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

描述(申请人提供)：胃癌(GC)是全球癌症相关死亡的第二大常见原因。此外，最近在美国和许多其他西方人口中，近端胃食道交界处(GEJ)和食管腺癌的发病率急剧上升。驱动胃肿瘤发生的关键分子改变在很大程度上仍未确定。总体相对5年存活率目前不到20%。改善我们目前有限的胃癌诊断、预防和治疗方法是目前一个紧迫的问题。在之前的资助期间，我们成功地完成了所有最初的目标，并系统地表征了胃癌的染色体17q扩增子。我们首次克隆并鉴定了多巴胺和cAMP调节的神经元磷酸蛋白32 kDa(DARPP-32)和一个新的转录剪接变异体，它编码一个截短的蛋白质异构体，我们将其命名为t-DARPP作为新的癌症基因，具有强大的抗凋亡和耐药特性。DARPP-32和t-DARPP的mRNAs和蛋白在超过三分之二的GC中过表达，从而成为这些肿瘤中普遍存在的分子变化。在这个提案中，我们计划继续我们的工作，并在体外和体内表征DARPP-32和t-DARPP蛋白在调节胃肿瘤发生和促进生存途径中的作用(S)。根据我们的初步数据，我们推测，DARPP-32蛋白的过度表达是胃肿瘤发生过程中的一个重要分子机制。在这个方案中，我们将研究DARPP-32和t-DARPP在GCs中的临床、分子和病理生物学作用。在这项提案中，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生存的蛋白质(PACT和PTEN)的表达。我们将探讨DARPP-32和t-DARPP调控PTEN-PI3K/AKT信号通路的机制(S)。DARPP-32/t-DARPP在PI3K生存通路调控中的作用是GCs中一种新的、未知的机制。我们还将探索DARPP-32/t-DARPP在调节bcl2家族蛋白中促凋亡和促生存成员之间的平衡中的作用。利用先进的蛋白质组学方法，我们计划在癌症中识别DARPP-32和t-DARPP蛋白的下游信号靶点。这一步骤有望揭示GC中受这些蛋白质调控的新的分子信号通路。为了研究t-DARPP在体内胃肿瘤发生中的作用，我们利用TFF1启动子驱动t-DARPP在腺胃的表达，建立了转基因小鼠模型。我们希望这项提案的完成将提供重要的临床、分子和病理生物学信息，对胃腺癌患者的临床治疗具有重大影响。公共卫生相关性：这项建议连接了体外和体内实验，以表征DARPP-32蛋白在胃癌发生中的作用(S)。我们计划研究DARPP-32蛋白在PI3K/Akt生存通路中的作用。利用最先进的蛋白质组学方法，我们希望揭示这些蛋白质在癌症中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.