## Abstract ## Background. Although cyclooxygenase‐2 (COX‐2) has been suggested to play an important role in carcinogenesis, the effects of tumor suppressors on COX‐2 gene expression and the combined antitumor effects of tumor suppressors and COX‐2 inhibitors have rarely been investigated. ## Met
The effect of nitric oxide on cyclooxygenase-2 (COX-2) overexpression in head and neck cancer cell lines
✍ Scribed by Seok-Woo Park; Sang-Goo Lee; Sang-Hyun Song; Dae-Seog Heo; Bum-Jung Park; Dong-Wook Lee; Kwang-Hyun Kim; Myung-Whun Sung
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- French
- Weight
- 645 KB
- Volume
- 107
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
Abstract
The overexpression of cyclooxygenase‐2 (COX‐2) and inducible nitric oxide synthase (iNOS) has been previously reported in head and neck squamous cell carcinoma (HNSCC), as well as in many cancers. We hypothesized that endogenous nitric oxide (NO) might increase the expression of COX‐2 in cancer cells. Therefore, we investigated the cross‐talk between NO and the prostaglandin (PG) pathways in HNSCC cell lines. We found that COX‐2 and iNOS expressions were elevated simultaneously. On adding the NO donor, SNAP, the PGE~2~ level was increased 2–20 times due to increased COX‐2 expression. This increase of COX‐2 expression by SNAP or PMA (potent inducer of both iNOS and COX‐2) was blocked to various degrees by NO scavengers and NOS inhibitors (L‐NAME and 1400W). Also, the expression of COX‐2 in resting cells was inhibited by NOS inhibitors. Moreover, COX‐2 expression, induced by SNAP, was inhibited by ODQ, a soluble guanylate cyclase (sGC) inhibitor. The effect of dibutyryl‐cGMP on COX‐2 expression was similar to that of SNAP. These results imply that endogenous or exogenous NO activates sGC and that the resulting increase of cGMP induces a signaling that upregulates the expression of COX‐2 in HNSCC cell lines. We also observed that NO increased COX‐2 expression in different cancer cell lines, including cervic and gastric cancer cell lines. These findings further support the notion that NO can be associated with carcinogenesis through the upregulation of COX‐2, and that NOS inhibitor may be also useful for cancer prevention. © 2003 Wiley‐Liss, Inc.
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