Tumor suppression by sphingolipids: role of beta-catenin

鞘脂抑制肿瘤：β-连环蛋白的作用

基本信息

批准号：
7110276
负责人：
EVA M SCHMELZ
金额：
$ 25.72万
依托单位：
WAYNE STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2005
资助国家：
美国
起止时间：
2005-08-11 至 2007-05-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): This grant will investigate the central hypothesis that non-toxic doses of sphingolipids down-regulate cytosolic and nuclear beta-catenin, thereby lowering the expression of growth-promoting proteins and subsequently normalize cell growth and prevent tumor formation. This hypothesis has been formulated based on our preliminary in vivo data showing a suppression of tumor formation by dietary sphingolipids in mice, a modulation of beta-catenin localization and a reduction of the proliferation rate to a normal level. The objective of this proposal is to determine the importance of beta-catenin regulation by low doses of sphingolipids in the normalization of cell growth and, ultimately, in the prevention of colon cancer. The central hypothesis will be tested by pursuing three specific aims: 1) Identify the pathways of how low doses of exogenous sphingolipids down-regulate cytosolic beta-catenin. The working hypothesis is that exogenous sphingolipids lower cytosolic beta-catenin by enhancing degradation (early event) and suppressing transcription (late event). Key events in the proteasomal beta-catenin degradation and transcription will be evaluated. 2) Determine the mechanism of beta-catenin regulation by exogenous sphingolipids. The working hypothesis is that sphingolipids regulate beta-catenin metabolism indirectly via serine/threonine kinases and phosphatases that alter beta-catenin phosphorylation and thereby its fate. Changes in the activity of key protein kinases (i.e, PKC isozymes) and phosphatases (i.e., PP2A) will be quantitated and correlated to beta-catenin expression and localization. 3) Identify down-stream targets of low doses of sphingolipids and assess the relevance for sphingolipid-mediated regulation of cell growth. The working hypothesis for this aim is that low doses of sphingolipids suppress unlimited cell growth and tumor formation by inhibition of the transcription of beta- catenin targets. The approach will be to determine changes in gene transcription and expression/localization of proteins that are both targets of beta-catenin and sphingolipids in vitro and in vivo, and determine the association of sphingolipid-mediated beta-catenin regulation and transcriptional activity with changes in aberrant cell behavior, and therefore the importance of betat-catenin regulation in tumor suppression by sphingolipids. The proposed research is significant because the reversal of aberrant li-catenin localization and its transcriptional activity are thought to be critical steps in colon cancer prevention. The outcomes of the proposed studies are expected to provide the basis for a colon cancer prevention strategy based on dietary or orally administered sphingolipids.

描述（由申请人提供）：这项资助将研究中心假设，即无毒剂量的鞘脂下调胞质和核β-连环蛋白，从而降低生长促进蛋白的表达，从而使细胞生长正常化并防止肿瘤形成。这一假设是根据我们的初步体内数据提出的，该数据显示饮食中的鞘脂可以抑制小鼠中的肿瘤形成，调节β-连环蛋白定位并将增殖率降低至正常水平。该提案的目的是确定低剂量鞘脂调节 β-连环蛋白在细胞生长正常化以及最终预防结肠癌中的重要性。我们将通过追求三个具体目标来检验中心假设：1）确定低剂量外源鞘脂如何下调胞质 β-连环蛋白的途径。工作假设是外源鞘脂通过增强降解（早期事件）和抑制转录（晚期事件）来降低胞质 β-连环蛋白。将评估蛋白酶体β-连环蛋白降解和转录中的关键事件。 2)确定外源鞘脂调节β-连环蛋白的机制。工作假设是，鞘脂通过丝氨酸/苏氨酸激酶和磷酸酶间接调节 β-连环蛋白代谢，从而改变 β-连环蛋白磷酸化，从而改变其命运。关键蛋白激酶（即 PKC 同工酶）和磷酸酶（即 PP2A）活性的变化将被定量并与 β-连环蛋白表达和定位相关。 3) 确定低剂量鞘脂的下游靶标并评估鞘脂介导的细胞生长调节的相关性。这一目标的工作假设是，低剂量的鞘脂通过抑制β-连环蛋白靶标的转录来抑制无限的细胞生长和肿瘤形成。该方法将在体外和体内确定基因转录和蛋白质表达/定位的变化，这些蛋白质都是β-连环蛋白和鞘脂的靶标，并确定鞘脂介导的β-连环蛋白调节和转录活性与基因变化的关系。异常的细胞行为，以及β-连环蛋白调节在鞘脂抑制肿瘤中的重要性。这项研究具有重要意义，因为异常的 li-catenin 定位及其转录活性的逆转被认为是预防结肠癌的关键步骤。拟议研究的结果预计将为基于饮食或口服鞘脂的结肠癌预防策略提供基础。