Carcinogenesis Advance Access originally published online on February 17, 2005
Carcinogenesis 2005 26(6):1035-1043; doi:10.1093/carcin/bgi052
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Carcinogenesis vol.26 no.6 © Oxford University Press 2005; all rights reserved.
Differential requirement of signal pathways for benzo[a]pyrene (B[a]P)-induced nitric oxide synthase (iNOS) in rat esophageal epithelial cells



1 Nelson Institute of Environmental Medicine, New York University School of Medicine, 57 Old Forge Road, Tuxedo, NY 10987, USA, 2 Department of Occupational and Environmental Health Sciences, Fourth Military Medical University, Xi'an, Shaanxi, 710032, China, 3 Division of Environmental Health Sciences, School of Public Health, The Ohio State University, Columbus, OH 43210, USA and 4 Pennington Biomedical Research Center, Louisiana State University, 6400 Perkins Road, Baton Rouge, LA 70808, USA
* To whom correspondence should be addressed. Tel: +1 845 731 3519; Fax: +1 845 351 2118; Email: chuanshu{at}env.med.nyu.edu
Overexpression of inducible nitric oxide synthase (iNOS) has been reported in several human cancers, including esophageal squamous cell carcinoma (SCC). Benzo[a]pyrene (B[a]P), a polycyclic hydrocarbon carcinogen found in tobacco smoke and in the environment, induces cancer in multiple organ sites in animals and may be a causative agent for certain human cancers, such as esophageal cancer. In the present study, the effects of B[a]P on the induction of iNOS and the signaling pathways that lead to the induction were investigated in cultured rat esophageal epithelial (RE-149) cells. Treatment of RE-149 cells with B[a]P led to a marked increase in the expression of iNOS. The induction of iNOS by B[a]P was found to occur through an extracellular signal-regulated protein kinases (ERKs)-dependent pathway, since inhibition of ERKs by either pretreatment of RE-149 cells with PD98059, an inhibitor of ERKs upstream kinase MEK1/2, or overexpression of DN-ERK2, blocked the induction of iNOS by B[a]P. Furthermore, impairing nuclear factor-
B (NF
B) activation by either NEMO-BDBP, an NF
B specific inhibitor, or overexpression of DN-I
B
or IKK-KM markedly inhibited the expression of B[a]P-induced iNOS, suggesting that the NF
B pathway is also required for the induction of iNOS by B[a]P. In addition, treatment of RE-149 cells with either SB202190