阻遏MDSCs联合γδT细胞过继免疫治疗改善抗血管生成诱导的肿瘤微环境免疫抑制的作用及机理研究

At present, the anti-angiogenic therapy has become a common anti-cancer therapy. However, accumulating evidence suggests that the anti-angiogenic therapy is not satisfactory for inhibiting tumor growth , and even has a risk of tumor recurrence and metastasis. This phenomenon is associated with a series of reactive changes that have occurred in the tumor microenvironment, especially recruiting a large number of immunosuppressive cells such as MDSCs and Treg cells, and infiltrating the T cells and NK cells with anergy. These changes resulted in the immunosuppressive state of tumor microenvironment. Our recent study have found that, the number of MDSCs increased in the tumor microenvironment after Endostatin treatment, suggesting that the anti-angiogenic therapy may induce the immunosuppressive state of tumor microenvironment. To test this hypothesis, we plan to study the changes of immunosuppressive state in tumor microenvironment induced by Endostatin ,and the important roles of MDSCs in such tumor microenvironment. Furthermore, we will explore the efficacy and mechanism of combination of blocking MDSCs with the γδT cell adoptive immunotherapy to improve the immunosuppressive state in tumor microenvironment after anti-angiogenic therapy. An foundation stone might be established by this study in the understanding of profound mechanism of tumor angiogenesis, the inevitable link between the changes of immunosuppressive state of tumor microenvironment and the tumor recurrence and metastasis. And this study might provide the new perspective expanding on cancer research and the potential clinical application of cancer therapy.

目前，抗血管生成已是常见的抗肿瘤治疗方法。然而，有研究表明，抗血管生成疗效不理想，还有增加肿瘤复发转移风险；深入分析发现，这主要涉及肿瘤微环境发生的反应性改变，尤其是MDSCs、Treg等免疫抑制细胞聚集，T细胞、NK细胞等免疫效应细胞功能障碍，造成了肿瘤微环境免疫抑制状态。最近，我们研究发现，Endostatin抗血管生成后肿瘤进展的小鼠，肿瘤组织中MDSCs增加，提示Endostatin可能通过MDSCs介导肿瘤微环境免疫抑制。为证实该假设，本项目拟在原有研究的基础上，开展Endostatin引发肿瘤微环境免疫抑制改变的研究，MDSCs在肿瘤微环境免疫抑制中重要作用的研究，进而开展阻遏MDSCs联合γδT细胞过继免疫治疗改善抗血管生成诱导的肿瘤微环境免疫抑制的作用及机理研究。这对进一步阐明肿瘤血管生长机理，肿瘤微环境免疫状态改变与肿瘤复发转移关系，拓展肿瘤治疗新思维具有开创性科学意义。

抗血管生成药物已广泛用于肿瘤的临床治疗，然而新近研究表明，抗血管生成治疗疗效有限，究其原因可能与抗血管生成治疗后，肿瘤微环境发生的一系列反应性变化有关，其中的机制有待深入阐明。在本次研究中，我们在原有研究的基础上，进一步观察了持续使用抗血管生成药物Endostatin对肺癌肿瘤微环境中骨髓来源的免疫抑制细胞（MDSCs）、肿瘤相关巨噬细胞（TAM），免疫效应细胞γδT、NK，以及免疫相关细胞因子如IL-2、IL-10、IFN-γ等的影响。结果显示持续Endostatin治疗后，可以促进肿瘤微环境中免疫抑制细胞的聚集，加重肿瘤微环境的免疫抑制状态，不利于Endostain抗肺癌的疗效。接着我们发现Endostatin治疗后可以加重肿瘤微环境的缺氧，缺氧促进肺癌细胞表达干细胞因子（stem cell factor，SCF），SCF又可以刺激肺癌细胞分泌CCL2诱导MDSCs聚集，这可能是Endostatin治疗后肿瘤微环境中免疫抑制细胞增多的原因，沉默肺癌细胞的SCF可以减少荷瘤小鼠肿瘤组织内MDSCs的数量。同时我们还发现SCF具有诱导和维持肺癌干细胞干性的作用，这为SCF在肺癌发生发展中的作用研究提供了新证据。最后我们分离和富集了γδT细胞，初步观察了Endostatin联合沉默SCF阻遏MDSCs，再予以γδT细胞过继免疫的组合策略对肺癌荷瘤小鼠的治疗效果，实验结果为抗血管生成治疗联合免疫治疗抗肿瘤的研究提供了新的证据。