Objective. While appendectomy may reduce colorectal inflammation in patients with ulcerative colitis (UC), appendectomy has been suggested to be associated with an increased risk of colitis-associated cancer (CAC). The aim of this study was to explore the mechanism underlying the appendectomy-associated increased risk of CAC.
Design. Five-week-old male BALB/c mice underwent appendectomy, appendicitis induction or sham laparotomy. They were then exposed to azoxymethane/dextran sodium sulfate (AOM/DSS) to induce CAC. Mice were sacrificed 12 weeks later, and colons were taken for pathological analysis and immunohistochemistry (CD3 and CD8 staining). Human colonic tumors from 21 UC patients who underwent surgical resection for CAC were immunophenotyped and stratified according to the appendectomy status.
Results. While appendectomy significantly reduced colitis severity and increased CAC number, appendicitis induction without appendectomy led to opposite results. Intra-tumor CD3+ and CD8+ T-cell densities were lower after appendectomy and higher after appendicitis induction compared to the sham laparotomy group. Blocking lymphocyte trafficking to the colon with the anti-alpha4-beta7 integrin antibody or a sphingosine-1-phosphate receptor agonist suppressed the inducing effect of the appendectomy on tumors′ number and on CD3+/CD8+ intra-tumoral density. CD8+ or CD3+ T cells isolated from inflammatory neo-appendix and intravenously injected into AOM/DSS-treated recipient mice increased CD3+/CD8+ T-cell tumor infiltration and decreased tumor number. In UC patients with a history of appendectomy, intra-tumor CD3+ and CD8+ T-cell densities were decreased compared to UC patients without history of appendectomy.
Conclusions. In UC, appendectomy could suppress a major site of T-cell priming resulting in a less efficient CAC immunosurveillance.
The appendix orchestrates T-cell mediated immunosurveillance in colitis-associated cancer