抑癌基因Menin在胰腺癌中的功能和表观遗传调控机制研究

Our previous study identified that Menin was decreased in pancreatic cancer comprared with that in the normal pancreatic tissue,and that Menin overexpression could inhibit the pancreatic cancer cell proliferation, which revealed that Menin-DNMT1 interaction collaboratively regulated DNA methylation. However, the function and molecular mechanism of Menin in pancreatic cancer cell migration and apoptosis is unclear. This study will investigate the Menin in pancreatic cancer cells using adenovirus-mediated overexpression and knockdown. Mechanistically, on one hand, we will perform immunoprecipitation (IP) in Menin-overexpressed pancreatic cancer cells. On the other hand, mass Spectrometry analysis of IP products was performed to screen Menin-interacting protein. Then the verified factors will be subjected to functional analysis to elucidate the molecular mechanism underlying Menin's roles through interacting with its functional partners. Moreover, the mechanisms controlling the loss of Menin activity in pancreatic cancer tissues will be also investigated. This study tries to reveal the mechanism of Menin-related molecular circuitry, and provides novel insights into pancreatic cancer treatment.

课题组前期研究发现Menin在胰腺癌中的表达低于正常胰腺组织，Menin过表达能显著抑制胰腺癌细胞增殖，并揭示Menin与DNMT1通过相互作用协同调控DNA甲基化。但是，Menin是否在胰腺癌细胞的迁移和凋亡中发挥功能和Menin发挥功能的分子机制目前尚不清楚。本项目将以胰腺癌细胞系为研究模型，通过腺病毒介导的过表达和knockdown研究Menin在胰腺癌细胞迁移和凋亡中的功能。分子机制方面，我们将通过在过表达Menin的胰腺癌细胞中对Menin进行免疫沉淀（IP）实验，将其产物行质谱鉴定，然后挑取表观遗传调控因子，进行体外免疫共沉淀和IP验证实验。之后，对Menin的相互作用因子进行功能学分析，阐述Menin如何与相互作用因子协同发挥抑制胰腺癌的功能。并且，我们也将研究Menin在胰腺癌组织中失活的分子机理并揭示Menin的分子调控环路，为胰腺癌的治疗提供理论基础。

作为消化系统恶性肿瘤，胰腺癌是致死率最高的恶性肿瘤之一，被称为“癌中之王”。研究证实，Menin表现出抑癌或促进功能是取决于不同的肿瘤类型或者同一肿瘤内不同的上下游调控因子。课题组前期研究发现Menin在胰腺癌中的表达低于正常胰腺组织，Menin过表达能显著抑制胰腺癌细胞增殖，并揭示Menin与DNMT1通过相互作用协同调控DNA甲基化。在此基础上，我们深入对Menin促癌或抑癌作用的研究。结果发现，Menin可以作为上皮-间质转化（EMT）的促进因子，并参与肿瘤细胞迁移或转移。过表达Menin可通过组蛋白去乙酰化作用抑制CCAAT/增强子结合蛋白beta（CCAAT/enhancer-binding protein beta，CEBPB）和上皮特异性基因表达，并进一步增强TGF-β信号相关的EMT过程。我们还证明CCAAT/增强子结合蛋白（C/EBP）beta（C/EBPβ；由CEBPB编码）作为Menin和TGF-β信号传导下游并发挥平衡生长抑制和EMT的作用。而C/EBPβ过表达可以恢复Menin在胰腺癌中的抑癌功能，其机制依赖于激活CDKN2A/B基因并拮抗EMT。总之，这些发现表明，一方面Menin可发挥癌基因的作用，其机制依赖于抑制C/EBPβ表达并降低肿瘤转移能力；另一方面，Menin可发挥抑癌作用，其机制依赖于通过与C/EBPβ相互作用激活CDKN2A转录。