Epi)Genomic drivers of primary and metastatic pancreatic islet cell carcinoma

胰腺癌研究的一个主要问题是缺乏临床相关的动物模型，可以更忠实地复制人类疾病。在这里，我们建议进行详细的表征合作突变驱动一个强大的动物模型胰岛细胞癌，我们偶然创建的结果，细胞特异性删除floxed Rb和p53基因座内的胰腺的肾素表达细胞室。初步评估表明，该模型具有表达高水平胰高血糖素的转移性胰岛细胞癌的特征。它以高转移率出现，就像其人类等同物一样，表现出严重的转移性扩散到临床相关部位，导致4-5个月死亡。我们认为，这是重要的，以进一步表征该模型，因为它表现出独特的功能，这将促进更好地了解胰岛细胞的发展，其中的作用，肾素-血管紧张素系统，胰岛细胞癌变，以及相关的转移过程。为了表征在胰腺肿瘤中观察到的协同基因组改变以及向肝脏的转移，已经开发了一种复杂的交叉，其中肿瘤抑制因子p53和Rb被缺失沿着利用RenCre转基因在表达肾素的细胞中激活GFP报告基因。在当前的提议中，我们将利用外显子组和甲基化组的下一代测序（NGS）来鉴定在正常胰岛的Rb-p53-肾素表达细胞的直系后代内发生的协同突变和DNA甲基化变化，其与随机产生的原发性肿瘤和相应的肝转移相关，目的是最终鉴定这些过程的遗传标记。此外，我们将确定从α胰岛祖细胞中的第一次肾素表达到原发性和转移性胰腺神经内分泌肿瘤发展的p53和Rb等位基因丢失的时间轴。提出了一个组织化假说，将肾素的表达与特定的胰岛细胞瘤联系起来。此外，利用GFP追踪导致疾病发生和进展的细胞谱系的能力提供了一个独特的机会，可以在DNA拷贝数变化、突变和DNA甲基化变化的获取方面剖析疾病病理学的时间轴。总的来说，这些数据将产生一种新的转移性胰腺癌模型，可用于测试新的治疗方法，并将有助于更全面地了解胰岛细胞癌。

A major problem in pancreatic cancer research is the lack of clinically relevant animal models that can more faithfully replicate human disease. Here we propose to undertake a detailed characterization of co-operating mutations driving a robust animal model for pancreatic islet cell cancer that we have serendipitously created as a result of cell-specifically deleting floxed Rb and p53 loci within the renin-expressing cell compartment of pancreas. Preliminary assessments suggest the model has the hallmarks of a metastatic islet cell carcinoma that expresses high levels of glucagon. It arises with high penetrance and, just like its human equivalent, exhibits profound metastatic spread to clinically relevant sites resulting in death by 4-5 months. We believe it is important to characterize this model further as it exhibits unique features which will foster better understanding of pancreatic islet cell development, the role of the renin-angiotensin system therein, islet cell carcinogenesis, and the associated metastatic process. To characterize co-operating genomic alterations observed in pancreatic tumors, as well as metastases to the liver, a complex cross has been developed where the tumor suppressors p53 and Rb are deleted along with activation of a GFP reporter in renin-expressing cells utilizing the RenCre transgene. In the current proposal we will utilize Next Generation Sequencing (NGS) of the exome and of the methylome to identify co-operating mutations and DNA methylation changes occurring within lineal descendants of the Rb- p53- renin-expressing cells of normal pancreatic islets that are associated with the stochastically arising primary tumors and corresponding liver metastases, with the aim of ultimately identifying genetic signatures for these processes. In addition we will determine the timeline of allelic loss of p53 and Rb from the first expression of renin in alpha islet cell progenitors to development of primary and metastatic pancreatic neuroendocrine tumors. An organizing hypothesis linking the expression of renin to the specific islet cell neoplasia is put forth. Furthermore, the ability to se GFP for lineage tracing of the cells contributing to disease initiation and progression provides a unique opportunity to dissect the timeline of disease pathology in terms of acquisition of DNA copy number changes, mutations, and DNA methylation changes. Overall, these data will result in a newly characterized model of metastatic pancreas cancer that can be used for testing of novel therapeutics and will contribute to a more complete understanding of islet cell cancers.