RAsGRP1 signals in breast development and cancer

 描述（由申请人提供）：乳腺癌是女性癌症死亡的第二大原因。在美国，近12%的女性会在一生中患上乳腺癌，每年约有40，000人死于这种疾病。乳腺癌的分子和细胞起源是高度异质性的。基因图谱显示至少有五种不同的亚型。一种这样的亚型是“Her 2”，其占所有诊断的乳腺癌的约30%。Her 2乳腺癌是由于表皮生长因子受体（EGFR）家族蛋白Her 2/EGFR 2的过度表达或扩增而发展的。因此，更好地了解乳腺中的EGFR信号传导至关重要。EGFR信号转导已被证明在调节乳腺发育中起关键作用。有证据表明EGFR失活突变导致发育缺陷。此外，多能祖细胞中增强的EGFR信号驱动特异性分支效应和细胞命运决定。这些发育观察结果也与乳腺癌相关，因为据认为异质性主要来自作为起源细胞的不同乳腺上皮细胞（MEC）。Ras通路在受体酪氨酸激酶（如EGFR）下游被激活。Ras信号部分由Ras激活蛋白控制，包括Ras鸟苷酸释放蛋白1（Rasgrp 1）。我们实验室的工作表明，Ras信号强度，由Rasgrp 1调节，通常用于控制增殖和分化的平衡。淋巴细胞中Rasgrp 1的异常表达导致发育迟缓，并有助于白血病的发生和进展。此外，我们最近发现Rasgrp 1的行为矛盾，以限制肠上皮细胞内的EGFR-Ras信号，导致增强的增殖和变化，肠祖细胞分化时，Rasgrp 1功能受到干扰。特异性EGFR-RasGEF-Ras信号如何影响MEC谱系的发展、癌症起始和进展以及Rasgrp 1在本文中的特异性作用仍然未知。鉴于已知的滴定EGFR-Ras信号在正常和恶性乳腺生长的重要性，我假设Rasgrp 1起着重要的，但未探索的作用，在乳腺上皮祖细胞的生长和分化，通过控制这些细胞中的EGFR-Ras信号的强度。为了验证我们的假设，我们的实验室已经生成了具有消融（Rasgrp 1-/-）和受损（Rasgrp 1Anaef）Rasgrp 1的小鼠模型。我们还开发了生物化学，细胞生物学和体内方法来揭示分子见解，并获得了关键的初步数据。我将描述Rasgrp 1在MEC中的表达（目标1），并确定不同的EGFR-Rasgrp 1信号如何影响MEC谱系在发展过程中（目标2）。最后，我将研究EGFR-Rasgrp 1信号在乳腺癌中的作用（目的3）。我们预计，我们的研究将为Rasgrp 1如何在发育和癌症期间塑造MEC谱系中EGFR-Ras信号的特征提供重要见解。

 DESCRIPTION (provided by applicant): Breast cancer is the second leading cause of cancer death in women. Nearly 12% of women in the U.S. will develop breast cancer over the course of their life and about 40,000 will die each year from the disease. The molecular and cellular origins of breast cancer are highly heterogeneous. Gene profiling has revealed at least five distinct subtypes. One such subtype is "Her2", which account for approximately 30% of all diagnosed breast cancers. Her2 breast cancers develop as a result of the overexpression or amplification of the epidermal growth factor receptor (EGFR) family protein Her2/EGFR2. Therefore, gaining better insight into EGFR signaling in the breast is critically important. EGFR signaling has been shown to play a key role in regulating mammary gland development. Evidence has emerged that shows inactivating mutations in EGFR lead to developmental defects. Further, augmented EGFR signals in multipotent progenitor cells drive specific branching effects and cell fate decisions. These developmental observations are also of relevance to breast cancer, since it is thought that the heterogeneity predominantly derives from distinct mammary epithelial cells (MECs) serving as the cell of origin. The Ras pathway is activated downstream of receptor tyrosine kinases, like EGFR. Ras signals are controlled in part by Ras activating proteins, including Ras guanyl-nucleotide releasing protein 1 (Rasgrp1). Work from our lab has shown that Ras signal intensity, as modulated by Rasgrp1, often acts to control the balance of proliferation and differentiation. Aberrant Rasgrp1 expression in lymphocytes leads to developmental delay and contributes to onset and progression of leukemia. Further, we have recently discovered Rasgrp1 acts paradoxically to limit EGFR-Ras signals within intestinal epithelial cells, resulting in enhanced proliferation and changes to intestinal progenitor cell differentiation when Rasgrp1 function is perturbed. How specific EGFR- RasGEF-Ras signals impact development of MEC lineages, cancer initiation and progression, and the specific role of Rasgrp1 herein remains unknown. Given the known importance of titrated EGFR-Ras signals during normal and malignant breast growth, I hypothesize that Rasgrp1 plays an important but unexplored role in mammary epithelial progenitor cell growth and differentiation by controlling the intensity of EGFR-Ras signals in these cells. To test our hypotheses, our lab has generated mouse models with ablated (Rasgrp1-/-) and impaired (Rasgrp1Anaef) Rasgrp1. We have also developed biochemical-, cell biological-, and in vivo- approaches to reveal molecular insights and have acquired critical preliminary data. I will characterize the expression of Rasgrp1 in MECs (Aim 1) and determine how distinct EGFR-Rasgrp1 signals impact MEC lineages during development (Aim 2). Lastly, I will investigate the role of EGFR-Rasgrp1 signaling in breast cancer (Aim 3). We anticipate that our studies will provide significant insights into how Rasgrp1 shapes the character of EGFR-Ras signals in MECs lineages during development and cancer.