The Role Of Regulatory T Cells In The Development Of Hepatocellular Carcinoma

Objectives:1. To explore the mechanism by which regulatory T cells of peripheral blood migrate into tumor tissue in hepatocellular carcinoma patients.2. To investigate the association of tumor-infiltrating lymphocytes, especially regulatory T cells, with prognosis of hepatocellular carcinoma patients.Methods:Taking peripheral blood and tumor tissue of patients as subject, we detected the density, distribution, phenotype and function of tumor-derived regulatory T cells by flow cytometry, immunohistochemical staining, immunosuppressive assay; we investigated the level of selective chemokines in liver tumor tissue by real-time PCR and immunohistochemical staining, as well as chemotaxis of regulatory to these chemokines in vitro. Besides, we evaluated the association of tumor-infiltrating lymphocytes with prognosis of hepatocellular carcinoma patients by detecting the expression of CD3, CD4, CD8and FoxP3using immunohistochemical staining, and analyzing using Kaplan-Meier and Cox regression model.Results:Both the density and prevalence of regulatory T cells was significantly higher in liver tumor tissue than in non-tumor or normal tissue (P<0.001). Regulatory T cells were prone to keep close contact with liver tumor cells. Regulatory T cells were in an activated phenotype in the tumor site, where they can suppress the proliferation and INF-y secretion of effector T cells. Increased chemokine CCL20, secreted by liver tumor cells, was associated with the number of tumor-infiltrating regulatory T cells. Moreover, circulating regulatory T cells highly expressed CCR6, exclusive receptor of CCL20, and selectively migrate under recruitment of CCL20in vitro. The prevalence of regulatory T cells among CD4+T cells was independently associated with prognosis of hepatocellular carcinoma patients post-transplantation. Additionally, receiver operating characteristic curve showed that the combined analysis of regulatory with cytotoxic T cells had a bigger area under curve than that of regulatory T cell alone (P<0.05).Conclusion:1. CCL20-CCR6signal mediates the migration of circulating regulatory T cells into tumor tissue in hepatocellular carcinoma patients.2. The prevalence of regulatory T cells in tumor tissue is negatively associated with prognosis of patients, and the combination of regulatory with cytotoxic T cells had a better power to predict prognosis.