Ron Receptor Tyrosine Kinase Signaling in Breast Cancer

描述(由申请人提供)： RON受体酪氨酸激酶最近被证明在一组人类癌症中过度表达和激活，其中在乳腺癌中发现的最令人信服的数据。RON在大约50%的人类乳腺癌中过度表达，并已被证明是女性乳腺癌患者转移和预后不良的独立预测因子。虽然RON的过度表达似乎是人类乳腺癌和转移的一个重要因素，但我们对RON在乳腺肿瘤中激活的信号通路以及这些通路在整个肿瘤生长和转移转移中的重要性的认识存在着显著的差距。我们实验室的研究表明，RON在乳腺上皮细胞中的选择性过表达导致了100%的雌性小鼠乳腺肿瘤的发生，并与高度乳腺癌的肝、肺转移有关。在这个模型中，乳腺肿瘤的发生与RON的表达增加、受体磷酸化增加和RON相关的酪氨酸激酶活性增加有关。然而，在这个模型中，RON配体，肝细胞生长因子样蛋白(HGFL)的依赖程度仍然未知。对这些小鼠的原发乳腺肿瘤的生化分析表明，RON的过度表达与酪氨酸磷酸化的2-连环蛋白水平升高以及下游2-连环蛋白靶基因的上调有关。与RON相似，2-连环蛋白的表达也与乳腺癌患者的不良预后有关。此外，我们的初步数据显示，在人类乳腺癌标本中，高RON表达和高2-连环蛋白水平之间存在关联。我们还表明，HGFL诱导的人乳腺癌细胞株RON的激活导致2-连环蛋白的快速积累和2-连环蛋白的酪氨酸磷酸化，2-连环蛋白被转移到细胞核。根据我们的初步和已发表的数据，我们假设配体介导的RON激活增强了2-连环蛋白信号，导致乳腺癌生长、存活率和转移转移的增加。为了验证这一假说，我们提出了三个具体的目标：(I)描述RON配体HGFL在体内乳腺癌细胞生长、存活和转移扩散中的作用；(Ii)检测2-连环蛋白在RON介导的乳腺肿瘤发生和转移中的体内生物学意义；以及(Iii)确定HGFL诱导的、依赖于RON的2-连环蛋白酪氨酸磷酸化在乳腺癌细胞中的关联、机制和生物学相关性。总之，这项建议中概述的研究将是第一次直接测试配体诱导的RON受体在肿瘤发生过程中的重要性，以及确定乳腺癌中RON和2-连环蛋白信号通路之间的分子串扰。我们将利用体内的尖端方法，在存在RON癌基因过表达的情况下，有条件地丢失2-连环蛋白，或基因靶向丢失RON配体，以分析临床相关小鼠模型中自发的乳腺癌形成和转移。 公共卫生相关性： 除皮肤癌外，乳腺癌是女性最常见的癌症，也是女性癌症死亡的第二大原因。大约18万例新的浸润性癌症病例将被诊断出来，估计约有4万名妇女死于这种疾病。由于乳腺癌发病率和死亡率随着年龄的增长而增加，乳腺癌的发病率和发病率可能会随着人口老龄化而增加，退伍军人管理局对这种疾病患者的支出和护理随后也会相应增加。虽然退伍军人管理局和其他机构在治疗这种疾病方面做出了重大努力并取得了进展，但我们对乳腺癌患者的新治疗方案的了解仍然存在重大差距。这项提议的重点是确定一种名为RON的新蛋白质的作用，以及RON依赖的信号通路作为潜在的新的治疗靶点来对抗这种疾病。

DESCRIPTION (provided by applicant): The Ron receptor tyrosine kinase has recently been shown to be overexpressed and activated in a cohort of human cancers, with the most compelling data found in breast cancer. Ron is overexpressed in approximately 50% of human breast cancers, and has been shown to be an independent predictor of both metastases and poor prognosis in women with this disease. While Ron overexpression appears to be an important factor in human breast cancer and metastasis, a significant gap exists in our knowledge about the signaling pathways that Ron activates in breast tumors, and about the importance of these pathways with respect to overall tumor growth and metastatic dissemination. Studies from our laboratory have shown that Ron overexpression selectively in the mammary epithelium leads to mammary tumorigenesis in female mice with 100% incidence and is associated with a high degree of breast cancer metastasis to the liver and lungs. In this model, mammary tumorigenesis is associated with elevated expression of Ron, increased receptor phosphorylation and increased Ron-associated tyrosine kinase activity. However, the degree of dependency of the Ron ligand, hepatocyte growth factor-like protein (HGFL), in this model remains unknown. Biochemical analyses of primary mammary tumors from these mice demonstrate that Ron overexpression is associated with elevated levels of tyrosine phosphorylated 2-catenin and with the upregulation of downstream 2-catenin target genes. Similar to Ron, 2-catenin expression is also associated with poor prognosis in breast cancer patients. Moreover, our preliminary data show an association between high Ron expression and high2-catenin levels in human breast cancer specimens. We also show that HGFL-induced Ron activation in human breast cancer cell lines induces rapid 2-catenin accumulation and tyrosine phosphorylation of2-catenin that is translocated to the nucleus. Based on our preliminary and published data we hypothesize that ligand-mediated activation of Ron augments 2-catenin signaling, leading to increased breast cancer growth, survival, and metastatic dissemination. To test this hypothesis three Specific Aims are proposed: (i) to delineate the role of the Ron ligand, HGFL, in breast cancer cell growth, survival and metastatic dissemination in vivo; (ii) to examine the in vivo biological significance of2-catenin expression in Ron-mediated mammary tumorigenesis and metastasis, and (iii) to determine the association, mechanism, and biological relevance of HGFL-induced, Ron-dependent 2-catenin tyrosine phosphorylation in breast cancer cells. In total, the studies outlined in this proposal will be the first to directly test the significance of ligand-induced Ron receptor activation during tumorigenesis as well as to define the molecular cross-talk between the Ron and 2-catenin signaling pathways in breast cancer. We will utilize cutting edge in vivo approaches involving the conditional loss of2-catenin, or a gene targeted loss of the Ron ligand, in the presence of Ron oncogene overexpression to analyze spontaneous breast tumor formation and metastasis in a clinically relevant murine model. PUBLIC HEALTH RELEVANCE: Excluding skin cancer, breast cancer is the most common cancer in women and is the second leading cause of cancer death in women. Approximately 180,000 new cases of invasive cancer will be diagnosed and about 40,000 women are estimated to die of this disease. As breast cancer incidence and death rates increase with age, the prevalence and morbidity of breast cancer are likely to increase with the aging population and the Veteran's Administration's expenditures and care for patients with this disease will subsequently increase accordingly. While significant effort and advancement into the treatment of this disease have occurred at the VA and other institutions, a significant gap still exists in our knowledge of new treatment options for patients with breast cancer. The focus of this proposal is to define the role of a novel protein, termed Ron, and Ron- dependent signaling pathways as potential new therapeutic targets to combat this disease.