The role of the Kras4A isoform in epithelial carcinogenesis

描述（由申请人提供）：大约30年前，RAS家族的基因在人类癌症中被发现发生突变，该项目的长期目标是更深入地了解这些基因导致恶性转化的机制。KRAS基因是最常见的突变家族成员，特别是在胰腺癌、结肠癌和肺癌中。这些肿瘤每年在全世界造成数十万人死亡。利用基因工程小鼠模型，该实验室发现Kras的一个次要亚型（Kras4A）对Kras突变肿瘤的发展至关重要。缺乏这种异构体的小鼠对Kras突变的肺或皮肤肿瘤的发展具有高度抗性，这表明抑制Kras4A的功能可能会给患者带来治疗益处。该项目涉及对Kras蛋白这种特定形式激活的信号通路的全面分析。许多新方法将被用来了解Kras4A如何在细胞和组织内发出信号。最近开发的一种新的成像方法（光激活定位显微镜，或PALM）将成像Kras4A在细胞中的单个分子位置，并发现突变型和野生型Kras4A蛋白之间是否存在相互作用。在缺乏Kras4A或同时缺乏Kras4A和4B的细胞中，通过典型RAS通路组分进行信号传导将被研究，以确定这些细胞中缺乏的任何特定信号通路。最后，我们将利用新的基因表达网络分析工具，对小鼠肺中的Kras信号进行公正的观察。比较肺癌易感小鼠的基因表达网络与由于Kras4A缺失而产生耐药性的小鼠的基因表达网络，可能会发现以前与Ras不相关的途径，这些途径可能解释了Kras4A在转化中的关键作用。通过小鼠体内模型，研究Kras4A在损伤后肺上皮干细胞再生中的可能功能，并开发可诱导shRNA抑制Kras4A的新模型，研究该蛋白在Kras基因突变的肿瘤增殖和维持中的作用。

DESCRIPTION (provided by applicant): Genes of the RAS family were found to be mutated in human cancers around 30 years ago, and the long term goal of this project is to develop a deeper understanding of the mechanisms by which these genes cause malignant transformation. The KRAS gene is the most commonly mutated family member, particularly in carcinomas of the pancreas, colon and lung. Together, these tumors account for hundreds of thousands of deaths worldwide each year. Using genetically engineered mouse models, this laboratory showed that a minor isoform of Kras (Kras4A) is essential for development of Kras mutant tumors. Mice deficient in this isoform are highly resistant to development of lung or skin tumors with Kras mutations, suggesting that inhibition of the function of Kras4A could result in therapeutic benefit for patients. This project involves a comprehensive analysis of the signaling pathway that is activated by this specific form of the Kras protein. A number of novel approaches will be used to understand how Kras4A signals within cells and tissues. A recently developed new imaging approach (Photo-activated localization microscopy, or PALM) will image the location of single molecules of Kras4A in cells, and find out whether there is an interaction between mutant and wild type Kras4A proteins. Signaling through canonical RAS pathway components in cells lacking Kras4A or both Kras4A and 4B, will be investigated in order to identify any specific signaling pathways that are deficient in these cells. Finally, an unbiased view of Kras signaling in vivo in mouse lungs will be developed, using novel gene expression network analysis tools. Comparison of gene expression networks from mice that are susceptible to lung cancer with those that are resistant due to deletion of Kras4A may identify pathways not previously associated with Ras that may account for the critical role of Kras4A in transformation. Using mouse models in vivo, the possible function of Kras4A in regeneration of lung epithelium from stem cells after damage will be studied, and new models in which Kras4A can be inhibited using inducible shRNA will be developed to investigate the role of this protein in the propagation and maintenance of tumors with mutant Kras genes. PUBLIC HEALTH RELEVANCE: Cancers are caused by mutations in genes, and one of the most commonly mutated genes is known as KRAS. These specific mutations are found in hundreds of thousands of tumors each year, and the goal of this project is to find new ways to treat these cancers.