Mechanisms governing metastatic reactivation of breast cancer.

描述(申请人提供)：乳腺癌的转移性复发通常发生在原发肿瘤的初步诊断和手术治疗数年后。现在，它被广泛地 假设一旦肿瘤细胞在靶器官中渗出，由于它们无法退出静止状态，它们就会保持休眠较长时间。强制休眠的信号以及那些最终使有限数量的休眠细胞退出其状态并成长为宏观转移的信号在很大程度上是神秘的。由于缺乏能够进行遗传分析的小鼠模型，这一关键研究领域的进展一直受到阻碍。我们设计了一种功能获得屏幕，它使用乳腺癌在肺中休眠的小鼠模型作为过滤器，分离促进该器官重新激活的cDNA、microRNAs和sh-RNAs。我们分离到的第一个cDNA编码的是分泌型的转化生长因子拮抗剂？配基可可。COCO通过阻断肺间质分泌的BMP蛋白抑制其自我更新的能力，诱导转移启动细胞(MIC)退出休眠并经历重新激活。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，他们暗示这些细胞需要克服器官特异性的抗转移信号(Gao等人，Cell 2012，正在出版中)。通过使用相同的方法，我们已经确定了其他介导转移重新激活的基因，例如非典型的Tetraspanin TM4SF1，它似乎通过将胶原受体DDR1连接到STAT3来发挥功能，以及microRNAs miR-138和miR-346。此外，我们已经确定Notch抑制器号是休眠状态执行者。在这个应用中，我们将检验这样一个假设，即肿瘤休眠和重新激活是由与干细胞更新相似的信号通路控制的。我们的具体目标是：1)检测COCO促转移活性的生化基础和单抗阻断COCO的临床前疗效；2)阐明非典型四环素TM4SF1促进转移再激活的机制；3)研究不对称细胞分裂决定簇加强肿瘤休眠的机制；以及4)研究miR-138和miR-346促进转移再激活的机制。通过确定调控乳腺癌休眠和再激活的核心信号通路，这些研究将提供一个合理的框架来理解这些过程的逻辑。此外，这些研究可能导致新的治疗干预靶点的确定，以及新的基于机制的转移潜能生物标记物的确定。

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.