The role of RalA in pancreatic tumorigenesis

描述(申请人提供)：胰腺癌预后很差，很大程度上是由于目前的治疗方案无效。我们的长期目标是确定胰腺癌发展的关键因素，以便将它们作为新的治疗策略的目标。我们的假设是K-RAS和Aurora-A激酶激活Rala是胰腺肿瘤发生的关键步骤。这一假说基于下列假设：1)几乎所有的胰腺癌都有对肿瘤发生至关重要的癌基因K-RAS的激活突变，而这种致癌信号在很大程度上是由人类的RalGlobal途径介导的；2)转化的RalGlobal效应因子Rala对于胰腺癌细胞的转化和致瘤生长都是至关重要的；3)Rala丝氨酸194被Aurora-A激酶磷酸化，是依赖RalGlobal的人类癌细胞转化所必需的；以及4)抑制Aurora-A可以降低胰腺癌细胞系的致瘤生长。我们建议评估Rala和Aurora-A在胰腺肿瘤发生中的作用。 具体目标1：确定Rala的缺失是否抑制K-ras诱导的小鼠胰腺肿瘤的发生。我们将评估有条件地在胰腺中表达致癌K-ras等位基因而不是Rala的转基因小鼠的自发胰腺肿瘤发生。 具体目标2：确定Rala是否通过其已知的效应分子RalBP1、Exo84或Sec5发挥作用，以介导胰腺癌的发展。我们将a)对候选的Rala下游效应因子RalBP1、Exo84或Sec5进行功能丧失分析，并确定对胰腺癌细胞系转化和致瘤生长的影响，以及b)确定Rala S194的磷酸化是否改变了Rala与RalBP1、Exo84或Sec5的结合亲和力。 具体目标3：确定Rala S194的Aurora-A磷酸化是否促进胰腺癌的生长。我们将a)确定Aurora-A对Rala S194的磷酸化是否是胰腺癌细胞转化和致瘤生长所必需的，b)确定Aurora-A抑制是否需要Rala S194来减少胰腺癌细胞的生长，以及c)确定Rala S194磷酸化是否导致Rala在胰腺癌细胞中的细胞内重新定位。

DESCRIPTION (provided by applicant): Pancreatic cancer has a dismal prognosis due in large part to the ineffectiveness of current treatment regimens. Our long-term goal is to identify key factors underlying pancreatic cancer development so that they can be targeted for new therapeutic strategies. Our hypothesis is that activation of RalA by both K-Ras and Aurora-A kinase is a key step in pancreatic tumorigenesis. This hypothesis is based on the following: 1) Nearly all pancreatic cancers have an activating mutation in the oncogene K-Ras critical for tumorigenesis, and this oncogenic signal is mediated in large part by the RalGEF pathway in humans; 2) the transforming RalGEF effector RalA is crucial for both transformed and tumorigenic growth of pancreatic cancer cell lines; 3) RalA serine 194, which is phosphorylated by Aurora-A kinase, is required for transformation of RalGEF-dependent human cancer cells; and 4) Aurora-A inhibition decreases tumorigenic growth of pancreatic cancer cell lines. We propose to evaluate the roles of RalA and Aurora-A in pancreatic tumorigenesis. Specific Aim 1: Determine if loss of RalA inhibits K-ras-driven pancreatic tumorigenesis in mice. We will evaluate spontaneous pancreatic tumorigenesis in transgenic mice which conditionally express an oncogenic K-ras allele but not RalA in the pancreas. Specific Aim 2: Determine whether RalA functions through its known effectors RalBP1, Exo84, or Sec5 to mediate the development of pancreatic cancer. We will a) perform loss-of-function analysis of the candidate RalA downstream effectors RalBP1, Exo84, or Sec5, and determine the effect on the transformation and tumorigenic growth of pancreatic cancer cell lines, and b) determine whether phosphorylation of RalA S194 alters the binding affinities of RalA for RalBP1, Exo84, or Sec5. Specific Aim 3: Determine whether Aurora-A phosphorylation of RalA S194 enhances pancreatic cancer growth. We will a) establish whether phosphorylation of RalA S194 by Aurora-A is required for transformed and tumorigenic growth in pancreatic cancer cell lines, b) establish whether Aurora-A inhibition requires RalA S194 to decrease growth of pancreatic cancer cells, and c) determine whether RalA S194 phosphorylation causes intracellular relocalization of RalA in pancreatic cancer cells.