The Role of Syndecan-1 in Mouse Mammary Neoplasia

通过使用小鼠模型，可以识别和操纵影响乳腺肿瘤发展的分子。肿瘤形成途径的不同阶段可以被表征，包括作为肿瘤细胞前体的初始生长失调，在小鼠和人类中都是如此。硫酸肝素蛋白聚糖结合许多细胞外分子，并至少影响其中一些分子的功能，包括FGF。细胞表面硫酸肝素蛋白多糖syndecan-1 （Sdc1）已被证明与致癌基因Wnt-1协同诱导小鼠乳腺增生并随后产生肿瘤（Alexander et al, 2000）。Nature Genetics 25, p329)。鉴于Writ信号通路的广泛失调与许多不同来源的人类癌症有关，这是一种在分子水平上表征的重要遗传相互作用。因此，我们的目标是确定Sdc1如何与Wnt信号通路相互作用，使用转基因小鼠和基因操纵的原代乳腺上皮细胞。通过将转基因细胞接种到宿主脂肪垫中，在体内重建乳腺，并通过测量上皮增生来评估Wnt信号通路的活性。这种新方法可以方便地在体内检测多个基因产物的相互作用。因此，将在体外和体内评估表达各种Sdc1和Wnt信号突变体的Sdc1+/+和-/-乳腺上皮细胞的生长和失调。可溶性Sdc1在果蝇培养模型中促进Wnt信号传导，并可能作为合作者增强细胞表面受体复合物的信号传导。我们将通过检测Sdc1与主要Wnt信号传感器β -连环蛋白的上位性相互作用，以及测试Sdc1与Wnt配体的直接相互作用来验证这一假设。在此背景下，将Sdc1- /-小鼠感染小鼠乳腺肿瘤病毒（MMTV），以评估特定基因座的相对致瘤性，拓宽肿瘤易感性试验。MMTV是一种可用于鉴定致癌基因座的诱变原。总之，本研究旨在建立Sdc1和Wnt信号通路之间协作的分子机制，该机制已在小鼠中得到证实，可能对人类也很重要。

By using mouse models, the molecules that affect the development of mammary tumors can be identified and manipulated. Various stages in the pathway to neoplasia can be characterized, including the initial growth dysregulation that serves as a precursor for tumor cells in both mouse and man. Heparan sulfate proteoglycans bind many extracellular molecules, and affect the function of at least some of them, including FGF. The cell surface heparan sulfate proteoglycan syndecan-1 (Sdc1) has been shown to collaborate with the oncogene Wnt-1 to induce hyperplasia and subsequently tumors in mouse mammary glands (Alexander et al, 2000. Nature Genetics 25, p329). Given the widespread dysregulation of Writ signaling pathways implicated in human carcinomas of many different origins, this is an important genetic interaction to characterize at the molecular level. Therefore, we aim to determine how Sdc1 interacts with the Wnt signaling pathway, using transgenic mice and genetically manipulated primary mammary epithelial cells. Mammary glands will be reconstituted in vivo by inoculating transgenic cells into host fat pads, and the activity of the Wnt signaling pathway assessed by measuring epithelial hyperplasia. This novel method conveniently tests the interaction of multiple gene products in vivo. Thus, the growth and dysregulation of Sdc1+/+ and -/- mammary epithelial cells, expressing various Sdc1 and Wnt signaling mutants, will be assessed both in vitro and in vivo. Soluble Sdc1 promotes Wnt signaling in a Drosophila culture model, and may function as a collaborator to augment signaling from the cell surface receptor complex. We will test this hypothesis by examining the epistatic interaction of Sdc1 with the primary Wnt signaling transducer, beta-catenin, and by testing for a direct interaction of Sdc1 with Wnt ligands. Sdc1- /- mice will be infected with mouse mammary tumor virus (MMTV), a mutagen that can be used to identify oncogenic loci, in order to evaluate the relative oncogenicity of specific loci and to broaden the test of tumor susceptibility in this background. In summary, this proposal aims to establish the molecular mechanism underlying the collaboration between Sdc1 and the Wnt signaling pathway that has been demonstrated in mice and may be important to man.