CELLULAR AND MOLECULAR MECHANISMS OF GASTROINTESTINAL CANCERS

前肠的癌症（肝细胞癌、胃癌和胰腺癌）是致命的，并且由于诊断晚、几乎没有可行的靶向治疗以及肿瘤发展的每个阶段（从化生到异型增生到癌）的分子谱不清楚而难以治疗。最近的研究支持TGF-β信号在抑制这些肿瘤中的关键作用，但其作用机制和重要的具体阶段仍不清楚。Smad 3/4衔接蛋白ELF是TGF-β肿瘤抑制功能的强大效应子。我们以前发现，ELF的缺失导致肝脏（HCC）和胃肠道（GI）癌症的戏剧性和自发形成，迄今为止，在11%的人HCC和胃癌细胞系中检测到外显子15突变。Elf[+/-]和elf[+/-]/Smad 3 [+/-]小鼠自发地发展内脏肿大和多种GI癌（70%的小鼠），包括转移性胰腺癌、HCC、肠腺癌和其他。这种表型提供了令人信服的证据，证明elf[+/-]和elf[+/-]/Smad 3 [+/-]小鼠是遗传性人类癌症综合征Beckwith-Wiedemann（BWS）的模型。高水平的细胞周期调节剂，包括CDK 4，c-Myc，h-TERT，B-连环蛋白和E3连接酶PRAJA出现在这些动物的肿瘤中。该P01申请的总体假设是TGF-B肿瘤抑制剂途径（通过ELF、Smad 3和Smad 4）的破坏导致细胞中的增殖潜力，然后获得次级事件，例如包括wnt途径（B-连环蛋白）、细胞周期调节剂如CDK 4、c-Myc、端粒酶、包括PRAJA的E3连接酶等的途径的激活，导致胃肠癌。该PO 1建议1）使用在特定途径中具有预定突变的动物模型，包括wnt，TGF-B，myc，端粒酶（TERT），CDK 4，以确定它们在BWS和前肠癌形成中的作用; 2）开发针对这些致命人类癌症的标记物和靶向治疗。一号工程，L博士。Mishra利用小鼠模型系统，计划找出TGF-β信号传导和细胞周期蛋白（CDK 4）与E3连接酶PRAJA之间的串扰如何调节前肠肿瘤抑制，并确定ELF/Smads作为BWS和人类胃肠道（GI）癌症检测和治疗反应的功能性新标志物的潜在作用。项目2. Dr. S. Byers计划描述活化β-连环蛋白/TCF在上述小鼠模型系统中的作用，并开发一种用维生素D类似物治疗人类癌症的治疗策略，该策略也将用于项目1、3和4。在项目3中，R.施莱格尔和B。Mishra计划确定ELF和Smad 3在前肠癌症中调节人类TERT和c-Myc的作用，并将这些研究与项目1、2和4一起转化为人类标志物和治疗策略。第四章E博士P. Reddy，旨在用转基因模型系统确定CDK 4在前肠癌中的作用，并启动CDK 4的小分子CDK抑制剂的开发，用于将在项目1、2和3中使用的治疗。该计划将由三个核心提供后勤支持：动物核心（A）、细胞和组织核心（B）以及管理核心（C）。这些核心将实现所有研究项目所必需的高效合作和成本节约。本计划项目下提出的研究应使科学界更好地了解调节前肠癌发展的机制。值得注意的是，该计划有望在实验室针对这些难以治疗的致命癌症产生新的疗法，然后将结果迅速转化为临床护理。

Cancers of the foregut (hepatocellular, gastric and pancreatic) are lethal and difficult to treat due to late diagnosis, few viable targeted therapeutics and unclear molecular profiling of each stage of tumon development, from metaplasia to dysplasia to carcinoma. Recent studies support a key role for TGF-B signaling in suppressing these tumors, yet its mechanism of action and the specific stages at which it is important remain unclear. The Smad3/4 adaptor protein ELF is a powerful effector of TGF-B tumor suppressor function. We previously found that deletion of ELF results in a dramatic and spontaneous formation of liver (HCC) and gastrointestinal (GI) cancers, with exon 15 mutations in 11% of human HCC and gastric cancer cell lines tested so far. Elf[+/-] and elf[+/-]/Smad3[+/-] mice develop visceromegaly and multiple Gl cancers (70% of mice), including metastatic pancreatic, HCC, intestinal adenocarcinomas and others spontaneously. This phenotype provides compelling evidence that elf[+/-] and elf[+/-]/Smad3[+/-] mice are a model of the hereditary human cancer syndrome, Beckwith-Wiedemann (BWS). High levels of cell cycle regulators including CDK4, c-Myc, h-TERT, B-catenin, and the E3 ligase PRAJA occur in tumors in these animals. The overall hypothesis of this P01 application, is that disruption of the TGF-B tumor suppressor pathway (through ELF, Smad3 and Smad4) leads to a proliferative potential in cells that then acquire secondary events such as activation of pathways that include the wnt pathway (B-catenin), cell cycle regulators such as CDK4, c-Myc, telomerase, E3 ligases that include PRAJA and others, resulting in gastrointestinal cancers. This PO1 proposes to 1) Use animal models that have predetermined mutations in specific pathways that include wnt, TGF-B, myc, telomerase (TERT), CDK4 to determine their role in BWS and foregut cancer formation; 2) Develop markers and targeted therapeutics to these lethal human cancers. Project 1, Dr. L. Mishra, utilizing a mouse model system, plans to find out how cross talk between TGF-beta signaling and cell cycle proteins (CDK4) and the E3 ligase PRAJA modulate foregut tumor suppression and to determine the potential role of ELF/Smads as functional new markers for the detection and treatment response of BWS and human gastrointestinal (GI) cancers. Project 2. Dr. S. Byers plans to characterize the role of activated (B-catenin/TCF in the mouse model systems above, and develop a therapeutics strategy to human cancers with Vitamin D analogs which will also be utilized in Project 1, 3 and 4. In Project 3, Drs. R. Schlegel and B. Mishra, plan to determine the role of ELF and Smad3 in modulation of human TERT and c- Myc in cancers of the foregut, and translate these studies with Projects 1, 2 and 4 in terms of human markers and treatment strategies. Project 4 by Dr. E. P. Reddy, aims to determine the role of CDK4 in foregut cancers with transgenic model systems and initiate the development of small-molecule CDK inhibitors of CDK4 for therapy that will be utilized in Projects 1, 2 and 3. The program will be logistically supported by three cores: an Animal Core (A), a Cell and Tissue Core (B), and an Administrative Core (C). The cores will enable efficient cooperation and cost savings essential for all the research projects. The studies proposed under this Program Project should provide the scientific community with a better understanding of the mechanisms that regulate foregut cancer development. Significantly, this program promises to yield new therapies targeted at these difficult-to-treat lethal cancers at the bench, and then to translate the results rapidly into clinical care, at the bedside.