B7-H3在Tie-2表达阳性单核巨噬细胞（TEM）介导的肾癌肿瘤血管新生中的作用机制研究

Tumor-induced angiogenesis is crucial for tumor growth and metastasis. Previous studies showed that B7-H3 is significantly expressed by tumor vascular endothelial cells, and prognosticates a poor clinical outcome of renal carcinoma. However, the role of B7-H3 on tumor-induced angiogenesis remains unknown. Our recent studies indicated that B7-H3 is expressed by Tie-2 expressing monocytes (TEM), a population of Myeloid-derived cells, induced by tumor environment. TEM plays an important role in tumor vessel formation through differentiation into vascular endothelial cells (ECs),secration of bFGF and VEGF to support ECs growth or as pericyte progenitors to provide base membrane for ECs adhesion. In our previous work, we found that B7-H3 is important in adhesion between cell and cellular matrix, secreation of ctyokines such as TNF-α and promotion of cell differentiation in vitro. According to our findings and previous reports, we hypothesize that B7-H3 plays a critical role in promoting tumor vessel formation mediated by TEM. To test this hypothesis, this project will to confirm the location of B7-H3+population on tumor vessel tissues and analyze the contribution proportion of TEM on the expression of B7-H3; to assess the correlation between B7-H3 levels on TEM and intratumoral microvessel density; to investigate the effect and biofunctional mechanism of B7-H3 on tumor vessel formation mediated by TEM in vitro and in vivi. This project aims to analyze the effect and mechanism of B7-H3 on tumor-induced angiogenesis mediated by TEM in renal carcinoma.

已有研究证实B7-H3在肾癌血管组织特异表达，且与临床预后密切相关，但其在肿瘤血管形成中是否存在作用尚不清楚。髓系细胞TEM（Tie-2 expressing monocytes）通过分泌促血管生长因子、分化为内皮细胞或提供物理支撑的周细胞，在肿瘤新生血管形成中发挥关键作用，但确切分子机制仍待阐明。最近，本课题组发现肿瘤浸润TEM异常高表达B7-H3，且前期工作还发现该分子可促进细胞粘附、单核巨噬细胞分泌炎性细胞因子以及干细胞诱导分化。因此我们推测B7-H3参与了TEM介导的肿瘤新生血管形成。鉴此，本项目拟开展下列研究：1）从形态学及细胞水平分析B7-H3+细胞在肿瘤血管中的精确定位、来源以及TEM上B7-H3的表达与微血管密度的关系和表达调控机制；2）从TEM促血管形成的三种方式入手，通过体内外实验，从分子、细胞以及整体水平分析B7-H3在TEM介导的肿瘤血管形成中的作用及分子机制。

受项目资助《B7-H3在Tie-2表达阳性单核巨噬细胞（TEM）介导的肾癌肿瘤血管新生中的作用机制研究（81272839）》，课题获得了如下研究成果：.1）项目组研究发现，肿瘤组织中TEM数量与肿瘤分期、分级呈正相关，但与年龄、性别、肿瘤病理类型无显著关系。肾癌组织中的浸润TEM数量显著高于癌旁组织。高TEM肾癌组的MVD显著高于低TEM组，且两者呈正相关。2）肾癌组织CD14与B7-H3均呈阳性表达；肾癌组织CD14与B7-H3共表达主要存在于富含血管的肿瘤间质；肾癌组织中CD14+单核细胞表面B7-H3表达水平显著高于正常肾脏组织，且B7-H3表达水平与肿瘤的TNM分期、分级有关。3）B7-H3，Tie-2在肾癌血管组织中的表达分析显示，B7-H3特异性表达于肿瘤血管，提示B7-H3有望成为ccRCC抗血管生成治疗有效的靶标。血管内Tie-2和B7-H3表达均与CD34标记的微血管密度（MVD）呈正相关，且B7-H3血管内表达与Tie-2 表达呈正相关（r=0.322, P=0.019）。4）利用核素131I标记抗人B7-H3单抗4H7，观察B7-H3作为靶点在肿瘤治疗中的价值。通过体内外实验，项目组发现131I-4H7能够显著抑制肿瘤生长；小鼠移植瘤标本组化分析发现，131I-4H7治疗组移植瘤组织坏死和血管破坏显著增加；对移植瘤标本的微血管密度检测发现，131I-4H7治疗组能显著降低瘤组织微血管密度，并且显著降低裸鼠移植瘤体组织中VEGF的表达，且呈现量效关系。课题组推测，131I-4H7可以通过下调VEGF的表达，抑制肿瘤血管形成，发挥抗肿瘤的作用。.总之，受基金资助，本项目围绕肿瘤血管新生，较为系统的探讨了肾癌组织中B7-H3，Tie-2与单核细胞的关系及临床意义。更为重要的是发现B7-H3可以作为潜在靶点开展靶向生物治疗，具有较好的实用性。部分研究内容并未完成，原因如下：自肾癌实体瘤组织中分选TEM十分困难，而外周血中TEM并不存在B7-H3+TEM，因此关于siRNA干扰TEM上B7-H3表达研究其功能的研究设计并没能实现。标注基金资助，申请者为通讯作者共发表相关研究研究论文（SCI源）2篇。培养与课题相关博士研究生1名；硕士研究生1名。