Targeting Translation Dependence in Colorectal Cancer Progression

描述(申请人提供)：RAS/RAF/MEK/ERK和PI3K/AKT通路的突变激活与结直肠癌(CRC)的进展和转移有关。几种小分子靶向PI3K、AKT、RAF和MEK抑制剂已在临床上用于治疗结直肠癌，但作为单一药物仅显示出有限的活性。我们最近发现，通过有效地抑制eIF4E启动的帽依赖翻译，抑制ERK和AKT通路在体外和体内都显示出强大的协同抗结直肠癌作用。我们的主要假设是，协同ERK和AKT信号激活帽依赖的翻译可以选择性地上调关键的癌蛋白，从而促进CRC的进展和转移。通过研究协同ERK和AKT信号激活帽依赖翻译的分子细节，我们旨在了解翻译激活在结直肠癌转移进展中的分子机制，并探索靶向翻译调控在结直肠癌治疗中的应用。我们的具体目标是：目的1.确定协同ERK和AKT信号在结直肠癌中翻译激活的生物学和治疗后果。我们将确定1)mTOR激酶在多大程度上整合了ERK和AKT信号在翻译调控结直肠癌细胞生长和运动中的功能；2)mTOR抑制诱导ERK和AKT的反馈激活如何解除对帽依赖的翻译的调控，并导致mTOR非依赖性；以及3)使用我们建立的结直肠癌原位转移模型，转移进展调节翻译活动的分子基础。目的2.研究ERK和AKT信号协同翻译激活在大肠癌进展和转移中的分子机制。我们证明Survivin是ERK和AKT通路的关键翻译靶点。我们将探索翻译调控的Survivin作为这些途径的重要生长/转移促进效应因子的可能机制。我们将使用多聚体图谱和蛋白质组学相结合的方法，系统地鉴定选择性地招募到多聚体并由ERK和AKT信号协同翻译的其他mRNAs，并详细描述这些基因在结直肠癌进展和转移中的功能重要性。目的3.评价联合抑制MEK/ERK和AKT/mTOR信号通路的体内效用，并针对它们在翻译启动时的信号趋同来加强对结直肠癌的治疗。我们将使用小鼠原位结直肠癌模型和患者肿瘤来源的异种移植模型来确定MEK、AKT和mTOR抑制剂单独和联合使用的有效性，并表征翻译起始抑制物4EGI-1预防肿瘤进展和转移的能力。EIF4E、4E-BP1和Survivin的表达和调控以及它们与ERK和AKT通路突变激活状态的相关性也将在靶向治疗和临床标本中得到表征。

DESCRIPTION (provided by applicant): Mutational activation of the RAS/RAF/MEK/ERK and PI3K/AKT pathways is associated with colorectal cancer (CRC) progression and metastasis. Several small molecularly-targeted PI3K, AKT, RAF and MEK inhibitors have been tested in the clinic for the treatment of CRC but have shown only limited activity as a single agent. We have recently discovered that inhibition of both the ERK and AKT pathways exhibits potent, synergistic anti-CRC effects, both in vitro and in vivo, by effectively inhibiting eIF4E-initiated cap-dependent translation. Our overarching hypothesis is that the activation of cap-dependent translation by cooperative ERK and AKT signaling can selectively upregulate key oncoproteins that confer CRC progression and metastasis. By characterizing the molecular details of the activation of cap-dependent translation by cooperative ERK and AKT signaling, we aim to understand the molecular mechanisms underlying translational activation for CRC metastatic progression, and to explore the therapeutic applications of targeting translational regulation for CRC treatment. Our Specific Aims are: Aim 1. Determine the biologic and therapeutic consequences of translational activation by cooperative ERK and AKT signaling in CRC. We will determine 1) the extent to which the mTOR kinase integrates the function of ERK and AKT signaling in translational regulation of CRC cell growth and motility; 2) how mTOR inhibition-induced feedback activation of ERK and AKT deregulates cap-dependent translation and causes mTOR-independence; and 3) the molecular basis of metastatic progression-modulated translational activity using our well-established orthotopic metastastic model of CRC. Aim 2. Characterize the molecular mechanism of translational activation by cooperative ERK and AKT signaling for CRC progression and metastasis. We demonstrate that survivin is a key translational target of the ERK and AKT pathways. We will explore the possible mechanism by which the translationally-regulated survivin acts as an important growth/metastasis-promoting effector of these pathways. We will use combined polysome profiling and proteomic approaches to systematically identify other mRNAs that are selectively recruited to polysomes and translated by cooperative ERK and AKT signaling, and characterize in detail the functional importance of these genes in CRC progression and metastasis. Aim 3. Evaluate the in vivo utility of combined inhibition of the MEK/ERK and AKT/mTOR pathways and targeting the convergence of their signals on translation initiation for enhancing CRC therapy. We will use both the mouse orthotopic model of CRC and the patient tumor-derived xenograft model to determine the effectiveness of MEK, AKT and mTOR inhibitors alone and in combination, and to characterize the ability of the translation initiation inhibitor 4EGI-1 to prevent tumor progressio and metastasis. The expression and modulation of eIF4E, 4E-BP1 and survivin, and their correlation with the mutational activation status of ERK and AKT pathways will also be characterized in response to the targeted therapies and in clinical specimens.