Roles of class 1A PI3K isoforms in mammary epithelium function and breast cancer

描述(申请人提供)：IA类磷脂酰肌醇3-激酶(PI3K)被生长因子受体酪氨酸激酶(RTK)和RAS激活，以产生主要的细胞内脂质信号--磷脂酰肌醇3，4，5-三磷酸(PIP3)，对包括生存、增殖和分化在内的多种细胞过程至关重要。肿瘤抑制因子PTEN是一种脂质磷酸酶，它能使PIP3去磷酸化，从而抵消PI3Ks的作用。通过直接或间接诱变事件激活IA类PI3K信号通路是人类乳腺癌中最常见的事件之一。因此，1A型PI3K是乳腺癌治疗干预的有吸引力的靶点。在哺乳动物中，存在两种1A型PI3K催化亚型：p110？和p110？，它们在上皮组织/器官等部位普遍表达。尽管它们在分子结构和酶活性上相似，但最近的研究表明，这两种异构体在细胞信号转导和致癌转化中具有不同的功能。然而，我们对每种类型的PI3K的具体功能的了解非常有限。所有IA类PI3K对经典的PI3K抑制剂Wortmannin和LY294002表现出相同的敏感性。缺乏p110的小鼠？还是p110？是早期胚胎致死的，这排除了对其特定功能的进一步描述。我们最近为p110产生了有条件的基因敲除动物？那么p110呢？基因通过Cre/loxP重组系统促进对1A型PI3K的研究。在这个应用程序中，我们想要检验我们的假设：p110？那么p110呢？在乳腺上皮细胞功能和肿瘤发生中具有不同的生物学作用。这一假设导致了我们建议在细胞培养和动物模型中进行测试的预测。具体目标如下。1.为了验证p110的预测？那么p110呢？在小鼠乳腺上皮细胞(MMECs)的信号转导和细胞增殖中具有不同的作用。2.为了验证p110的预测？那么p110呢？在乳腺发育中有不同的作用。3.为了验证p110的预测？那么p110呢？在由致癌基因Her2/Neu驱动的乳腺肿瘤发生中具有不同的功能。这些研究将促进我们对PI3K亚型功能的理解，并为开发有效、特异和毒性较低的癌症治疗PI3K抑制剂提供关键信息。公共卫生相关性：IA类PI3K信号通路在包括乳腺癌、脑癌和结肠癌在内的高比例人类癌症中高度激活，也非常适合进行药物干预。然而，由于PI3K活性涉及多种基本生理功能，因此抑制PI3K活性有相当大的风险，可能会产生毒副作用。从这项研究中获得的信息不仅将为我们提供关于PI3K亚型在正常乳腺组织功能和肿瘤发病机制中的全面知识，还将有助于我们评估关键的药物靶点，以促进开发更特异、毒性更低的乳腺癌治疗药物。

DESCRIPTION (provided by applicant): Class IA phosphatidylinositol 3-kinases (PI3Ks) are activated by growth factor receptor tyrosine kinases (RTKs) and Ras to generate the primary intracellular lipid signal, phosphatidylinositol 3,4,5-trisphosphate (PIP3), essential for multiple cellular processes, including survival, proliferation and differentiation. The tumor suppressor PTEN, a lipid phosphatase, dephosphorylates PIP3 and therefore counteracts the action of PI3Ks. Constitutive activation of the class IA PI3K signaling pathway via direct or indirect mutagenic events is amongst the most frequent events in human breast cancer. Thus, class 1A PI3Ks are attractive targets for therapeutic intervention in breast cancer. In mammals, there are two class 1A PI3K catalytic isoforms, p110? and p110?, which are ubiquitously expressed in epithelial tissues/organs, among other sites. Despite their similarity in molecular structure and enzymatic activity, recent studies suggest that the two isoforms have distinct functions in cell signaling and oncogenic transformation. However, we have very limited understanding of the specific functions for each type of PI3K. All class IA PI3Ks display the same sensitivity to the classical PI3K inhibitors wortmannin and LY294002. Mice lacking p110? or p110? are early embryonic lethal, which precluded further delineation of their specific functions. We recently generated conditional knockout animals for the p110? and p110? genes via the Cre/loxP recombination system to facilitate the study of class 1A PI3Ks. In this application, we want to test our hypothesis that p110? and p110? have distinct biological roles in mammary epithelium function and tumorigenesis. This hypothesis leads to predictions that we propose to test in cell culture and animal models. The Specific Aims are as follows. 1. To test the prediction that p110? and p110? have distinct roles in signal transduction and cell proliferation in mouse mammary epithelial cells (MMECs). 2. To test the prediction that p110? and p110? have distinct roles in mammary gland development. 3. To test the prediction that p110? and p110? have distinct functions in breast tumorigenesis driven by oncogenic Her2/Neu. These studies will advance our understanding of the functions of PI3K isoforms and provide information critical to developing effective, specific and less toxic PI3K inhibitors for cancer treatment. PUBLIC HEALTH RELEVANCE: The Class IA PI3K signaling pathway is hyper-activated in a high percentage of human cancers, including breast, brain and colon cancers, and is also highly suited for pharmacologic intervention. However, because PI3K activity is involved in multiple fundamental physiological functions, there is a considerable risk that its inhibition may have toxic side effects. The information derived from this study will not only provide us with comprehensive knowledge of PI3K isoforms in normal breast tissue function and tumor pathogenesis, but will also help us to evaluate critical drug targets to facilitate the development of more specific and less toxic drugs for breast cancer treatment.