CAV-1, Stat5a Signaling, and Estrogen-Dependent Breast Cancer

描述（由申请人提供）：人Caveolin-1（Cav-1）基因作为乳腺肿瘤抑制因子。我们先前已经在高达35%的雌激素受体（ER）阳性乳腺癌患者中鉴定出Cav-1失活（显性阴性（DN））突变。我们的假设是ER水平和活性的上调是由Cav-1失活突变引起的。由于Cav-1作为Jak-2激酶的抑制剂发挥作用，我们认为Stat 5a激活是Cav-1功能丧失导致ER-α水平升高的机制。为了支持这一假设，我们提出了新的证据，即Stat 5a激活足以上调ER阴性人乳腺癌细胞中的ER-α水平。因此，我们的初步研究现在已经确定了一种新的导致乳腺癌的信号通路：Cav-1基因失活（DN突变）-> Stat 5a激活-> ER-α上调-> Cyclin D1过表达。该项目的三个具体目标是： 1)确定Stat 5a激活和ER-α在Cav-1相关乳腺增生、增殖和3D管腔形成中的作用。我们将分析Cav-1/Stat 5a双敲除小鼠的乳腺，并研究来自这些小鼠的乳腺上皮原代培养物的离体行为。 2)确定Stat 5a激活和ER-α在Cav-1相关乳腺肿瘤发生和转移中的作用。为此，我们将进行原位移植的Met-1细胞表达Cav-1显性阴性（DN）突变体（如P132 L），发现在人类乳腺癌。将使用Stat 5a和Jak-2的DN突变体评估Stat 5a信号传导的作用。雌激素的作用将通过卵巢切除术和补充雌激素丸来评估。还将研究他莫昔芬耐药性。 3)确定ER（+）人乳腺癌样本中Cav-1突变是否与Stat 5a激活共分离。在这里，我们建议研究这种新定义的信号通路在人类乳腺癌发病机制的相关性，使用Cav-1突变，ER-α表达水平和Stat 5a激活作为新的预后标志物。由于超过40%的ER-α阳性患者显示出他莫昔芬耐药，我们还将检查Cav-1突变和Stat 5a激活是否是他莫昔芬耐药的关键预测因子。

DESCRIPTION (provided by applicant): The human Caveolin-1 (Cav-1) gene acts as a mammary gland tumor suppressor. We have previously identified Cav-1 inactivating (dominant-negative (DN)) mutations in up to 35 % of estrogen receptor (ER) positive breast cancer patients. Our hypothesis is that up-regulation of ER levels and activity are caused by Cav-1 inactivating mutations. As Cav-1 functions as an inhibitor of the Jak-2 kinase, we propose that Stat5a activation is the mechanism by which loss of Cav-1 function results in increased ER-alpha levels. In support of this hypothesis, we present novel evidence that Stat5a activation is sufficient to upregulate ER-alpha levels in ER-negative human breast cancer cells. As such, our preliminary studies have now defined a novel signaling pathway leading to breast cancer: Cav-1 gene inactivation (DN-mutations) --> Stat5a activation --> ER-alpha upregulation --> Cyclin D1 over-expression. The three Specific Aims of the project are: 1) Determine the role of Stat5a activation and ER-alpha in Cav-1-related mammary hyperplasia, proliferation, and 3D lumen formation. We will analyze the mammary glands of Cav-1/Stat5a double- knockout mice and study the ex vivo behavior of primary cultures of mammary epithelia from these mice. 2) Determine the role of Stat5a activation and ER-alpha in Cav-1-related mammary tumorigenesis and metastasis. For this purpose, we will perform orthotopic transplantation of Met-1 cells expressing Cav-1 dominant-negative (DN) mutants (such as P132L) that are found in human breast cancer. The role of Stat5a signaling will be assessed using DN mutants of Stat5a and Jak-2. The role of estrogen will be assessed by ovariectomy and supplementation with estrogen pellets. Tamoxifen-resistance will also be investigated. 3) Determine if Cav-1 mutations co-segregate with Stat5a activation in ER(+) human breast cancer samples. Here, we propose to examine the relevance of this newly defined signaling pathway in human breast cancer pathogenesis, using Cav-1 mutations, ER-alpha expression levels, and Stat5a activation as novel prognostic markers. Since greater than 40% of ER-alpha positive patients show tamoxifen-resistance, we will also examine if Cav-1 mutations and Stat5a activation are critical predictors of tamoxifen-resistance.