Inhibition of Grb2-mediated activation of MAPK signal transduction suppresses NOR1/CB1954-induced cytotoxicity in the HepG2 cell line
| Autor: | Xin-min Nie, Ali Suhad, Rong Gui, Dengqing Li, Guannan Qi |
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| Rok vydání: | 2012 |
| Předmět: | |
| Zdroj: | Oncology Letters. 4:566-570 |
| ISSN: | 1792-1082 1792-1074 |
| DOI: | 10.3892/ol.2012.774 |
| Popis: | The nitroreductase oxidored-nitro domain containing protein 1 (NOR1) gene may be involved in the chemical carcinogenesis of hepatic cancer and nasopharyngeal carcinoma (NPC). We have previously demonstrated that NOR1 overexpression is capable of converting the monofunctional alkylating agent 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954) into a toxic form by reducing the 4-nitro group of CB1954. Toxic CB1954 is able to enhance cell killing in the NPC cell line CNE1; however, the underlying mechanisms remain unknown. Using cDNA microarrays and quantitative real-time PCR, we previously discovered that NOR1 increases the expression of growth factor receptor-bound protein 2 (Grb2) mRNA by 4.8-fold in the human hepatocellular carcinoma cell line HepG2. In the present study, we revealed that NOR1 increased Grb2 protein expression by 3-fold in HepG2 cells. Additionally, we demonstrated that NOR1 enhanced CB1954-induced cell killing in HepG2 cells, and cell cytotoxicity was inhibited with the tyrosine kinase inhibitor genistein, or by stable transfection of Grb2 small hairpin RNA (shRNA) pU6+27-shGrb2 to silence the expression of Grb2. Western blot analysis revealed that Grb2 downregulation may reduce the activity of the mitogen-activated protein kinase (MAPK). Inhibiting the activation of MAPK using the methyl ethyl ketone (MEK) inhibtor PD98059 suppressed CB1954-induced cell killing. These results suggested that the NOR1 gene enhances CB1954-mediated cell cytotoxicity through the upregulation of Grb2 expression and the activation of MAPK signal transduction in the HepG2 cell line. |
| Databáze: | OpenAIRE |
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