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Chronic inflammation, such as that seen in patients with inflammatory bowel disease (IBD), greatly increases the risk of developing colon cancer. Growing evidence supports a role for T cell-mediated immune response and release of various cytokines in the pathogenesis of colitis-associated cancer (CAC). In fact, CD4+ effector T cells promote chronic inflammation associated with IBD through release of proinflammatory cytokines, which leads to initiation and progression of colon cancer. Furthermore, CD8+ T cells reduce tumor growth through cancer immunosurveillance, which can also contribute to intestinal inflammation and thereby might promote tumor growth. In contrast, regulatory T cells (Tregs) release the immunosuppressive cytokines IL-10, TGF-β and thus have protective effects in CAC. In addition, dendritic cells (DCs) are important components of antitumor immunity. Recently, a novel mouse model that was associated with repeated inflammation was established for investigating the immunopathogenesis of CAC. This review discusses the role of T cell-mediated immune response, and DCs and involved cytokines in the immunopathogenesis of CAC in an animal model, which may also provide future therapeutic targets in CAC.

Inflammatory bowel disease (IBD) can lead to an increased risk of developing colorectal cancer (CRC). The aim of this study was to establish a model for combined bone marrow transplantation (BMT) and colitis-associated colorectal cancer (CAC) and to define the contribution of BM-derived cells during the inflammation associated with carcinogenesis. We established a model for BMT using green fluorescent protein (GFP) transgenic mice, followed by AOM/DSS-induced CAC, and performed confocal microscopy analysis on in vivo living tissue and frozen tumor sections. Our imaging analyses showed that GFP-positive cells extensively infiltrated the tumor stroma and that some WGA and GFP or CD31 and GFP double-positive cells were observed in the lining of tumor vessels. Flow cytometry analysis of the tumor-infiltrating cells showed that the GFP-positive CD11c+ DCs cells were one-third of the GFP+/CD11C- cells, and that half of these DCs (0.96% vs 1.02%) were GFP-positive BM-derived cells. The majority of CD4(+) T cells were GFP-negative (12.02% vs 1.9%), and we discovered a novel CD4(+) CD11c(+) DC subset (0.34% vs 1.64%). In conclusion, we defined the distribution of BM-derived endothelial cells, CD11c(+) DCs and CD4(+) T cells in tumors. This model might be useful for elucidating the diverse BM-derived cell types and functions during the progression of colitis-associated colorectal cancer.