Cellular Interations of TGS-B Pathyway Members and Regulators of Foregut Cancers

Smad3/4接头蛋白ELF通过其影响TGF-B肿瘤抑制功能的能力而成为肿瘤发生的有效调节剂。然而，迄今为止，TGF-B通路在胃肠道（Gl）肿瘤发展的特定阶段（如化生、不典型增生和癌）的作用仍然知之甚少，特别是与致癌途径的激活有关。我们之前发现，ELF的缺失会导致肝脏和胃肠道（Gl）癌症的急剧自发形成，到目前为止，在11%的人类Gl癌细胞系中，ELF外显子15的剪接位点发生突变。我们最近的一个令人惊讶和偶然的发现是，elf[+/-]和elf[+/-]/Smad3[+/-]小鼠（70%的小鼠）会自发地发生内脏肥大和多种Gl癌，包括转移性胰腺癌、肝细胞癌、肠腺癌等，为人类遗传性癌症综合征beckwithi - wiedemann综合征（BWS）的小鼠模型提供了令人信服的证据。此外，90%的elf'' /Smad4*/~小鼠发生胃癌，20%发生结肠腺瘤，elf在人胃癌和Dukes B1腺瘤中缺失表达，提示elf在早期人类胃肠道肿瘤的抑制中起作用。这些小鼠和人类Gl肿瘤的分子分析表明，细胞周期调节因子包括CDK4、cyclin D1和PRAJA以及ELF/Smad3特异性E3连接酶的水平明显高。有趣的是，SmadS最近被证明是一种CDK4底物，然而Smad3突变小鼠不会发生癌症。因此，激活的CDK4和PRAJA与具有或不具有Smad3的ELF相关，并且很可能通过抑制ELF/Smad3来发挥其致癌活性。我们的目标是：1。确定ELF、Smad3和CDK4之间的功能相互作用，以及丢失ELF、Smad3或Smad4对CDK4酶活性的影响，以测试项目4中的CDK4抑制剂、项目2中的维生素D类似物，以及开发针对CDK4 -ELF-Smad3相互作用的新疗法。2. 研究PRAJA对ELF和Smad3差异作用的分子基础，以产生针对PRAJA的新抑制剂。3. 检测ELF是否在BWS中发生突变，以及ELF缺失与PRAJA、CDK4、Smad3、Smad4、TBRII、TERT和c-Myc（后两者来自项目3）联合是否代表肝细胞癌、胃癌和胰腺癌早期肿瘤检测/治疗反应的新的特异性分子标志物。这项研究的结果有望产生重要的新疗法，并将是迈向基于这些致命肿瘤的功能分子特征的个体化癌症治疗目标的第一步。

The Smad3/4 adaptor protein ELF is emerging as a potent regulator of tumorigenesis by its ability to effect TGF-B tumor suppressor function. However, to date the role of the TGF-B pathway at specific stages in gastrointestinal (Gl) tumor development such as metaplasia, dysplasia and carcinoma remains poorly delineated, particularly in conjunction with activation of oncogenic pathways. We previously found that deletion of ELF results in a dramatic and spontaneous formation of liver and gastrointestinal (Gl) cancers, with a splice site mutation in elf exon 15 in 11% of human Gl cancer cell lines tested so far. A surprising and serendipitous recent discovery by us is that elf[+/-] and elf[+/-]/Smad3[+/-] mice develop visceromegaly and multiple Gl cancers (70% of mice), including metastatic pancreatic, hepatocellular, intestinal adenocarcinomas and others spontaneously, providing compelling evidence as a mouse model of Beckwith-Wiedemann syndrome (BWS), a hereditary human cancer syndrome. In addition, 90% of elf''' /Smad4*/~ mice develop gastric cancer, 20% develop colonic adenomas, and ELF expression is lost in human gastric cancer as well as Dukes B1 adenomas indicating a role for ELF in suppression of early human gastrointestinal cancer. Molecular profiling of the tumors in these mice and human Gl cancers demonstrate markedly high levels of cell cycle regulators that include CDK4, cyclin D1 and PRAJA an ELF/Smad3 specific E3 ligase. Interestingly, SmadS has recently been shown to be a CDK4 substrate, yet Smad3 mutant mice do not develop cancers. Thus, activated CDK4 and PRAJA associate with ELF with or without Smad3 and most likely exert their oncogenic activity through suppression of ELF/Smad3. Our AIMS are to: 1. Determine a functional interaction between ELF, Smad3, and CDK4, and the effect of loss elf, Smad3 or Smad4 on CDK4 enzyme activity, towards testing CDK4 inhibitors from project 4, Vitamin D analogs from project 2, as well as developing new therapeutics targeted allosterically at CDK4 -ELF-Smad3 interaction. 2. Investigate the molecular basis for the differential effects of PRAJA on ELF and Smad3 towards generating new inhibitors targeted at PRAJA. 3. Test whether ELF is mutated in BWS, and potentially whether loss of ELF in combination with PRAJA, CDK4, Smad3, Smad4,TBRII, TERT and c-Myc (the latter two from project 3) represent new specific molecular markers for early tumor detection/ treatment response of hepatocellular, gastric and pancreatic cancers. Results from this study promise to yield important new therapeutics and will be a first step toward the goal of individualized cancer treatment based on the functional molecular characteristics of these lethal tumors.