Targeting Fra-1 in Toxicant-Induced Lung Tumor Initiation & Development

描述（由申请人提供）：该探索性资助提案的重点是研究Fra-1原癌基因在体内香烟烟雾致癌物促进的肺肿瘤发生和进展中的功能相关性。Fra-1是AP-1转录因子的二聚体伴侣，并调节与正常和病理过程有关的基因表达。从基于细胞培养的研究中获得的新兴数据已经明确证明了Fra-1在各种癌细胞进展和侵袭中的致病作用。我们已经证明，Fra-1在肺上皮细胞中被香烟烟雾强烈激活，这是肺癌的主要决定因素，也是肿瘤促进有丝分裂和促炎刺激的主要因素。我们已经证明，Fra-1的过表达在体外促进肺上皮细胞的运动和侵袭，但它需要其他激活的原癌基因才能在免疫功能低下的小鼠体内赋予其致癌潜力。我们的初步结果表明，基质金属蛋白酶（MMP）介导的EGFR激活的Ras-ERK途径是至关重要的香烟烟雾诱导的Fra-1的表达。该途径对于Fra-1诱导的肺上皮细胞运动和侵袭也是关键的。基于这些初步观察，我们推测Fra-1是体内肺癌发生和发展的关键决定因子，该转录因子可能为肺癌治疗提供一个良好的靶点。为了验证这一假设，我们将确定Fra-1原芋螺基因是否是致癌K-Ras诱导的肺肿瘤发生和发展的关键介质（具体目标1）。在补充研究中，我们将研究肺上皮细胞中Fra-1的靶向破坏是否抑制体内香烟烟雾致癌物促进的肺肿瘤发生和进展（具体目标2）。Fra-1的常规缺失导致胚胎致死。因此，我们将首次使用具有Fra-1“floxed”等位基因的小鼠来检查Fra-1在肺肿瘤中的特定作用，以有条件地删除肺细胞类型中的Fra- 1。拟议的研究不仅在阐明Fra-1的生物学和功能方面是新颖的，而且还将为毒物诱导的肺肿瘤发展的机制基础提供重要的见解。由于原癌基因转录因子控制促进肺肿瘤发生和生长的基因表达，这些结果使我们能够靶向Fra-1或特异性调节Fra-1的步骤，作为后续研究中针对香烟烟雾诱导的肺肿瘤的新型治疗剂。 公共卫生相关性：肺肿瘤的发生和进展涉及分子变化，如肿瘤抑制基因的沉默和原癌基因表达的失调和/或促进细胞生长和转化导致肿瘤发展的激活。因此，特异性靶向由促进肺肿瘤起始、生长和/或维持的毒物激活的效应原癌基因转录因子可以提供新的治疗机会，以开发用于预防和/或治疗二手烟草烟雾诱导的肺肿瘤的新治疗策略。

DESCRIPTION (provided by applicant): This exploratory grant proposal is focused on investigating the functional relevance of Fra-1 protooncogene in lung tumor initiation and progression promoted by cigarette smoke carcinogens in vivo. Fra-1 is a dimeric partner of AP-1 transcription factor and regulates gene expression implicated in both normal and pathologic processes. Emerging data obtained from cell culture based studies have unequivocally demonstrated a causative role for Fra-1 in various cancer cell progression and invasion. We have shown that Fra-1 is strongly activated in lung epithelial cells by cigarette smoke, a major determinant of lung cancer, as well as tumor promoting mitogenic and pro-inflammatory stimuli. We have demonstrated that overexpression of Fra-1 promotes lung epithelial cell motility and invasion in vitro, but it requires other activated protooncogene(s) to impart its oncogenic potential in vivo in immunocompromised mice. Our preliminary results suggests that a matrix mettalloproteinase (MMP) mediated EGFR-activated Ras-ERK pathway is crucial for cigarette smoke induced Fra-1 expression. This pathway is also critical for Fra-1 induced lung epithelial cell motility and invasion. Based on these preliminary observations, we hypothesize that Fra-1is a critical determinant of lung tumorogenesis and progression in vivo and this transcription factor may provide a good target for lung cancer therapy. To test this hypothesis, we will determine whether Fra-1 protoconogene is a critical mediator of oncogenic K-Ras-induced lung tumor initiation and development in vivo (Specific Aim 1). In complimentary studies, we will investigate whether a targeted disruption of Fra-1 in lung epithelium inhibits lung tumor initiation and progression promoted by cigarette smoke carcinogens in vivo (Specific Aim 2). Conventional deletion of Fra-1 results in embryonic lethality. Thus, we will examine for the first time the specific roles of Fra-1 in lung neoplasms using mice with a Fra-1 "floxed" allele to conditionally delete Fra- 1 in lung cell types. The proposed studies are not only novel in terms of elucidating the biology and functions of Fra-1 but will also provide critical insights into the mechanistic basis underlying toxicant-induced lung tumor development. As protooncogenic transcription factors control expression of genes that promote lung tumor initiation and growth, these results could enable us to target Fra-1, or steps that specifically regulate Fra-1, as novel therapeutic agent(s) against cigarette smoke-induced lung neoplasms in subsequent studies. PUBLIC HEALTH RELEVANCE: Lung tumor initiation and progression involves molecular changes such as silencing of tumor suppressor genes and deregulation of proto-oncogene expression and/or activation that promote cell growth and transformation leading to tumor development. Thus, specifically targeting the effector proto-oncogenic transcription factors activated by toxicants that promote lung tumor initiation, growth and/or maintenance may provide new therapeutic opportunities to develop novel treatment strategies for the prevention and/or treatment of second hand tobacco smoke -induced lung neoplasms.