RORγt(+) hematopoietic cells are necessary for tumor cell proliferation during colitis-associated tumorigenesis in mice.

Colorectal cancer (CRC) is one of the most common tumor entities. In patients with inflammatory bowel diseases, the development of colitis-associated colon cancer is considered a dangerous long-term complication. IL-17A and the transcription factor retinoic acid receptor-related orphan receptor γt (RORγt) play fundamental roles in the pathogenesis of inflammatory bowel diseases; in human studies, we detected a dense infiltration of RORγt-dependent CD4(+) IL17A(+) T helper (Th)17 cells in specimens of CRC, ulcerative colitis, and ulcerative colitis-associated colorectal cancer. However, the mechanistic role of RORγt(+) hematopoietic cells in colitis-associated tumorigenesis remains unclear. To investigate colitis-associated colon tumorigenesis, we conducted studies in the AOM+DSS mouse model that revealed the importance of RORγt for colon tumor progression. In the absence of RORγt-dependent Th17 lymphocytes, mice showed signs of intense chronic colitis, but developed significantly fewer macroscopic tumor nodules. The reduction of tumor development in RORγt(-/-) mice was not due to reduced colon tumor initiation. However, the proliferation rate of tumor cells was reduced in the absence of RORγt-dependent Th17 cells and tumor cells showed pronounced signs of senescence-associated epigenetic and lysosomal changes. These results indicate an important role for the immunological milieu in colitis-associated cancer, which is shaped in-part by RORγt-dependent Th17 lymphocytes that support CRC growth.

Basophils inhibit proliferation of CD4⁺ T cells in autologous and allogeneic mixed lymphocyte reactions and limit disease activity in a murine model of graft versus host disease.

Basophils are known to modulate the phenotype of CD4(+) T cells and to enhance T helper type 2 responses in vitro and in vivo. In this study, we demonstrate that murine basophils inhibit proliferation of CD4(+) T cells in autologous and allogeneic mixed lymphocyte reactions. The inhibition is independent of Fas and MHC class II, but dependent on activation of basophils with subsequent release of interleukin-4 (IL-4) and IL-6. The inhibitory effect of basophils on T-cell proliferation can be blocked with antibodies against IL-4 and IL-6 and is absent in IL-4/IL-6 double-deficient mice. In addition, we show that basophils and IL-4 have beneficial effects on disease activity in a murine model of acute graft-versus-host disease (GvHD). When basophils were depleted with the antibody MAR-1 before induction of GvHD, weight loss, GvHD score, mortality and plasma tumour necrosis factor levels were increased while injection of IL-4 improved GvHD. Basophil-depleted mice with GvHD also have increased numbers of CD4(+) T cells in the mesenteric lymph nodes. Our data show for the first time that basophils suppress autologous and allogeneic CD4(+) T-cell proliferation in an IL-4-dependent manner.

Interleukin 21 controls tumour growth and tumour immunosurveillance in colitis-associated tumorigenesis in mice.

BACKGROUND AND AIMS: Colitis-associated tumorigenesis is a balance between proliferation of tumour cells and tumour immunosurveillance. The role of T-helper-cell-derived cytokines in tumour growth is not fully understood. In this study the authors investigated the influence of interleukin (IL) 21 on intestinal tumorigenesis. METHODS: Chronic colitis was induced in IL-21(-/-) and littermate control wild-type mice with three cycles of 1.5% dextran sulphate sodium (DSS) over 7 days followed by 7 days of drinking water. Mice received an azoxymethane injection on day 0 of DSS-colitis to induce tumorigenesis. Immunohistochemistry was performed on inflamed and tumour-bearing areas of colons. Cytokine expression of isolated colonic CD4 T cells was determined by ELISA. Cytotoxic capacity of isolated colonic CD8 T cells targeting tumour cells was evaluated by flow cytometry and quantitative cytotoxicity assay. Apoptosis of tumour cells was determined by TUNEL assay of colonic sections. RESULTS: Increasing expression of IL-21 was observed in chronic colitis, which showed functional importance, since IL-21 deficiency prevented chronic DSS-colitis development. Further, in the absence of IL-21, significantly fewer tumour nodules were detected, despite a similar extent of intestinal inflammation. In wild-type mice, 8.6±1.9 tumour nodules were found compared with 1.0±1.2 in IL-21-deficient mice. In tumour-bearing IL-21-deficient mice, intestinal inflammation was restored and partly dependent on interferon (IFN)-γ, whereas the inflammation in wild-type mice showed high IL-17A concentrations. In these rare tumours in IL-21-deficient mice, tumour cell proliferation (Ki-67) was decreased, while cell apoptosis was increased, compared with wild-type mice. Increased IFNγ expression in tumour-bearing IL-21-deficient mice led to increased tumour immunosurveillance mediated by cytotoxic CD8CD103 T cells targeting E-cadherin(+) colonic tumour cells and therefore limited tumour growth. CONCLUSION: These results indicate that IL-21 orchestrates colitis-associated tumorigenesis, leading to the hypothesis that high IFNγ and low IL-17A expression reduces tumour cell proliferation and increases tumour immunosurveillance.

Tumor development in murine ulcerative colitis depends on MyD88 signaling of colonic F4/80+CD11b(high)Gr1(low) macrophages.

Patients with prolonged ulcerative colitis (UC) frequently develop colorectal adenocarcinoma for reasons that are not fully clear. To analyze inflammation-associated colonic tumorigenesis, we developed a chronic form of oxazolone-induced colitis in mice that, similar to UC, was distinguished by the presence of IL-13-producing NKT cells. In this model, the induction of tumors using azoxymethane was accompanied by the coappearance of F4/80+CD11b(high)Gr1(low) M2 macrophages, cells that undergo polarization by IL-13 and are absent in tumors that lack high level IL-13 production. Importantly, this subset of macrophages was a source of tumor-promoting factors, including IL-6. Similar to dextran sodium sulfate-induced colitis, F4/80+CD11b(high)Gr1(intermediate) macrophages were present in the mouse model of chronic oxazolone-induced colitis and may influence tumor development through production of TGF-ß1, a cytokine that inhibits tumor immunosurveillance. Finally, while robust chronic oxazolone-induced colitis developed in myeloid differentiation primary response gene 88-deficient (Myd88-/-) mice, these mice did not support tumor development. The inhibition of tumor development in Myd88-/- mice correlated with cessation of IL-6 and TGF-ß1 production by M2 and F4/80+CD11b(high)Gr1(intermediate) macrophages, respectively, and was reversed by exogenous IL-6. These data show that an UC-like inflammation may facilitate tumor development by providing a milieu favoring development of MyD88-dependent tumor-supporting macrophages.