CELLULAR AND MOLECULAR MECHANISMS OF GASTROINTESTINAL CANCERS

前肠癌（肝细胞癌、胃癌和胰腺癌）是致命的，由于诊断较晚，缺乏可行的靶向治疗方法，以及从化生到不典型增生到癌的每个肿瘤发展阶段的分子谱不清楚，因此难以治疗。最近的研究支持TGF-B信号在抑制这些肿瘤中的关键作用，但其作用机制及其重要的具体阶段尚不清楚。Smad3/4接头蛋白ELF是TGF-B肿瘤抑制功能的强大效应物。我们之前发现，ELF的缺失会导致肝脏（HCC）和胃肠道（GI）癌症的急剧自发形成，到目前为止，在11%的人类HCC和胃癌细胞系中有15号外显子突变。Elf[+/-]和Elf[+/-] /Smad3[+/-]小鼠发生内脏肿大和多种Gl癌（70%的小鼠），包括自发性转移性胰腺、HCC、肠腺癌等。这种表型提供了令人信服的证据，证明elf[+/-]和elf[+/-]/Smad3[+/-]小鼠是遗传性人类癌症综合征Beckwith-Wiedemann （BWS）的模型。这些动物的肿瘤中存在高水平的细胞周期调节因子，包括CDK4、c-Myc、h-TERT、b -连环蛋白和E3连接酶PRAJA。该P01应用的总体假设是，TGF-B肿瘤抑制通路的破坏（通过ELF、Smad3和Smad4）导致细胞的增殖潜力，然后获得继发性事件，如wnt通路（b -连环蛋白）、细胞周期调节因子如CDK4、c-Myc、端粒酶、包括PRAJA等的E3连接酶的激活，导致胃肠道癌症。本研究建议：1)使用在特定通路（包括wnt、TGF-B、myc、端粒酶（TERT）、CDK4）中具有预定突变的动物模型来确定它们在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志物和靶向治疗方法。项目1，L. Mishra博士利用小鼠模型系统，计划找出tgf - β信号和细胞周期蛋白（CDK4）以及E3连接酶PRAJA之间的串音如何调节前肠肿瘤抑制，并确定ELF/Smads作为功能性新标志物在BWS和人类胃肠道（GI）癌症的检测和治疗反应中的潜在作用。项目2。S. Byers博士计划描述激活的b -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，这也将在项目1、3和4中使用。在项目3中，dr。R. Schlegel和B. Mishra计划确定ELF和Smad3在前肠癌症中对人类TERT和c- Myc的调节中的作用，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。项目4由E. P. Reddy博士负责，旨在通过转基因模型系统确定CDK4在前肠癌中的作用，并启动CDK4的小分子CDK抑制剂的开发，用于项目1、2和3。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)和行政核心(C)。这些核心将使所有研究项目的有效合作和成本节约成为可能。在这个项目下提出的研究应该为科学界提供更好地理解调节前肠癌发展的机制。值得注意的是，这个项目有望产生针对这些难以治疗的致命癌症的新疗法，然后将结果迅速转化为临床护理，在床边。

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.