Increased nitric oxide levels and iNOS over-expression in oral squamous cell carcinoma.
Inducible nitric oxide synthase (iNOS) is responsible for generating high levels of nitric oxide (NO) in tissues. Increased iNOS expression has been demonstrated in a number of carcinomas including head and neck squamous cell carcinoma (SCC). However, iNOS levels have not been evaluated specifically in oral cavity SCC, or in the precancerous lesions that progress to oral SCC. Also, NO levels have not been measured in oral precancerous or cancerous tissues. We therefore measured iNOS mRNA, iNOS protein and NO in oral SCC, oral dysplasias and normal oral epithelium. We used RT-PCR to quantify and compare iNOS mRNA levels in these oral tissue specimens. We found that iNOS mRNA was overexpressed in 41% of oral SCC but in only 8% of dysplasia specimens (P = 0.003). Immunohistochemistry was used to evaluate iNOS protein levels in oral SCC, oral dysplasias and normal oral epithelium. A significantly higher percentage of oral SCC specimens showed the highest level of iNOS staining relative to the oral dysplasias and normal oral epithelial samples (95% of oral SCC, 50% of dysplasias, and only 0% of normal epithelial controls, P < 0.0001). The positive staining for iNOS was limited to the SCC cells. Production of NO from iNOS was quantified using HPLC and found to be significantly higher in oral SCC (1.45 +/- 0.56 microg/ml) than normal epithelial controls (0.43 +/- 0.26 microg/ml) (P = 0.0013). We conclude that iNOS mRNA levels and NO production are significantly increased, in oral SCC compared to oral dysplasias and normal epithelial controls. These findings suggest that increased iNOS expression and the generation of high NO levels might have a role in oral SCC development.
Connelly
Stephen T
ST
Department of Oral and Maxillofacial Surgery, University of California, San Francisco, CA 94143-0440, USA.
Macabeo-Ong
Maricris
M
Dekker
Nusi
N
Jordan
Richard C K
RC
Schmidt
Brian L
BL
D002294:Carcinoma, Squamous Cell / Q000201:enzymology*; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D009061:Mouth Mucosa / Q000201:enzymology / Q000473:pathology; D009062:Mouth Neoplasms / Q000201:enzymology*; D009569:Nitric Oxide / Q000032:analysis*; D019001:Nitric Oxide Synthase / Q000032:analysis* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D012333:RNA, Messenger; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II