Mechanisms governing metastatic reactivation of breast cancer.

描述（由申请人提供）：乳腺癌的转移性复发通常发生在原发性肿瘤初次诊断和手术治疗后数年。现在人们普遍 假设一旦肿瘤细胞已经外渗到靶器官中，由于它们不能从静止状态中退出，它们保持长时间的休眠。强制休眠的信号以及最终使有限数量的休眠细胞从其状态中退出并生长成宏观转移的信号在很大程度上是神秘的。由于缺乏适合遗传分析的小鼠模型，这一关键研究领域的进展受到阻碍。我们设计了一种功能获得性筛选，该筛选使用小鼠肺中乳腺癌休眠模型作为筛选器，以分离促进该器官再激活的cDNA、microRNA和sh-RNA。第一个cDNA，我们已经分离，编码分泌的拮抗剂TGF-？配体Coco.可可诱导转移起始细胞（MIC）退出休眠状态，并通过阻断肺间质分泌的BMP蛋白抑制其自我更新的能力进行再活化。这些结果表明，播散性乳腺癌细胞需要通常与干细胞相关的自我更新能力，以便在转移部位生长。此外，它们暗示这些细胞需要克服器官特异性抗转移信号（Gao等人，Cell 2012，in press）。通过使用相同的方法，我们已经确定了介导转移性再激活的其他基因，例如非典型的四跨膜蛋白TM 4SF 1，其似乎通过将胶原受体DDR 1偶联到STAT 3以及microRNA miR-138和miR-346来发挥作用。此外，我们已经确定Notch抑制剂Numb是休眠状态的执行者。在这个应用程序中，我们将测试的假设，即肿瘤休眠和再激活是由类似的干细胞更新参与的信号通路。我们的具体目标是：1）检测Coco促转移活性的生化基础和阻断Coco的单克隆抗体的临床前效力; 2）阐明非典型四跨膜蛋白TM 4SF 1促进转移性再活化的机制; 3）研究不对称细胞分裂决定因子Numb强制肿瘤休眠的机制;和4）检查miR-138和miR-346促进转移性再活化的机制。通过确定调节乳腺癌休眠和再激活的核心信号通路，这些研究将为理解这些过程的逻辑提供一个合理的框架。此外，这些研究可能导致识别治疗干预的新靶点以及转移潜力的新机制生物标志物。

DESCRIPTION (provided by applicant): Metastatic relapse of breast cancer usually occurs several years after initial diagnosis and surgical treatment of the primary tumor. It is now widely assumed that, once tumor cells have extravasated in the target organ, they remain dormant for extended periods as a consequence of their inability to exit from quiescence. The signals that enforce dormancy as well as those that eventually enable a limited number of dormant cells to exit from their state and outgrow into macroscopic metastases are largely mysterious. Progress in this critical area of research has been hampered by the lack of mouse models amenable to genetic analysis. We have designed a gain-of-function screen that uses a mouse model of breast cancer dormancy in the lung as a filter to isolate cDNAs, microRNAs, and sh-RNAs that promote reactivation in this organ. The first cDNA, which we have isolated, encodes for the secreted antagonist of TGF-? ligands Coco. Coco induces metastasis-initiating cells (MICs) to exit from dormancy and undergo reactivation by blocking the ability of BMP proteins secreted by the lung stroma to inhibit their self-renewal. These results suggest that disseminated breast cancer cells require the self-renewal capability typically associated with stem cells in order to outgrow at metastatic sites. In addition, they imply that these cells need to overcome organ-specific anti-metastatic signals (Gao et al., Cell 2012, in press). By using the same approach, we have identified additional genes that mediate metastatic reactivation, such as the atypical tetraspanin TM4SF1, which appears to function by coupling the collagen receptor DDR1 to STAT3, and the microRNAs miR-138 and miR-346. In addition, we have identified the Notch inhibitor Numb as an enforcer of the dormant state. In this application, we will test the hypothesis that tumor dormancy and reactivation are governed by signalling pathways similar to those involved in stem cell renewal. Our Specific Aims are: 1) To Examine the Biochemical Basis of the Pro-metastatic Activity of Coco and the Preclinical Efficacy of Monoclonal Antibodies Blocking Coco; 2) To Elucidate the Mechanism by which the Atypical Tetraspanin TM4SF1 Promotes Metastatic Reactivation; 3) To Study the Mechanism by which the Asymmetric Cell Division Determinant Numb Enforces Tumor Dormancy; and 4) To Examine the Mechanism by which miR-138 and miR-346 Promote Metastatic Reactivation. By identifying the core signaling pathways that regulate breast cancer dormancy and reactivation, these studies will provide a rational framework to understand the logic of these processes. In addition, these studies are likely to lead to the identification of novel targets for therapeutic interventio as well novel mechanism-based biomarkers of metastatic potential.