(PQ4A) Metabolic Plasticity of Pre-Malignant Cells During Tumor Progression

 描述(申请人提供)：小细胞肺癌(SCLC)每年在全球范围内导致超过20万人死亡。与许多实体肿瘤一样，导致小细胞肺癌结果惨淡的一个主要因素是对目前治疗方法的抵抗力，这些治疗方法在过去30年里基本保持不变。小细胞肺癌复发和进展的细胞起源和分子决定因素是具有巨大临床重要性的引人入胜但知之甚少的课题。尽管有证据表明癌前细胞具有相同的肿瘤启动突变和在肿瘤进展中的潜在意义，但由于缺乏可处理的模型和定义异常过程的知情方法，对这些细胞的表征一直是具有挑战性的。利用小鼠小细胞肺癌的基因工程模型，我们用特定的谱系示踪剂分离癌前细胞，并建立了缺乏已知致癌异常且在培养和同种异体移植模型中不发生自发转化的细胞系。通过比较癌前细胞和小细胞肺癌细胞的分子图谱，可以确定与肿瘤进展有关的“驱动因素”，而不是通过比较整个肺和肿瘤的常规方法确定的驱动因素。本研究的目的是利用整合的基因表达分析和功能遗传学来确定前SC的分子特性及其恶性进展，并评估前SC作为治疗的靶点。假设胆固醇代谢的可塑性定义了肿瘤进展过程中的小细胞肺癌癌前前体细胞(PreSC)。这一假说是基于我们的初步发现提出的，这些发现指出，恶性进展过程中胆固醇代谢增加，癌基因转化细胞的生长减少，对一种具有抗胆固醇特性的药物的反应。我们提出了以下具体目标。在目标1中，我们将利用病毒介导的基因表达方法，在体内和体外确定胆固醇代谢基因及其相关信号通路的作用。在目标2中，我们将测试全身胆固醇代谢水平的变化是否通过使用高胆固醇饮食或已知的调节胆固醇合成和运输的药物来调节身体胆固醇水平来影响肿瘤进展。在目标3中，我们将通过分析在胆固醇摄取和合成中起作用的蛋白质来检查人类肺肿瘤胆固醇代谢的失调。为了验证胆固醇代谢在肿瘤进展中的临床意义，我们旨在建立人癌前细胞，并检测调控胆固醇代谢对癌基因诱导的人癌前细胞转化的影响。这项提议概述了了解肿瘤进展过程中关键驱动分子的详细分子机制的第一步，这将为旨在开发新的预防和治疗策略的更令人兴奋的实验铺平道路。最后，鉴于许多癌症的起源细胞和谱系标记将在不久的将来被知道，这一提议的成功结果可能为确定许多癌症的关键决定因素提供一个范例。

 DESCRIPTION (provided by applicant): Small cell lung cancer (SCLC) causes over 200,000 patient deaths worldwide each year. A major factor contributing to the dismal outcome of SCLC, as in many solid tumors, is resistance to current therapies that have remained largely the same for the past 30 years. Cell-of-origin and molecular determinants of SCLC recurrence as well as progression are fascinating yet poorly understood subjects of immense clinical importance. Despite evidence of pre-malignant cells possessing the same tumor-initiating mutations and potential implications in tumor progression, characterization of these cells has been challenging due to lack of tractable model and informed ways of defining aberrant processes. Using genetically engineered mouse models of SCLC, we isolated pre-malignant cells with specific lineage-tracer and established lines of the cells that lack known oncogenic aberrations and do not undergo spontaneous transformation in culture and allograft model. Comparative molecular profiling of the pre-malignant cell and SCLC cell resulted in identification of `drivers' pathologically relevant to tumor progression as opposed to ones identified in conventional approaches comparing whole lung and tumor. The objectives of this proposal are to define molecular properties of preSC as well as its malignant progression using integrative gene expression analyses and functional genetics, and to assess preSC as therapeutic target. The hypothesis is that plasticity in cholesterol metabolism defines pre- malignant precursor cells of SCLC (preSC) during tumor progression. This hypothesis has been formulated based on our preliminary findings pointing to increased cholesterol metabolism during malignant progression and the reduced growth of oncogene-transformed cells in response to a drug with anti-cholesterol properties. We propose the following specific aims. In Aim 1, we will determine roles of genes for cholesterol metabolism and its related signaling pathways, using virus-mediated gene expression approaches in vivo and in vitro. In Aim 2, we will test whether changes in systemic level of cholesterol metabolism influences tumor progression by modulating body cholesterol level using high-cholesterol diet or drugs known to regulate cholesterol synthesis and transport. In Aim 3, we will examine human lung tumors for deregulated cholesterol metabolism by analyzing proteins that play role in cholesterol intake and synthesis. To validate clinical significance of cholesterol metabolism in tumor progression, we aim to establish human pre-malignant cells and test effect of modulating cholesterol metabolism on oncogene-induced transformation of human pre-malignant cells. This proposal outlines a first step toward understanding detailed molecular mechanisms of key driver molecules during tumor progression, which will pave the way for even more exciting experiments aimed at developing novel strategies for prevention and treatment. Lastly, successful outcomes of this proposal could provide a paradigm of identifying key determinant of many cancers given that cell-of-origins and lineage markers for those caners will be known in the near future.