肿瘤相关性炎症微环境下蛋白磷酸酶SHP-2在免疫功能转向中的调控机制

The host immunity is prone to switch from antitumour to protumour properties in cancer-related inflammation. However, the mechanisms by which a protective tumour-inhibiting immune response can be switched towards a tumour-promoting immune response in tumor microenvironment are not entirely clear. To elucidate the modulatory role of SHP-2 for the balance between antitumour and protumour immune responses, we will firstly analyze the relationship between SHP-2 and tumour development by means of studies on the murine tumour models and clinical tumour samples. Secondly, we will investigate the effects of SHP-2 ablation on tumour progression,inflammatory microenvironment, immune responses and immune cells including the number, phenotypes and antitumour verse protumour function in tumor-bearing T cell-or macrophage-specific SHP-2 knockout mice. Moreover, the signaling mechanisms will be clarified by methods of overexpression, knockdown or knochout of SHP-2. Lastly, we will test whether small molecules which can modulate the expression or function of SHP-2 have the potential to reverse tumour-promoting towards tumour-inhibiting immune responses in the murine tumor models. Taken together, this study will be of importance to identify a molecular switch to modulate the balance between antitumour and protumour immune response, and shed light on the molecular basis of cancer progression. Furthermore, the molecular switch could be not only a novel tumour biomarker for prognosis and diagnosis, but also a new drug target for cancer therapy.

肿瘤相关性炎症微环境下机体免疫系统易发生由抗肿瘤向促肿瘤的功能转向，但是介导这种转向的分子机制尚不明确。基于前期研究结果，本课题拟通过不同类型的小鼠肿瘤模型，并结合临床样本考察在肿瘤相关性炎症微环境中SHP-2与抗肿瘤免疫功能转向促瘤的相关性，以期确定SHP-2是决定肿瘤免疫走向的关键分子。进一步借助T细胞或巨噬细胞SHP-2条件性敲除小鼠考察SHP-2对肿瘤进展、炎症水平、肿瘤免疫应答的影响以及调控免疫细胞数目、表型、促瘤功能转向的作用方式；运用SHP-2过表达、突变、基因敲低或敲除等方法阐明SHP-2调控肿瘤免疫促瘤转向的分子机制。最后运用化学小分子针对SHP-2进行干预，考察其对肿瘤生长和转移的治疗作用以及对免疫功能促瘤转向的逆转作用。通过上述研究有望发现肿瘤相关性炎症微环境中调控免疫功能转向的重要分子，有助于找到预测和诊断肿瘤的新分子标志或防治肿瘤的新药物靶点。

蛋白酪氨酸磷酸酶SHP-2在细胞因子受体信号转导中具有重要的调节作用，SHP-2磷酸化对其发挥功能至关重要。虽然SHP-2磷酸化失调与肿瘤的发生发展密切相关，但SHP-2在肿瘤免疫中的作用仍不清楚。本研究中我们发现黑色素瘤进展过程中，荷瘤鼠CD4+ T细胞中磷酸化SHP-2 （pSHP-2）表达逐渐降低；临床组织样本也验证了肿瘤浸润CD4+ T细胞中pSHP-2表达下降与黑色素瘤恶性程度呈正相关。进一步利用SHP-2条件性敲除小鼠发现CD4+ T细胞中SHP-2的敲除显著诱导了IL-6等炎性因子的持续分泌，进而导致髓系来源抑制性细胞(myeloid-derived suppressor cells, MDSC)在肿瘤部位积累且功能增强，最终促进了黑色素瘤的生长和转移。这些结果揭示了T细胞中SHP-2在肿瘤免疫中的抑癌作用，其缺失促进炎性微环境的形成，导致肿瘤免疫由“抗肿瘤”向“促肿瘤”转变。另一方面，在乳腺癌进展中我们却发现肿瘤浸润的巨噬细胞(tumor-associated macrophages, TAMs)中SHP-2的磷酸化水平逐渐上调。利用巨噬细胞SHP-2条件性敲除小鼠，发现小鼠乳腺癌细胞E0771在敲除小鼠体内生长缓慢，而且肺转移能力明显低于野生型小鼠。敲除小鼠肿瘤中TAM浸润程度上升，并且M1型巨噬细胞的比例和数量均显著增加。此外，血清中M1型巨噬细胞相关的细胞因子IL-6、IL-12、TNF-的浓度高于WT小鼠，而M2型相关因子IL-10的浓度则显著低于WT小鼠。SHP-2的敲除显著促进巨噬细胞向M1极化。同样，给予SHP-2抑制剂PHS-1抑制了E0771的体内生长和肺转移。这些结果提示巨噬细胞中SHP-2可能促进M2型巨噬细胞的极化和浸润，其活化水平上调促进了乳腺瘤的增殖和转移。可见，SHP-2在肿瘤免疫中是个极其重要的调控分子，在肿瘤微环境下通过不同的机制控制不同免疫细胞的功能发挥，最终导致偏向促肿瘤的功能转向。本研究不仅揭示了SHP-2决定肿瘤免疫走向的重要作用，而且也为发现新的肿瘤诊断分子标志或肿瘤防治的药物靶点奠定理论基础。