Targeting RON Receptor Signaling in Pancreatic Cancer

描述（由申请人提供）：胰腺癌患者的中位生存期仍然不到一年。在过去的3年中，已经有10个阴性的III期试验研究了化疗和生物制剂对晚期胰腺癌的全身治疗。这些试验的失败，在很大程度上反映了我们对胰腺癌生物学的了解有限，需要合理开发新的药物。我们最近发现，大多数原发性和转移性胰腺腺癌过表达RON受体酪氨酸激酶（RTK）。RON在结构上与c-met同源，c-met是一种在许多人类癌症中过度表达和突变的致癌蛋白。我们已经证明，通过其特异性配体肝细胞生长因子样蛋白（HGFL）激活RON受体信号，可诱导胰腺癌细胞的凋亡抵抗、迁移、侵袭，并与EGFR和VEGF产生相关。我们已经确定了几个关键的生存途径，这些途径通过磷酸化事件和启动一个独特的转录程序被RON信号激活。阻断细胞培养中的RON信号通路可使胰腺癌细胞对吉西他滨诱导的凋亡敏感。最后，我们最近的研究表明，缺乏氮的胰腺癌异种移植物对吉西他滨非常敏感。利用基于结构的方法，我们开发并合成了一种新的小分子RON抑制剂（命名为MCC5），它保持了激酶结构域的非活性构象。初步研究表明，该化合物可以防止hgfl诱导的AKT和ERK1/2磷酸化。我们的研究提出了以下假设；1) RON受体信号通路调节胰腺癌细胞存活的关键通路，因此2)RON信号轴的破坏将使胰腺癌对化学和生物治疗敏感。本建议的具体目的是：1)在胰腺癌原位模型中，确定下调RON信号是否会使胰腺癌对吉西他滨和EGFR定向治疗敏感；2)完成基于结构/活性的新型RON抑制剂MCC5的研究，以确定其最具生物活性的形式，并确定其是否可以抑制配体依赖性的胰腺癌细胞中的RON信号。为了实现这些目标，我们将利用细胞培养试验和体内荧光成像来监测肿瘤诱导的新生血管形成和对RON靶向单一和联合治疗的反应。这项工作将为RON靶向治疗胰腺癌的前景提供有力的临床前证据。公共卫生相关性：诊断为胰腺癌的患者的预期寿命仍然不到1年，只有4%的患者在诊断后存活5年。我们的研究小组已经证明，RON受体蛋白存在于几乎所有胰腺癌细胞的表面，并且RON影响这些细胞的行为，导致它们抵抗癌症化疗并入侵和扩散。在本提案中，我们将通过两种不同的方法来研究阻断RON受体功能的作用，以确定这是否可以单独或联合化疗逆转胰腺癌的生长。

DESCRIPTION (provided by applicant): The median survival for pancreatic cancer patients remains less than one year. Over the past 3 years, there have been 10 negative Phase III trials investigating systemic treatment of advanced pancreatic cancer with chemo- and biologic agents. The failure of these trials, in large part, reflects our limited understanding of pancreatic cancer biology and demands the rational development of novel agents. We have recently found that the majority of primary and metastatic pancreatic adenocarcinomas over-express the RON receptor tyrosine kinase (RTK). RON is structurally homologous to c-met, an oncogenic protein which is over-expressed and mutated in numerous human cancers. We have shown that activation of RON receptor signaling by its specific ligand, hepatocyte growth factor-like protein (HGFL), induces apoptotic resistance, migration, invasion, association with EGFR, and VEGF production in pancreatic cancer cells. We have identified several key survival pathways that are activated by RON signaling via phosphorylation events and initiation of a unique transcriptional program. Blockade of RON signaling in cell culture can sensitize pancreatic cancer cells to Gemcitabine-induced apoptosis. Finally, we have recently shown that RON-deficient pancreatic cancer xenografts are exquisitely sensitive to Gemcitabine. Using a structure-based approach, we have developed and synthesized a novel small molecule inhibitor to RON (designated MCC5), which maintains the kinase domain in its inactive conformation. Preliminary studies suggest this compound can prevent HGFL-induced phosphorylation of AKT and ERK1/2. Our studies have prompted the following hypotheses; 1) RON receptor signaling regulates pathways critical to pancreatic cancer cell survival and therefore 2) Disruption of the RON signaling axis will sensitize pancreatic cancer to chemo- and biologic therapies. The specific aims of this proposal are; 1) To determine if down-regulation of RON signaling will sensitize pancreatic cancer to Gemcitabine and EGFR directed therapies in an orthotopic model of pancreatic cancer and 2) To complete structure/activity based studies of the novel RON inhibitor, MCC5, in order to define its most biologically active form, and determine whether it can inhibit ligand dependent RON signaling in pancreatic cancer cells. To complete these aims, we will utilize both cell culture assays as well as in vivo fluorescence imaging to monitor tumor-induced nascent blood vessel formation and response to RON targeted mono- and combination therapies. This work will provide powerful preclinical evidence as to the promise of RON targeted therapy for pancreatic cancer. PUBLIC HEALTH RELEVANCE: The life expectancy for patients diagnosed with pancreatic cancer remains less than 1 year and only 4% of patients survive 5 years following diagnosis. Our research group has demonstrated that the RON receptor protein is present on the surface of nearly all pancreatic cancer cells and that RON influences the behavior of these cells, causing them to resist cancer chemotherapies and to invade and spread. In this proposal, we will examine the effects of blocking RON receptor function by two different methods in order to determine if this can reverse pancreatic cancer growth alone and in combination with chemotherapy.