Elucidating the Molecular Mechanisms of Ect2 in cytokinesis and oncogenesis

描述（由申请人提供）：在过去的几年里，Ras，一个小的GTPase癌基因一直是癌症研究的焦点，因为它是与所有人类癌症相关的最常见突变基因之一（33%）。Ras是一个由小gtpase组成的大超家族的创始成员，最近的研究已经将Ras超家族蛋白的异常活性，特别是Ras同源（Rho） gtpase与肿瘤发生联系起来。然而，与Ras不同的是，Rho GTPases并不直接在癌症中发生突变，相反，它们的异常活性与它们的异常表达和/或调控有关。Rho GTPase异常活性的最重要机制可能是rhogef（鸟嘌呤核苷酸交换因子）激活蛋白异常的结果。我的研究重点是一个RhoGEF， Ect2（上皮细胞转化序列2）。Ect2是人类rhogef的Dbl家族成员。先前的研究表明，Ect2在正常的哺乳动物细胞分裂中是必不可少的。相反，在许多癌症中都观察到异常过表达的Ect2，最近的一项研究表明，Ect2在肺癌细胞系生长和致瘤性中起着关键作用。我们发现Ect2在结直肠癌（CRC）患者肿瘤组织、自发性肠腺瘤APCmin小鼠和人CRC细胞系中表达升高。有证据表明，存在于正常细胞核中的Ect2在肺癌和脑癌中被错误地定位到细胞质中。这种错误定位可能导致细胞质中不适当的Rho激活。除了RhoGEF催化结构域外，Ect2还由多个加成结构域组成。关于Ect2在癌症中如何异常激活，以及Ect2在正常细胞和肿瘤细胞中的作用机制是否不同，目前还不清楚，也是我研究的重点。我们假设Ect2在细胞分裂中的功能与促进肿瘤发生的功能不同，错误定位可能导致Ect2在癌症中的激活。这些研究将需要我应用非常多样化的实验技术，培养我成为一名独立的研究人员，并建立我进行基础和转化癌症研究的能力。

DESCRIPTION (provided by applicant): In previous years, Ras, a small GTPase oncogene has been a focus in cancer research because it is one of the most commonly mutated genes associated with all human cancers (33%). Ras is the founding member of a large superfamily of small GTPases, and recent studies have linked the abnormal activity implicated Ras superfamily proteins, in particular, the Ras homologous (Rho) GTPases to tumorigenesis. However, unlike Ras, Rho GTPases are not mutated directly in cancer, but instead their abnormal activity has been linked to their abnormal expression and/or regulation. Perhaps the most significant mechanism that has emerged in which aberrant activity of Rho GTPase is the result of abnormalities in activating proteins called RhoGEFs (guanine nucleotide exchange factors). My studies are focused on one RhoGEF, Ect2 (Epithelial cell transforming sequence 2). Ect2 is a member of the human Dbl family of RhoGEFs. Previous studies indicate that Ect2 is essential in normal mammalian cytokinesis. In contrast, abnormal overexpression of Ect2 has been observed in many cancers, and a recent study demonstrated a critical role for Ect2 in lung carcinoma cell line growth and tumorigenicity. We have found that Ect2 expression is elevated in colorectal carcinoma (CRC) patient tumor tissue, APCmin mice with spontaneous intestinal adenomas, and human CRC cell lines. There is evidence that Ect2, which is present in the nucleus of normal cells, is mislocalized into the cytoplasm in lung and brain cancers. This mislocalization may lead to inappropriate Rho activation in the cytoplasm. In addition to its RhoGEF catalytic domain, Ect2 is comprised of multiple addition domains. How Ect2 becomes aberrantly activated in cancer and whether the mechanisms of Ect2 function in normal and neoplastic cells are distinct, are poorly understood and the focus of my studies. We hypothesize that the functions of Ect2 in cytokinesis are distinct from functions which promote oncogenesis and that mislocalization may contribute to Ect2 activation in cancer. These studies will require my application of a very diverse repertoire of experimental techniques, foster my development into an independent researcher and establish my abilities to do basic and translational cancer research.