胃癌微环境Treg发挥免疫抑制作用机制的初步研究

Mechanism of the immune suppression mediated by regulatory T cells in the microenvironment of gastric cancer

初步探讨胃癌中异常增高的调节性T细胞(Treg)发挥免疫抑制的作用机制。利用多参数流式细胞术检测胃癌肿瘤局部CD4+CD25+Foxp3+Treg的Foxp3和环氧合酶2(COX-2)表达强度。CFSE增殖实验检测不同Foxp3表达强度的Treg对效应性T细胞的增殖抑制作用。在Treg与效应性T细胞共培养体系中加入COX-2抑制剂和前列腺素E2(PGE2)拮抗剂,观察PGE2的分泌水平以及Treg其对效应性T细胞的增殖抑制。结果发现,癌旁淋巴结和肿瘤浸润淋巴细胞(TIL)中Treg的Foxp3表达强度显著高于外周血(P<0.05);高表达Foxp3的Treg具有更强的抑制活性(P<0.05)。胃癌微环境中TregCOX-2表达强度与Foxp3表达强度显著相关(r=0.675,P<0.05)。应用COX抑制剂处理发现能阻断Treg分泌PGE2,COX抑制剂和PGE2拮抗剂均能降低Treg对效应T细胞增殖的抑制作用(P<0.05)。这表明胃癌局部高表达Foxp3的Treg具有较强的免疫抑制活性,COX-2-PGE2-EP2/EP4通路可能为胃癌微环境中Treg抑制效应T细胞增殖的机制之一。

To investigate the mechanism of the immune suppression mediated by the increased numbers of regulatory T cells（Tregs）,the expression of Foxp3 and COX-2 in Tregs were analyzed by flow cytometry,and the PGE2 level in the supernatant from the co-culture system was determined by ELISA.The suppression of the effector T-cell response was detected by CFSE assay.In some experiments,COX inhibitors and PGE2 receptor-specific antagonists were added to the co-culture system.It was found that the expression of Foxp3 in tumor-draining lymph nodes and TILs was higher than that in PBMCs（P0.05）.Tregs with higher levels of Foxp3 suppressed the proliferation of autologous CD4＋CD25-T cells more strongly（P0.05）.Elevated expression of Foxp3 in tumor-infiltrating Tregs correlated with the up-regulation of COX-2（r=0.675,P0.05）.The Tregs suppression on the effector T-cell response could be reversed by PGE2 and COX-2 inhibitors（P0.05）.Our data demonstrate a possible mechanism by which tumor-infiltrating Tregs with increased Foxp3 expression can mediate immune suppression via COX-2/PGE2 production in the gastric cancer microenvironment.