Role of a Novel TROY-EGFR Complex in Gliobastoma Invasion and Resistance

 描述(申请人提供)：胶质母细胞瘤是成人最常见的原发脑肿瘤，是一种高度致命的恶性肿瘤，中位生存期约15个月。对周围正常大脑的侵袭使完全手术切除变得不可能，增加了对放疗和化疗的抵抗力，几乎保证了肿瘤的复发。因此，有一个重要的未得到满足的临床需求，即开发针对侵袭性肿瘤细胞的创新方法，以改进对这种疾病的治疗。作为TNFR家族的一员，Troy的表达随着神经胶质瘤分级的增加而增加，与患者的生存期呈负相关。Troy的高表达刺激胶质母细胞瘤细胞在体外和体内的侵袭，并增加对替莫唑胺和放射治疗的抵抗力。相反，沉默Troy的表达抑制了胶质母细胞瘤细胞的侵袭，增加了对替莫唑胺的敏感性，并延长了颅内异种移植模型的存活时间。初步研究证实，Troy与EGFR形成一种新的信号复合体，并调节EGFR生存信号。Troy的表达显着增强了EGF刺激胶质母细胞瘤细胞侵袭的能力，而通过shRNA或重新定位的小分子丙戊茶碱抑制Troy的表达则阻断了EGF对胶质瘤细胞迁移的刺激，提示Troy-EGFR复合体是一种尚未被认识的抑制胶质瘤侵袭和降低治疗耐药的治疗靶点。尽管这种新的复合体对胶质母细胞瘤细胞迁移、侵袭、增殖和耐药的信号机制仍不清楚，但初步研究表明，Troy通过PDZ-Rhogef信号转导，PDZ-Rhogef是一种鸟嘌呤交换因子，调节Rho GTPase RhoA和RhoC，将Troy与细胞骨架组织和细胞运动联系起来。PDZ-Rhogef的敲除显著抑制了Troy和EGF刺激的侵袭定位PDZ-Rhogef作为Troy-EGFR复合体的潜在重要效应器。目前提案的总体目标是确定Troy和EGFR之间相互作用的机制基础，并确定这一独特的信号复合体在胶质母细胞瘤细胞侵袭、生存和治疗耐药中的功能作用。我们在这项建议中的基本原理是，确定胶质母细胞瘤中Troy信号的机制基础具有确定降低侵袭性胶质母细胞瘤细胞治疗耐药性的候选靶点的潜力。我们假设，Troy-EGFR信号复合体增强了恶性胶质母细胞瘤细胞的侵袭和存活。目的1确定Troy与EGFR相互作用的机制基础、相互作用的特异性，并确定其对胶质母细胞瘤细胞侵袭和耐药的影响。目的2研究PDZ-Rhogef作为Troy-EGFR信号转导的关键效应因子的作用。目的3将作为联合治疗的一个组成部分，评估抑制Troy表达和信号转导对胶质母细胞瘤异种移植瘤存活的影响。这一结果可能为克服胶质母细胞瘤的治疗耐药性和确定改善临床结果的新靶点提供新的见解。

 DESCRIPTION (provided by applicant): Glioblastoma is the most frequent primary brain tumor in adults and a highly lethal malignancy with a median survival of about 15 months. The aggressive invasion of the surrounding normal brain makes complete surgical resection impossible, increases the resistance to radiation and chemotherapy, and virtually assures tumor recurrence. Thus, there is a significant unmet clinical need to develop innovative approaches to target the invasive tumor cells for improved treatment of this disease. Expression of TROY, a member of the TNFR family, increases with increasing glial tumor grade and inversely correlates with patient survival. Increased expression of TROY stimulates glioblastoma cell invasion in vitro and in vivo and increases resistance to temozolomide and radiation treatment. Conversely, silencing TROY expression inhibits glioblastoma cell invasion, increases sensitivity to temozolomide, and prolongs survival in an intracranial xenograft model. Preliminary studies identified that TROY forms a novel signaling complex with EGFR and modulates EGFR survival signaling. TROY expression significantly increases the capacity of EGF to stimulate glioblastoma cell invasion while knockdown of TROY expression by shRNA or by the repurposed small molecule propentofylline blocked EGF stimulation of glioma cell migration suggesting that the TROY-EGFR complex represents an unappreciated therapeutic target to inhibit glioma invasion and decrease therapeutic resistance. Although the mechanistic basis of signaling from this novel complex on glioblastoma cell migration, invasion, proliferation, and resistance remain largely undefined, initial studies indicate that TROY signals through PDZ-RhoGEF, a guanine exchange factor that regulates the Rho GTPases RhoA and RhoC, linking TROY to cytoskeletal organization and cell motility. Knockdown of PDZ-RhoGEF significantly inhibits TROY and EGF stimulated invasion positioning PDZ-RhoGEF as a potential important effector of the TROY-EGFR complex. The overall objective of the current proposal is to determine the mechanistic basis of the interaction between TROY and EGFR and define the functional role of this unique signaling complex in glioblastoma cell invasion, survival, and therapeutic resistance. Our rationale in this proposal is that defining the mechanistic basis of TROY signaling in glioblastoma holds potential to identify candidate targets to decrease the therapeutic resistance of invasive glioblastoma cells. We hypothesize that the TROY-EGFR signaling complex enhances malignant glioblastoma cell invasion and survival. Aim 1 seeks to define the mechanistic basis of the interaction of TROY with EGFR, the specificity of the interaction, and determine its effect on glioblastoma cell invasion and resistance. Aim 2 will investigate the role of PDZ-RhoGEF as a critical effector for TROY-EGFR signaling. Aim 3 will assess the effect of inhibition of TROY expression and signaling on survival in glioblastoma xenografts as a component of combinatorial therapy. The results may provide new insights into overcoming the therapeutic resistance of glioblastoma and the identification of novel targets for improved clinical outcomes.