CAV-1 in Jak/STAT Signaling, Lactation, & Breast Cancer

描述（由申请人提供）：本申请的长期目标是了解caveolin-1在i) Jak/STAT信号，ii)哺乳和iii)乳腺癌发病机制中的作用。小泡是调节信号转导的“信息中心”。小窝蛋白-1 （Cav-1）是在大多数细胞中发现的小窝膜的主要结构蛋白。我们将人类CAV-1定位到一个可疑的肿瘤抑制位点（7q31.1/D7S522）。此外，Cav-1基因（P132L）在多达16%的人类乳腺癌中发生突变。本研究的目的是验证Cav-1表达通过Jak/STAT信号调节泌乳的重要作用，以及Cav-1的缺失导致乳腺癌细胞的致癌性。为了验证这一假设，我们将使用多种互补的体内方法，例如i) Cav-1缺失小鼠模型和ii)开发表达在人类乳腺癌中发现的显性阴性Cav-1 （PI32L）的转基因小鼠。该项目的三个具体目的是：1)确定Cav-1在负调控Jak/STAT信号传导中的作用。我们将研究Cav-1对泌乳素应答的乳腺上皮细胞中Jak/STAT信号激活的影响。我们的初步结果表明，Cav-1通过抑制Jak介导的STAT5a磷酸化来负向调节Jak/STAT5a信号通路；2)探讨Cav-1在泌乳和上皮细胞增生中的作用。泌乳素激素发出的信号通过Jak/STAT通路控制正常乳腺发育。因此，如果Cav-1是Jak/STAT信号的负调控因子，我们可以预测Cav-1表达的缺失会导致早产。事实上，我们的初步结果表明，Cav-1缺失的小鼠表现出早泌，以及Jak/STAT5a信号级联的过度激活；3)确定转基因Cav-1 （P132L）的表达是否易导致乳腺肿瘤的发生。为此，我们将产生在乳腺中转基因表达这种形式的Cav-1 （P132L）小鼠。我们的初步结果表明，Cav-1 （P132L）在培养细胞中以显性阴性方式起作用。此外，我们对Cav-1缺失小鼠的初步结果显示，广泛乳腺上皮增生的早期发展。我们预测这种表型将加速Cav-1 （P132L）转基因小鼠。我们将把Cav-1 （P132L）转基因小鼠与其他已建立的乳腺肿瘤发生模型，如MMTVErbB2和mmtv -多瘤中T小鼠进行杂交。预计这些研究将为了解Cav-1在Jak/STAT信号传导和体内乳腺肿瘤发生中的作用提供基础知识。

DESCRIPTION (provided by applicant): The long-term objective of this proposal is to understand the role of caveolin-1 in i) Jak/STAT signaling, ii) lactation, and iii) the pathogenesis of breast cancer. Caveolae function as "message centers" for regulating signal transduction. Caveolin-1 (Cav-1) is the principal structural protein of caveolae membranes that are found in most cells. We mapped human CAV-1 to a suspected tumor suppressor locus (7q31.1/D7S522). In addition, the Cav-1 gene is mutated (P132L) in up to 16% of human breast cancers. The aim of this proposal is to test the hypothesis that Cav-1 expression is important for regulating lactation via modulation of Jak/STAT signaling and that loss of Cav-1 contributes to the oncogenicity of breast cancer cells. To test this hypothesis, we will use a variety of complementary in vivo approaches, such as i) a Cav-1 null mouse model and ii) the development of transgenic mice that express dominant-negative Cav-1 (PI32L) found in human breast cancers. The three Specific Aims of the project are: 1) To determine the role of Cav-1 in negatively regulating Jak/STAT signaling. We will examine the effects of Cav-1 on the activation of Jak/STAT signaling in cultured mammary epithelial cells that are responsive to prolactin. Our preliminary results indicate that Cav-1 negatively regulates Jak/STAT5a signaling by inhibiting Jak-mediated phosphorylation of STAT5a; 2) To examine the role of Cav-1 in lactation and epithelial cell hyperplasia. Signaling from the hormone prolactin vial the Jak/STAT pathway controls normal mammary gland development. Thus, if Cav-1 were a negative regulator of Jak/STAT signaling, we would predict that a loss of Cav-1 expression leads to premature lactation. Indeed, our preliminary results show that Cav-1 null mice exhibit premature lactation, as well as hyper-activation of the Jak/STAT5a signaling cascade; and 3) To determine if transgenic expression of Cav-1 (P132L) predisposes towards mammary tumor development. For this purpose, we will generate Cav-1 (P132L) mice that transgenically express this form of Cav-1 in the mammary gland. Our preliminary results indicate that Cav-1 (P132L) acts in a dominant-negative fashion in cultured cells. In addition, our preliminary results with Cav-1 null mice show early development of wide-spread mammary epithelial hyperplasia. We predict that this phenotype will be accelerated Cav-1 (P132L) transgenic mice. We will cross Cav-1 (P132L) transgenic mice with other well-established models of mammary tumorigenesis, such as MMTVErbB2 and MMTV-polyoma middle T mice. It is expected that these studies will contribute fundamental knowledge towards understanding the role of Cav-1 in Jak/STAT signaling and mammary tumorigenesis in vivo.