血管内皮细胞endoglin对乳腺癌肺转移前灶形成的抑制性作用及其机制研究

The effct of anti-angiogenic therapy seems to be relatively limited. Targeting endoglin (TRC105) anti-tumor angiogenesis drugs is now undergoing a phase I/II clinical trials. Recent literatures report anti-angiogenic therapy may lead to increased tumor metastases, the underlying mechanisms, however, are unclear. Using specific vascular endothelial endoglin conditionally induciable knockout (Eng - iKOe) technology, we surprisingly found that: there is a significant increase of pulmonary metastasis in Eng-iKOe mammary mouse tumour model; further experiments indicate that the increase of metastases is due to an increased trans-endothelial-migration (TEM) of circulating tumour cells (CTCs); an increased TEM results from an accelerating release of inflammatory cytokines from Eng- iKOe mouse lung endothelial cells (MLECs)and accumulated macrophages. We hypothesize that endothelial endoglin can inhibit pulmonary pre-metastatic niches of breast cancer by mediating inflammatory cytokines release and their induced macrophages. In molecular, cellular, tissue and animal multiple levels, using mouse cytokine array, cells transmigration assay and antibody neutrolization experiments,the mechanism of endothelial endoglin regulating inflammatory cytokines and mediating macrophages to form pulmonary pre-metastatic niches will be clarified. It will be a novel clinical idea to blocking the relevant inflammatory factors to inhibit pre-metastatic niches' formation.

目前抗肿瘤血管生成治疗的临床疗效有限。以血管内皮细胞endoglin为靶向的药物TRC105, 正在进行I/II期临床实验。有文献报道，抗肿瘤新生血管治疗可能导致肿瘤转移增加, 但机制不清。我们应用特异性血管内皮细胞endoglin条件性敲除技术（Eng-iKOe），在研究中发现：Eng-iKOe 导致小鼠乳腺癌肺转移显著增加；肺转移的增加是由于循环血中肿瘤细胞跨膜增加所致；而跨膜的增加与Eng-iKOe 的肺血管内皮细胞释放炎性因子及其介导的巨噬细胞有关。我们提出假说：endoglin能抑制由炎性因子介导的巨噬细胞参与的乳腺癌肺转移前灶形成。从分子，细胞，组织及动物等多个水平，应用炎性因子检测，细胞跨膜及抗体中和等实验，明确endoglin调控炎性因子介导巨噬细胞，共同参与肺转移前灶形成的机制。探索通过阻滞相关炎性因子，抑制抗肿瘤血管药物治疗导致的转移前灶的形成，为临床治疗提供新的思路。

抗肿瘤血管生成治疗的临床疗效有限，有文献报道，靶向VEGF信号通路的抗肿瘤新生血管治疗可以影响肿瘤免疫微环境，而肿瘤免疫微环境的改变与抗肿瘤新生血管治疗疗效密切相关。血管内皮细胞endoglin为TGF-beta共受体，可以促肿瘤新生血管生成，靶向endoglin的III期临床研究也在进行中。然而，靶向endoglin的抗肿瘤新生血管治疗疗效是否也与肿瘤免疫相关联并不清楚。我们应用特异性血管内皮细胞endoglin条件性敲除技术（Eng-iKOe）小鼠动物模型，在研究中发现：endoglin条件性敲除后小鼠乳腺肿瘤早期新生血管减少-生长受抑，而晚期新生血管增加-受抑的肿瘤快速生长，而这一现象是由肿瘤微环境中IL-6的释放增加，趋化更多的M2型巨噬细胞引起的。此外，我们的研究证实，敲除endoglin的小鼠肺血管内皮细胞可以释放更多的CCL5和CXCL10，而CCL5可以在体外趋化巨噬细胞转跨膜。这说明血管内皮细胞endoglin的缺失，一方面影响了肿瘤新生血管的生成，而另一方面也促进肿瘤微环境中炎性因子释放，进而改变肿瘤免疫微环境，影响靶向endoglin抗肿瘤新生血管治疗疗效。这将为抗肿瘤新生血管治疗与肿瘤免疫联合治疗提供更多的研究基础，为临床提高抗肿瘤新生血管疗效提供新的思路。