Molecular Mechanisms of Stellate Cell Activation in Liver Fibrosis

肝纤维化星状细胞激活的分子机制

基本信息

批准号：
10292434
负责人：
HIDEKAZU TSUKAMOTO
金额：
--
依托单位：
VA GREATER LOS ANGELES HEALTHCARE SYSTEM
依托单位国家：
美国
项目类别：
财政年份：
2013
资助国家：
美国
起止时间：
2013-10-01 至 2022-09-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10292434
关键词：
3&apos Untranslated Regions ADD-1 protein Ablation Address Attenuated Binding Binding Proteins Biological Cell Fate Control Cells Cholesterol Cholesterol Homeostasis Cirrhosis Development Down-Regulation Eicosanoids Encapsulated Enhancers Enzymes Epigenetic Process Fatty Liver Gene Expression Profiling Generations Genes Genetic Genetic Transcription Goals Guanosine Triphosphate Phosphohydrolases Hepatic Hepatic Fibrogenesis Hepatic Stellate Cell Hepatocyte Heterochromatin HuR protein Karyopherins Lipids Liver Fibrosis Liver neoplasms Malignant neoplasm of liver Mediating Messenger RNA Metabolism Methyl-CpG-Binding Protein 2 Modality Modeling Molecular Monounsaturated Fatty Acids Mus Nitrosamines Nuclear Import Nude Mice Oleic Acids PPAR gamma Pathway interactions Patients Protein Isoforms Published Comment Regulation Research Research Support Role Saturated Fatty Acids Series Stearoyl-CoA Desaturase Testing Therapeutic Tissues Transcriptional Regulation Tumor Promotion Tumor Suppression Veterans base beta catenin cell type chronic liver disease desaturase design eicosanoid metabolism hepatocellular carcinoma cell line innovation insight lipid metabolism lipidomics liver development mRNA Stability morphogens mouse model neoplastic cell new therapeutic target novel palmitoleic acid patient derived xenograft model prevent recruit screening self-renewal stellate cell stem-like cell stemness transcriptome transcriptomics tumor tumor growth tumor initiation tumor microenvironment tumorigenic wound response

项目摘要

Activated HSCs (aHSCs) participate in liver fibrogenesis and promote the development of liver tumor, the two most devastating sequela of chronic liver disease. Our rigorous efforts to screen Wnt- β-catenin target genes in aHSCs, identified Scd (stearoyl-CoA desaturase) which encodes an ER enzyme responsible for the synthesis of mono-unsaturated fatty acids (MUFA) and is implicated in fatty liver, cancer and stemness. Scd is upregulated in a Wnt-dependent manner by the ability of β- catenin to bind to SREBP-1c and potentiate nearly 10-fold SREBP-1c-induce transcription. Induction of Scd2, an isoform dominantly expressed in HSCs is required for HSC activation and provides a positive forward loop to amplify canonical Wnt pathway via Lrp5/6 mRNA stability. This novel loop is initiated by SCD-generated MUFA interfering nuclear import of the mRNA binding protein HuR via Transportin (TNPO) and Ran1 GTPase, resulting in HuR cytoplasmic accumulation, HuR binding to Lrp5/6 mRNA 3'UTR, and their stabilization. SCD inhibition or Scd2 silencing abrogates LRP5/6 expression and stabilization of β-catenin in aHSCs, and attenuates liver fibrosis in mice. Intriguingly, the Wnt-SCD2-LRP5/6 loop also exists in liver tumor-initiating stem-cell like cells (TICs) and Huh7 cells and is required for their self-renewal and tumor-initiating activity, establishing this novel pathway as a functional core in both aHSCs and TICs/HCC cells. We further demonstrate that conditional Scd2 KO in aHSCs (Scd2 cKO) incapacitates aHSCs to promote TIC-initiated tumor growth in nude mice and suppresses tumor cell Scd2 expression and natural development of liver tumors induced by diethyl nitrosamine (DEN) in mice. Our most recent lipidomic and transcriptomic analyses of non-tumor liver tissues of Scd2 cKO mice, reveal global suppression of tumor-promoting lipid reprogramming in cholesterol synthesis and eicosanoid metabolism. Based on these results, we hypothesize that SCD2-HuR-Wnt positive loop established by aHSCs induces tumor-promoting lipid reprogramming in microenvironment by targeting genes involved in cholesterol synthesis and eicosanoid generation and metabolism. To test this hypothesis and the mechanisms of the tumor enhancer role of HSC SCD2, we will address the following aims: Aim 1. To determine whether Scd2 conditional KO in hepatocytes prevents DEN-induced liver tumor development by using Scd2ff;Alb-Cre vs. Scd2ff mice. Aim 2. To determine whether HSC SCD2 enhances tumor initiation vs. tumor promotion by timing Scd2 ablation using Scd2ff;Col1a1-Cre-ERT2. Aim-3. To determine how SCD2 in aHSCs supports tumor promoting lipid microenvironment. Aim 3-1. To determine the mechanism of β-catenin dependent regulation of HMGCR transcription. Aim 3-2. To determine whether β-catenin transcriptionally stimulates FADS1/2 and LTA4H via TCF. Aim 3-3. To determine if LTA4H mRNA is up-regulated by HuR via SCD. Aim 3-4. To validate SCD-mediated lipid reprogramming in HCC-PDX (patient-derived xenograft) model. Collectively, these efforts will define the mechanisms of the novel tumor enhancer role of HSC SCD2 and help identify new therapeutic targets for HCC.

活化的HSCs（aHSCs）参与肝纤维化并促进肝脏的发育肿瘤，慢性肝病的两种最具破坏性的后遗症，我们严格努力筛查 Wnt-。 aHSC 中的 β-连环蛋白目标基因，鉴定出编码 ER 的 Scd（硬脂酰辅酶 A 去饱和酶）负责合成单不饱和脂肪酸（MUFA）的酶，与脂肪肝、癌症和干细胞性 Scd 通过 β- 的能力以 Wnt 依赖性方式上调。连环蛋白与 SREBP-1c 结合并增强近 10 倍的 SREBP-1c 诱导转录。 Scd2 是 HSC 激活所必需的一种主要在 HSC 中表达的亚型，并提供了正向循环通过 Lrp5/6 mRNA 稳定性放大经典 Wnt 通路。由 SCD 生成的 MUFA 引发，通过干扰 mRNA 结合蛋白 HuR 的核输入转运蛋白 (TNPO) 和 Ran1 GTPase，导致 HuR 细胞质积累，HuR 结合 Lrp5/6 mRNA 3'UTR 及其稳定化 SCD 抑制或 Scd2 沉默会消除 LRP5/6。有趣的是，β-连环蛋白在 aHSC 中的表达和稳定性，并减轻小鼠的肝纤维化。 Wnt-SCD2-LRP5/6 环也存在于肝肿瘤起始干细胞样细胞 (TIC) 和 Huh7 中细胞的自我更新和肿瘤启动活性所必需的，建立了这种新颖的我们进一步证明了该途径作为 aHSC 和 TIC/HCC 细胞的功能核心。 aHSC 中条件性 Scd2 KO (Scd2 cKO) 使 aHSC 丧失能力，促进 TIC 引发的肿瘤小鼠裸体生长并抑制肿瘤细胞Scd2表达和肝脏自然发育我们最新的脂质组学和转录组学研究在小鼠体内由二乙基亚硝胺（DEN）诱导的肿瘤。对 Scd2 cKO 小鼠非肿瘤肝组织的分析揭示了肿瘤促进的整体抑制胆固醇合成和类二十烷酸代谢中的脂质重编程。基于这些结果，我们勇敢地承认aHSCs建立了SCD2-HuR-Wnt正环通过靶向参与的基因诱导微环境中促进肿瘤的脂质重编程胆固醇合成和类二十烷酸生成和代谢来检验这一假设和。为了研究HSC SCD2的肿瘤增强剂作用机制，我们将致力于以下目标：目标 1. 确定肝细胞中 Scd2 条件性 KO 是否可以预防 DEN 诱导的肝脏使用 Scd2ff;Alb-Cre 与 Scd2ff 小鼠进行肿瘤发育。目标 2. 通过时间确定 HSC SCD2 是否增强肿瘤发生与肿瘤促进使用 Scd2ff;Col1a1-Cre-ERT2 消融 Scd2。 Aim-3. 确定 aHSC 中的 SCD2 如何支持肿瘤促进脂质微环境。目标 3-1. 确定 HMGCR 转录的 β-连环蛋白依赖性调节机制。目标 3-2。确定 β-catenin 是否通过 TCF 转录刺激 FADS1/2 和 LTA4H。目标 3-3。确定 HuR 是否通过 SCD 上调 LTA4H mRNA。目标 3-4。在 HCC-PDX（患者来源的异种移植物）中验证 SCD 介导的脂质重编程。模型。总的来说，这些努力将明确 HSC 新型肿瘤增强剂作用的机制 SCD2 有助于确定 HCC 的新治疗靶点。