Immunohistochemical expression of inducible nitric oxide synthase in DMBA-induced hamster buccal pouch carcinogenesis

Nitric oxide (NO) plays a key role ill the processes of inflammation and carcinogenesis. Three isoforms of NO synthase have been identified: endothelial nitric oxide synthase (NOS), neuronal NOS, and inducible NOS (iNOS). The purpose of this study was to investigate the characteristics of iNOS in 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. Thirty outbred young (6-week-old) male Syrian golden hamsters were randomly divided into three groups: DMBA (0.5%) painted group (n = 10); mineral oil-treated group (n = 10); and non-treated group (n = 10). The average number of iNOS positive foci per section in the DMBA-treated group was approximately 12.2 +/- 4.7. Both cytoplasmic and nuclear stainings were observed in the DMBA-treated pouch kelatinocytes. No iNOS activity could be detected in the untreated or mineral oil-treated pouches. In con elusion. this study has demonstrated that iNOS is expressed in DMBA-induced hamster pouch carcinomas. This finding suggests that iNOS expression may be associated with the development of chemically induced oral carcinomas. (C) 2000 Elsevier Science Ltd. All rights reserved.