Surgical Studies on the Role on Gastrin-releasing Peptide in Neuroblastoma

 描述(申请人提供)：神经母细胞瘤(NB)仍然是最难治疗的儿科癌症之一，因为近三分之二的患者在诊断时存在转移。尽管采取了积极的治疗方案，但18个月以上儿童的高危NB4期肿瘤和/或MYCN扩增，总体存活率只有50%，令人沮丧。对于肿瘤的难治性和疾病复发，人们对肿瘤生物学的全面理解存在很大差距，因此，阐明导致肿瘤侵袭性行为的信号机制对于开发新的靶向临床治疗方法具有重要意义。G蛋白偶联受体超家族的成员代表着药物开发活动的中枢，占所有靶向治疗的40%。我们的实验室先前已经证明，靶向其中一个GPCR，胃泌素释放肽受体(GRP-R)及其配体GRP通过调节关键的细胞生存途径-磷脂酰肌醇3-激酶(PI3K)/AKT途径来抑制NB的致瘤性。在之前的资助期间(见进展报告)，我们报道了GRP-R信号调节NB转移，特别是通过激活AKT2和下调AKT的内源性负调控因子PTEN。GRP-R信号和特定的AKT亚型AKT2在NB从组织侵袭到远处器官转移的多步骤进展中的确切作用尚不清楚。靶向PI3K/AKT2，以及AKT下游的mTOR，Axis可能是一种潜在的策略，因为这一途径调节肿瘤血管和微环境(TME)。在这一竞争性更新应用中，我们计划确定GRP-R/AKT2轴调节启动转移细胞的形成和维持以及它们向远处器官扩散的确切机制，并促进转移灶的建立。因此，这一建议的中心假设是，通过AKT2的GRP/GRP-R信号调节对传统疗法的抵抗和转移灶的形成，从而暗示该轴在NB难治性和疾病复发中发挥关键作用。为了验证这一假设，我们提出了以下三个具体目标：1)确定GRP-R/AKT2信号在诱导对传统疗法的耐药性和肿瘤进展中的作用。2)确定AKT2在介导GRP/GRP-R在难治性和/或转移性NB中的致癌作用中的作用。3)确定靶向GRP-R/AKT2治疗难治性和/或转移性神经母细胞瘤的临床前疗效。我们的目标的成功完成将对GRP/GRP-R介导的NB难治和疾病复发的机制产生重要的新知识，包括肿瘤干细胞在转移中的作用以及肿瘤细胞的渗出及其与TME的相互作用。提出的目标具有直接的翻译相关性，因为它们解决了对传统疗法和TME耐药的一个重要分子机制。最后，临床前研究将进一步提供有关 针对强毒“高危”新药的安全性和有效性。

 DESCRIPTION (provided by applicant): Neuroblastoma (NB) remains one of the most difficult pediatric cancers to treat, as nearly two-thirds of the patients present with metastasis at the tim of diagnosis. Despite aggressive treatment protocols, `high-risk' NB, stage 4 tumors in children older than 18 months of age and/or MYCN amplification, have dismal overall survival of only 50%. There is a significant gap in the comprehensive understanding of the tumor biology for tumor refractoriness and disease relapse, and therefore, elucidation of signaling mechanisms responsible for the aggressive tumor behavior would be highly significant for development of novel targeted clinical therapies. Members of the G-protein coupled receptor (GPCR) superfamily represent the hub of drug development activities and accounts for 40% of all targeted therapies. Our laboratory has previously shown that targeting one such GPCR, gastrin-releasing peptide receptor (GRP-R) and its ligand GRP inhibited NB tumorigenicity via regulation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, a key cell survival pathway. During the previous funding period (see Progress Report), we reported that the GRP-R signaling regulates NB metastasis, specifically through activation of AKT2, and downregulation of PTEN, an endogenous negative regulator of AKT. The exact role of the GRP-R signaling and specific AKT isoform, AKT2, in the multi-step NB progression from tissue invasion to distant organ metastasis is yet to be elucidated. Targeting PI3K/AKT2, as well as mTOR, downstream of AKT, axis may be a potential strategy as this pathway regulates tumor vasculature and microenvironment (TME). In this competitive renewal application, we plan to determine the exact mechanisms by which GRP-R/AKT2 axis regulates the formation and maintenance of metastasis-initiating cells and their dissemination to distant organs and facilitate establishment of metastatic lesions. Hence, the central hypothesis of this proposal is that GRP/GRP-R signaling via AKT2 regulates resistance to conventional therapies and formation of metastatic foci, thereby, implicating a critical role for this axis in NB refractoriness and disease relapse. o examine this hypothesis, we propose the following three Specific Aims: 1) Determine the role of GRP-R/AKT2 signaling in inducing resistance to conventional therapies and tumor progression. 2) Determine the role of AKT2 in mediating the oncogenic effects of GRP/GRP-R in refractory and/or metastatic NB. 3) Determine the preclinical efficacy of targeting GRP-R/AKT2 in refractory and/or metastatic NB. Successful completion of our Aims will yield significant new knowledge regarding the mechanisms of GRP/GRP-R mediated NB refractoriness and disease relapse, including the role of cancer stem cell in metastasis as well as the extravasation of tumor cells and their interactions with TME. The aims proposed have direct translational relevance as they address an important molecular mechanism of resistance to conventional therapies and the TME. Finally, preclinical study will further provide important information on the safety and efficacy of novel therapeutics against virulent `high-risk' NB.