CHARACTERIZING THE ROLE OF IQGAP1 IN ERK MAPK-DRIVEN EPIDERMAL NEOPLASIA

描述(由申请人提供)：治疗上有用的靶向人类肿瘤需要在不破坏正常组织的情况下选择性地破坏已建立的癌症中的特定通路功能。ERK MAPK通路是一个高度保守的信号通路，在大约三分之一的人类癌症和大多数鳞状细胞癌(SCC)中异常激活。此外，ERK MAPK级联激活与G1期细胞逃逸相结合，可将正常人表皮转化为鳞状细胞癌。因此，这一途径仍然是癌症治疗的一个有希望的靶点。不幸的是，我们实验室最近的工作表明，在MEK1/2和ERK1/2水平上消融ERK MAPK级联信号不仅阻止了RAS/Raf驱动的肿瘤改变，而且还导致了生长抑制和周围表皮的破坏。这些研究强调了在不破坏正常皮肤的情况下，找到有选择性地针对癌症MAPK功能的方法的重要性。靶向MAPK相互作用蛋白(MAPK-IPs)是实现选择性抑制ERK MAPK途径的一种有前景的方法。MAPK-IP与ERK MAPK通路的核心激酶结合，作为支架、接头和调节蛋白，从而改变通路的输出。含有IQ基序的GTPase激活蛋白1(IQGAP1)是一种MAPK-IP，它能结合所有的MEK和Erk亚型，并在特定的环境中激活Erk MAPK。我们最近发现，靶向IQGAP1选择性地阻止早期表皮癌变，而不会破坏正常表皮组织的动态平衡。这项Ruth L.Kirschstein NRSA博士后奖学金申请的目标是确定IQGAP1在已建立的表皮肿瘤中的作用，并确定ERK MAPK驱动的表皮肿瘤所需的IQGAP1的功能结构域。在AIM I中，我们将开发一系列缺失IQGAP1蛋白每个已知结构域的突变体，并确定这些突变体是否具有支持Erk-MAPK驱动的表皮转化的能力。在AIM II中，我们将从功能上评估IQGAP1对侵袭性表皮肿瘤的支持需求。SiRNAs和shRNA表达逆转录载体将被用于靶向IQGAP在侵袭性表皮肿瘤中的作用，并将评估IQGAP1缺失对肿瘤支持的影响。在拟议的资助期结束时，我们希望已经定义了IQGAP1结构域与肿瘤发生有关，并定义了它在致癌光谱中的作用。 公共卫生相关性：这项建议旨在确定和表征治疗有用的靶点，这些靶点选择性地阻断表皮肿瘤中的ERK MAPK信号，而不是在动态平衡中，从而帮助未来癌症治疗的发展。

DESCRIPTION (provided by applicant): Therapeutically useful targeting of human neoplasia requires selective disruption of specific pathway functions in established cancers without destruction of normal tissue. The Erk MAPK pathway is a highly conserved signaling cascade that is aberrantly activated in approximately one third of human cancers and in the majority of squamous cell cancers (SCC). In addition, the combination of Erk MAPK cascade activation with G1 cell cycle escape can transform normal human epidermis into SCC. As such, this pathway remains a promising target for cancer therapeutics. Unfortunately, recent work from our laboratory revealed that ablation of Erk MAPK cascade signaling at the level of both Mek1/2 and Erk1/2 not only blocked Ras/Raf driven neoplastic changes but also resulted in growth inhibition and destruction of the surrounding epidermis. These studies highlight the importance of finding methods to target MAPK function selectively in cancer without disrupting normal skin. One promising method of achieving selective inhibition of the Erk MAPK pathway is through targeting MAPK-interacting proteins (MAPK-IPs). MAPK-IPs bind to the core kinases of the Erk MAPK pathway serving as scaffold, adaptor and regulatory proteins and thereby alter pathway output. IQ motif-containing GTPase activating protein 1 (IQGAP1) is a MAPK-IP that binds all Mek and Erk isoforms and enables Erk MAPK activation in specific settings. We recently showed that targeting IQGAP1 selectively blocks early epidermal carcinogenesis without disrupting homeostasis in normal epidermal tissue. The goal of this Ruth L. Kirschstein NRSA Postdoctoral fellowship application is to determine the role of IQGAP1 in established epidermal tumors and to define the functional domains of IQGAP1 required for Erk MAPK-driven epidermal neoplasia. In AIM I, we will develop a series of mutants lacking each known domain the IQGAP1 protein and determine if these mutants retain the ability to support Erk-MAPK driven epidermal transformation. In AIM II, we will functionally assess the requirement for IQGAP1 on the sustenance of invasive epidermal tumors. siRNAs and shRNA expression retrovectors will be used to target IQGAP in invasive epidermal tumors and the effect of IQGAP1 depletion on tumor sustenance will be evaluated. At the end of the proposed funding period, we hope to have defined the IQGAP1 domains responsible for tumorigenesis and to have defined where in the carcinogenesis spectrum it acts. PUBLIC HEALTH RELEVANCE: This proposal aims to identify and characterize therapeutically useful targets which selectively block Erk MAPK signaling in epidermal tumors but not in homeostasis and thereby aid in the development of future cancer therapeutics.