Analysis of a novel regulator of hepatocellular carcinoma

描述（由申请人提供）：肝细胞癌（HCC）是一种高度侵袭性的癌症，目前尚无有效的治疗方法。了解HCC发生和进展的分子机制对于开发针对这一致命疾病的新颖、有效和靶向治疗方法至关重要。我们最近的研究结果表明星形胶质细胞升高基因-1 （AEG-1）在HCC发病中起重要作用。在人类HCC样本中，与正常肝脏相比，AEG-1 mRNA和蛋白显着过表达，并且在一部分HCC患者中，AEG-1基因本身被扩增。109例HCC患者中，90%以上的患者存在AEG-1蛋白过表达，且AEG-1表达水平与HCC的分期、分级有显著相关性。在低侵袭性HCC细胞中强迫过表达AEG-1导致裸鼠高侵袭性、血管生成和转移性肿瘤。相反，抑制AEG-1可显著抑制裸鼠体内高侵袭性HCC细胞的生长。在HCC细胞中，AEG-1激活促生存信号通路，如MEK/ERK、PI3K/Akt、NF-？已知与肝癌发生有关的B和Wnt信号通路和AEG-1可调节侵袭、血管生成、化疗耐药和衰老的特定基因。此外，AEG-1保护原代人肝细胞免于诱导衰老。这些发现有力地表明，AEG-1在调节HCC的发生和进展中起着重要的作用。AEG-1既位于细胞表面，也位于包括细胞核在内的细胞内区室。虽然位于细胞表面的AEG-1通过粘附内皮促进转移，但我们的研究结果表明，细胞内的AEG-1可能通过开启促生存信号和调节基因表达，参与肿瘤发生的初始步骤，如永生化和转化。我们之前已经证明了AEG-1作为转录共激活因子的功能，目前我们确定了AEG-1的相互作用伙伴葡萄球菌核酸酶结构域包含-1 （SND1）通过调节转录、mRNA剪接、RNA干扰和mRNA稳定性来调节基因表达。本提案的长期目标是确定调节HCC发病机制的关键因素，并将这些知识转化为开发新颖有效的靶向治疗方法。本提案的直接目标是分析转基因小鼠模型中AEG-1在肝癌发生中的作用；阐明AEG-1- snd1相互作用在介导AEG-1功能和肝癌发生中的作用；并通过分析患者来源的HCC样本，建立AEG-1作为HCC的诊断和预后标志物。这些研究的成功完成将为深入了解AEG-1的结构和功能领域提供深入的见解，从而促进阻断AEG-1作为HCC潜在治疗方案的策略的发展。

DESCRIPTION (provided by applicant): Hepatocellular carcinoma (HCC) is a highly aggressive cancer with no currently available effective treatment. Understanding the molecular mechanism of HCC development and progression is imperative to develop novel, effective and targeted therapies for this lethal disease. Our recent findings reveal that Astrocyte Elevated Gene-1 (AEG-1) plays an important role in HCC pathogenesis. In human HCC samples AEG-1 mRNA and protein were significantly overexpressed compared to normal liver and in a subset of HCC patients AEG-1 gene itself was amplified. In 109 HCC patients, AEG-1 protein was overexpressed in >90% cases and AEG-1 expression level showed significant correlation with the stages and grades of the disease. Forced overexpression of AEG-1 in less aggressive HCC cells resulted in highly aggressive, angiogenic and metastatic tumors in nude mice. Conversely, inhibition of AEG-1 significantly abrogated growth of highly aggressive HCC cells in nude mice. In HCC cells, AEG-1 activated pro-survival signaling pathways such as MEK/ERK, PI3K/Akt, NF-?B and Wnt signaling pathways that are known to contribute to hepatocarcinogenesis and AEG-1 modulated specific genes regulating invasion, angiogenesis, chemoresistance and senescence. Additionally, AEG-1 protected primary human hepatocytes from induction of senescence. These findings strongly indicate that AEG-1 plays an important role in regulating HCC development and progression. AEG-1 is located both on the cell surface and in intracellular compartments including the nucleus. While the cell surface located AEG-1 facilitates metastasis by adhering to the endothelium, our findings indicate that the intracellular AEG-1 might contribute to the initial steps of tumorigenesis, such as immortalization and transformation, by turning on pro-survival signals and modulating gene expression. We have previously shown that AEG-1 functions as a transcriptional co-activator and presently we identify as an AEG-1 interacting partner Staphylococcal Nuclease Domain Containing-1 (SND1) which regulates gene expression by modulating transcription, mRNA splicing, RNA interference and mRNA stability. The long-term objectives of the present proposal are to identify key players regulating HCC pathogenesis and translate that knowledge for developing novel and effective targeted therapies. The immediate objectives of the present proposal are to analyze the role of AEG-1 in hepatocarcinogenesis in a transgenic mouse model; elucidate the role of AEG-1-SND1 interaction in mediating AEG-1 function as well as hepatocarcinogenesis; and establish AEG-1 as a diagnostic and prognostic marker for HCC by analyzing patient-derived HCC samples. Successful completion of the proposed studies will provide in-depth insights into structural and functional realms of AEG-1 thus facilitating development of strategies to block AEG-1 as a potential therapeutic regimen for HCC. PUBLIC HEALTH RELEVANCE: Astrocyte elevated gene-1 (AEG-1) is overexpressed in hepatocellular carcinoma (HCC) patients and plays a key role in regulating hepatocarcinogenesis by turning on pro- survival signals and modulating global gene expression. The proposed studies aim at understanding AEG-1 function by using a transgenic mouse model and analyzing AEG-1 interacting proteins and establishing AEG-1 as a diagnostic and prognostic marker for HCC.