Background: The local and systemic regulation of the immune system may play important roles in the process of liver metastasis of colorectal carcinoma. The aim of this study was to establish a reproducible experimental liver metastasis model, to identify changes in T cells and cytokines TGF-β1 and IL-10, and to explore a possible mechanism of liver metastasis of colon carcinoma.
Methods: We used a colon carcinoma liver metastasis model, in which different numbers of CT-26 murine colon carcinoma cells (1 × 10(3), 5 × 10(3), 1 × 10(4), 5 × 10(4), and 1 × 10(5)) were injected into the spleen. The liver and spleen tissues were examined for T cell markers using flow cytometry. Liver tissues were analyzed for IL-10 and transforming growth factor beta 1 (TGF-β1) expression using immunohistochemistry.
Results: Spleen injection of colon carcinoma cells is a reproducible animal model for liver metastases, which resulted in quantity-dependent metastatic growth. We provided a snapshot of the hepatic immune microenvironment in the mouse liver metastasis model. Injection of A large number of tumor cells (5 × 10(4) and 1 × 10 (5) ) decreased anti-tumor cell counts, such as CD4(+) and CD8(+) T cells, and increased immune-suppressive cell counts (CD4(+)CD25(+) Treg cells). In addition, the expression levels of immunosuppressive cytokines IL-10 and TGF-β1 were also increased with the number of tumor cells.
Conclusions: Changes in the systemic and local immunological environment contribute to immunological escape mechanisms during liver metastasis of colon carcinoma, and therapies aiming at immune microenvironment may prove a useful strategy in the treatment of metastatic disease in the future.