胃癌微环境中TNF/TNFR2介导的巨噬细胞与调节性T细胞相互作用的机制研究

Tumor microenvironment is an important aspect of gastric cancer and other cancer development. Regulatory T cells (Tregs) play an important role in tumor microenvironment through inhibiting the activity of effector cells. It has been shown that the expression of TNFR2 identified a subpopulation of Tregs with the maximally suppressive function. Our preliminary data showed that TNFR2+ Tregs in peripheral blood and tumor tissue of cancer patients were more proliferative and expressed higher levels of the immunosuppressive molecule CTLA-4, and consequently more potently suppressed IFNγ production by co-cultured CD8+ CTLs. More importantly, higher TNFR2 expression levels on Tregs were associated with lymphatic invasion, distant metastasis and more advanced clinical stage of lung cancer patients. However, the mechanism of expansion of TNFR2+ Tregs in tumor microenvironment and the effects of TNF-α/TNFR2 signaling has not been identified. It has been reported that macrophage could induce the expansion of Tregs in inflammatory model. So we hypothesize that TNF-α/TNFR2 promotes the tumor suppression in gastric cancer, through promoting the expansion and immune suppressive activity of Tregs. First, we will analyze the number and phenotype of TNFR2+ Tregs in cancer tissue, and determine the relationship between the level of TNFR2+ Tregs and TNF-α expressed on macrophage as well as clinicopathological factors. Second, we will determine whether the tumor cells could increase the expression level of TNF-α, especially trans-membrane TNF-α (m TNF-α) on macrophage. Third, we will analyze the mechanisms of macrophage induced expansion and suppressive activity of Tregs through TNF-α/TNFR2, including activation of NF-κB and JNK/AP-1, up-regulation of GARP and membrane TGF-β. Results from this project will provide information to elucidate how TNF-α/TNFR2 signaling regulate tumor immune microenvironment.

TNFR2+调节性T细胞（Tregs）是具有高免疫抑制活性的Tregs亚群。我们的前期研究证实肿瘤患者外周血及肿瘤组织中TNFR2+Tregs比例升高，且与肿瘤转移相关，但TNFR2+ Tregs数量及功能上调的机制尚未明确。炎症模型的研究提示：巨噬细胞通过TNFα/TNFR2信号促进Tregs的扩增及活性，我们的前期工作也证实肿瘤细胞可上调巨噬细胞的跨膜型TNF-α（mTNF-α）表达。因此提出研究假设：肿瘤细胞刺激微环境中的巨噬细胞，使其TNF-α及mTNF-α表达升高，与Tregs表面的TNFR2结合促进其扩增和活化。将检测胃癌组织中TNFR2+Tregs的比例和表型特点，分析与巨噬细胞TNF-α表达及临床指标的相关性；探讨巨噬细胞通过TNFα/TNFR2信号对TNFR2+Tregs的扩增、表型及功能的影响，并分析其作用的分子机制。从而为肿瘤微环境的个体化干预提供新的思路和理论基础。

肿瘤免疫微环境中的TNFR2+调节性T细胞（TNFR2+ Tregs）高表达多种免疫抑制分子，具有很强的免疫抑制活性。本研究证明了胃癌微环境中TNFR2+ Tregs的浸润水平随着肿瘤的进展显著升高，是胃癌患者预后的标志物。应用单细胞转录组技术对胃癌组织和外周血中的Tregs 进行分析，结果显示肿瘤浸润Tregs高表达TNFR2，TNF-α/TNFR2信号通路处于激活状态；与外周血Tregs相比，肿瘤浸润Tregs呈现活化和效应状态，显著高表达共刺激因子TNFR2, 4-1BB, OX40 和GITR， 免疫检查点分子CTLA-4 和 TIGIT 以及趋化因子受体 CCR6。TNF-α/TNFR2通路的活化能够增加CD4+ T细胞中Foxp3+细胞比例，上调Tregs产生的latent TGF-β及其免疫抑制功能。总之，本研究发现TNFR2+ Tregs在肿瘤微环境中具有较高的浸润水平并且与患者预后相关；肿瘤浸润Tregs具有活化和效应细胞特征，TNF-α/TNFR2通路的激活可促进Tregs的免疫抑制表型和功能，本研究为TNFR2+ Tregs作为胃癌治疗靶点提供了新的理论依据。