Reactive Oxygen Species Mediated Sustained Activation of Protein Kinase C α and Extracellular Signal-Regulated Kinase for Migration of Human Hepatoma Cell Hepg2

• Published in: Molecular cancer research Vol. 4; no. 10; pp. 747 - 758
• Main Authors: Wu, Wen-Sheng, Tsai, Rong Kung, Chang, Chung Hsing, Wang, Sindy, Wu, Jia-Ru, Chang, Yu-Xun
• Format: Journal Article
• Language: English
• Published: United States American Association for Cancer Research 01.10.2006
• Subjects: Acetylcysteine - pharmacology; Carcinogens - pharmacology; Carcinoma, Hepatocellular - metabolism; Cell Line, Tumor; Cell Movement; EMT; Enzyme Activation; ERK; Extracellular Signal-Regulated MAP Kinases - metabolism; Extracellular Signal-Regulated MAP Kinases - physiology; Gene Expression Regulation, Neoplastic; hepatoma cell; Humans; Indoles - pharmacology; Maleimides - pharmacology; migration; Models, Biological; PKC; Protein Kinase C-alpha - metabolism; Protein Kinase C-alpha - physiology; Reactive Oxygen Species - pharmacology; ROS; Signal Transduction; Tetradecanoylphorbol Acetate - pharmacology; TPA
• ISSN: 1541-7786; 1557-3125
• DOI: 10.1158/1541-7786.MCR-06-0096

The tumor promoter 12- O -tetradecanoylphorbol-13-acetate (TPA) can trigger growth inhibition, epithelial-mesenchymal transition (EMT)–like cell scattering, and migration of hepatoma cells HepG2 in a protein kinase C-α (PKC-α)–dependent manner. Saikosaponin a, an ingredient of antitumorigenic Chinese herb Sho-Saiko-to, inhibited cell growth but did not induce EMT-like cell scattering and cell migration of HepG2. Saikosaponin a and TPA induced transient (for 30 minutes) and sustained (until 6 hours) phosphorylation of extracellular signal-regulated kinase (ERK), respectively. Generation of the reactive oxygen species (ROS) was induced by TPA, but not saikosaponin a, for 3 hours. As expected, scavengers of ROS, such as superoxide dismutase, catalase, and mannitol, and the thiol-containing antioxidant N -acetylcystein dramatically suppressed the TPA-triggered cell migration but not growth inhibition of HepG2. The generation of ROS induced by TPA was PKC, but not ERK, dependent. On the other hand, scavengers of ROS and N -acetylcystein also prevented PKC activation and ERK phosphorylation induced by TPA. On the transcriptional level, TPA can induce gene expression of integrins α 5 , α 6 , and β 1 and reduce gene expression of E-cahedrin in a PKC- and ROS-dependent manner. In conclusion, ROS play a central role in mediating TPA-triggered sustained PKC and ERK signaling for regulation of gene expression of integrins and E-cahedrin that are responsible for EMT and migration of HepG2. (Mol Cancer Res 2006;4(10):747–58)