受超级增强子驱动的转录因子MEIS1与尤文氏肉瘤特异融合蛋白EWS-FLI1互作的分子机制及功能研究

Ewing sarcoma is initiated and exacerbated by the disease-defining fusion protein EWS-FLI1. Recently, super-enhancers (SE) have been discovered as large clusters of cis-regulatory DNA elements densely bound by transcription factors and cofactors. Studies have shown that SEs play critical roles in defining cell fate and identity, and are enriched at genes with known oncogenic function in several cancer cells. However, whether and how SEs are involved in Ewing sarcoma pathophysiology remains still unknown. In the preliminary experiments, we annotated SEs in two Ewing sarcoma cells by performing ChIP-seq using H3K27ac antibody. Further investigation based on the biological attributes of SEs revealed that SE-associated genes contain a number of known Ewing sarcoma oncogenes such as CCND1, JAK1 and LINGO1. Through integrative analysis, we also identified MEIS1 as a candidate super-enhancer-driven oncogene, which co-operates with EWS-FLI1 in transcriptional regulation, and plays a key pro-survival role in Ewing sarcoma. In this proposal, we will comprehensively characterize SEs in two Ewing sarcoma specimens and two bone-marrow-derived mesenchymal stem cells by ChIP-seq experiments, in order to verify that MEIS1 is a Ewing sarcoma specific super-enhancer-driven gene; we will also further elucidate the biological functions and molecular mechanisms of the interaction between MEIS1 and EWS-FLI1, and explore their potential applied prospects for early diagnosis and targeted therapy in Ewing sarcoma.

尤文氏肉瘤中，特异性融合蛋白EWS-FLI1是导致该肿瘤发生发展的关键转录因子，然而其调控机制仍不明确。最新研究显示，“超级增强子”作为基因组中大量增强子富集的转录调控区域，可驱动许多癌基因的高表达。我们前期发现：超级增强子可驱动尤文氏肉瘤特异转录因子MEIS1的高表达，ChIP-seq结果表明MEIS1与EWS-FLI1具有相似的DNA结合序列，且co-IP发现两者存在相互作用，这提示MEIS1可能与EWS-FLI1共同促进尤文氏肉瘤的发生发展。本项目中，我们将利用ChIP-seq技术，在临床标本中进一步验证MEIS1的表达受超级增强子驱动，且具有尤文氏肉瘤特异性；其次进行体内外实验，进一步证实MEIS1与EWS-FLI1相互作用，并详细阐明两者互作对尤文氏肉瘤生物学特性和关键信号通路的影响，探讨临床意义。该项目将有助于揭示尤文氏肉瘤发生发展的关键分子机理，为其诊治提供新思路和新靶点。

尤文氏肉瘤是一种高度恶性的小圆细胞恶性骨肿瘤。特异性融合蛋白EWS-FLI1是导致该肿瘤发生发展的关键转录因子，然而其调控机制仍不明确。本项目中，我们通过搜索公共数据库中尤文氏肉瘤细胞和临床样本的H3K27ac ChIP-seq数据，结合生物信息学分析，鉴定了尤文氏肉瘤的超级增强子谱，并发现超级增强子可驱动许多尤文氏肉瘤特异性基因及关键原癌基因的表达；我们对其中一个超级增强子驱动基因MEIS1进行了全面、细致的生物学功能和机制探索：证实了MEIS1在尤文氏肉瘤中发挥原癌基因的功能，阐明了MEIS1与尤文氏肉瘤特异融合蛋白EWS-FLI1相互依赖，通过识别相似的DNA序列，共同调控下游基因，从而驱动肿瘤的发生发展。综上，本项目从“超级增强子”这一最新发现的表观遗传改变入手，揭示了尤文氏肉瘤发生发展的关键分子机理，为其诊治提供了新思路和新靶点。