Drp1介导的线粒体分裂促进肝癌细胞生长的功能机制研究

Mitochondria are highly dynamic, constantly changing their morphology to satisfy the variable need of cells and adapt to the cellular environment. Mitochondrial network is precisely regulated by two opposing processes: fusion and fission. Dysregulation of mitochondrial dynamic is associated with many human diseases. However, most previous studies of mitochondrial dynamic have paid no attention on tumorgenesis. In previous study, we found a significantly decreased average mitochondrial length (a typical indicator of mitochondrial fission) in hepatocellular carcimomar (HCC) tissues than those in adjacent non-tumor tissues. Western blot and immunohistochemical staining analysis demonstrated that mitochondrial fission protein dynamin related protein 1 (Drp1) was remarkably upregulated in HCC tissues. Furthermore, we found that HCC patients with high Drp1 expression had a significantly poorer overall survival than those with low Drp1 expression. Moreover, inhibition of mitochondrial fission in BEL7402 cells by treatment with siRNA against Drp1 induced cell apoptosis and decreased cell proliferation. Meanwhile, the result also demonstrated decreased ROS production and activity of NF-κB, and increased p53 protein level in BEL7402 cells treated with siRNA against Drp1. Therefore, based on our data and understanding on HCC, we aim to elucidate the biological functions and explain the mechanisms of Drp1-mediated mitochondrial fission on tumor cell growth of HCC cells by using Drp1-knockdown and Drp1-overexpression HCC cells. Furthermore, mitochondrial division inhibitor Midiv-1 will be also tested as a potential antitumor drug to suppress in vivo tumor growth in this study. Taken together, this project will facililate the understanding on molecular pathology of HCC and provide new potential targets for HCC treatment.

线粒体功能异常与肿瘤发生发展密切相关，相关功能机制研究已成为肿瘤学领域的热点问题。线粒体分裂融合对线粒体功能具有关键影响，并参与多种疾病发生，然而其在肿瘤中作用机制的研究尚未系统开展。我们前期研究发现：肝癌组织中Drp1分子及线粒体分裂显著上调。细胞学实验证实Drp1介导线粒体分裂增加，并显著促进肝癌细胞增殖和凋亡抵抗。此外，我们还发现干涉Drp1分子表达可降低ROS产生与NF-κB活性，并抑制p53降解。这些结果表明Drp1介导的线粒体分裂可能通过调控线粒体ROS产生及其下游相关通路促进肝癌恶性进展。进而，本项目拟从线粒体分裂融合动态平衡的崭新视角，利用Drp1稳定干涉和过表达细胞株，深入分析线粒体分裂上调影响肝癌生长的生物学作用，系统阐明相关分子信号通路，进而探讨Drp1抑制剂的治疗作用。本项目的开展不但可进一步加深对肝癌分子病理机制的理解，同时也可为其治疗提供新的潜在靶点。

线粒体功能异常与肿瘤发生发展密切相关，相关功能机制研究已成为肿瘤学领域的热点问题。本项目系统研究了线粒体分裂融合在肝癌发生进展中的作用机制。创新性发现：①肝癌组织中线粒体分裂显著上调，而融合受到抑制，且线粒体分裂效应分子Drp1表达显著上调、融合分子MFN1表达显著下调，并与患者较差预后相关。进一步机制研究发现线粒体分裂增强可以通过调控p53及NF-κB通路的交互作用，促进肝癌细胞自噬并抑制线粒体依赖的凋亡，进而促进肝癌细胞的体内外生长。利用 Drp1抑制剂抑制线粒体分裂，可以显著抑制荷瘤裸鼠模型中肝癌的生长，相关结果发表在Autophagy. 2016 (IF: 8.59);②肿瘤细胞中异常升高的钙信号可通过钙应答转录因子NFATC2与c-Myc促进线粒体分裂效应分子Drp1及Fis1的表达，另一方面，增强的线粒体分裂又可通过调节细胞ROS激活NF-κB通路介导的STIM1分子的表达，进而促进钙库操纵的钙内流（SOCE）及钙振荡频率。进而形成线粒体分裂与胞浆钙信号的正反馈环路。进一步我们还发现该环路可通过促进钙依赖的蛋白激酶促进肝癌细胞伪足形成与黏着斑的更迭，进而促进肝癌转移，相关结果发表在Cancer Lett. 2017 (IF: 6.49)和Liver int. 2018（IF：5.54）等杂志。③线粒体分裂融合相关分子MFN1在AKT/CAT诱导的小鼠肝癌中的表达显著降低，参与肝癌发生过程。上述研究用强有力的实验数据证实了线粒体分裂增强对肿瘤细胞多种恶性表型具有显著的促进作用。