Role of Nix in pancreatic ductal adenocarcinoma

 描述（由申请人提供）：胰腺癌是美国癌症相关死亡的第四大原因，并且仍然是一种很难治疗的疾病。几乎所有胰腺导管腺癌（PDAC）病例的特征都是Kras基因的激活突变。迄今为止，在PDAC中药理学抑制Kras及其下游信号传导效应物的尝试尚未成功。癌细胞代谢已成为靶向治疗发展的新领域。通过激活各种信号通路，致癌Kras诱导代谢转化，使胰腺癌细胞更依赖于糖酵解，而不太依赖于基于胰蛋白酶的代谢。这项研究的重点是Nix，这是一种参与线粒体维持和周转的蛋白质，可能是Kras突变细胞中代谢转化的原因。我们的初步研究表明，在小鼠胰腺肿瘤中，Nix在RNA和蛋白质水平上上调。此外，Nix或Kras的消融导致线粒体数量的减少和Kras突变型癌细胞的增殖能力的降低，但Kras野生型癌细胞则不然。这些结果表明，Nix可能是治疗Kras突变胰腺癌的合法药物靶标。该研究将使用基因工程小鼠模型和新型胰腺导管类器官培养系统进一步阐明Nix在胰腺癌中的作用。首先，我们将使用类器官系统评估Nix消融的代谢后果。对于第一次在体外，该系统将使我们能够比较正常的，前肿瘤和肿瘤胰腺细胞表达或缺乏Nix的代谢表型。第二，我们将确定Nix在胰腺肿瘤的启动和维持中的作用，使用基因工程小鼠模型和原位移植的类器官小鼠模型（分别）。我们将表达条件性Nix等位基因的小鼠杂交到我们的“KPC”小鼠模型中，以研究Nix对胰腺肿瘤发生的影响，所述“KPC”小鼠模型的特征在于突变型Kras和突变型p53的胰腺特异性表达。为了研究PDAC的维持，我们将用靶向Nix的诱导型短发夹RNA（shRNA）感染的类器官移植到野生型小鼠的胰腺中。这些shRNA将在体内肿瘤形成后诱导，以评估Nix敲低对肿瘤维持的影响。这些研究的结果不仅将验证Nix作为胰腺癌合适药物靶点的合法性，而且还将阐明Nix在胰腺癌代谢转化中的作用，以更好地理解这一治疗靶点。

 DESCRIPTION (provided by applicant): Pancreatic cancer is the fourth-leading cause of cancer-related death in the U.S. and remains a largely intractable disease. Nearly all cases of pancreatic ductal adenocarcinoma(PDAC) are characterized by activating mutations in the Kras gene. Attempts at pharmacological inhibition of Kras and its downstream signaling effectors in PDAC have so far been unsuccessful. Cancer cell metabolism has become a new area of interest for the development of targeted therapies. Through activation of various signaling pathways, oncogenic Kras induces a metabolic transformation that makes pancreatic cancer cells more reliant on glycolysis and less reliant on mitochondria-based metabolism. The proposed study focuses on Nix, a protein involved in mitochondrial maintenance and turnover, which might be responsible for the metabolic transformation seen in Kras-mutant cells. Our preliminary studies show that Nix is upregulated at the RNA and protein levels in murine pancreatic tumors. Additionally, ablation of Nix or Kras leads to a decrease in the number of mitochondria and the proliferative capacity of Kras-mutant, but not Kras wild-type, cancer cells. These results suggest the exciting possibility that Nix might be a legitimate drug target for the treatment of Kras-mutant pancreatic cancer. The proposed study will further elucidate the role of Nix in pancreatic cancer using genetically engineered mouse models and a novel pancreatic ductal organoid culture system. First, we will evaluate the metabolic consequences of Nix ablation using the organoid system. For the first time in vitro, this system will allow us to compare the metabolic phenotype of normal, pre-neoplastic and neoplastic pancreatic cells expressing or lacking Nix. Second, we will determine the role of Nix in pancreatic tumor intiation and maintenance using genetically engineered mouse models and an orthotopically transplanted organoid mouse model (respectively). We have crossed mice expressing a conditional Nix allele into our "KPC" mouse model, characterized by pancreas- specific expression of mutant Kras and mutant p53, to study the effects of Nix on pancreatic tumorigenesis. To study PDAC maintenance, we will transplant organoids infected with inducible short hairpin RNAs (shRNAs) targeting Nix into the pancreata of wildtype mice. These shRNAs will be induced after tumor formation in vivo to assess the effects of Nix knockdown on tumor maintenance. Results from these studies will not only validate the legitimacy of Nix as a suitable drug target for pancreatic cancer, but will also elucidate the role of Nix in the metaboli transformation of pancreatic cancer to provide a better understanding of this therapeutic target.