Clinical Significance And Mechanism Of B7-H1 Expression In Tumor Microenvironment Of Human Colorectal Carcinoma

Objective: To detect the expression of negative costimulatory molecule B7-H1 and the infiltration density of T cells subsets in colorectal carcinoma for the exploration of their clinical significances.Methods: Specimens of 112 colorectal carcinoma (CRC) patients were collected for the study. IHC (immunohistochemistry) staining was used for the detection of B7-H1 expression and CD3~+T/CD8~+T cells infiltration. Statistic software was used to analyze the correlations between parameters.Results: Strong B7-H1 expression was found in colorectal carcinoma tissues but little in adjacent normal colorectal tissues.B7-H1 expression was significantly correlated with the tumor site (P <0.05) and Duke's stage(P<0.05), and inversely related to the overall survival of patients (P <0.05). The CD3~+T cells infiltration density was negatively correlated with B7-H1 expression(P <0.05),and was positively correlated with prognosis of patients(P <0.05), while CD8~+T cells infiltration didn't show any significance in the prognosis.Conclusion: Negative costimulatory molecule B7-H1 was highly expressed by human colorectal carcinoma, and possibly inhibiting T cell-mediated tumor immune response by reducing T cell infiltration. So the detection of it may have some clinical value for diagnosis and prognosis in colorectal carcinoma.PartⅡTumor B7-H1 signal promotes the induction of regulatory T cellsObjective: Detected the T cell infiltration and B7-H1 molecule expression in peripheral blood and tissue of patients with colorectal carcinoma. By constructing transgenic cell lines SW480/B7-H1 and SW480/Mock, testing the induction of Tregs, and then explore the mechanism of B7-H1 signal for tumor infiltrating T lymphocytes.Methods: Separate peripheral blood and tumor tissues from colorectal carcinoma (CRC) patients, and collect peripheral blood mononuclear cells (PBMC), tissue-infiltrating lymphocytes (TILs) and tumor cells; Analyze the infitration of T cell subsets by immunofluorescence assay; Detect B7-H1 molecule expression on tumor cell surface, and discuss the correlation between the number of Tregs and tumor B7-H1 expression. Construct transgenic cell lines SW480/B7-H1 and SW480/Mock by the use of liposome, co-culture with CD4~+T cells for 24 ~ 72h, immunofluorescence labeling method (FCM) and Enzyme-linked immunosorbent assay (ELISA) were used to detect the expression of CD4/CD25/CD103 on cell surface and the secretion of TGF-βand IL-10 in cell culture supernatant; and then explore the mechanism of B7-H1 signal for the tumor infiltrating T lymphocytes.Results: Immunofluorescence assay showed that patients with colorectal carcinoma infiltrating CD3~+T cells accounted for 67.1% of the total number of infiltrating lymphocytes in tumor tissues, which CD4~+T/CD8~+T ratio appeared upside down, and the number of CD4~+CD25~+T cells was significantly more than normal human peripheral blood. In addition, tissues with high B7-H1 expression had more CD4~+CD25~+CD103~+T cell infiltration than the tissues with low B7-H1 expression. Experiments in vitro also showed that SW480/B7-H1 transgenic cells could promote the induction of CD4~+T cells into Tregs when CD3 monoclonal antibody and TGF-βexistence, while SW480/Mock cells couldn't.Conclusion: T cells remains the major effector cells in colorectal carcinoma immune response, and negative costimulatory molecules B7-H1 possibly inhibit T cell-mediated tumor immune response by promoting the infiltration of Tregs in tumor microenvironment, thereby inhibiting the T cell-mediated anti-tumor immune response to help the tumor to evade immune surveillance. Therefore, interfere the B7-H1-PD-1 signaling pathway may be expected to open an avenue for colorectal carcinoma immunotherapy.