Clinical Significance And Function Of B7-H4Expression On Tumor Cells And Infiltrating Lymphocytes In Colorectal Cancer

Negative costimulatory molecule B7-H4is a novel member of B7family that wasnewly discovered in2003. Although its mRNA was extensively expressed in humannormal tissues, the protein of B7-H4was expressed weakly. However, recent studieshave found that tumor cells and tumor infiltrating immunocytes in tumor tissues such asovarian cancer, pancreatic cancer, gastric cancer, renal cell carcinoma overexpressB7-H4molecules. This shows that B7-H4was stringently regulated at thepost-transcriptional level in normal tissues, but the regulatory mechanism was inhibitedor changed in tumor environment. B7-H4could not only inhibit anti-tumor immuneresponse by reducing CD3+T cells infiltration and inducing apoptosis of activated CTL,but also could keep tumor cells away from immune surveillance, which provides allnecessary conditions for tumor immune escape. Clinical studies have showed that theexpression of B7-H4in tumor tissues is closely related with adverse clinical andpathological features, high expression of B7-H4in patients usually suggest poorerprognosis and lower survival rate. With the deep study of the B7-H4as negativecostimulatory molecule, more attention was paid to its function in tumor immune.In this study, we detected the expression of B7-H4and the infiltration of T cellsand TAM in the colorectal cancer specimens to analyze the clinical significance ofB7-H4expressed in colorectal carcinoma tissues, then combined the experiments invitro to further explore the significance and role of B7-H4expression on colon cancercells and infiltrating lymphocytes.Part Ⅰ Expression and clinical significance of B7-H4in humancolorectal carcinoma and tumor microenvironment Objective: To detect the expression of B7-H4on tumor cells andTumor-infiltrating lymphocytes(TILs) and analyze the infiltration density ofmacrophages and T cell subsets in human colon and rectal cancer(CRC) for theexploration of their clinical significance.Methods: The expression of B7-H4on tumor cells and TILs and the infiltration ofmacrophages and T cell subsets in98excised colorectal tumors was evaluatedimmunohistochemiscally, then analyzing their correlations to patients’ clinicalparameters and postoperative prognosis statistically.Results: B7-H4was abnormally expressed in colorectal cancer tissues, includingtumor cells and TILs, but not or slightly in normal tissues. The B7-H4expression onTILs was significantly correlated with patients’ age, lymph node metastasis, mucusadenocarcinoma status, inversely correlated with patients’ overall survival rate(P<0.05).The number of cases of severe CD3+T cells infiltration increased more markedly inB7-H4high expression tissues than in low expression tissues. But the expression ofB7-H4on tumor cells was significantly correlated with tumor stage, lymph nodemetastasis, distant metastasis and Duke’s stage(P<0.05).Conclusion: Negative costimulatory molecule B7-H4was abnormally expressedon both tumor cells and TILs in human colorectal carcinoma. The intensity of CD3+Tcells infiltrating was significantly correlated with B7-H4expression on TILs but nottumor cells, the expression on tumor cells was significantly correlated with tumor stage,lymph node metastasis, distant metastasis and Duke’s stage(P<0.05). These resultssuggested that B7-H4expression on TILs and tumor cells in coloretal cancers playeddifferent roles in the development of colorectal carcinoma. In addition, it has importantvalue for further analysis of biological and clinical significance of B7-H4expression ondifferent cells in tumor tissue.PartⅡ Research on the function of B7-H4expression on tumorcell and mononuclear macrophageObjective: To detect the influence of T cell proliferation after the co-culture ofmononuclear macrophage strain U937and activated T cells, and the situation of theproliferation and apoptosis of the B7-H4+tumor cells intervened with5-fluorouracil, then analyze the possible function of B7-H4expression on tumor cells and mononuclearmacrophage.Methods: Separating T cells from peripheral blood mononuclear cells(PBMC)collected from healthy peripheral blood with immunize magnetic sand, co-culturingmononuclear macrophage strain U937with activated T cells; Inducing transgenic cellline293/B7-H4with antineoplastic5-Fu, and then detecting the situation of theproliferation and apoptosis of the T cells and293/B7-H4cell line with FACS.Results: B7-H4transgenic cell strain U937could inhibit proliferation and induceapoptosis of the activated T cells;293cell line with B7-H4expression could resist orpartly resist apoptosis induced by5-Fu.Conclusion: The costimulatory molecule B7-H4expression on mononuclearmacrophage may negatively regulate immune response by inhibiting proliferation andinducing apoptosis of T cells, and the B7-H4expression on tumor cells may breakimmune surveillance and mediate tumor immune evasion by enhancing immunetolerance.In summary, the results of this study showed that the negative costimulatorymolecule B7-H4abnormally expressed on tumor cells and infiltrating lymphocytes incolorectal tumor tissues, and possibly negatively regulated the anti-tumor immuneresponse and mediated tumor immune evasion through different mechanisms involvedin tumorigenesis and development. Research on the B7-H4expressed respectively ontumor cells and infiltrating immune cells provided a new basis for further exploration ofthe significance and mechanism of B7-H4expression in the tumor microenvironment.