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描述，包括最初的生长失调，这是老鼠和人的肿瘤细胞的前驱。硫酸乙酰肝素蛋白多糖结合了许多细胞外分子，并至少影响其中一些分子的功能，包括成纤维细胞生长因子。细胞表面硫酸乙酰肝素蛋白多糖-1(SDc1)已被证明与癌基因Wnt-1合作，诱导小鼠乳腺的增生和随后的肿瘤(Alexander等，2000)。《自然遗传学》25，第329页)。鉴于在许多不同来源的人类癌症中广泛存在的WRIT信号通路的失调，这是一种重要的遗传相互作用，需要在分子水平上进行表征。因此，我们的目标是利用转基因小鼠和基因操纵的原代乳腺上皮细胞来确定Sdc1如何与Wnt信号通路相互作用。通过将转基因细胞接种到宿主脂肪垫中，将在体内重建乳腺，并通过测量上皮增生来评估Wnt信号通路的活性。这种新的方法可以方便地测试体内多个基因产物的相互作用。因此，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将在体外和体内进行评估。在果蝇培养模型中，可溶性Sdc1促进Wnt信号，并可能作为协作者增强来自细胞表面受体复合体的信号。我们将通过检验Sdc1与主要的Wnt信号转导因子β-catenin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检验这一假说。用小鼠乳腺肿瘤病毒(MMTV)感染Sdc1-/-小鼠，以评价特定基因座的相对致癌性，扩大肿瘤易感性的检测范围。综上所述，这项建议旨在建立Sdc1和Wnt信号通路之间合作的分子机制，该信号通路已经在小鼠中得到证实，可能对人类很重要。

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.