Mechanisms of RelA Activation in Cancer

描述（由申请人提供）：胰腺腺癌是美国成人癌症死亡的第四大原因。5年生存率维持在1-3%，诊断后的中位生存期不到6个月。在诊断时，大多数胰腺癌患者表现为局部晚期或转移性疾病。胰腺癌的特点是预后差，对常规治疗缺乏反应。因此，胰腺癌是癌症研究中最大的挑战之一。基于这种疾病中最常检测到的突变，胰腺癌的基因谱正在出现。例如，K-ras的突变激活是胰腺癌发生的早期事件，已在80-95%的胰腺癌中检测到；p16/Ink4a/Arf和p53肿瘤抑制基因失活可以在大约50-75%的胰腺癌中被发现。然而，我们对这种基因改变如何影响胰腺癌的发生和进展的理解仍然存在重大差距。例如，尽管NF-？在近70%的人胰腺癌组织和大多数胰腺癌细胞系中，B被组成性激活，目前尚不清楚组成性NF-？体内胰腺细胞的致瘤性转化或进展为转移性胰腺癌需要B活化，胰腺癌的分子发病机制是否可以通过NF-？基因工程小鼠模型中B组成激活与其他特征突变的结合。自分泌刺激促炎细胞因子IL-1激活NF-？B在胰腺癌细胞系中的表达，进而诱导IL-1， I?B？及其下游靶基因对炎症反应、血管生成、细胞凋亡、肿瘤发生和转移至关重要。然而，目前尚不清楚NF-？B激活最初被触发。因此，本构性NF-？在体内诱导B活化也有待进一步研究。转化生长因子-？激活激酶1 （TAK1）在胰腺癌细胞系和标本中过表达。我们的初步数据显示TAK1shRNA完全抑制构成性NF-？胰腺癌细胞中B的活化。然而，TAK1过表达诱导NF-？B活化仍然是一个正在进行的研究领域。我们研究的长期目标是通过建立具有胰腺癌特征分子和遗传改变的小鼠模型来概括该疾病的分子发病机制，并阐明TAK1过表达介导的NF-？B激活。基于我们的初步结果，我们假设TAK1的过表达诱导了本构性NF-？B活性和NF-？b介导的促炎反应，进而促进胰腺癌的发展。为了验证我们的相关假设，我们提出了三个具体目标：(1)确定ikk2介导的NF-？在KrasG12D和KrasG12D/p16/Ink4a复合突变小鼠中，使用胰腺特异性IKK2敲除方法激活B在胰腺癌发展中的作用；(2)测定本构NF-？B活性在诱导胰腺癌K-rasG12D I?B?m？B条件突变小鼠，其中NF-？B是通过敲入突变的？I中的B增强子？启动子抑制I?B？介导的NF- B负反馈调节；(3)利用永生化胰腺导管上皮细胞和组织特异性转基因小鼠，确定TAK1过表达是否促进k - rasg12d诱导的肿瘤发生，并阐明TAK1过表达诱导NF-？B激活。我们提出的研究结果将为MAP3K激活在诱导炎症反应和胰腺癌中的调控提供见解。最重要的是，这项研究可能会发现新的分子靶点，以改善胰腺癌的治疗。

DESCRIPTION (provided by applicant): Pancreatic adenocarcinoma is the fourth leading cause of adult cancer mortality in the United States. The five-year survival rate continues at 1-3% and the median survival after diagnosis is less than six months. At the time of diagnosis, most pancreatic cancer patients present with locally advanced or metastatic disease. Pancreatic cancer is characterized by poor prognosis and lack of response to conventional therapy. Hence, pancreatic cancer poses one of the greatest challenges in cancer research. A genetic profile for pancreatic cancer is emerging based on the most frequently detected mutations in this disease. For example, the mutational activation of K-ras is an early event in pancreatic carcinogenesis and has been detected in 80-95% of pancreatic cancers; and inactivation of p16/Ink4a/Arf and p53 tumor suppressor genes can be identified approximately 50-75% of pancreas cancers. However, significant gaps still exist in our understanding of how such genetic alterations affect pancreatic cancer development and progression. For example, although NF-?B is constitutively activated in nearly 70% human pancreatic cancer tissues and most pancreatic cancer cell lines, it is still unclear whether constitutive NF-?B activation is required for tumorigenic transformation of pancreatic cells or progression to metastatic pancreatic cancer in vivo, and whether the molecular pathogenesis of pancreatic cancer can be recapitulated by NF-?B constitutive activation in combination with other signature mutations in genetic engineered mouse models. Autocrine stimulation of pro-inflammatory cytokine IL-1 activates NF-?B in pancreatic cancer cell lines, which in turn induces expression of IL-1, I?B? and its downstream target genes that are essential for inflammatory responses, angiogenesis, apoptosis, tumorigenesis, and metastasis. However, it is unclear how constitutive NF-?B activation is initially triggered. Thus, the underlying mechanisms by which constitutive NF-?B activation is induced in vivo also remain to be further investigated. Transforming growth factor-? activating kinase 1 (TAK1) is overexpressed in pancreatic cancer cell lines and specimens. Our preliminary data show that TAK1shRNA completely inhibited constitutive NF-?B activation in pancreatic cancer cells. However, the underlying molecular mechanism of TAK1 overexpression-induced NF-?B activation still remains an area of ongoing study. The long-term goal of our research is to recapitulate the molecular pathogenesis of this disease by establishing mouse models with signature molecular and genetic alterations found in pancreatic cancer, and elucidate the mechanisms for TAK1 overexpression-mediated NF-?B activation. Based on our preliminary results, we hypothesize that overexpression of TAK1 induces constitutive NF-?B activity and NF-?B-mediated pro-inflammatory responses, which in turn promotes development of pancreatic cancer. To test our related hypotheses, three specific aims were proposed: (1) Determine the role of IKK2-mediated NF-?B activation in the development of pancreatic cancer using pancreatic specific IKK2 knockout approach in KrasG12D and KrasG12D/p16/Ink4a compound mutant mice; (2) Determine the function of constitutive NF-?B activity in induction of pancreatic cancer in K-rasG12D I?B?m?Bm?B conditional mutant mice, in which NF-?B is constitutively activated by knocking in mutated ?B enhancer in I?B? promoter to inhibit the I?B?-mediated negative feedback regulation of NF-?B; (3) Determine whether TAK1 overexpression promotes K-rasG12D-induced tumorigenesis using immortalized pancreatic ductal epithelial cells and tissue-specific transgenic mice and elucidate the mechanisms by which TAK1 overexpression induced NF-?B activation. The findings from our proposed study will provide an insight into the regulation of MAP3K activation in induction of inflammatory responses and pancreatic cancer. Most importantly, this study may discover novel molecular targets for improving the treatment for pancreatic cancer.