Gene Amplification and Overexpression at 17q in Gastric Cancer: Darpp-32

描述（由申请人提供）：胃癌（GC）是全球第二大癌症相关死亡原因。此外，最近在美国以及许多其他西方人群中，胃食管交界区近端（GEJ）和食管腺癌的发病率急剧增加。驱动胃肿瘤发生的关键分子改变在很大程度上仍未被描述。总的相对5年生存率目前低于20%。改善我们目前有限的诊断、预防和治疗胃癌的方法是目前一个紧迫的问题。在之前的资助期内，我们已经成功完成了所有最初的目标，并系统地表征了胃癌染色体17q扩增子。我们首次克隆并鉴定了多巴胺和camp调节的神经元磷酸化蛋白32 kDa （DARPP-32）和一种新的转录剪接变体，该变体编码截断的蛋白异构体，我们将其命名为t-DARPP，作为具有强抗凋亡和耐药特性的新型癌症基因。DARPP-32和t-DARPP mrna和蛋白在超过三分之二的GCs中过表达，因此成为这些肿瘤中普遍存在的分子变化。在这项提案中，我们计划继续我们的工作，并表征DARPP-32和t-DARPP蛋白在调节胃肿瘤发生和促生存途径中的体外和体内作用。根据我们的初步数据，我们假设DARPP-32蛋白的过表达是胃肿瘤发生过程中的一个重要分子机制。在本研究中，我们将探讨DARPP-32和t-DARPP在GCs中的临床、分子和病理生物学作用。在这一提议中，我们将在包含300多个肿瘤样本的组织微阵列上分析DARPP-32蛋白与其他调节癌细胞存活的蛋白（pAkt和PTEN）的表达。我们将研究DARPP-32和t-DARPP调控PTEN-PI3K/AKT信号通路的机制。在GCs中，DARPP-32/t-DARPP调控PI3K存活通路的作用是一种新的、以前未被探索的机制。我们还将探讨DARPP-32/t-DARPP在调节BCL-2家族蛋白中促凋亡和促存活成员之间平衡中的作用。利用先进的蛋白质组学方法，我们计划确定DARPP-32和t-DARPP蛋白在癌症中的下游信号靶点。这一步有望揭示GC中由这些蛋白调控的新的分子信号通路。为了在体内研究t-DARPP在胃肿瘤发生中的作用，我们将建立一种利用TFF1启动子驱动t-DARPP在腺胃中的表达的转基因小鼠模型。我们期望这项研究的完成将为胃腺癌患者的临床治疗提供重要的临床、分子和病理生物学信息。公共卫生相关性：本建议将体外和体内实验联系起来，以表征Darpp-32蛋白在胃癌发生中的作用。我们计划研究Darpp-32蛋白在PI3K/Akt存活通路中的作用。使用最先进的蛋白质组学方法，我们期望揭示癌症中这些蛋白质的新信号分子和途径。

DESCRIPTION (provided by applicant): Gastric carcinoma (GC) is the second most common cause of cancer-related death worldwide. Moreover, a sharp increase in incidence of proximal Gastroesophageal Junctional (GEJ) and esophageal adenocarcinomas was recently noted in the United States as well as many other Western populations. The critical molecular alterations that drive gastric tumorigenesis remain largely uncharacterized. Overall relative 5- year survival rates are currently less than 20%. Improvement in our presently limited diagnostic, preventive, and therapeutic approach to gastric cancer is currently a pressing issue. During the previous funding period, we have successfully completed all original aims and systematically characterized the chromosome 17q amplicon in gastric cancer. We have cloned and identified, for the first time, Dopamine- and cAMP-regulated neuronal phosphoprotein 32 kDa (DARPP-32) and a novel transcriptional splice variant that encodes a truncated protein isoform that we named t-DARPP as novel cancer genes with potent anti-apoptotic and drug resistance properties. DARPP-32 and t-DARPP mRNAs and proteins are overexpressed in more than two- thirds of GCs, thus becoming prevalent molecular changes in these tumors. In this proposal, we plan to continue our work and characterize the in vitro and in vivo role(s) of DARPP-32 and t-DARPP proteins in modulation of gastric tumorigenesis and pro-survival pathways. We hypothesize, based on our preliminary data, that over-expression of DARPP-32 proteins is an important molecular mechanism during gastric tumorigenesis. In this proposal, we will investigate the clinical, molecular, and pathobiological roles of DARPP-32 and t-DARPP in GCs. In this proposal, we will analyze, on tissue microarrays that contain more than 300 tumor samples, the expression of DARPP-32 proteins with other proteins (pAkt and PTEN) that regulate cancer cell survival. We will investigate the mechanism(s) by which DARPP-32 and t-DARPP regulate the PTEN-PI3K/AKT signaling pathway. The role of DARPP-32/t-DARPP in modulation of PI3K survival pathway is a novel and a previously unexplored mechanism in GCs. We will also explore the role of DARPP-32/t-DARPP in regulating the balance between the pro-apoptotic and pro-survival members of the BCL-2 family proteins. Using advanced proteomic approaches, we plan to identify downstream signaling targets of DARPP-32 and t-DARPP proteins in cancer. This step is expected to reveal novel molecular signaling pathways that are regulated by these proteins in GC. In order to study the role of t-DARPP in gastric tumorigeneses in vivo, we will develop a transgenic mouse model using the TFF1 promoter to drive the t-DARPP expression in the glandular stomach. We expect that completion of this proposal will provide important clinical, molecular, and pathobiological information that have significant impact on the clinical management of patients with adenocarcinomas of the stomach. PUBLIC HEALTH RELEVANCE: This proposal connects in vitro and in vivo experiments in order to characterize the role(s) of Darpp-32 proteins in gastric carcinogenesis. We plan to investigate the contribution of Darpp-32 proteins to PI3K/Akt survival pathway. Using state-of-the-art proteomics approaches, we expect to reveal novel signaling molecules and pathways for these proteins in cancer.