Targeting SMURF2 as a novel therapy for EGFR driven tumors

描述（由申请人提供）：表皮生长因子受体（EGFR）的过度表达驱动多种癌症，包括肺癌，头颈部（H&N）和结直肠癌，其中靶向EGFR激酶活性已经产生了明确但有限的成功。基于先前的报告和我们的初步研究，我们假设通过促进EGFR蛋白降解而不是简单地抑制其激酶活性，抗EGFR治疗的有效性可以大大提高。为了实现这一目标，我们已经确定了EGFR与HECT型泛素连接酶Smad泛素化调节因子2 （SMURF2）之间的一种新的相互作用，这对EGFR蛋白的稳定性至关重要，通过靶向SMURF2，我们可以有效地降解EGFR以杀死EGFR成瘾的癌细胞并阻止人类肿瘤异种移植物的生长。我们也发现了这两种蛋白在RNA和蛋白水平上的表达在一大群肺癌和H&N癌患者中具有显著的相关性。本提案的主要目标是了解EGFR和SMURF2在上气消化癌中的分子相互作用，并通过靶向SMURF2诱导EGFR降解来开发一种新的治疗策略。我们认为，通过下调SMURF2， EGFR将更容易降解，独立于其在癌症中的过度表达或突变状态，这种策略将在治疗上更有效，因为它可以在物理上消除EGFR。我们提出通过3个具体目标来实现这些目标：在目标1中，我们假设某些赖氨酸残基对SMURF2介导的蛋白质泛素化至关重要，负责EGFR蛋白稳定性。具体目的1是确定smurf2介导的泛素化是否可以共价修饰EGFR上的某些赖氨酸残基，以稳定其降解。在特定目标2中，我们假设通过shRNA下调SMURF2，我们可以减少肿瘤负担作为个体治疗或可以使目前可用的化疗/放疗耐药的肿瘤细胞敏感。具体目的2是探索SMURF2靶向治疗上消化道肿瘤的新方法。在目标3中，我们假设EGFR和SMURF2与某些辅因子以序列特定的方式相互作用。具体目标3，我们将确定EGFR的结构域和协助其稳定相互作用和SMURF2蛋白修饰的辅因子。这项研究的结果将帮助我们建立一种新的靶向EGFR的方法，通过SMURF2靶向改变其泛素化状态，而不依赖于耐药的EGFR突变。我们预计，本项目的成功完成不仅将为探究泛素化在EGFR蛋白稳定性中的作用提供更好的机制洞察，还将为开发可破坏EGFR- smurf2相互作用杀死癌细胞的拟肽支架或小分子抑制剂提供坚实的基础，并将对某些患者有益。

DESCRIPTION (provided by applicant): Over-expression of epidermal growth factor receptor (EGFR) drives several cancers including lung, head & neck (H&N) and colorectal, where targeting EGFR kinase activity has produced definite but limited successes. Based on previous reports and our preliminary studies, we hypothesize that the effectiveness of an anti-EGFR therapy can be greatly increased by facilitating EGFR protein degradation as opposed to simple inhibition of its kinase activity. Towards this goal, we have identified a novel interaction between EGFR and a HECT type ubiquitin ligase, Smad ubiquitination regulatory factor 2 (SMURF2), which is critical for EGFR protein stability and by targeting SMURF2 we can efficiently degrade EGFR to kill EGFR addicted cancer cells and stop the growth of human tumor xenografts. We have also discovered significant correlation of expression of the two proteins at the RNA and protein levels in a large group of lung and H&N cancer patients. The main goal of this proposal is to understand the molecular interaction between EGFR and SMURF2 in upper aerodigestive cancers and to develop a novel therapeutic strategy by inducing EGFR degradation via targeting SMURF2. We believe that by down-regulating SMURF2, EGFR will be more vulnerable to degradation, independent of its overexpression or mutation status in cancer and such a strategy will be therapeutically more potent as it can physically abolish EGFR. We propose to achieve these goals through 3 specific aims: In aim 1, we hypothesize that certain lysine residues are critical for SMURF2 mediated protein ubiquitination, responsible for EGFR protein stability. Specific aim 1 is to determine whether SMURF2-mediated ubiquitination can covalently modify certain lysine residues on EGFR to stabilize it from undergoing degradation. In specific aim 2, we hypothesize that by down-regulating SMURF2 via shRNA, we can reduce the tumor burden as individual therapy or can sensitize tumor cells that are resistant to currently available chemo-/radiotherapy. Specific aim 2 is to explore the therapeutic potential of SMURF2 targeting as a novel approach in upper aerodigestive cancer treatment. In aim 3, we hypothesize that EGFR and SMURF2 interacts in sequence specific manner in association with certain cofactors. Specific aim 3 we will identify the domain(s) of EGFR and cofactors that are assisting in its stable interaction and protein modification by SMURF2. Results obtained from this study will help us establish a novel approach targeting EGFR, independent of a drug resistant EGFR mutation by altering its ubiquitination status via SMURF2 targeting. We anticipate that successful completion of this project will not only provide a better mechanistic insight exploring the roles of ubiquitination in EGFR protein stability, it will also provide a strong foundation for the development of peptidomimetic scaffold or small molecule inhibitor, which can disrupt EGFR-SMURF2 interaction to kill cancer cells and will be beneficial for certain patients. PUBLIC HEALTH RELEVANCE: This project deals with developing a novel strategy to target EGFR, a widely accepted, druggable target in variety of epithelial cancers. In this project we want to establish the involvement of a ubiquitin ligase in EGFR protein stability and develop a novel strategy to target the ligase to degrade EGFR protein to kill EGFR- addicted cancer cells.