翻译起始因子eIF4A调控MYC/miR-9信号促进胰腺癌细胞EMT和转移的机制及靶向干预研究

Epithelial mesenchymal transition is a critical mechanism of metastasis in early stage of pancreatic cancer. The applicant found that eIF4A was highly expressed and promoted EMT and metastasis in pancreatic cancer. RocA of eIF4A inhibitor down-regulated MYC/miR-9 signaling to inhibit EMT and metastasis of pancreatic cancer. However, the mechanism of eIF4A controlling MYC/miR-9 signaling is unclear. Combined with literature and previous studies, the applicant proposed a hypothesis: high expression of eIF4A in pancreatic cancer cells, which unwinds the helix structure of MYC mRNA 5ʹUTR, regulates translation of MYC protein and enhanced MYC/miR-9 signaling and down-regulates E-cadherin, and ultimately promoted EMT and metastasis of pancreatic cancer. This study investigates the correlation between eIF4A and MYC expression in pancreatic cancer tissues. In vitro, a cell model of high and low eIF4A and MYC expression in pancreatic carcinoma is established. The model of lung metastasis in SCID mice with high or low expression of eIF4A and MYC is established, and the regulatory role of eIF4A in EMT and metastasis of pancreatic cancer was detected and analyzed. This study will unravel the molecular mechanism of eIF4A regulating MYC/miR-9 signaling, and the effect of eIF4A and MYC intervention was observed. This work will provide an experimental and theoretical basis for targeted intervention of pancreatic cancer.

上皮间质转化(EMT)是胰腺癌早期转移的重要机制。申请者前期研究发现胰腺癌中eIF4A高表达，且促进胰腺癌EMT和转移；而eIF4A干预下调MYC/miR-9信号抑制胰腺癌的EMT和转移。但eIF4A调控MYC/miR-9信号参与EMT的机制尚不清楚。我们结合文献及前期研究提出假说：胰腺癌细胞高表达eIF4A，其解开MYC-mRNA-5ʹUTR螺旋结构，启动MYC蛋白翻译而增强MYC/miR-9信号进而下调E-cadherin表达，促进胰腺癌EMT和转移。本项目检测胰腺癌组织中eIF4A和MYC表达相关性；体外建立eIF4A和MYC高低表达胰腺癌细胞模型，体内建立eIF4A和MYC高低表达SCID小鼠尾静脉注射肺转移模型，解析eIF4A在胰腺癌EMT和转移中的作用，揭示eIF4A调控MYC/miR-9信号的分子机制，并观察eIF4A和MYC干预效应，为胰腺癌靶向干预提供实验及理论依据。

背景：胰腺导管腺癌（Pancreatic ductal adenocarcinoma, PDAC）近年来在我国发病率和死亡率均明显上升。尽管近几十年来胰腺癌手术切除率显著提高，但由于其早期转移等重要特征，胰腺癌术后长期生存率仍处于极低水平。近期研究表明，在胰腺癌形成初期，胰腺癌细胞即可通过上皮间质转化（Epithelial mesenchymal transition, EMT）在远处器官种植，其中翻译起始因子eIF（eukaryotic initiation factor, eIF）在胰腺癌EMT和转移中起重要作用。前期研究结果证明，原癌基因MYC的翻译高度依赖于eIF4A的调控，而MYC/miR-9是促进肿瘤细胞EMT和转移的重要信号。本研究旨在探讨eIF4A通过调控MYC/mir-9信号促进胰腺癌细胞EMT和转移的机制。.研究内容：使用生物信息学方法分析eIF4A1在胰腺癌组织及癌旁组织中的表达差异，随后使用53例胰腺癌组织的基因芯片验证并进行临床相关性分析。通过eIF4A1以及c-MYC的表达调控与药物干预，体内外水平检验其在胰腺癌细胞EMT以及转移中的调控作用。.结果：研究结果显示，胰腺癌组织中eIF4A1高表达与淋巴结浸润，肿瘤大小等不良预后特征呈正相关。eIF4A1可通过c-MYC/miR-9信号下调E-cadherin的表达水平，从而促进胰腺癌细胞EMT的发生，下调胰腺癌细胞eIF4A1或c-MYC表达水平显著抑制了其EMT水平及侵袭转移能力。序贯调控实验显示，eIF4A1过表达可部分代偿c-MYC敲除所致胰腺癌细胞EMT水平和迁移侵袭能力的下降。单独或联合使用eIF4A1抑制剂（RocA）以及c-MYC抑制剂（Mycro3）均可显著减少胰腺癌细胞EMT标志物的表达水平，但RocA单独使用对胰腺癌细胞侵袭转移的抑制能力以及安全性均不劣于两种药物联合使用。.科学意义：1. 通过临床相关性分析证明eIF4A1的异常表达与胰腺癌不良预后相；2. 验证eIF4A可通过MYC/miR-9信号下调肿瘤细胞E-cadherin表达水平，从而促使肿瘤细胞EMT和侵袭转移的发生；3. eIF4A1可部分代偿c-MYC敲除所致胰腺癌细胞侵袭转移能力下降，eIF4A抑制剂RocA可有效抑制胰腺癌细胞的侵袭转移，其安全性及有效性均不劣于RocA及Mycro3联用。