Role of Sphingosine Kinase in p53 Cancer Biology

本项目的长期目标是确定鞘氨醇介导的新型脂质途径的作用 激酶（SK）及其生物活性产物鞘氨醇-1-磷酸（S1 P）在癌症中的作用，并建立 这一途径的组成部分作为癌症治疗的潜在新靶点。以前资助的研究 近年来，SK/S1 P在肿瘤中的作用和调控研究进入了一个新的激动人心的方向。S1 P是 由鞘脂神经酰胺分解为鞘氨醇，然后被SK磷酸化产生， 然后介导/调节几种重要的生物活性，包括细胞发生、细胞存活和 血管生成在上一个资助期间，我们确定SK 1在人乳腺癌中显著过表达。 几种癌症，并通过缺氧上调。此外，我们发现了一种新的调节机制， SK 1的蛋白水解反应的基因毒性应激在p53依赖的方式，并表明损失的 SK 1可导致癌细胞的生长停滞和凋亡。这些数据使我们提出以下建议 假设：p53激活引起SK 1的丢失，这种SK 1蛋白水解介导p53肿瘤 抑制功能，SK 1/S1 P途径介导无效/突变型p53诱导的癌症。为了验证这一 我们提出了以下假设：1）确定p53调控SK 1/S1 P通路 A）证明SK 1响应于p53蛋白水解， 活化剂、UV辐射和DMA损害细胞中的化疗剂。B）确定p53是否为 细胞中SK 1蛋白水解所必需的。C）测定SK 1在p53无效和突变组织中的表达 并与来自p53无效/突变动物模型和人癌组织的匹配正常组织进行比较。D）、 确定p53激活导致SK 1蛋白水解的机制和切割位点。 E）评估诱导p53和SK 1蛋白水解对细胞鞘脂谱的影响。 2)确定SK 1/S1 P通路的持续性是否是介导无效/突变型p53肿瘤所必需的 A）确定SK 1/S1 P途径在介导细胞内和体内的进展途径中的作用， p53在细胞中诱导生长反应。B）通过合成开发更有效和特异性的抑制剂 SK 1的。C）评价这些化合物诱导细胞凋亡/衰老样生长的能力 阻止细胞中无效/突变型p53的生长。D）为了确定SK 1/S1 P在无效/突变型p53介导的细胞凋亡中的作用， 使用与p53缺失或突变小鼠杂交的SK 1 K/O小鼠体内检测癌症，并确定它们是否 防止肿瘤形成。这些研究可能为p53和p54之间的分子联系提供了新的途径。 细胞应激调节的鞘脂途径，两者在调节生长，凋亡， 和衰老。这项研究中的先导化合物可能为特异性治疗铺平道路。 开发针对SK 1

The long-term goal of this project is to define the role of the novel lipid pathway mediated by sphingosine kinase (SK) and its bioactive product sphingosine-1-phosphate (S1P) in cancer, and to establish components of this pathway as potential novel targets for cancer therapy. Studies from the previous funding period have led us into a novel exciting direction on the role and regulation of SK/S1P in cancer. S1P is generated by breakdown of the sphingolipid ceramide to sphingosine, followed by phosphorylation by SK, and it then mediates/modulates several important biologic activities, including mrtogenesis, cell survival, and angiogenesis. During the previous funding period, we established that SK1 is significantly overexpressed in several cancers and is upregulated by hypoxia. Moreover, we discovered a novel mechanism of regulation of SK1 by proteolysis in response to genotoxic stress in a p53-dependent manner, and showed that loss of SK1 led to growth arrest and apoptosis of cancer cells. These data have led us to propose the following hypothesis: that activation of p53 causes the loss of SK1, that this SK1 proteolysis mediates p53 tumor suppressor function, and that the SK1/S1P pathway mediates null/mutant p53-induced cancer. To test this hypothesis we propose the following specific aims: 1} To establish that p53 regulates the SK1/S1P pathway and decipher the mechanisms involved by A) Demonstrating that SK1 is proteolyzed in response to the p53 activators, UV radiation and DMA damaging chemotherapeutic agents in cells. B) Determining if p53 is required for SK1 proteolysis in cells. C) Determining the expression of SK1 in p53 null and mutant tissues and compare to matched normal tissues from p53 null/mutant animal models and human cancer tissues. D) Determining the mechanism by which activation of p53 leads to SK1 proteolysis, and the sites of cleavage. E) Evaluating the consequences of induction of p53 and SK1 proteolysis on the cellular sphingolipid profile. 2) To determine if the persistence of the SK1/S1P pathway is necessary to mediate null/mutant p53 tumor progression pathways in cells and in vivo by A) determining the role of the SK1/S1P pathway in mediating p53 induced growth responses in cells. B) To develop through synthesis more potent and specific inhibitors of SK1. C) To evaluate these compounds as to their ability to induce apoptosis/senescence-like growth arrest in null/mutant p53 growth in cells. D) To determine the role of SK1/S1P in null/mutant p53 mediated cancer in vivo using SK1 K/O mice crossed with p53 null or mutant mice and determining if they are protected from tumor formation. These studies may provide a novel molecular link between the p53 and the sphingolipid pathways of cell stress regulation, both of which play key roles in regulating growth, apoptosis, and senescence. Lead compounds from this study may pave the way towards specific therapeutic development targeting SK1