Cross regulation of TGSB/elf, B-catenin and vitamin D pathways in Gastrointestin

项目2.胃肠道癌症中TGFb/ELF、B-连环蛋白和维生素D通路的交叉调节。人肝细胞癌和胃癌的特点是钙粘附素/连环蛋白黏附和信号系统的改变。在某些情况下，这是由于P-连环蛋白的激活突变，而在另一些情况下，这是E-钙粘蛋白基因失活或突变的结果。伴随着这些基因变化的细胞信号和细胞黏附的变化可能有助于这些和其他前肠肿瘤的致癌潜力。TGFb/Smad信号缺陷在肝癌和肠道癌中也很常见。TGFb/Smad途径除了具有典型的作用外，还可以与B-catenin/Tcf转录机制相互作用，共同调节一些基因的转录。精灵[/-]和精灵[/-]/smacd4[-/-]小鼠的表型，其中TGFb信号的改变伴随着E-钙粘蛋白和B-连环蛋白的变化，这在人类疾病中首次将这两条途径联系在一起，并提供了关于人类前肠癌发生的潜在共同基础的重要线索。在我们的第一个目标中，我们将使用转基因动物模型、细胞系和外植体来研究B-连环蛋白信号在肝细胞癌、胃癌和胰腺癌中的作用，并确定其通过TGFb/Smad信号进行交叉调控的分子基础。我们将特别询问WNT/catenin信号和WNT/catenin调节基因FGFBP的激活是否对ELF[/-]、ELF[/-]/Smad4[-/-]和ELF[/-]/Smad3[/-]小鼠的肿瘤表型是必需的。在目标2中，我们将检验这一假设，即维生素D途径为肝癌和GC的治疗提供了潜在的预防和治疗选择。初步数据表明，WNT/B-连环蛋白/TCF通路是维生素D及其类似物防癌作用的关键中介。维生素D抑制B-连环蛋白信号转导，而B-连环蛋白激活VDR。Smads和B-catenin都能与维生素D受体(VDR)直接结合，增强其反式激活活性。维生素D及其类似物对包括肝细胞癌和胃癌在内的几种不同肿瘤类型的生长有很强的抑制作用，维生素D已经在治疗肝细胞癌的早期临床试验中。在目的2中，我们将在上述动物模型中检测维生素D和新开发的“B-连环蛋白特异性”维生素D类似物的活性，并利用体外VDR基因敲除和VDR转基因动物来检测维生素D受体的作用。一种涉及配体介导的VDR激活的治疗策略提供了潜在的好处，即在VDR激活的同时抑制B-连环蛋白信号并激活TGFb通路。这些数据将与120例冷冻肝细胞癌和配对对照组织中激活的B-连环蛋白的表达和TGFb/Smad信号改变的标志有关。这一带有病理、临床和结果数据注释的收集将提供一个前所未有的机会，将我们的转基因动物数据直接与人类材料进行比较。

Project 2. Cross regulation of TGFB/elf, B-catenin and vitamin D pathways in gastrointestinal cancers. Human hepatocellular carcinoma and gastric cancer are characterized by alterations in the cadherin/catenin adhesion and signaling system. In some situations this is a result of activating mutations in P-catenin and in others, inactivation or mutation of the E-cadherin gene. The alterations in cell signaling and cell adhesion that accompany these genetic changes likely contribute to the oncogenic potential of these and other foregut cancers. Defects in TGFB/smad signaling are also common in cancers of the liver and intestinal tract. In addition to its "canonical" effects the TGFB/smad pathway can also interact with the B-catenin/TCF transcriptional machinery and co-operatively regulate transcription of a number of genes. The phenotype of the elf[+/-] and elf[+/-]/smacd4[-/-]mice, in which altered TGFB signaling is accompanied by changes in E-cadherin and B-catenin links these two pathways for the first time in a human disease and provides important clues regarding a potential common basis for the development of human foregut cancers. In our first aim we will use transgenic animal models, cell lines and explants to investigate the role of B-catenin signaling in hepatocellular, gastric and pancreatic cancers and determine the molecular basis of its cross-regulation by TGFB/smad signaling. We will specifically ask if activation of wnt/catenin signaling and the wnt/catenin regulated gene FGFBP is required for the tumorigenic phenotype of the elf[+/-] and elf[+/-]/smad4[-/-] and elf[+/-] /smad3[+/-] mice. In aim 2 we will test the hypothesis that the vitamin D pathway provides a potential preventive and therapeutic option for the treatment of HCC and GC. Preliminary data demonstrates that the wnt/B-catenin/TCF pathway is a key intermediary in the cancer preventive action of vitamin D and its analogues. Vitamin D represses B-catenin signaling and B-catenin activates VDR. Both smads and B-catenin can bind directly to the vitamin D receptor (VDR) and potentiate its transactivation activity. Vitamin D and its analogues are potent repressers of the growth of several different tumor types including hepatocellular and gastric cancer and vitamin D is already in early clinical trials for the treatment of hepatocellular cancer. In aim 2 we will test the activity of vitamin D and of newly developed "B-catenin specific" vitamin D analogues in the animal models described above and use VDR knockdown in vitro and VDR transgenic animals to examine to role of the vitamin D receptor. A therapeutic strategy involving ligand-mediated activation of the VDR offers the potential benefit of repressing B-catenin signaling and activating the TGFB pathway at the same time as VDR is activated. These data will be linked to the expression of activated B-catenin and markers of altered TGFB/smad signaling in 120 frozen hepatocellular carcinomas and paired control tissues. This collection, annotated with pathological, clinical and outcome data will provide an unprecedented opportunity to compare our transgenic animal data directly with human material.