2 macrophages in colon tissues. In cell experiments, we established a co-culture model of Fn and colon cancer cells and intervened with BXD-containing serum. Malignant behaviors such as cell proliferation, invasion, and migration were detected, as well as changes in their cell cycle. We examined the protein levels of E-cadherin, β-catenin, Axin2, and Cyclin D1 in each group were detected by Western blot. We used US1 strain (fadA-) as a control and observed the effects of BXD-containing serum on Fn attachment and invasion of colon cancer cells through attachment and invasion experiments. BXD can inhibit the colitis-to-cancer transition in mice infected with Fn, reduce crypt structure damage, improve gut microbiota dysbiosis, upregulate E-cadherin and decrease β-catenin expression, and reduce infiltration of M2 macrophages, thus inhibiting the process of colitis-to-cancer transition. Cell experiments revealed that BXD-containing serum can inhibit the proliferation, migration, and invasion of colon cancer cells infected with Fn and regulate their cell cycle. More importantly, we found that BXD-containing serum can inhibit the binding of Fn's FadA adhesin to E-cadherin, reduce Fn's attachment and invasion of colon cancer cells, thereby downregulating the E-cadherin/β-catenin signaling pathway. These findings show that BXD can inhibit Fn colonization by interfering with the binding of FadA to E-cadherin, reducing the activation of the E-cadherin/β-catenin signaling pathway, and ultimately delaying colitis-to-cancer transition.