胃癌微囊泡介导miR-155靶向血管内皮细胞c-myb-VEGF轴促进血管生成的机制研究

In the microenvironment of tumor, cancer cells can regulate angiogenesis, and the malignant growth of blood vessels plays a key role in the proliferation and metastasis of tumors. Recent studies found that secreted microvesicles (MVs) from cancer cells can transport miRNAs to work in target cells. Considering that the effect of anti-angiogenesis therapy in gastric cancer (GC) is limited, the current study is focused on the regulation of GC secreted MVs on vascular endothelial cells. We have previously reported miR-155 was up-regulated in tissues and serum of GC and was enriched in MVs. In this study, we found that GC-MVs can fuse into vascular endothelial cells, leading to the change of biological behavior; overexpressed miR-155 in vascular endothelial cells also have similar functions. Subsequently, c-myb was found to be the direct target of miR-155. Down-regulation of c-myb promotes cell migration and up-regulates autocrine-type VEGF of vascular endothelial cells. Therefore, c-myb plays an important role in regulating the proliferation and migration of vascular endothelial cells. The current study is designed to find that GC-MV transport miR-155 can regulate the process of angiogenesis by targeting the c-myb-VEGF pathway both in vivo and in vitro, and explore the novel regulatory mechanism of angiogenesis in tumor microenvironment. Moreover, we will try to inhibit angiogenesis in gastric cancer by using anti-miR-155. Hence, this project possesses not only scientific value, but clinical translation and application value.

肿瘤微环境中，癌细胞主动调控血管的生长；恶性生长的血管对肿瘤生长和转移具有重要作用。研究发现，癌细胞可通过分泌的微囊泡(MV)携带miRNAs作用于其他靶细胞。鉴于胃癌抗血管治疗疗效极为有限，本课题着眼于胃癌MV对血管内皮细胞的调控机制。课题组报道过miR-155在胃癌组织和血清中高表达，并在胃癌MV中富集。我们发现胃癌MV可融合到血管内皮细胞中，引起其生物学行为的变化；而在血管内皮细胞中过表达miR-155也有类似功能。进一步发现c-myb是miR-155在血管内皮细胞中重要的靶基因；其下调会促进细胞迁移，并引起自分泌型VEGF表达增高，所以c-myb对血管增殖和迁移具有重要作用。本课题拟证实胃癌通过MV运输miR-155靶向血管内皮细胞c-myb-VEGF轴，探索微环境中血管生成调控的新机制；并尝试anti-miR-155来抑制肿瘤血管生成。本课题对抗肿瘤血管生成研究有重要的促进作用。

外泌体是膜性纳米级微小囊泡，被认为是人体内的天然运载体，可以携带蛋白质、mRNAs、microRNAs (miRNAs)等生物活性物质。研究报道外泌体在肿瘤发病机制中也具有重要作用。在此，我们证明胃癌细胞来源的外泌体可以作为载体传递miR-155以促进胃癌血管生成。在本研究中，我们首先检测到miR-155在胃癌中的表达与c-MYB呈负相关，证实了c-MYB是miR-155的直接靶点。接下来，我们验证了外泌体递送的miR-155对胃癌血管生成和肿瘤生长的促进作用。我们发现miR-155可以抑制c-MYB的表达水平，同时，提升了血管内皮生长因子(VEGF)的表达，促进血管细胞的生长、转移和成环——这是肿瘤发生发展的一个重要原因。我们还建立了一个肿瘤异种植入小鼠模型，证实了含有miR-155的外泌体在体内显著增加了血管系统和肿瘤的生长速度。总之，我们的研究结果阐明了miR-155与胃癌血管生成之间的潜在机制。这些发现有助于我们理解miR-155和外泌体在胃癌发生发展中的作用，以及为胃癌的临床治疗发掘了新的可能性。