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

Smad 3/4衔接蛋白ELF通过其影响TGF-β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途径在胃肠道（GI）肿瘤发展的特定阶段（例如化生、异型增生和癌）的作用仍然不清楚，特别是与致癌途径的激活有关。我们先前发现，ELF的缺失导致肝脏和胃肠道（GI）癌的显著和自发形成，到目前为止，在测试的11%的人GI癌细胞系中，elf外显子15中存在剪接位点突变。我们最近的一个令人惊讶和偶然的发现是，elf[+/-]和elf[+/-]/Smad 3 [+/-]小鼠自发地发展内脏肿大和多种GI癌症（70%的小鼠），包括转移性胰腺癌、肝细胞癌、肠腺癌和其他癌症，提供了令人信服的证据作为Beckwith-Wiedemann综合征（BWS）（一种遗传性人类癌症综合征）的小鼠模型。此外，90%的elf-/-/Smad 4 +/-小鼠发展胃癌，20%发展结肠腺瘤，并且ELF表达在人胃癌以及Dukes B1腺瘤中丧失，表明ELF在抑制早期人胃肠癌中的作用。这些小鼠和人G1癌中肿瘤的分子谱显示显著高水平的细胞周期调节剂，包括CDK 4、细胞周期蛋白D1和PRAJA（ELF/Smad 3特异性E3连接酶）。有趣的是，SmadS最近被证明是CDK 4底物，但Smad 3突变小鼠不会发生癌症。因此，活化的CDK 4和PRAJA与有或没有Smad 3的ELF相关，并且最有可能通过抑制ELF/Smad 3来发挥其致癌活性。我们的目标是：1。确定ELF、Smad 3和CDK 4之间的功能性相互作用，以及elf、Smad 3或Smad 4缺失对CDK 4酶活性的影响，以测试项目4的CDK 4抑制剂，项目2的维生素D类似物，以及开发以CDK 4-ELF-Smad 3相互作用为变构靶向的新疗法。2.研究PRAJA对ELF和Smad 3产生不同作用的分子基础，以产生靶向PRAJA的新抑制剂。3.测试ELF是否在BWS中突变，以及ELF的缺失与PRAJA、CDK 4、Smad 3、Smad 4、TBRII、TERT和c-Myc（项目3的后两项）的组合是否可能代表肝细胞癌、胃癌和胰腺癌早期肿瘤检测/治疗反应的新特异性分子标志物。这项研究的结果有望产生重要的新疗法，并将成为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.