TLR4受体信号与结肠癌新生血管形成的关系

Angiogenesis defines the growth of new blood vessels from preexisting vascular endothelial networks. It plays a key role in the maintenance of tumor growth and metastasis. Our prevous works in GISTs have shown that anti-angiogenesis therapy can control tumor growth.Toll-like receptor 4(TLR4) which is strongly expressed on the endothelium of blood vessels, can be triggered by endogenous ligands and play a critical role in promoting angiogenesis induced by wound healing and inflammation. However, it is not clear whether endothelial TLR4 signaling plays a critical role in tumor related angiogenesis. Tumor cells can secrete lots of endogenous TLR4 ligands, such as High-mobility group box-1(HMGB1）and heat shock proteins. It is reasonable to make a hypothesis that endothelial TLR4 signaling can promote tumor related angiogenesis. In order to certify our hypothesis, the following experiments were designed. Firstly, C3H/HeJ mice which carry a TLR4 functional deficiency mutant and C3H/HeN mice animal models bearing orthotopically transplanted murine colon 38 tumor(MCA38) or murine colon tumor 26(CT26) will be established. Tumor related angiogenesis, tumor growth and liver metastasis of the two animal models will be observed, and the effect of TLR4 on angiogenesis can be studied then. Secondly, the effect of a TLR4 blocking antibody on angiogenesis in vitro and the effect of a TLR4 antagonist on angiogenesis in vivo will be observed. Lastly, the TLR4 signaling pathways which can promote proliferation will be determined. The significance of endothelial TLR4 signaling in colon cancer related angiogenesis can be certified then. TLR4 may be a new target of anti-angiogenesis therapy in colon cancers.

新生血管形成在肿瘤的生长、转移中起着中心作用,我们的研究表明抑制新生血管形成可抑制肿瘤生长。我们还发现TLR4强表达于血管内皮细胞，TLR4是一种多功能的信号受体。血管内皮细胞TLR4被内源性配体激活后，可以促进炎症或创伤损伤诱导的新生血管形成，但其在肿瘤新生血管形成中的作用尚未被证实。肿瘤细胞可以分泌多种TLR4的内源性配体，我们推测这些配体可以通过作用于血管内皮细胞TLR4受体促进肿瘤新生血管形成。为验证该假设，本研究拟1）建立TLR4失活突变的C3H/HeJ小鼠和未突变的C3H/HeN小鼠之CT26、MCA380细胞系原位移植癌动物模型，观察二者原位移植癌的新生血管形成、肿瘤生长、肝脏转移的差异；2）观察干预血管内皮细胞TLR4信号对体内外新生血管形成的影响；3）明确TLR4促进增殖的信号通路；以明确血管内皮TLR4是否是结肠癌新生血管形成的关键性信号，可否可成为治疗新靶点。

本研究发现C3H/HeN小鼠来源的原代结肠黏膜微血管内皮细胞（colon mucosal microvascular endothelial cells，CMMVECs）与C3H/HeJ小鼠来源的CMMVECs细胞经过内毒素（脂多糖，lps）刺激后，前者的细胞增殖、细胞迁移和体外脉管形成能力显著为高；在血管内皮细胞中ERK1/2 和 p38 MAPK通路不是介导TLR4作用的关键性下游信号通路；在结肠癌CT26细胞移植瘤模型中应用中和性抗体中和TLR4信号并不能抑制肿瘤的新生血管形成以及肿瘤的生长，提示在肿瘤的新生血管形成当中应该存在多种信号通路，TLR4信号通路在肿瘤的新生血管形成可能并不是关键性的信号分子。