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

 描述(申请人提供)：近25%的美国人口患有非酒精性脂肪性肝病(NAFLD)，可发展为脂肪性肝炎(NASH)、纤维化、肝硬变和肝细胞癌(HCC)。我们最近的研究以及其他研究，将内质网应激(ER应激)与非酒精性脂肪性肝病(NAFLD)联系起来。然而，目前尚不清楚内质网应激是否/如何影响NASH的发生和/或肝细胞癌的发生和发展。与Michael Karin博士(UCSD)合作，我们令人兴奋的初步数据表明，通过过量转基因表达尿激酶或错误折叠的蛋白质结合高脂肪饮食(HFD)在肝细胞中诱导内质网应激，激活未折叠蛋白反应(UPR)，并足以导致类似于人类NASH的症状并进展为肝细胞癌。这一基本发现为我们提出的通过使用携带选择性UPR信号成分条件性基因缺失的小鼠模型来确定ER应激和细胞死亡信号在细胞转化和肿瘤微环境中的作用的研究提供了基础。虽然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形成的因素。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)来检验四个假说。SA1：内质网应激可启动NASH和肝细胞癌的形成。我们将使用两个独立的内质网应激模型来测试内质网应激的诱导是否有助于NASH和肝细胞癌的发生。我们还将测试内质网稳态的恢复是否会减少肿瘤的形成。此外，与麦吉尔大学的Peter Metrakos博士合作，我们将能够在人类患者的老鼠模型中验证这一发现。SA2：消除UPR的促凋亡臂(PERK/eIF2/ATF4/CHOP)将促进NASH和肝癌的启动。我们将消除肝细胞中eIF2ATF4或CHOP的磷酸化，以确定它们在肝癌发展中的需求，并测试通过将肝癌前体细胞接种于饲喂高脂饲料的MUP-uPA小鼠，在肝癌发展中增加或减少ATF4和/或CHOP的作用是否具有细胞自主性。在微环境中，PERK/eIF2/α/ATF4/CHOP通路抑制了NASH/肝癌的发展。基质细胞中的ATF4和CHOP将被特别删除，eIF2的磷酸化将被消除，以测试它们对肝细胞癌进展的要求，并确定它们对炎症和血管生成的影响。尽管针对癌症中的UPR信号转导正进行了广泛的努力，但UPR是否促进或限制了肿瘤的启动和/或发展仍是未知的。我们提出的研究将为这些问题提供重要的、关键的、前所未有的见解，这些问题应该会影响针对癌症的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.