Laboratory of Neuroimmunology and Regenerative Therapy, Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5930, USA.
Biochem Biophys Res Commun. 2013 Jul 26;437(2):300-6. doi: 10.1016/j.bbrc.2013.06.072. Epub 2013 Jun 28.
Apoptosis and autophagy are crucial mechanisms regulating cell death, and the relationship between apoptosis and autophagy in the liver has yet to be thoroughly explored. TIGAR (TP53-induced glycolysis and apoptosis regulator), which is a p53-inducible gene, functions in the suppression of ROS (reactive oxygen species) and protects U2OS cells from undergoing cell death. In this study, silencing TIGAR by RNAi (RNA interference) in HepG2 cells down-regulated both TIGAR mRNA (∼75%) and protein levels (∼80%) and led to the inhibition of cell growth (P<0.01) by apoptosis (P<0.001) and autophagy. We demonstrated that TIGAR can increase ROS levels in HepG2 cells. The down-regulation of TIGAR led to the induction of LC-3 II (specific autophagic marker), the formation of the autophagosome, and increased Beclin-1 expression. 3-MA (3-Methyladenine), an inhibitor of autophagic sequestration blocker, inhibited TIGAR siRNA-enhanced autophagy, as indicated by the decrease in LC-3 II levels. Consequently, these data provide the first evidence that targeted silencing of TIGAR induces apoptotic and autophagic cell death in HepG2 cells, and our data raise hope for the future successful application of TIGAR siRNA in patients with hepatocellular carcinoma (HCC).
细胞凋亡和自噬是调控细胞死亡的关键机制，而凋亡和自噬之间的关系在肝脏中尚未得到充分探索。TIGAR（p53 诱导的糖酵解和凋亡调节因子）是一种 p53 诱导基因，其功能是抑制 ROS（活性氧），保护 U2OS 细胞免于发生细胞死亡。在这项研究中，用 RNAi（RNA 干扰）沉默 HepG2 细胞中的 TIGAR，使 TIGAR mRNA（约 75%）和蛋白水平（约 80%）下调，并导致细胞生长受到抑制（P<0.01），凋亡（P<0.001）和自噬（P<0.001）。我们证明 TIGAR 可以增加 HepG2 细胞中的 ROS 水平。下调 TIGAR 导致 LC-3 II（特异性自噬标记物）的诱导、自噬体的形成和 Beclin-1 表达的增加。3-MA（3-甲基腺嘌呤），一种自噬隔离阻断剂的抑制剂，抑制了 TIGAR siRNA 增强的自噬，如 LC-3 II 水平的降低所示。因此，这些数据首次提供了证据，表明靶向沉默 TIGAR 可诱导 HepG2 细胞发生凋亡和自噬性细胞死亡，我们的数据为未来成功应用 TIGAR siRNA 治疗肝细胞癌（HCC）患者带来了希望。
