Carcinogenesis Advance Access published online on May 23, 2007
Carcinogenesis, doi:10.1093/carcin/bgm115
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Direct Evidence for the Critical Role of NFAT3 in Benzo[a]pyrene Diol-Epoxide-Induced Cell Transformation through Mediation of Inflammatory Cytokine TNF induction in Mouse Epidermal Cl41 Cells
Nelson Institute of Environmental Medicine, New York University School of Medicine, 57 Old Forge Road, Tuxedo, NY 10987
¶ Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505
# Department of Pharmacology, School of Medicine, The Pennsylvania State University, Hershey, PA 17033
* Corresponding Author: Chuanshu Huang, M.D. & Ph.D., Nelson Institute of Environmental Medicine, New York University School of Medicine, 57 Old Forge Road, Tuxedo, NY, 10987. Tel: 845-731-3519, Fax: 845-351-2320. E-mail: chuanshu{at}env.med.nyu.edu
NFAT3 is a member of the transcription factor NFAT family, which has been demonstrated for the up-regulation of the pro-inflammatory cytokine tumor necrosis factor (TNF) in the immune system. Our most recent studies have also shown that TNF is able to induce cell transformation in mouse epidermal Cl41 cells by induction of COX-2 expression. To provide direct evidence for NFAT3 in the environmental carcinogen-caused carcinogenic effect, benzo[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE), an ultimate environmental carcinogen metabolized from benzo[a]pyrene (B[a]P), was utilized. We found that exposure of Cl41 cells to B[a]PDE was able to induce cell transformation in Cl41 cells, while specific knockdown of NFAT3 resulted in the dramatic inhibition of this cell transformation. The tumorigenicity of B[a]PDE-caused transformed cells was confirmed in nude mice, whereas the tumor formation of B[a]PDE-treated NFAT3 siRNA knockdown cells was significantly reduced. Further studies showed that the role of NFAT3 in B[a]PDE-caused cell transformation was mediated by up-regulation of its downstream targeted gene TNF. This conclusion was based on the findings that inhibition of NFAT3 activation by either FK506 or NFAT3 siRNA dramatically down-regulated the TNF induction upon B[a]PDE exposure, and that knockdown of TNF by its specific siRNA also led to abrogation of B[a]PDE-induced cell transformation in Cl41 cells and their tumorigenicity in nude mice. Collectively, these results provide direct evidence for the important role of NFAT3 activation in B[a]PDE-induced cell transformation by up-regulation of TNF expression in mouse epidermal Cl41 cells, further suggesting that B[a]PDE may exert its tumor promotion effect on skin carcinogenesis, at least partially, by inducing TNF expression.
Key Words: Carcinogenesis • TNF • NFAT • gene regulation • Benzo[a]pyrene Diol-Epoxide
Received December 31, 2006; revised April 19, 2007; accepted May 9, 2007.