Department of Oral and Maxillofacial Surgery, Kochi Medical School, Kochi University, Nankoku-city, Kochi 783-8505, Japan.
Free Radic Biol Med. 2010 May 15;48(10):1321-9. doi: 10.1016/j.freeradbiomed.2010.02.013. Epub 2010 Feb 24.
Hypoxia-inducible factor-1alpha (HIF-1alpha) is a central regulator that controls the hypoxic response of mammalian cells through the induction of various target genes, and its expression contributes to the development and malignant progression of many tumors. We previously reported that some chemotherapeutic drugs and gamma-rays induce HIF-1alpha expression through increased production of reactive oxygen species (ROS) in oral squamous cell carcinoma (OSCC) cells. However, the mechanism by which intracellular ROS activate HIF-1alpha expression is poorly understood. In this study, we investigated the influence of ROS on HIF-1alpha signaling in OSCC cells by the transfection of manganese-superoxide dismutase (Mn-SOD)-specific small interfering RNA (siRNA). The levels of HIF-1alpha protein and mRNA were increased by siRNA under both normoxic and hypoxic conditions in parallel with the increase in intracellular ROS levels. The accumulation of HIF-1alpha protein was enhanced through inhibition of the recruitment of von Hippel-Lindau protein and HIF-1alpha ubiquitination without a change in prolyl hydroxylase mRNA and protein levels. Furthermore, the transactivation of HIF-1alpha was enhanced via cap-dependent and internal ribosome entry site-mediated mechanisms. These results suggest that intracellular ROS produced by the knockdown of Mn-SOD enhance HIF-1alpha expression in OSCC cells through transcriptional, translational, and posttranslational regulation.
缺氧诱导因子-1α（HIF-1α）是一种核心调节剂，通过诱导各种靶基因来控制哺乳动物细胞的缺氧反应，其表达有助于许多肿瘤的发展和恶性进展。我们之前报道过，一些化疗药物和γ射线通过增加口腔鳞状细胞癌（OSCC）细胞中活性氧（ROS）的产生来诱导 HIF-1α 的表达。然而，细胞内 ROS 如何激活 HIF-1α 表达的机制尚不清楚。在这项研究中，我们通过转染锰超氧化物歧化酶（Mn-SOD）特异性小干扰 RNA（siRNA），研究了 ROS 对 OSCC 细胞中 HIF-1α 信号的影响。在常氧和缺氧条件下，Mn-SOD-siRNA 转染均平行增加细胞内 ROS 水平，同时增加 HIF-1α 蛋白和 mRNA 水平。HIF-1α 蛋白的积累通过抑制 von Hippel-Lindau 蛋白的募集和 HIF-1α 泛素化而增强，而脯氨酰羟化酶 mRNA 和蛋白水平没有变化。此外，通过帽依赖性和内部核糖体进入位点介导的机制增强了 HIF-1α 的转录激活。这些结果表明，Mn-SOD 敲低产生的细胞内 ROS 通过转录、翻译和翻译后调节增强 OSCC 细胞中的 HIF-1α 表达。
