Expression And Biological Function Of Tim-3on Myeloid-derived Suppressor Cells In Tumor-bearing Hosts With Gastric Cancer

【Objective】To investigate the expression of Tim-3on MDSCs in tumor-bearing hosts withgastric cancer，and explore the role of Tim-3in the development of gastric cancer and itsmechanism.【Methods】1.46patients with newly diagnosed gastric cancer and25healthy volunteers wereinvolved in the study from February2013to November2013. The expression of Tim-3onMDSCs in blood samples from gastric cancer patients and normal controls were evaluatedby flow cytometry and were correlated with clinicopathological parameters.2. We established a tumor-bearing mouse model of gastric cancer and evaluated theexpressions of Tim-3on MDSCs in mice peripheral blood, spleen and tumor tissue by flowcytometry at different time to dynamically study the law of its expression.3. T cells, stained by CFSE, were co-cultured with MDSCs, and then Tim-3blockingantibody was added to intervene the proliferation. The proliferation were evaluated by flowcytometry after96hours.【Results】1. Patients with gastric cancer(32.57±15.887,%) showed higher expression of Tim-3on CD14+HLA-DR-/lowMDSCs in peripheral blood than normal controls(7.52±5.943,%),and the difference were statistically significant(P<0.0001).2. The expression of Tim-3on CD14+HLA-DR-/lowMDSCs in peripheral blood hadpositive correlation with distant metastasis and the clinical stage(P<0.01), but not gender, age, tumor size, pathologic differentiation grade, depth of invasion or lymph node(P>0.05).The expression of Tim-3in the patients with distant metastasis (M1)(42.34±11.857,%)wassignificantly higher than those without distant metastasis(M0)(27.36±15.435,%)(P=0.0015). Compared with the patients staged Ⅰ-Ⅱ(18.40±5.956,%), the expression of Tim-3in patients staged Ⅲ-Ⅳ(35.82±15.299,%)significantly increased(P=0.0030). The expressions of Tim-3in different stages of gastriccancer patients were analyzed by one-way ANOVA. The expressions of Tim-3in patientsof stage Ⅳ(42.34±11.857,%) were significantly higher than stageⅠ-Ⅱ(18.40±5.956,%),stage Ⅲ(31.07±16.000,%), the difference was statistically significant (P=0.0006).3. The expression of Tim-3on MDSCs in peripheral blood of tumor-bearingmice(22.24±12.312,%) was statistically higher than that in the healthygroup(6.31±1.808,%)(P<0.05). Analyzed by one-way ANOVA, the group oftumor-bearing23days mice(40.93±2.663,%) showed higher expression of Tim-3than8days(11.50±1.127,%),13days(13.61±2.410,%) and18days(22.93±3.140,%), and thedifference was statistically significant (P<0.0001).4. Compared with the healthy group(3.46±1.126,%), the tumor-bearingmice(15.51±7.631,%) showed statistically higher expression levels of Tim-3on MDSCs inspleen(P<0.05). Tim-3’s expressions on MDSCs in spleen of tumor-bearing mice atdifferent time: tumor-bearing8days,13days,18days and23days were (5.62±2.396,%),(12.80±0.200,%),(18.80±2.606,%) and (24.83±1.795,%), and the difference, analyzed byone-way ANOVA, was statistically significant (P<0.0001).5. With the growth of tumor, Tim-3’s expression levels on MDSCs in tumor tissuegradually increased. The group of tumor-bearing23days(54.33±7.560,%) showedsignificantly higher expression level of Tim-3than the group of8days(12.83±1.124,%),13days(27.50±1.153,%) and18days(30.97±2.301,%)(P<0.0001).6. The expression levels of Tim-3on MDSCs in tumor tissue were higher than thosein spleen. And when the mice beared tumor more than13days, the Tim-3’s expressionlevels in tumor tissue were also higher than those in peripheral blood (P<0.05). 7. The ratio of T cell proliferation in T cells+MDSCs group was (35.43±11.357,%),lower than the T cell group(72.47±2.532,%), and T cells+MDSCs+Tim-3blockingantibody group(62.00±1.552,%), and the difference was statistically significant(P=0.0014).【Conclusion】1. The expression of Tim-3on CD14+HLA-DR-/lowMDSCs in peripheral blood of thepatients with gastric cancer increases，and it has positive correlation with distant metastasisand the TNM clinical stage. The expression of Tim-3in patients with distant metastasis(M1) is higher than those without (M0). And the expression of Tim-3in patients withadvanced stage is higher than those with early stage. It detects that the expression ofTim-3would contribute to prediction of the disease progression and prognosis.2. Compared with the healthy mice, the tumor-bearing mice shows higher expressionof Tim-3on MDSCs no matter in peripheral blood or spleen. Tim-3’s expression levels onMDSCs in the peripheral blood, spleen and tumor tissue increases with the growth oftumor, and the level in tumor tissue is higher than that in peripheral blood. The expressionof Tim-3on MDSCs may increase in tumor microenvironment. T cells could partiallyrestore their function after blocking the Tim-3and Tim-3may act as an important role in Tcells anti-tumor responses mediated by MDSCs.