Investigating the not so minor role of the minor isoform Kras4A in cancer

描述（由申请人提供）：我们才刚刚开始触及KRAS在癌症中潜在作用的复杂性的表面，为了开发有效的靶向治疗，迫切需要更深入地了解KRAS生物学。有趣的是，KRAS基因编码两种蛋白，KRAS4A和KRAS4B，并且有来自体内小鼠模型的深刻证据表明，经常被忽视和知之甚少的KRAS4A蛋白是突变KRAS肿瘤发展的主要参与者。具体来说，携带Kras4B而不携带Kras4A的小鼠对致癌物诱导的肺肿瘤具有高度的抗性，有证据表明Kras4A可能在肺干细胞和肿瘤启动细胞中发挥作用。此外，我们有令人信服的初步证据表明，Kras4A原癌基因（WT Kras4A）与突变的Kras相互作用，这种相互作用取决于Kras中激活突变的类型，并影响肿瘤启动细胞的选择。目的：本研究将(1)明确Kras4A表达细胞在体内正常肺和肿瘤发展中的作用；(2)明确Kras4A独有的信号特征以及Kras4A在肿瘤细胞选择中作用的生化相互作用；(3)发现在肿瘤发生过程中调节Kras4A这些特征的新基因位点，这将拓宽我们对Kras功能的遗传背景的理解，并可能揭示与Kras功能趋同的新途径和基因，从而可以在药理学上靶向治疗癌症。目的1：利用体内模型确定Kras4A在肺再生和肿瘤发生中的作用。将使用一种新的小鼠模型（Kras4ACreERT2）耦合crre -重组酶和Kras4A表达来标记肺中表达Kras4A的细胞，并询问这些细胞在肺再生和肿瘤发生中的作用。Kras4A表达细胞将在气道损伤和肿瘤诱导后被追踪。目的2：体外功能分析Kras4A信号通路将通过mef和上皮细胞中典型Ras效应通路的生化分析和全基因组表达阵列实验来确定Kras4A信号通路。WT Kras4A与Kras的不同突变癌蛋白的生化相互作用将通过分析信号和Kras二聚化，与实验室合作探索

DESCRIPTION (provided by applicant): We are only beginning to scratch the surface of the complexity underlying the role of KRAS in cancer, and there is a pressing need for a deeper understanding of KRAS biology in order to develop effective targeted therapeutics. Intriguingly, the KRAS gene encodes two proteins, KRAS4A and KRAS4B, and there is profound evidence from in vivo mouse models that suggests that the often ignored and poorly understood Kras4A protein is the main player in the development of mutant Kras tumors. Specifically, mice with Kras4B but not Kras4A are highly resistant to carcinogen-induced lung tumors, and there is evidence that Kras4A may play a role in lung stem cells and tumor initiating cells. Furthermore, we have compelling preliminary evidence showing that the Kras4A proto-oncogene (WT Kras4A) interacts with mutant Kras, and that this interaction depends on the type of activating mutation in Kras and influences the selection of tumor initiating cells. Objectives: This study wil (1) define the role of Kras4A expressing cells in vivo in the normal lung and in cancer development; (2) define the signaling features unique to Kras4A and the biochemical interactions underlying the role of Kras4A in tumor cell selection; and (3) identify novel genetic loci which modulate these features of Kras4A in tumorigenesis, which will broaden our understanding of the genetic context in which Kras functions, and may reveal new pathways and genes that converge with KRAS function that can be pharmacologically targeted to treat cancer. Three specific aims are proposed to address these objectives: Aim 1: Determine the role of Kras4A in lung regeneration and tumorigenesis using in vivo models A novel mouse model coupling Cre-recombinase and Kras4A expression (Kras4ACreERT2) will be used to label Kras4A expressing cells in the lung, and to interrogate the role of these cells in lung regeneration and tumor initiation. Kras4A expressing cells will be traced after airway damage, and after tumor induction. Aim 2: Functionally analyze Kras4A signaling in vitro Kras4A signaling pathways will be determined by biochemical analyses of canonical Ras effector pathways and genome-wide expression array experiments in MEFs and epithelial cells with and without Kras4A. The biochemical interaction of WT Kras4A with different mutant oncoproteins of Kras will be explored by analysis of signaling and Kras dimerization, in collaboration with the lab of Dr. Xiaolin Nan. Aim 3: Identify genetic factors in mice that interact with Kras in modulating lung tumor initiation. Tissue already collected from 3 populations of backcrossed mice totaling nearly 400 animals will be used to map genetic factors that are involved in the selection of tumor cells harboring specific mutations at Kras, as well as genetic factors involved in the regulation o Kras splicing and Kras4A expression.