Defining the contributions by macrophages in BRAFV600E induced lung tumorigenesis

 描述（由申请人提供）：肺癌是世界上最致命的癌症，2-3%的非小细胞肺癌（NSCLC）是由BRAF激酶突变引起的。这些激活的BRAFV 600 E突变在许多癌症类型中发现，并且已经成为许多研究的目标。已经开发了许多BRAFV 600 E抑制剂，包括维罗非尼和达拉非尼，然而，由于缺乏初始应答（即使在BRAFV 600 E阳性癌症中）或出现耐药性疾病，它们的成功受到限制。虽然直接靶向BRAFV 600 E癌蛋白的努力取得了不同的结果，但另一条研究路线已经出现。很明显，肿瘤细胞可能受到周围肿瘤微环境的支持，从而提供了肿瘤促进细胞和治疗靶向信号的新来源。微环境的主要成分之一是肿瘤相关巨噬细胞（TAM），这些细胞已被证明可促进多种癌症类型的肿瘤发生。肿瘤浸润性TAM的存在是NSCLC患者生存的阴性预测因子，表明这些细胞也在肺癌中发挥作用。虽然相关数据表明TAM在NSCLC中的作用，但尚未确定它们促进肺肿瘤发生的机制。该项目使用BRAFV 600 E诱导的肺肿瘤发生的复杂基因工程小鼠模型来探测TAM在NSCLC中的作用。目的1集中于TAM在促进BRAFV 600 E诱导的肺肿瘤起始中的作用。使用巨噬细胞的药理学耗竭，我将确定BRAFV 600 E肿瘤启动是否需要TAM。来自申办者实验室的最近工作已经证明，BRAFV 600 E诱导的肺肿瘤需要完整的WNT/β-连环蛋白/c-MYC信号传导轴来形成。因此，目标1的子目标试图确定TAM是否是这些WNT配体的来源。这将使用另一种小鼠模型来实现，所述小鼠模型除了表达BRAFV 600 E之外还含有组成型活性β-连环蛋白蛋白。目的1的结果将描述：（1）TAM在BRAFV 600 E诱导的肺肿瘤形成中的必要性和（2）TAM是否是BRAFV 600 E肿瘤起始所必需的WNT配体的来源。虽然目标1关注肿瘤起始，但目标2关注肿瘤维持和/或进展所需的TAM这一临床上更重要的问题。目标2的第一个子目标将测试在已建立的BRAFV 600 E诱导的肺肿瘤中的巨噬细胞消耗是否可导致肿瘤停滞和/或消退。目的2的第二子目的旨在确定巨噬细胞消耗是否可以与BRAF抑制协同作用，以导致与单独的BRAF抑制相比增加的肿瘤消退。目标2中提出的问题有可能导致开发巨噬细胞耗竭作为NSCLC患者的治疗方法。总之，本文提出的实验有可能阐明TAM支持NSCLC的分子机制，并直接影响目前几乎没有其他治疗选择的患者的治疗方法的发展。

 DESCRIPTION (provided by applicant): Lung cancer is the deadliest cancer in the world and 2-3% of non-small cell lung cancers (NSCLC) are caused by mutations in the BRAF kinase. These activating BRAFV600E mutations are found in many cancer types and have been the target of much investigation. Many BRAFV600E inhibitors have been developed, including vemurafenib and dabrafenib, however, their success has been limited due to either lack of initial response (even in BRAFV600E positive cancers) or the emergence of drug-resistant disease. While efforts to target the BRAFV600E oncoprotein directly have had mixed results, another line of investigation has emerged. It has become apparent that tumor cells may be supported by the surrounding tumor microenvironment, providing a new source of tumor promoting cells and signals to be targeted for therapy. One of the main component of the microenvironment are the tumor associated macrophages (TAMs), and these cells have been shown to promote tumorigenesis in multiple cancer types. The presence of tumor infiltrating TAMs is a negative predicator of survival in NSCLC patients, suggesting these cells also play a role in lung cancer. While correlative data suggests a role for TAMs in NSCLC, no mechanisms by which they promote lung tumorigenesis has yet been identified. This project uses sophisticated genetically engineered mouse models of BRAFV600E induced lung tumorigenesis to probe the role of TAMs in NSCLC. Aim 1 focuses on the role of TAMs in promoting BRAFV600E induced lung tumor initiation. Using pharmacologic depletion of macrophages, I will determine if TAMs are required for BRAFV600E tumor initiation. Recent work from the sponsor's lab has demonstrated that BRAFV600E induced lung tumors require an intact WNT/ß-catenin/c-MYC signaling axis to form. Thus, a sub aim of aim 1 seeks to determine if TAMs are the source of these WNT ligands. This will be achieved using another mouse model which harbors a constitutively active ß-catenin protein in addition to expression of BRAFV600E. Results from aim 1 will delineate both: (1) the necessity of TAMs in BRAFV600E induced lung tumor formation and (2) if TAMs are the source of WNT ligands necessary for BRAFV600E tumor initiation. While aim 1 focuses on tumor initiation, aim 2 focuses on the more clinically important question of TAMs requirement for tumor maintenance and/or progression. The first sub aim of aim 2 will test, whether macrophage depletion in established BRAFV600E induced lung tumors can lead to tumor stasis and/or regression. The second sub aim of aim 2 seeks to determine if macrophage depletion can synergize with BRAF inhibition to lead to increased tumor regression compared to BRAF inhibition alone. Together the questions addressed in aim 2 have the potential to lead to the development of macrophage depletion as therapy for NSCLC patients. Together the experiments proposed here have the potential to elucidate molecular mechanisms by which TAMs support NSCLC and directly impact the development of therapies for patients with few other therapeutic options currently available.