Blocking angiogenesis by targeting PP-2A pathways

描述(申请人提供)：肿瘤刺激的血管生成涉及内皮细胞迁移和重组为血管结构，这一过程受激酶和磷酸酶之间的平衡调节。我们已经证明，几种肿瘤产生的主要运动刺激因子是PGE2和TGFbeta，它们反过来抑制丝氨酸/苏氨酸蛋白磷酸酶PP-2A的活性。PP-2A的药理抑制增加了细胞的运动性。 我们的假设是，通过产生运动刺激因子PGE2和TGFbeta，肿瘤抑制内皮细胞PP-2A的活性，而内皮细胞PP-2A通过两条相互关联的途径刺激内皮细胞的运动：(I)paxlin的丝氨酸/苏氨酸磷酸化，它破坏FAK/Src/paxlin复合体的稳定，并触发p130(Cas)/Crk和PI3K运动刺激途径的Src激活；(Ii)PTEN的丝氨酸/苏氨酸磷酸化，从而抑制其限制PI3K和p130(Cas)/Crk途径的激活。定义这些运动刺激通路还将确定可以靶向干扰内皮细胞运动的信号成分，进而干扰肿瘤生长所需的新生血管。 我们的假说将在体外和体内小鼠Lewis肺癌(LLC)模型中得到验证，方法是评估PGE2/TGFbeta对PP-2A的抑制是否刺激：(I)paxlin的丝氨酸/苏氨酸磷酸化，FAK/Src/paxlin复合体的溶解，以及作为运动刺激途径的一条臂的Src的激活；(Ii)丝氨酸/苏氨酸的磷酸化，从而使PTEN失活是运动刺激途径的第二臂；(Iii)运动刺激p130(Cas)/Crk和PI3K通路的激活由产生活跃的Src和不活跃的PTEN的级联的两个臂激活。 完成后，这些研究将确定PP-2A的肿瘤抑制如何增加内皮细胞的运动性，这是血管生成过程中所必需的。这些研究还将确定可以靶向阻断运动刺激通路的信号成分。虽然是在LLC模型中进行的，但建议的研究一般适用于实体癌，因为它们的生长依赖于血管生成。

DESCRIPTION (provided by applicant): Tumor-stimulated angiogenesis involves endothelial cell migration and reorganization into vessel structures, a process that is regulated by the balance between kinases and phosphatases. We have shown that the principal motility-stimulatory factors produced by several tumors are PGE2 and TGFbeta which, in turn, inhibit the activity of the serine/threonine protein phosphatase PP-2A. Pharmacological inhibition of PP-2A increases cellular motility. Our hypothesis is that by producing the motility-stimulatory factors PGE2 and TGFbeta, tumors inhibit endothelial cell PP-2A activity, which stimulates endothelial cell motility through two interconnected pathways: (i) serine/threonine phosphorylation of paxillin, which destabilizes FAK/Src/paxillin complexes and triggers Src activation of the p130(Cas)/Crk and PI3K motility-stimulatory pathways, (ii) serine/threonine phosphorylation of PTEN, thus inhibiting its ability to limit activation of the PI3K and p130(Cas)/Crk pathways. Defining these motility-stimulatory pathways will also identify signaling components that can be targeted to interrupt endothelial cell motility and, in turn, the neovascularization that is required for tumor growth. Our hypothesis will be tested in vitro and in vivo in a murine Lewis lung carcinoma (LLC) model by assessing if the inhibition of PP-2A by PGE2/TGFbeta stimulates: (i) serine/threonine phosphorylation of paxillin, dissolution of FAK/Src/paxillin complexes and activation of Src as one arm of a motility-stimulatory pathway; (ii) serine/threonine phosphorylation and, consequently, inactivation of PTEN is the second arm of a motility-stimulatory pathway; (iii) activation of the motility-stimulatory p130(Cas)/Crk and PI3K pathways by the two arms of the of the cascade that yield active Src and inactive PTEN. Upon completion, these studies will identify how tumor inhibition of PP-2A increases endothelial cell motility, a requirement for the process of angiogenesis. These studies will also identify signaling components that can be targeted to block the motility-stimulatory pathways. Although being conducted in the LLC model, the proposed studies are applicable to solid cancers in general, as their growth is dependent on angiogenesis.