Cyclooxygenase-2 Inhibition Suppresses αvβ6 Integrin–Dependent Oral Squamous Carcinoma Invasion

Maria L. Nystrom,Shelia M. Violette,Paul H. Weinreb,Diana McCulloch,John F. Marshall,Paul M. Speight,Ian R. Hart,Gareth J. Thomas

doi:10.1158/0008-5472.can-06-1640

Abstract

Worldwide oral squamous cell carcinoma (OSCC) represents about 5.5% of all malignancies, with approximately 30,000 new cases each year in the United States. The integrin alpha(v)beta(6) and the enzyme cyclooxygenase-2 (COX-2) are implicated in OSCC progression and have been suggested as possible therapeutic targets. Each protein also is reported to identify dysplasias at high risk of malignant transformation, and current clinical trials are testing the efficacy of nonsteroidal anti-inflammatory drugs (NSAID) at preventing OSCC development. Given the probable increased expression of alpha(v)beta(6) and COX-2 in OSCC and the inhibition of several integrins by NSAIDs, we investigated whether NSAIDs affected alpha(v)beta(6)-dependent cell functions. We found that expression of both alpha(v)beta(6) and COX-2 was significantly higher in OSCC compared with oral epithelial dysplasias. Neither protein preferentially identified those dysplastic lesions that became malignant. Using OSCC cell lines, modified to express varying levels of alpha(v)beta(6), we assessed the effect of COX-2 inhibition on cell invasion. We found that the COX-2 inhibitor NS398 inhibited specifically alpha(v)beta(6)-dependent, but not alpha(v)beta(6)-independent, OSCC invasion in vitro and in vivo, and this effect was modulated through prostaglandin E(2) (PGE(2))-dependent activation of Rac-1. Transient expression of constitutively active Rac-1, or addition of the COX-2 metabolite PGE(2), prevented the anti-invasive effect of NS398. Conversely, RNA interference down-regulation of Rac-1 inhibited alpha(v)beta(6)-dependent invasion. These findings suggest that COX-2 and alpha(v)beta(6) interact in promoting OSCC invasion. This is a novel mechanism that, given the ubiquity of alpha(v)beta(6) expression by head and neck cancers, raises the possibility that NSAIDs could protect against OSCC invasion.

Highlights

Cyclooxygenases (COX) catalyze the key step in prostanoid and thromboxane biosynthesis and are targets of nonsteroidal antiinflammatory drugs (NSAID)
Neither protein preferentially identified lesions, which subsequently transformed to oral squamous cell carcinoma (OSCC), and similar staining sometimes was found in hyperplastic epithelium
Expression of avh6 occurs in many carcinoma types [6,7,8,9,10, 35,36,37] but is found most consistently and at its highest levels in OSCC [7, 37], where experimental studies indicate that it promotes invasion [20, 21, 38, 39]

Summary

Introduction

Cyclooxygenases (COX) catalyze the key step in prostanoid and thromboxane biosynthesis and are targets of nonsteroidal antiinflammatory drugs (NSAID). Two human isoforms exist: COX-1, Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). The epithelial integrin avh is a receptor for fibronectin, vitronectin, tenascin, and the latency-associated peptide (LAP) of transforming growth factor-h Found to have minimal expression in adult epithelium, avh is up-regulated during epithelial remodeling (e.g., wound healing) and tumorigenesis. Aberrant avh expression occurs in numerous carcinoma types, OSCC [7,8,9,10,11]. Increased expression of both avh and COX-2 have been reported in oral dysplastic epithelium, suggesting a role in tumor progression [12, 13]

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Conclusion