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

项目2.胃肠道肿瘤中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征在于钙粘蛋白/连环蛋白粘附和信号系统的改变。在某些情况下，这是P-连环蛋白激活突变的结果，在其他情况下，E-钙粘蛋白基因失活或突变。伴随这些遗传变化的细胞信号传导和细胞粘附的改变可能有助于这些和其他前肠癌的致癌潜力。TGFB/smad信号传导的缺陷在肝癌和肠道癌中也很常见。除了其“典型”作用之外，TGFB/smad途径还可以与B-连环蛋白/TCF转录机制相互作用，并协同调节许多基因的转录。elf[+/-]和elf[+/-]/smacd 4 [-/-]小鼠的表型，其中改变的TGFB信号传导伴随着E-钙粘蛋白和B-连环蛋白的变化，这是人类疾病中第一次将这两种途径联系起来，并提供了关于人类前肠癌发展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信号交叉调节的分子基础。我们将特别询问wnt/连环蛋白信号传导和wnt/连环蛋白调节基因FGFBP的激活是否是elf[+/-]和elf[+/-]/smad 4 [-/-]和elf[+/-] /smad 3 [+/-]小鼠的致瘤表型所必需的。在目标2中，我们将检验维生素D途径为治疗HCC和GC提供潜在预防和治疗选择的假设。初步数据表明，wnt/B-catenin/TCF途径是维生素D及其类似物预防癌症作用的关键中介。维生素D抑制B-连环蛋白信号传导，B-连环蛋白激活VDR。Smads和B-连环蛋白都可以直接与维生素D受体（VDR）结合，并增强其反式激活活性。维生素D及其类似物是几种不同肿瘤类型（包括肝细胞癌和胃癌）生长的有效抑制剂，维生素D已经在治疗肝细胞癌的早期临床试验中。在目标2中，我们将在上述动物模型中测试维生素D和新开发的“B-连环蛋白特异性”维生素D类似物的活性，并使用VDR体外敲低和VDR转基因动物来检查维生素D受体的作用。涉及配体介导的VDR激活的治疗策略提供了在VDR激活的同时抑制B-连环蛋白信号传导和激活TGFB通路的潜在益处。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-连环蛋白和改变的TGFB/smad信号传导标志物的表达相关。这些收集的资料，加上病理、临床和结果数据的注释，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.