Molecular Mechanisms of Stellate Cell Activation in Liver Fibrosis

肝纤维化星状细胞激活的分子机制

• 批准号: 9559537
• 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
• 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/9559537
• 关键词: 3' 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 Initiators; Tumor Promotion; Tumor Suppression; Veterans; Xenograft Model; base; beta catenin; cell type; chronic liver disease; desaturase; design; eicosanoid metabolism; feeding; hepatocellular carcinoma cell line; innovation; insight; lipid metabolism; liver development; mRNA Stability; morphogens; mouse model; neoplastic cell; new therapeutic target; novel; palmitoleic acid; prevent; recruit; response; screening; self-renewal; stellate cell; stem-like cell; stemness; transcriptome; transcriptomics; tumor; tumor growth; tumor initiation; tumor microenvironment; tumorigenic; wound

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HSC（AHSC）参与肝纤维发生并促进肝脏的发展 肿瘤是慢性肝病的两个最具破坏性的后遗症。我们为筛选Wnt的严格努力 - AHSC中的β-catenin靶基因鉴定出编码ER的SCD（stearoyl-COA去饱和酶） 负责合成单不饱和脂肪酸（MUFA）的酶，并与 脂肪肝，癌症和干性。 SCD通过β-的能力以Wnt依赖性方式更新 Catenin与SREBP-1C结合，潜在的近10倍SREBP-1C诱导的转录。就职 在SCD2中，HSC激活需要在HSC中占主导地位的同工型，并提供了A 正向循环通过LRP5/6 mRNA稳定性扩增规范WNT途径。这个小说循环是 由SCD生成的MUFA发起 Transportin（TNPO）和RAN1 GTPase，导致HUR细胞质积累，HUR与 LRP5/6 mRNA 3'UTR及其稳定。 SCD抑制或SCD2沉默消除了LRP5/6 β-catenin在AHSC中的表达和稳定，并减轻小鼠的肝纤维化。有趣的是， Wnt-SCD2-LRP5/6环也存在于肝脏肿瘤发射干细胞（TICS）和HUH7中 细胞的自我更新和肿瘤发射活性是必需的，建立了这一新颖的 途径是AHSC和TICS/HCC细胞中的功能核心。我们进一步证明了 AHSC中的有条件SCD2 KO（SCD2 CKO）丧失了AHSC的能力以促进TIC引起的肿瘤 裸鼠的生长并抑制肿瘤细胞SCD2表达和肝的自然发育 小鼠二乙基亚硝基胺（DEN）诱导的肿瘤。我们最近的脂质组和转录组 SCD2 CKO小鼠的非肿瘤肝组织的分析揭示了全球抑制肿瘤的抑制 胆固醇合成和类花生酸代谢中的脂质重编程。 基于这些结果，我们假设AHSC建立的SCD2-HUR-WNT阳性环路 通过针对涉及的基因诱导微环境中促进肿瘤的脂质重编程 胆固醇的合成以及类花生素的产生和代谢。检验这一假设和 HSC SCD2的肿瘤增强剂作用机制，我们将解决以下目的： 目的1。确定肝细胞中的SCD2是否有条件KO可防止DEN诱导的肝脏 通过使用SCD2FF; Alb-Cre与SCD2FF小鼠的肿瘤发育。 目标2。确定HSC SCD2是否通过计时增强了肿瘤起始与肿瘤促进 SCD2使用SCD2FF; col1a1-cre-ert2消融。 AIM-3。确定AHSC中的SCD2如何支持促进脂质微环境的肿瘤。 目标3-1。确定β-catenin依赖性调节HMGCR转录的机制。 目标3-2。确定β-catenin是否通过TCF刺激了FADS1/2和LTA4H。 目标3-3。确定LTA4H mRNA是否通过SCD上调。 目标3-4。验证在HCC-PDX（患者衍生的Xenograpon）中验证SCD介导的脂质重编程 模型。 总的来说，这些努力将定义HSC的新型肿瘤增强剂作用的机制 SCD2并帮助确定HCC的新治疗靶标。