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  • Title: Opposite role of Ras in tumor necrosis factor-alpha-induced cell cycle regulation: competition for Raf kinase.
    Author: Park SJ, Kim YY, Lim JY, Seo GJ, Kim J, Park SI, Park BJ.
    Journal: Biochem Biophys Res Commun; 2001 Oct 12; 287(5):1140-7. PubMed ID: 11587542.
    Abstract:
    Ras, a well-known oncogene, induces cell cycle stimulation through the Raf/Erk pathway and leads to cellular transformation, accompanied by other oncogenes such as c-myc and viral oncogenic protein. Here we suggest the interfering role of Ras in tumor necrosis factor (TNF)-alpha-induced cell cycle regulation. In TSU-Pr1 and T24 (oncogenic Ras cell lines), TNF-alpha suppresses cell cycle progression without induction of apoptosis, whereas AGS (wild-type Ras) is stimulated in its cell cycle by TNF-alpha coupled with activation of Erk. However, in TSU-Pr1 and T24, TNF-alpha leads to dephosphorylation of Erk1/2. Inhibition or activation of Ras can restore or convert TNF-alpha-induced cell cycle regulation in the cell lines containing the oncogenic Ras (TSU-Pr1 and T24) or AGS, respectively. Regulation of Erk also shows the coincidental pattern. We suggest the competition between the Ras pathway and TNF signaling for the binding to Raf, a common downstream target, as the cause of such reciprocal response, based on co-immunoprecipitation (co-IP) with antibodies against Raf and Ras or cellular Flice-inhibitory protein (c-FLIP), which have been recently identified upstream of Raf in death-ligand-induced cell cycle stimulation. Overexpression of Raf in TSU-Pr1, to reduce the competition, overcomes TNF-induced cell cycle arrest, also supporting our hypotheses.
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