Project 1: Elucidating the genetics and cell of origin of pancreatic cancer initiation

摘要（项目1） 胰腺导管腺癌（PDAC）是一种常见且几乎一致致命的恶性肿瘤。人PDAC 基因组测序已经确定了Kras和几个主要肿瘤抑制基因的复发性突变 （TSGs），但这些改变在人类PDAC发育的启动和演变中的影响仍然存在。 在分子水平上知之甚少。了解肿瘤发生和发展的基础至关重要， 对改善早期诊断和治疗的意义。虽然PDAC最初被认为是由导管引起的， 细胞，来自小鼠模型的证据表明，腺泡细胞可以通过再生， 这是一个称为腺泡到导管化生（ADM）的转分化过程。ADM受慢性 胰腺炎是PDAC的一个已知风险因素，可产生癌前胰腺上皮内瘤变 （PanIN），导致PDAC。我们的初步数据表明，p53 TSG可以抑制ADM， 表达致癌KrasG 12 D的腺泡细胞的失活驱动PDAC。然而，癌基因的表达 导管细胞中KrasG 12 D和p53失活也可诱导PDAC，提示PDAC的替代途径 致癌作用有趣的是，我们发现腺泡细胞源性肿瘤和导管细胞源性肿瘤类似于 分别是人PDAC的经典亚型和基底样亚型。这些结果强调了 小鼠模型揭示决定PDAC进化不同路径的决定因素， 转化成人类PDAC其他常见PDAC TSG在早期肿瘤前病变中的作用，包括 然而，它们是否正常地在腺泡细胞和/或导管细胞中起作用仍不清楚。此外，委员会认为， 致癌Kras突变在PDAC中是多样的，但不知道不同的突变是否具有不同的遗传学特征。 对来自不同胰腺上皮细胞类型的PDAC发育的影响。我们假设细胞类型 起源和肿瘤基因型合作驱动PDAC发展的不同路径，为了验证这一想法，我们 将系统地表达几种主要的PDAC TSG，并在两种假定的细胞中表达不同的Kras等位基因， 起源的类型。我们将描述早期病变和肿瘤的转录组和细胞环境， 采用体细胞基因组编辑和分子条形码等创新方法。我们将比较我们的 从易处理的小鼠模型研究到人PDAC发育研究。这些变革性的 研究将确定遗传决定因素和起源细胞如何影响分子途径， 小鼠和人类PDAC进化过程中的细胞微环境，更好的临床应用的关键知识 管理这种致命的疾病。

ABSTRACT (Project 1) Pancreatic ductal adenocarcinoma (PDAC) is a prevalent and almost uniformly fatal malignancy. Human PDAC genome sequencing has identified recurrent mutations in Kras and several major tumor suppressor genes (TSGs), but the impact of these alterations in the initiation and evolution of human PDAC development remain poorly understood at the molecular level. Understanding the basis of tumor initiation and development has critical implications for improving early diagnosis and therapy. While PDACs were originally thought to arise from ductal cells, evidence from mouse models suggests that acinar cells can give rise to PDACs through a regenerative, transdifferentiation process known as Acinar to Ductal Metaplasia (ADM). ADM is stimulated by chronic pancreatitis, a known risk factor for PDAC, and generates premalignant Pancreatic Intraepithelial Neoplasias (PanINs), which lead to PDAC. Our preliminary data suggest that the p53 TSG can inhibit ADM and that p53 inactivation in acinar cells expressing oncogenic KrasG12D drives PDAC. However, expression of oncogenic KrasG12D and p53 inactivation in ductal cells can also induce PDAC, suggesting alternate routes of PDAC carcinogenesis. Interestingly, we find that acinar cell-derived and ductal cell-derived tumors resemble the classical and basal-like subtypes of human PDAC, respectively. These results underscore the unique value of mouse models in uncovering the determinants that dictate different paths of PDAC evolution to provide insight into human PDAC. The roles of other common PDAC TSGs in early stage pre-neoplastic lesions, including whether they normally function in acinar cells and/or ductal cells, however, remains unclear. Furthermore, oncogenic Kras mutations are diverse in PDAC, yet it is unknown whether different mutations have distinct impacts on PDAC development from different pancreatic epithelial cell types. We hypothesize that the cell type of origin and tumor genotype cooperate to drive different paths of PDAC development, and to test this idea, we will systematically inactivate several major PDAC TSGs and express different Kras alleles in both putative cell types of origin. We will characterize the transcriptomes and the cellular milieu of early lesions and tumors and employ innovative approaches like somatic genome editing and molecular barcoding. We will compare our studies in tractable mouse models to studies of human PDAC development. Together, these transformative studies will establish how genetic determinants and cell-of-origin influence the molecular pathways and the cellular microenvironment during PDAC evolution in mice and humans, critical knowledge for better clinical management of this deadly disease.