ER stress and UPR in non-alcoholic steatohepatitis and hepatocellular carcinoma

 描述（由申请人提供）：近25%的美国人口患有非酒精性脂肪性肝病（NAFLD），可进展为脂肪性肝炎（NASH）、纤维化、肝硬化和肝细胞癌（HCC）。我们最近的研究以及其他研究将内质网应激（ER应激）与非酒精性脂肪肝（NAFLD）联系起来。然而，ER应激是否/如何影响NASH发展和/或HCC发生和进展尚不清楚。与Michael Karin博士（UCSD）合作，我们令人兴奋的初步数据表明，通过尿激酶或错误折叠蛋白的过度转基因表达与高脂饮食（HFD）结合诱导肝细胞中的ER应激激活未折叠蛋白反应（UPR），足以引起与人类NASH相似的症状并进展为HCC。这一基本发现为我们提出的研究提供了基础，以确定ER应激和细胞死亡信号传导在细胞转化和肿瘤微环境中的作用，通过使用小鼠模型，携带选择性UPR信号传导组分的条件性基因缺失。尽管许多研究都集中在肿瘤进展上，但我们的研究是独一无二的，因为我们将确定启动肿瘤发生的因素。为了阐明UPR在癌症发生中的作用，我们将通过我们的特定目标（SA）测试四个假设。SA 1：ER应激可启动NASH和HCC形成。我们将使用两个独立的ER应激模型来测试ER应激的诱导是否有助于NASH和HCC的发展。我们还将测试ER稳态的恢复是否会减少肿瘤的形成。此外，通过与Peter Metrakos博士（麦吉尔大学）的合作，我们将能够在人类患者中验证小鼠模型的发现。SA 2：UPR（PERK/eIF 2/ATF 4/CHOP）的促凋亡臂的消除将促进NASH和HCC的启动。我们将消除肝细胞中eIF 2 β磷酸化、ATF 4或CHOP，以确定HCC发展中对它们的需求，并通过将HCC祖细胞接种到喂食HFD的MUP-uPA小鼠中来测试HCC发展中ATF 4和/或CHOP增加或减少的效果是否是细胞自主的。SA 3：NASH/HCC的发展受到微环境中PERK/eIF 2 α/ATF 4/CHOP通路的抑制。在基质细胞中，ATF 4和CHOP将被特异性删除，eIF 2磷酸化被消除，以测试它们对HCC进展的需要，并确定它们对炎症和血管生成的影响。尽管广泛的努力针对靶向癌症中的UPR信号传导，但UPR是否促进或限制肿瘤起始和/或发展仍是未知的。我们提出的研究将为这些问题提供前所未有的重要见解，这些问题将影响针对癌症的UPR的努力。

 DESCRIPTION (provided by applicant): Almost 25% of the US population suffers from non-alcoholic fatty liver disease (NAFLD) that can progress to steatohepatitis (NASH), fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Our recent studies, as well as others, link endoplasmic reticulum stress (ER stress) with non-alcoholic fatty liver disease (NAFLD). However, it is unknown whether/how ER stress impacts NASH development and/or HCC initiation and progression. In collaboration with Dr. Michael Karin (UCSD), our exciting preliminary data demonstrate that induction of ER stress in hepatocytes by excessive transgene expression of urokinase or a misfolded protein combined with a high fat diet (HFD) activates the unfolded protein response (UPR) and is sufficient to cause symptoms similar to human NASH with progression to HCC. This fundamental finding provides the basis for our proposed studies to identify the role of ER stress and cell death signaling in cell transformation and in the tumor microenvironment through the use of murine models harboring conditional gene deletion of selective UPR signaling components. Although many studies have focused on tumor progression, ours is unique because we will identify factors that initiate tumorigenesis. To elucidate the role of the UPR in cancer initiation we will test four hypotheses through our specific aims (SA). SA1: ER stress can initiate NASH and HCC formation. We will test whether induction of ER stress contributes to NASH and HCC development using two independent models of ER stress. We will also test whether restoration of ER homeostasis decreases tumor formation. Furthermore, in collaboration with Dr. Peter Metrakos (McGill University), we will be able to verify the findings from mouse model in human patients. SA2: Elimination of the proapoptotic arm of the UPR (PERK/eIF2/ATF4/CHOP) will promote NASH and HCC initiation. We will eliminate eIF2 phosphorylation, ATF4 or CHOP in hepatocytes to determine their requirement in HCC development, and test whether the effect increased or decreased ATF4 and/or CHOP in HCC development is cell autonomous by inoculation of HCC progenitors into MUP-uPA mice fed with HFD. SA3: NASH/HCC development is restrained by the PERK/eIF2α/ATF4/CHOP pathway in the microenvironment. ATF4 and CHOP will be specifically deleted and eIF2 phosphorylation eliminated in stromal cells to test their requirement for HCC progression and determine their impact on inflammation and angiogenesis. Although extensive efforts are being directed to target UPR signaling in cancer, it remains unknown whether the UPR promotes or limits tumor initiation and/or development. Our proposed studies will provide essential key unprecedented insight into these questions that should impact efforts to target the UPR in cancer.