P27Kip1 in Hepatocyte Proliferation

描述(申请人提供)：细胞周期调控领域的研究已经确定了许多重要的细胞周期调节因子，并提供了关于如何在各种环境下控制细胞增殖的丰富知识。蛋白激酶抑制剂p27Kipl通过抑制多种细胞周期蛋白依赖性蛋白激酶的活性来抑制细胞增殖。靶向灭活小鼠中的p27会导致多器官肿大的比例增大的动物。这些动物的肝脏含有大约25%明显正常的肝细胞，但并没有增加肝细胞癌的发病率。我们推测，肝细胞中p27的这一特性可能被用于肝细胞治疗。我们最近报道了从p27基因敲除小鼠分离的肝细胞在小鼠肝衰竭移植模型中表现出增强的增殖能力，为我们的假设提供了初步的实验支持，即操作p27可能是提高肝细胞移植效率的有用方法。这一应用的目的是通过下一水平的p27靶向策略来更好地了解肝细胞中的p27，从而使我们能够更好地评估靶向p27在人类肝细胞移植中的潜力。在具体目标1中，我们将建立肝细胞特异性的、可诱导的p23基因敲除小鼠，以研究p23在肝脏不同阶段的肝细胞中的作用。然后，我们将使用从这些小鼠分离的肝细胞来确定p27在体外(特异性目标2)和移植后肝细胞增殖(特异性目标3)中的功能作用和机制。在特定的目标4中，我们将确定p27在两个小鼠肝肿瘤模型中的作用，这两个模型涉及致癌前肝细胞的广泛增殖。这些研究的成功完成将为肝细胞中p27的研究提供坚实的知识。这些知识将构成控制肝细胞增殖的基础，这对于找到合理的方法来操纵肝细胞增殖以利于肝脏疾病的治疗和肝脏基因治疗是必不可少的。

DESCRIPTION (provided by applicant): Studies in the field of cell cycle regulation have identified many important cell cycle regulators and provided a wealth of knowledge about how cell proliferation is controlled in various settings. The kinase inhibitor p27Kipl inhibits the kinase activity of various cyclin-dependent kinases to restrain cell proliferation. Targeted inactivation of p27 in the mouse results in proportionally enlarged animals with multi-organomegaly. The livers of these animals contain about 25% more apparently normal hepatocytes but do not have increased incidence of hepatocellular carcinoma. We reasoned that this property of p27 in hepatocytes may be used to benefit hepatocyte-based therapies. We have recently reported that hepatocytes isolated from p27 knockout mice demonstrated improved proliferation ability in a mouse liver failure transplantation model, providing initial experimental support for our hypothesis that manipulation of p27 could be a useful approach to improving the efficiency of hepatocyte transplantation. The objective of this application is to gain a better understanding of p27 in hepatocytes with next-level p27 targeting strategies, which will then enable us to better evaluate the potentials of targeting p27 in human hepatocyte transplantation. In Specific Aim 1, we will generate hepatocyte-specific, inducible p23 knockout mice to study the role of p23 in hepatocytes at various stages in the liver. We will then use hepatocytes isolated from these mice to determine the functional role and mechanisms of p27 in hepatocyte proliferation in vitro (Specific Aim 2) and after transplantation (Specific Aim 3). In Specific Aim 4, we will determine the role of p27 in hepatocellular carcinogenesis in two mouse liver tumor models that involve extensive hepatocyte proliferation prior to oncogenic transformation. Successful completion of these studies will provide a solid knowledge of p27 in hepatocytes. This knowledge will form the foundation by which hepatocyte proliferation is controlled, which is essential for finding rationale ways to manipulate hepatocyte proliferation to benefit the treatment of liver diseases and liver gene therapy.