Cellular and molecular mechanism of Hippo signaling in suppressing liver tumor formation

摘要 最近的研究扩大了炎症是肿瘤进展的关键组成部分的概念。它是 现在清楚的是，肿瘤微环境在很大程度上是由炎性细胞精心策划的，是不可或缺的 参与肿瘤过程，促进增殖、生存和迁移。在过去的几十年里， 免疫疗法在治疗癌症方面变得越来越重要。因此，迫切需要 更好地了解癌症与免疫的相互作用，特别是在特定的细胞、组织和缺陷的背景下 涉及的分子途径。人肝细胞癌是肝脏的一种原发恶性肿瘤， 全球癌症死亡的第二大原因是炎症诱发的癌症。 慢性病毒性肝炎、代谢性肝病和酗酒会导致慢性炎症，从而导致 纤维化、肝硬变和癌症。巨噬细胞在炎症的启动和维持中的作用 纤维化和肿瘤相关巨噬细胞(TAMs)在肿瘤进展过程中起着关键作用。然而， 巨噬细胞与肿瘤前病变相互作用的细胞和分子机制 肿瘤细胞在很大程度上仍然不为人知。河马信号通路最近已经成为一种主要的 肿瘤抑制途径，在抑制肝细胞增殖、存活和肝细胞癌形成中起关键作用。 河马途径的中心是YAP/Taz转录因子被起始于 河马激酶，在哺乳动物中是Mst1和Mst2。因为巨噬细胞的渗透显著增加 在去除了肝细胞中Mst1和Mst2的肝脏中，这项提议的目标是确定以前的 肝细胞内Hippo信号通过以下途径抑制肝癌发生的作用机制未知 抑制巨噬细胞浸润和分化。我们的初步研究已经确定了 肝细胞中两种分泌的河马信号效应因子--单核细胞趋化蛋白1(Mcp1或CCL2) 和Jagge1(Jag1)，每个都部分介导河马抑制炎症反应和肿瘤的作用 成长。我们假设在肝细胞中Hippo信号的一个以前未知的功能是调节 至少部分抑制Mcp1和Jag1的表达，从而促进肿瘤免疫反应。在具体目标1中，我们将 确定河马信号调控分化的分子机制 肝细胞。在特定目标2中，我们将确定巨噬细胞在肿瘤发生中的功能。 肝细胞特异性Mst1/2 DKO、Mst1/2/Mcp1 TKO和Mst1/2/Jag1 TKO肝。在具体目标3中，我们将 确定肝细胞内Hippo信号抑制Mcp1等基因表达的机制 各种因素。从拟议研究中获得的知识将为进一步 肝脏河马信号诱导炎症、肿瘤微环境的机制研究 为肝细胞癌的治疗提供新的靶点和策略。

Summary Recent studies have expanded the concept that inflammation is a critical component of tumor progression. It is now clear that the tumor microenvironment largely orchestrated by inflammatory cells, is an indispensable participant in neoplastic process, fostering proliferation, survival and migration. In the last few decades, immunotherapy has become increasingly important in treating cancer. Therefore, there is an urgent need to better understand cancer-immune interactions, particular under specific contexts of cells, tissues and deficient molecular pathways involved. Human hepatocellular carcinoma (HCC), a primary malignancy of the liver and the second-leading cause of cancer mortality worldwide is an example of inflammation-induced cancer. Chronic viral hepatitis, metabolic liver diseases, and alcohol abuse cause chronic inflammation, which induces fibrosis, cirrhosis, and cancer. Macrophages function in the initiation and maintenance of inflammation and fibrosis and tumor associated macrophages (TAMs) play critical roles during cancer progression. However, the cellular and molecular mechanisms underlying reciprocal interaction between macrophages and pre-tumor/ tumor cells remain largely unknown. The Hippo signaling pathway has recently emerged as a major oncosuppressive pathway and play critical roles inhibiting hepatocyte proliferation, survival and HCC formation. Central to the Hippo pathway is the inhibition of Yap/Taz transcription factors by a kinase cascade starting from the Hippo kinase, which are Mst1 and Mst2 in mammals. As macrophage infiltration is dramatically increased in livers with Mst1 and Mst2 removed in hepatocytes, the goal of this proposal is to determine a previously unknown functional mechanism by which Hippo signaling in hepatocytes attenuates hepatocarcinogenesis by inhibiting macrophage infiltration and TAM differentiation. Our preliminary studies have led to the identification of two secreted effectors of Hippo signaling in hepatocytes, monocyte chemoattractant protein 1(Mcp1 or Ccl2) and Jagged 1 (Jag1), that each partially mediates Hippo effects in restricting inflammatory response and tumor growth. We hypothesize that a previously unknown function of Hippo signaling in hepatocytes is to regulate pro-tumor immune response by at least partially inhibiting Mcp1 and Jag1 expression. In Specific Aim 1, we will determine the molecular mechanism underlying TAM differentiation regulated by Hippo signaling in hepatocytes. In Specific Aim 2, we will determine the functions of macrophages in tumorigenesis in the hepatocyte specific Mst1/2 DKO, Mst1/2/Mcp1 TKO and Mst1/2/Jag1 TKO liver. In Specific Aim 3, we will determine the mechanisms whereby Hippo signaling in hepatocytes inhibits expression of Mcp1 and other factors. The knowledge gained from the proposed studies will establish a solid new foundation for further mechanistic investigation of hepatic Hippo signaling in inducing inflammation, tumor microenvironment remodeling and provide new targets and strategies to treat HCC.