Autologous fecal microbiota transplantation attenuates colitis-associated carcinogenesis in mice by suppressing NF-κB signaling and restoring CD8⁺ T cell/regulatory T cell balance

Abstract Objective ​ To investigate the effects of autologous fecal microbiota transplantation (AFMT) on immune regulation and tumor suppression in a murine model of colitis-associated colorectal cancer (CAC) induced by azoxymethane (AOM)/dextran sulfate sodium (DSS), with mechanistic emphasis on NF-κB pathway inhibition and CD8⁺ T cell/regulatory T cell (Treg) balance modulation. Methods Six-week-old female BALB/c mice [SPF grade, body weight (20±2) g] were randomly divided into 3 groups (n=5 per group): control group (Con), CAC model group (Mod), and AFMT intervention group (AFMT). The CAC model was established by a single intraperitoneal injection of AOM (10 mg/kg) followed by three cycles of DSS treatment (each cycle: 3.5%DSS in drinking water for 7 d plus 14 d of recovery with sterile water). Starting from day 7 post-modeling, the AFMT group received 0.1 mL of autologous fecal microbiota suspension via oral gavage every other day until the end of the experiment; control groups received equal volumes of sterile saline. At endpoint, colorectal tissues, spleen, serum, and fecal samples were collected. Colonic pathological injury and inflammatory cell infiltration were assessed by hematoxylin-eosin (HE) staining. NF-κB p65 and p-NF-κB p65 protein expression in colon tissue was detected by Western blot. Serum TNF-α levels were measured by ELISA. Flow cytometry was used to analyze the proportions of CD8+ T cells and regulatory T cells (Treg, defined as CD4+CD25+Foxp3+) in the spleen. Gut microbiota composition and diversity (α- and β-diversity) were analyzed by 16S rRNA sequencing. Results Compared with the Con group, the Mod group showed a reduction in goblet cells and significant inflammatory cell infiltration in HE-stained colon sections, an increased ratio of p-NF-κB p65 to NF-κB p65 in colon tissue (P