The Role of N-cadherin in Tumor Progresion

描述（申请人提供）：摘要癌症转移是一个复杂的多步骤过程，涉及癌细胞从原发肿瘤脱离、内渗、在血流中存活、外渗和在远处器官中建立新病灶。细胞-细胞和细胞-基质粘附的变化伴随着从良性肿瘤向侵袭性恶性肿瘤的转变以及随后的肿瘤细胞转移性播散。钙粘蛋白是在正常组织中以组织特异性方式表达的细胞粘附分子家族。E-钙粘蛋白负责维持上皮细胞的正常组织，并且通常在转移性肿瘤中下调。与此相反，从头表达的N-钙粘蛋白，经常观察到上皮来源的肿瘤。N-钙粘蛋白改变培养中乳腺癌细胞的细胞行为，使其更具运动性和侵袭性。钙粘蛋白亚型转换（E-钙粘蛋白到N-钙粘蛋白）是肿瘤进展的标志，但对N-钙粘蛋白如何影响体内肿瘤细胞行为知之甚少。我们产生了N-钙粘蛋白条件性敲除（CKO）小鼠（常规N-钙粘蛋白KO是胚胎致死的），提供了在遗传定义的动物模型中检查肿瘤进展和转移中对N-钙粘蛋白的需求的机会。将N-钙粘蛋白CKO模型与靶向突变K-ras至胰腺祖细胞的新型胰腺导管癌发生模型相结合。该动物模型概括了在患有胰腺癌的人类患者中观察到的胰腺上皮内瘤变（PanIN）到胰腺导管腺癌（PDA）的进展。我们描述了在体内的证据表明，N-钙粘蛋白的损失增加的肿瘤发生的结果。基于这些初步的数据，我们假设，N-钙粘蛋白介导的粘附/信号转导的损失减轻细胞接触抑制细胞生长，通过改变肌动蛋白细胞骨架。这一假设将通过以下相互关联的特定目的来实现：（1）表征在不存在N-钙粘蛋白的情况下PanIN向PDA的进展;（2）评价N-钙粘蛋白缺失对细胞骨架调节因子RhoA的影响;（3）确定粘着斑在调节N-钙粘蛋白介导的细胞生长接触抑制中的作用。这项探索性的R21资助将确定在胰腺癌中基因阻断从E-钙粘蛋白到N-钙粘蛋白的转换的后果。了解胰腺癌进展的分子机制可能为开发新的胰腺癌治疗提供见解。公共卫生相关性：我们的意外发现，即N-钙粘蛋白的缺失导致K-rasG 12 D; N-cadflox/flox; Pdx 1-Cre小鼠中PanIN发育增加，这为揭示调节肿瘤生长的新分子机制提供了一个切入点。此外，鉴于N-钙粘蛋白拮抗剂ADH-1目前处于IIb期临床试验（http：//www.example.com），更好地理解N-钙粘蛋白在体内的功能是必要的。www.adherex.com了解胰腺癌进展的分子机制可能为开发新的胰腺癌治疗提供见解。

DESCRIPTION (provided by applicant): Abstract Cancer metastasis is a complex multistep process, involving the detachment of cancer cells from the primary tumor, intravasation, survival in the bloodstream, extravasation, and establishment of new foci in distant organs. Changes in cell-cell and cell-matrix adhesion accompany the transition from benign tumors to invasive, malignant cancer and the subsequent metastatic dissemination of tumor cells. Cadherins are a family of cell adhesion molecules expressed in a tissue specific manner in normal tissues. E-cadherin is responsible for maintaining the normal organization of the epithelia and is often downregulated in metastatic tumors. In contrast, de novo expression of N-cadherin is often observed in tumors of epithelial origin. N-cadherin alters the cellular behavior of breast cancer cells in culture rendering them more motile and invasive. Cadherin subtype switching (E-cadherin to N- cadherin) is a hallmark of tumor progression, yet it is poorly understood how N-cadherin affects tumor cell behavior in vivo. We generated an N-cadherin conditional knockout (CKO) mouse (conventional N-cadherin KO is embryonic lethal), providing an opportunity to examine the requirement for N- cadherin in tumor progression and metastasis in a genetically defined animal model. The N-cadherin CKO model was combined with a novel pancreatic ductal carcinogenesis model that targets mutant K-ras to pancreatic progenitor cells. This animal model recapitulates the progression of pancreatic intraepithelial neoplasia (PanIN) to pancreatic ductal adenocarcinoma (PDA) observed in human patients with pancreatic cancer. We describe in vivo evidence that loss of N-cadherin results in increased tumorigenesis. Based on these preliminary data, we hypothesize that loss of N-cadherin- mediated adhesion/signaling relieves cell contact inhibition of cell growth by altering the actin cytoskeleton. This hypothesis will be pursued by the following interrelated Specific Aims: (1) To characterize the progression of PanIN to PDA in the absence of N-cadherin; (2) To evaluate the effects of loss of N-cadherin on the cytoskeletal regulator, RhoA; (3) To determine the role of focal adhesions in the regulation of N-cadherin-mediated contact inhibition of cell growth. This exploratory R21 grant will determine the consequences of genetically blocking the switch from E-cadherin to N- cadherin in pancreatic cancer. Understanding the molecular mechanisms underlying the progression of pancreatic cancer may provide insight for the development of novel antineoplastic therapies. PUBLIC HEALTH RELEVANCE: Our unexpected finding that loss of N-cadherin leads to increased PanIN development in K-rasG12D; N-cadflox/flox; Pdx1-Cre mice provides an entry point to uncover novel molecular mechanisms regulating tumor growth. Furthermore, a better understanding of N-cadherin function in vivo is imperative given that the N-cadherin antagonist, ADH-1, is now in Phase IIb clinical trial (http://www.adherex.com). Understanding the molecular mechanisms underlying the progression of pancreatic cancer may provide insight for the development of novel antineoplastic therapies.