ROS‐generating oxidases Nox1 and Nox4 contribute to oncogenic Ras‐induced premature senescence

• Published in: Genes to cells : devoted to molecular & cellular mechanisms 2013-01, Vol.18 (1), p.32-41
• Main Authors: Kodama, Ryo, Kato, Masayoshi, Furuta, Shuichi, Ueno, Shouta, Zhang, Yugen, Matsuno, Kuniharu, Yabe‐Nishimura, Chihiro, Tanaka, Eiji, Kamata, Tohru
• Format: Article
• Language: English
• Subjects: Aging; Animals; Cell Cycle; Cell Line; Cellular Senescence; Cyclin-Dependent Kinase Inhibitor p16 - metabolism; DNA Damage; Fibroblasts - cytology; Fibroblasts - enzymology; Humans; Mice; NADH, NADPH Oxidoreductases - genetics; NADH, NADPH Oxidoreductases - metabolism; NADPH Oxidase 1; NADPH Oxidase 4; NADPH Oxidases - genetics; NADPH Oxidases - metabolism; Oncogene Protein p21(ras) - metabolism; p38 Mitogen-Activated Protein Kinases - metabolism; Reactive Oxygen Species - metabolism; RNA, Small Interfering; Signal Transduction; Tumor Suppressor Protein p53 - metabolism; Up-Regulation
• ISSN: 1356-9597; 1365-2443
• DOI: 10.1111/gtc.12015

Activated oncogenes induce premature cellular senescence, a permanent state of proliferative arrest in primary rodent and human fibroblasts. Recent studies suggest that generation of reactive oxygen species (ROS) is involved in oncogenic Ras‐induced premature senescence. However, the signaling mechanism controlling this oxidant‐mediated irreversible growth arrest is not fully understood. Here, we show that through the Ras/MEK pathway, Ras oncogene up‐regulated the expression of superoxide‐generating oxidases, Nox1 in rat REF52 cells and Nox4 in primary human lung TIG‐3 cells, leading to an increase in intracellular level of ROS. Ablation of Nox1 and Nox4 by small interfering RNAs (siRNAs) blocked the RasV12 senescent phenotype including β‐galactosidase activity, growth arrest and accumulation of tumor suppressors such as p53 and p16Ink4a. This suggests that Nox‐generated ROS transduce senescence signals by activating the p53 and p16Ink4a pathway. Furthermore, Nox1 and Nox4 siRNAs inhibited both Ras‐induced DNA damage response and p38MAPK activation, whereas overexpression of Nox1 and Nox4 alone was able to induce senescence. The involvement of Nox1 in Ras‐induced senescence was also confirmed with embryonic fibroblasts derived from Nox1 knockout mice. Together, these findings suggest that Nox1‐ and Nox4‐generated ROS play an important role in Ras‐induced premature senescence, which may involve DNA damage response and p38MAPK signaling pathways.