MT1-MMP调控肿瘤相关巨噬细胞促淋巴管生成的机制研究

Lymphangiogenesis is responsible for regulating extracellular fluid, transporting lipids and coordinating immune response. Defective lymphatic growth causes lymphedema, a condition of localized fluid accumulation and tissue swelling. Aberrant lymphaniogenesis in tumors promotes metastatic spread of cancer cells, leading to high mortality. Despite its well-known important role in pathological conditions, the precise molecular mechanism underlying this process remains poorly understood. We have recently identified Membrane-type 1 Matrix Metalloproteinase (MT1-MMP), a membrane-bound protease, as an endogenous suppressor for lymphangiogenesis. In macrophages, MT1-MMP translocates into the nucleus where it serves as a previously unexpected transcriptional factor to regulate the expression of PI3kδ. MT1-MMP/ PI3kδ signaling suppresses NF-κB-mediated transcription of Vegf-c in macrophages, repressing the prolymphangiogenic potential of macrophages. Our study highlights the importance of MT1-MMP in the physiological lymphatic vascularization. However, the regulatory role for MT1-MMP in tumor associated macrophages and hence tumor lymphangiogenesis remains unknown. As such, we propose to (i) characterize the role of MT1-MMP in pathological lymphangiogenesis, (ii) identify transcriptional program regulated by MT1-MMP in tumor associated macrophages. The information derived from the above studies will contribute to a major breakthrough in the research field of metalloproteinase and have important implications in the lymphatic vascular biology, especially in the management of cancer metastasis and other lymphatic diseases.

淋巴管在组织间液调节，脂质运输以及协调免疫反应等方面具有重要作用。淋巴管生成异常可导致发育缺陷或肿瘤转移。与血管生成相比，淋巴管生成的调节机制知之甚少。我们最近发现了一种新的淋巴管生成抑制因子MT1-MMP，巨噬细胞中的MT1-MMP可以转移到细胞核，并作为转录因子调节PI3Kδ基因表达。MT1-MMP介导的PI3Kδ信號通過抑制NF-κB信號从而抑制促淋巴管生成因子VEGF-C的生成，继而阻止淋巴管生成。我们首次揭示了MT1-MMP在调节生理性淋巴管生成过程中的重要性。然而，MT1-MMP会如何影响肿瘤相关巨噬细胞的促淋巴管生成特性，及肿瘤淋巴管生成和转移的机制尚不明确。本课题拟利用分子细胞生物学手段结合小鼠为模型，(1) 阐述MT1-MMP在病理性淋巴管形成中的作用；(2) 阐明在肿瘤相关巨噬细胞中由 MT1-MMP调控的关键基因网络。

淋巴管生成负责调节细胞外液、运输脂质和协调免疫反应。淋巴管发育不良会导致淋巴水肿，即局部积液和组织肿胀。肿瘤中异常的淋巴管生成促进癌细胞的转移扩散，导致高死亡率。尽管它在病理条件中起着众所周知的重要作用，但这一过程背后的确切分子机制仍知之甚少。我们最近发现膜结合蛋白酶1型基质金属蛋白酶（MT1-MMP）是淋巴管生成的内源性抑制因子。在巨噬细胞中，MT1-MMP易位到细胞核中，在那里它作为一个先前意想不到的转录因子来调节PI3kδ的表达。MT1-MMP/PI3kδ信号传导抑制巨噬细胞中NF-κB介导的Vegf-c转录，抑制巨噬细胞的前淋巴管生成潜能。我们的研究强调了MT1-MMP在生理淋巴血管形成中的重要性。然而，MT1-MMP在肿瘤相关巨噬细胞和肿瘤淋巴管生成中的调节作用尚不清楚。在后续研究中，我们发现巨噬细胞中MT1-MMP的特异性基因消融导致肿瘤相关巨噬细胞中VEGF-C的产生增加，从而导致MMTV-PyMT小鼠乳腺癌模型中肿瘤淋巴管生成和淋巴转移增加。通过阻断VEGFR3活性，MT1-MMP缺乏所赋予的肿瘤相关巨噬细胞的淋巴管生成效应被有效地消除，这表明巨噬细胞MT1-MMP对VEGF-C/VEGFR3信号的调节在肿瘤淋巴管生成的发展中起着重要作用。我们进一步发现，MT1-MMP通过直接抑制NF-κB复合物关键亚单位p65的转录活性，抑制肿瘤相关巨噬细胞中VEGF-C的生成。它直接与p65结合，并抑制p65与Vegf-c启动子区域的结合，从而抑制Vegf-c的p65依赖性转录。从上述研究中获得的信息将有助于金属蛋白酶研究领域的重大突破，并在淋巴管生物学中具有重要意义，尤其是在治疗癌症转移和其他淋巴疾病方面。