Functional in vivo characterisation of the role of epigenetic regulators for pancreatic cancer development and maintenance

胰腺导管腺癌（PDAC）是一个主要的健康问题。它是美国癌症死亡的第四大原因，5年生存率仅为7%，并且在过去30年中，PDAC患者的预后没有显著改善。根治性手术是一种治疗选择，然而，由于诊断在晚期，往往不适用。全身化疗显示出有限的治疗效果，仅提供适度的生存增加。最近对患者来源的PDAC样本进行的高通量遗传分析显示，除了Kras、p53、CDKN2A和Smad4等众所周知的驱动病变外，还有一些新的突变是PDAC发生和进展的潜在驱动因素。有趣的是，许多这些突变影响了在表观遗传调控中具有既定作用的基因，如染色质组织或组蛋白修饰。这些基因中包括SWI/SNF染色质重塑复合体的组成部分（如Arid1a/b和Smarca4），这些基因被发现经常发生突变，并被假设为代表肿瘤抑制基因。到目前为止，还没有完全了解表观遗传调节因子的改变如何促进癌症的发展和维持。该项目的第一个目的是研究染色质重塑亚基Arid1a， Arid1b和Smarca4在PDAC的发展，维持和进展中的作用。为了解决这个问题，将使用一种新开发的基于胚胎干细胞的PDAC小鼠模型，并使用条件RNA干扰（RNAi）对SWI/SNF亚基在肿瘤发展过程中的作用进行遗传解剖。此外，我将研究是否需要SWI/SNF因子的持续损失来维持PDAC，以及改变的表观遗传景观是否也在PDAC的治疗耐药中发挥作用。最后，我的目标是进行负选择汇集shRNA筛选，以确定特异性的合成致死率，特别是在这些pdac中，其中包含SWI/SNF复杂亚基的改变。

Pancreatic Ductal Adenocarcinoma (PDAC) represents a major health problem. It constitutes fourth leading cause of cancer death in the United States with a 5-year survival rate of only ~7 %, and the prognosis of patients suffering from PDAC has not significantly improved over the past 30 years. Radical surgery is a curative option, however, due to diagnosis in advanced stages, often not applicable. Systemic chemotherapy shows limited therapeutic efficacy, providing only modest gain in survival. Recent high throughput genetic analyses of patient derived PDAC samples revealed, besides well known driver lesions like Kras, p53, CDKN2A and Smad4, several new mutations as potential drivers of PDAC initiation and progression. Interestingly many of these mutations affect genes with established roles in epigenetic regulation like chromatin organization or histone modifications. Among these genes are components of the SWI/SNF chromatin remodelling complex (e.g. Arid1a/b and Smarca4), which were found frequently mutated and were hypothesized to represent tumor suppressor genes. Until now it is not yet fully understood how alterations in epigenetic regulators contribute to the development and maintenance of cancer. The first aim of this project is to investigate the role of the chromatin remodelling subunits Arid1a, Arid1b and Smarca4 in the development, maintenance and progression of PDAC. To address this question a newly developed embryonic stem cell based PDAC mouse model will be used and the role of the SWI/SNF subunits during tumor development will be genetically dissected using conditional RNA interference (RNAi). Furthermore, I will investigate, whether sustained loss of SWI/SNF factors is required for PDAC maintenance and whether the altered epigenetic landscape also plays a role in therapy resistance of PDACs. Finally, I aim to conduct negative selection pooled shRNA screens to identify synthetic lethalities specifically in such PDACs, which harbour alterations in SWI/SNF complex subunits.