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

描述(由申请者提供)：这项探索性拨款计划的重点是研究Fra-1原癌基因在体内吸烟致癌物促进肺癌发生和发展中的功能相关性。FRA-1是AP-1转录因子的二聚体，调节正常和病理过程中的基因表达。从基于细胞培养的研究中获得的新数据已经明确地表明，Fra-1在各种癌细胞的进展和侵袭中起到了致病作用。我们已经证明，吸烟是肺癌的主要决定因素，以及肿瘤促进有丝分裂和促炎刺激，Fra-1在肺上皮细胞中被强烈激活。我们已经证明，在体外过表达FrA-1可以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(S)在体内传递其在免疫低下小鼠的致癌潜力。我们的初步结果表明，基质金属蛋白酶(MMPs)介导的EGFR激活的RAS-ERK通路在香烟烟雾诱导的Fra-1表达中起关键作用。该通路在Fra-1诱导的肺上皮细胞运动和侵袭中也起关键作用。基于这些初步观察，我们假设Fra-1是体内肺癌发生和发展的关键决定因素，该转录因子可能为肺癌治疗提供一个很好的靶点。为了验证这一假说，我们将确定Fra-1原癌基因是否是致癌K-RAS诱导的体内肺肿瘤发生和发展的关键介质(特定目标1)。在补充性研究中，我们将研究肺上皮中Fra-1的靶向干扰是否能抑制体内吸烟致癌物促进的肺癌的发生和发展(特定目标2)。传统的Fra-1基因缺失会导致胚胎死亡。因此，我们将首次研究Fra-1在肺部肿瘤中的特定作用，使用带有Fra-1“Flox”等位基因的小鼠有条件地删除肺细胞类型中的Fra-1。所提出的研究不仅在阐明Fra-1的生物学和功能方面具有新颖性，而且还将为毒物诱导的肺癌发生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癌启动和生长的基因的表达，这些结果使我们能够在后续的研究中将FRA1或特异性调节FRA1的步骤作为新的治疗药物(S)来对抗香烟烟雾诱导的肺肿瘤。 公共卫生相关性：肺癌的发生和发展涉及分子变化，例如肿瘤抑制基因的沉默和原癌基因表达和/或激活的解除调控，这些因素促进了细胞的生长和转化，从而导致肿瘤的发展。因此，针对由毒物激活的效应原癌基因转录因子，促进肺癌的启动、生长和/或维持，可能为开发新的治疗策略来预防和/或治疗二手烟诱发的肺肿瘤提供新的治疗机会。

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.