Analysis of a novel regulator of hepatocellular carcinoma

描述(申请人提供)：肝细胞癌是一种高度侵袭性的癌症，目前还没有有效的治疗方法。了解肝细胞癌发生和发展的分子机制对于开发新的、有效的和有针对性的治疗这种致命疾病是必不可少的。我们最近的研究结果表明，星形胶质细胞上调基因-1(AEG-1)在肝细胞癌的发病机制中起着重要作用。在人肝细胞癌组织中，AEG-1mRNA和蛋白的表达明显高于正常肝组织，并且在部分肝细胞癌患者中，AEG-1基因本身也被扩增。在109例肝细胞癌患者中，90%的病例AEG-1蛋白过度表达，且AEG-1的表达水平与疾病的分期和分级密切相关。在侵袭性较弱的肝癌细胞中强制过表达AEG-1导致了裸鼠体内高侵袭性、血管生成和转移的肿瘤。相反，抑制AEG-1显著抑制了裸鼠体内高侵袭性肝癌细胞的生长。在肝癌细胞中，AEG-1激活MEK/ERK、PI3K/Akt、NF-1b和Wnt等促生存信号通路，调控侵袭、血管生成、化疗耐药和衰老的特异性基因。此外，AEG-1保护原代人肝细胞免受衰老诱导。这些发现有力地表明AEG-1在调节肝细胞癌的发生发展中起着重要作用。AEG-1既存在于细胞表面，也存在于包括细胞核在内的细胞内。虽然AEG-1位于细胞表面，通过与内皮细胞的黏附促进肿瘤的转移，但我们的发现表明，细胞内的AEG-1可能通过启动促生存信号和调节基因表达而参与肿瘤发生的初始步骤，如永生化和转化。我们以前已经证明AEG-1是一个转录共激活因子，目前我们发现它是一个与AEG-1相互作用的伙伴葡萄球菌核酸酶结构域-1(SND1)，它通过调节转录、mRNA剪接、RNA干扰和mRNA稳定性来调节基因的表达。本提案的长期目标是确定调控肝癌发病机制的关键因素，并将这些知识转化为开发新的和有效的靶向治疗。本研究的近期目标是在转基因小鼠模型中分析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；通过分析患者来源的肝细胞癌样本，建立AEG-1作为肝癌诊断和预后标记物的作用。拟议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，从而促进开发阻断AEG-1作为潜在的肝癌治疗方案的策略。

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.