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

描述（由申请人提供）：胰腺的神经内分泌肿瘤相对罕见，但由于肿瘤谱的复杂性和不确定的组织发生，对这些实体仍然有相当大的兴趣。不幸的是，能够忠实地复制人类疾病并能够对疾病过程的病因进行更彻底调查的动物模型很少。我们已经创建了一个非常有用的胰岛细胞癌的新动物模型，这是由于细胞特异性地删除了胰腺肾素表达细胞室内的flxed Rb和p53位点。观察到的主要肿瘤是表达胰高血糖素的胰岛细胞癌，其出现具有高外显率，并表现出症状和深度转移扩散到具有代表性的人类疾病部位，导致5-6个月死亡。在人类疾病中，主要转移部位是局部淋巴结和肝脏，我们的模型模拟了这一点。该模型显示出独特的特征，将使我们能够更好地理解胰岛细胞的发育，肾素-血管紧张素系统在其中的作用，胰岛细胞的癌变和相关的转移过程，目的是最终确定这些过程的遗传特征。我们假设肾素在早期胰高血糖素谱系分化中短暂表达，p53和Rb的缺失使这些胰岛细胞在发生随机的协同遗传和表观遗传异常时易发生癌变。此外，我们提出额外的或特定的基因组损伤需要细胞获得转移表型。我们的假设得到了初步研究结果的支持，即表达肾素的细胞与表达胰高血糖素的α胰岛细胞共定位，并且随机产生的原发性和转移性肿瘤都继续表达胰高血糖素。最近的文献进一步支持了这一点，表明人类胰腺祖细胞在祖细胞分化为各种胰岛细胞类型的过程中，肾素-血管紧张素系统的各种成分的表达受到高度调控。当前的提案将使用Next

DESCRIPTION (provided by applicant): Neuroendocrine tumors of the pancreas are relatively rare but there remains considerable interest in these entities because of the complexity of the tumor spectrum and the uncertain histogenesis. Unfortunately, animal models that can faithfully replicate human disease and enable a more thorough investigation of the etiology of the disease process are few. We have created what appears to be a remarkably useful new animal model for pancreatic islet cell carcinoma as a result of cell-specifically deleting floxed Rb and p53 loc within the renin- expressing cell compartment of pancreas. The predominant neoplasia observed is an islet cell carcinoma, expressing glucagon, which arises with high penetrance and exhibits symptoms and profound metastatic spread to sites representative of the human disease, resulting in death by 5-6 months. In the human disease the primary metastatic sites are regional lymph nodes and liver, which is mimicked by our model. This model exhibits unique features which will allow us to foster better understanding of pancreatic islet cell development, the role the renin-angiotensin system therein, islet cell carcinogenesis, and the associated metastatic process, with the aim of ultimately identifying genetic signatures for these processes. We hypothesize that renin is transiently expressed in early glucagon lineage differentiation and that the loss of p53 and Rb predisposes these islet cells to frank carcinogenesis upon the occurrence of stochastic co-operating genetic and epigenetic abnormalities. Furthermore, we propose that additional or specific genomic insults are required for the cells to acquire a metastatic phenotype. Our hypothesis is supported by our preliminary findings that the renin expressing cells co-localize with the alpha islet cells expressing glucagon and that both primary and metastatic tumors, stochastically arising, continue to express glucagon. This is further supported by recent literature demonstrating that human pancreatic progenitor cells exhibit highly regulated expression of various components of the renin-angiotensin system throughout the progenitor cell differentiation to various islet cell types. The current proposal will use Next Generation Sequencing of the exome, all transcripts, and of the methylome to identify co-operating mutations, gene expression changes 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. Furthermore, the ability to use fluorescent reporters for lineage tracing of the cells contributing to disease initiation and progression provides a unique opportunity to dissect the timeline of disease pathology. We further expect that the Confetti reporter will assist in the identification o clonal expansion of individual colored cells in the islet for each primary tumor, and facilitate correctly pairing the colored metastatic tumor with the same colored primary tumor. This will increase the power of the pairwise comparisons between primary and metastatic tumors and will ultimately allow for dissection of multiple molecular routes of metastatic spread.