The role of endothelial cells in the formation of early metastatic niches in the lung

总结 转移性疾病是一个多步骤级联反应，是癌症相关死亡的主要原因。许多研究 他们正在研究肿瘤细胞如何获得转移到远处器官并逃离它们的能力。 主要位置。然而，对正常人的定植机制知之甚少。 器官的扩散和循环肿瘤细胞，可以说是转移进展的限速步骤。的 肺是最常见的转移部位之一，因此在本提案中，我们将研究 在循环癌细胞外渗出血管腔期间，正常肺中的内皮细胞（EC） 并定殖到正常肺中以建立肺转移。扩散的肿瘤细胞经历显著的 循环中的压力，使得在外渗到正常肺中期间，它们需要保护性小生境 由细胞外基质组成以提供物理锚定以防止失巢凋亡和凋亡。这个保护 小生境允许播散的肿瘤细胞有机会恢复，存活并最终在肺中扩展 变成大转移病灶我们正在研究激活肺内皮细胞将正常 肺组织进入适宜的“土壤”或早期转移小生境（EMN），以促进循环肿瘤的定植 细胞我们发表的研究和初步数据表明，肺EC在肿瘤到达之前被激活， 小鼠肺转移模型中的细胞。我们的数据还表明，基质细胞糖蛋白， 血小板反应蛋白-1（TSP 1）在转移进展过程中调节EC稳态中起重要作用。 特异性转移至肺的肿瘤细胞和肿瘤条件培养基下调肺中的TSP 1 EC促进EC活化。我们的初步研究确定了基质金属蛋白酶的表达增加， TSP 1低表达的内皮细胞中MMP-3的表达。我们的初步数据表明，MMP 3促进内皮细胞间质 通过与CD 44的相互作用，最终导致细胞外基质产生和重塑增加， 有助于肺中EMN的产生。我们的首要假设是 原发性肿瘤， 转移到肺通过TSP 1下调激活肺EC，导致EndoMT和增加 EMN中的细胞外基质产生支持肺定植。我们认为TSP 1是一个关键的 EC稳态的调节剂及其丧失促进EC活化并最终导致细胞外基质 通过MMP 3-CD 44轴产生和重塑。了解EC在正常肺中的作用 转移进展将为肺部最早阶段的机制提供新的见解 转移，并可提供用于预防转移性疾病的治疗靶点。

SUMMARY Metastatic disease is a multistep cascade and is the primary cause of cancer-related mortalities. Many studies are investigating how tumor cells acquire the ability to metastasize to distant organs and escape from their primary location. However much less is known about the mechanisms underlying the colonization of normal organs by disseminated and circulating tumor cells, arguably the rate limiting step in metastatic progression. The lung is one of the most common sites of metastases therefore in this proposal, we will investigate the role of endothelial cells (ECs) in the normal lung during extravasation of circulating cancer cells out of the vessel lumen and colonization into the normal lung to establish lung metastases. Disseminated tumor cells undergo significant stress in the circulation such that during extravasation into the normal lung, they require a protective niche composed of extracellular matrix to provide physical anchorage to prevent anoikis and apoptosis. This protective niche allows disseminated tumor cells the opportunity to recover, survive and expand in the lung eventually becoming macrometastatic lesions. We are investigating the processes that activate lung ECs converting normal lung tissue into hospitable “soil” or an early metastatic niche (EMN) to facilitate colonization by circulating tumor cells. Our published studies and preliminary data suggest that lung ECs are activated prior to the arrival of tumor cells in mouse models of lung metastases. Our data also indicate that the matricellular glycoprotein, thrombospondin-1 (TSP1) plays an important role in regulating EC homeostasis during metastatic progression. Tumor cells that specifically metastasize to the lung and tumor conditioned media downregulates TSP1 in lung ECs promoting EC activation. Our pilot studies identified increased expression of matrix metalloproteases (MMPs) 3 in TSP1low ECs. Our preliminary data suggest that MMP3 promotes endothelial-to-mesenchymal through interactions with CD44 ultimately leading to increased extracellular matrix production and remodeling contributing to EMN generation in the lung. Our overarching hypothesis is that primary tumors that metastasize to the lung activate lung ECs by TSP1 downregulation leading to EndoMT and increased extracellular matrix production in the EMN supporting lung colonization. We propose that TSP1 is a critical regulator of EC homeostasis and its loss promotes EC activation and ultimately leads to extracellular matrix production and remodeling via an MMP3-CD44 axis. Understanding the contribution of ECs in the normal lung towards metastatic progression will offer new insight into the mechanisms underlying the earliest stages of lung metastases and may offer therapeutic targets for the prevention of metastatic disease.