Identification and targeting of the signaling pathways underlying lung cancer.

描述(申请人提供)：肺癌是全球癌症死亡的主要原因，5年生存率为15%，这在很大程度上是由于对晚期疾病缺乏有效的治疗。在超过30%的肺腺癌中发现了K-ras基因的激活突变，这表明突变的K-ras是肺癌的驱动因素和治疗干预的重要靶点。然而，以前直接针对突变K-ras基因的尝试收效甚微。因此，以激活的K-RAS信令为目标的替代方法是必要的。我们的长期目标是确定突变的K-RAS驱动的肿瘤发生所需的效应器，并开发针对这些分子和途径的治疗方法。我们的初步研究以及其他研究人员的最新发现表明，Notch信号通路可能是非小细胞肺癌(NSCLC)的重要治疗靶点。Notch家族由哺乳动物中的四种受体(Notch1-4)组成，目前抑制Notch的方法包括使用β-分泌酶抑制剂(GSI)，它抑制所有四种受体的激活。不幸的是，由于全局Notch抑制导致的严重肠道毒性，GSI在患者中的使用受到限制。此外，最近的研究表明，不同的Notch受体在肿瘤发生中具有不同的、不重叠的功能，并且这些功能是细胞类型和时间依赖的。这些发现表明，针对Notch受体及其下游信号通路的抗癌治疗需要针对单个受体进行量身定制。鉴于之前的研究结果表明Notch1是K-ras诱导的肿瘤发生所必需的，我们通过将条件诱导的K-RasG12D敲入小鼠模型与Notch1条件敲除小鼠杂交，测试了Notch1是否对体内突变的K-ras驱动的NSCLC的发展是必需的。在这些小鼠中，Cre介导的重组同时激活了K-RasG12D等位基因，并使Notch1失活。我们发现Notch1的缺失显著降低了肿瘤的起始性和总的肿瘤负担，表明Notch1在K-ras诱导的肺肿瘤发生中是必需的。此外，我们的研究表明，Notch1通过抑制P53介导的细胞凋亡在K-ras驱动的NSCLC中发挥作用。重要的是，这些结果确定了Notch1活性与野生型p53非小细胞肺癌患者预后不良相关的分子基础，野生型P53占所有非小细胞肺癌患者的50%。根据我们的发现，我们假设Notch1是肺癌发生所必需的，它通过抑制 靶向Notch1和/或其下游效应子将抑制非小细胞肺癌的发生和/或维持。建议的研究将验证这一假说，并确定K-RAS驱动的非小细胞肺癌中Notch1需求的潜在机制。此外，我们将测试Notch1在K-ras突变以外的致癌事件驱动的NSCLC中的作用，以确定Notch1指导的治疗是否将为广泛的NSCLC患者提供好处。

DESCRIPTION (provided by applicant): Lung cancer is the leading cause of cancer deaths worldwide, with 5-year survival rates of <15%, and this is largely due to the lack of effective treatments for advanced disease. Activating mutations of the K-ras gene are found in more than 30% of lung adenocarcinoma, indicating that mutant K- ras is a driver of lung cancer and an important target for therapeutic intervention. However, previous attempts to directly target mutant K-ras have met with little success. Thus, alternative approaches to target activated K-Ras signaling are warranted. Our long-term goals are to identify effectors that are required for mutant K-Ras-driven tumorigenesis and to develop therapeutic approaches to targets these molecules and pathways. Our Preliminary Studies, along with recent findings from others, suggest that Notch signaling pathways are potentially important therapeutic targets in non-small cell lung cancer (NSCLC). The Notch family consists of four receptors in mammals (Notch1-4) and current approaches to Notch inhibition involve the use of ?-secretase inhibitors (GSIs), which inhibit the activation of all four receptors. Unfortunately, the use of GSIs in patients is limited due to severe intestinal toxicities that are a result of global Notch inhibition. In additin, recent studies indicate that the different Notch receptors have distinct and non-overlapping functions in tumorigenesis and that these functions are cell type and timing-dependent. These finding suggest that anti-cancer therapies targeting Notch receptors and their downstream signaling pathways need to be tailored to individual receptors. Given previous findings suggesting Notch1 is required for K-ras-induced tumorigenesis, we tested whether Notch1 is necessary for the development of mutant K-ras-driven NSCLC in vivo, by crossing the conditionally inducible K-rasG12D knock-in mouse model with a Notch1 conditional knockout mouse. In these mice, Cre-mediated recombination simultaneously activates the K-rasG12D allele and inactivates Notch1. We find that loss of Notch1 significantly reduced tumor initiation and overall tumor burden, indicating that Notch1 is required for K-ras-induced lung tumorigenesis. Moreover, our studies have shown that Notch1 contributes to K-ras-driven NSCLC by suppressing p53-mediated apoptosis. Importantly, these results identify the molecular basis for the documented correlation between Notch1 activity and poor prognosis in NSCLC patients having wild type p53, which represent 50% of all NSCLC cases. Based on our findings, we hypothesize that Notch1 is required for lung tumorigenesis via its ability to suppress p53, and that targeting Notch1 and/or its downstream effectors will inhibit the development and/or maintenance of NSCLC. The proposed studies will test this hypothesis and define the mechanisms underlying the requirement for Notch1 in K-Ras driven NSCLC. In addition, we will test the role of Notch1 in NSCLC driven by oncogenic events other than K-ras mutation, to determine if Notch1- directed therapies will provide benefit to a broad spectrum of NSCLC patients.