Role of Age in Liver Cancer

描述（由申请人提供）：年龄是肝癌发展的主要危险因素之一，肝癌是世界上第五大常见癌症和第三大常见癌症相关死亡原因。尽管癌症研究取得了重大进展，但肝癌的早期发现和治疗进展甚微，导致预后不良。在过去的15年里，我的实验室一直在进行研究，以确定随着年龄的增长而改变的关键信号通路，这些信号通路使肝细胞更容易患上肝癌。其中一种途径是转录因子CCAAT/增强子结合蛋白α (C/EBPa)在S193处的超磷酸化。我们已经成功培育出C/EBPa-S193D敲入小鼠（S193D），其模拟了C/EBPa的年龄相关的ph-S193亚型，并发现S193D小鼠在部分肝切除术后的肝脏增殖完全受到抑制。令我们惊讶的是，我们发现S193D小鼠的肝脏肿瘤的发展速度比WT小鼠快得多。此外，我们发现gankyrin特异性地与C/EBPa的S193D和ph-S193亚型相互作用并降解。该应用的主要假设是，gankyrin的激活和随后的C/EBPa的降解是肝癌发展的关键调控途径。我们最近的研究表明，farnesoid X受体（FXR）及其下游靶点SHP抑制gankyrin。FXR/SHP的缺失导致gankyrin的激活，导致C/EBPa的降解，并在12-17月龄之间形成自发性肝脏肿瘤。特异性目标1将探讨FXR/SHP通路抑制gankyrin的机制。为此，我们计划完成以下工作：a)研究单个FXR和SHP KO小鼠是否激活gankyrin， b)检测新生、2月、6月和12月大FXR/SHP DKO小鼠中gankyrin的激活，以确定gankyrin激活的年龄，c)鉴定参与gankyrin激活的FXR依赖性转录因子，d)通过测量不同年龄患者HCC样本中的gankyrin来验证gankyrin- c /EBPa通路的激活。特异性目的2将检测FXR的激活是否抑制肝脏肿瘤。我们将通过FXR特异性配体GW4064激活FXR，并研究这种激活是否会减少DEN介导的肝癌的发生率/数量。特异性目的3将研究抑制gankyrin-C/EBP1通路是否会阻止肝脏肿瘤的形成。我们计划采用以下方法：a)在WT den处理小鼠和FXR/SHP小鼠中通过siRNA抑制gankyrin的表达，并检查这种抑制是否会减少肝脏肿瘤的发生率/数量，b)开发阻断gankyrin与C/EBP1结合的方法。因此，本文提出的研究将为肝癌的预防提供新的基于甘肽的方法。

DESCRIPTION (provided by applicant): Age is one of the major risk factors for development of the liver cancer, which is the fifth most common cancer and the third most common cause of cancer related death in the world. Despite significant advances in cancer research, little progress has been made in early detection and treatment of liver cancer leading to poor prognosis. Over the past 15 years, my laboratory has pursued the studies to determine the key signaling pathways that are changed by aging and that make liver cells more susceptible to development of liver cancer. One of these pathways is the hyper-phosphorylation of a transcription factor, CCAAT/Enhancer Binding protein alpha, C/EBPa, at S193. We have successfully generated C/EBPa-S193D knockin mice (S193D) which mimic the age-associated ph-S193 isoform of C/EBPa and found that liver proliferation after partial hepatectomy is completely inhibited in S193D mice. To our surprise, we found that the development of liver tumors in S193D mice occurs much faster than in WT mice. Furthermore, we found that gankyrin specifically interacts with and degrades the S193D and ph-S193 isoforms of C/EBPa. The main hypothesis of the application is that the activation of gankyrin and following degradation of C/EBPa is a key regulatory pathway in development of liver cancer. Our recent studies show that farnesoid X receptor (FXR) and its down-stream target SHP suppress gankyrin. The deletion of FXR/SHP leads to activation of gankyrin resulting in the degradation of C/EBPa and the formation of spontaneous liver tumors at age between 12-17 months. Specific Aim 1 will address mechanisms by which FXR/SHP pathway represses gankyrin. In this aim, we plan to accomplish the following: a) Investigate if single FXR and SHP KO mice activate gankyrin, b) Examine the activation of gankyrin in newborn, 2 mo, 6 mo and 12 mo old FXR/SHP DKO mice in order to determine the age at which gankyrin is activated, c) Identify FXR-dependent transcription factors that are involved in the activation of gankyrin, and d) Verify the activation of gankyrin- C/EBPa pathway by measuring gankyrin in human HCC samples obtained from patients of different ages. Specific Aim 2 will examine if the activation of FXR inhibits liver tumor. We will activate FXR by FXR-specific ligand GW4064 and examine if this activation will reduce the incidence/number of liver tumors in DEN- mediated carcinogenesis. Specific Aim 3 will investigate if the inhibition of gankyrin-C/EBP1 pathway will prevent liver tumor formation. We plan to use the following approaches: a) Inhibit the expression of gankyrin by siRNA in both WT DEN-treated mice and FXR/SHP mice and examine if this inhibition will reduce the incidence/number of liver tumors, and b) Develop approaches to block gankyrin binding to C/EBP1. Thus, the proposed studies will provide novel gankyrin-based approaches for the prevention of liver cancer.