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Cyclooxygenase 2 expression in nasopharyngeal carcinoma: immunohistochemical findings and potential implications

¹ Department of Pathology, National University of Singapore, Lower Kent Ridge Road, Singapore 119074
² Department of Pathology, National University of Singapore

Correspondence to:
Dr K-B Tan
Department of Pathology, National University of Singapore, Lower Kent Ridge Road, Singapore 119074; pattankb{at}nus.edu.sg Background: Cyclooxygenase 2 (COX-2), an inducible prostaglandin synthase, participates in inflammatory and neoplastic processes. It is expressed by various tumours and contributes to carcinogenesis. Notably, COX-2 inhibitors appear to have tumour suppressor effects and are being evaluated in clinical trials.

Aims: To investigate COX-2 expression in nasopharyngeal carcinoma (NPC), a common tumour in parts of Asia, and to discuss potential implications.

Methods: Eighty five cases of NPC were reviewed. COX-2 immunohistochemistry and semiquantitative assessment of expression in nasopharyngeal biopsies were performed. Because COX-2 is proangiogenic, tumour microvessel density was also assessed with the use of CD31 immunohistochemistry.

Results: Histologically, 78 NPCs were undifferentiated, six were non-keratinising, and one was keratinising. Thirty nine NPCs had adjacent dysplastic epithelium. COX-2 expression was noted in 60 NPCs, 14 of 39 samples of dysplastic epithelium, and only one of 25 samples of normal epithelium (p < 0.01). Microvessel density was not significantly different between COX-2 positive and COX-2 negative tumours (p = 0.774). Tumour COX-2 positivity was not associated with higher tumour stage (p = 0.423).

Conclusion: COX-2 expression is more frequently seen as nasopharyngeal epithelium progresses from normal to dysplastic to carcinoma. This suggests that COX-2 contributes to the multistep process of NPC carcinogenesis. COX-2 represents a therapeutic target for COX-2 inhibitors, and there is thus a basis for the further investigation of this adjuvant treatment modality for NPC. COX-2 inhibitors are known to potentiate the antitumour effects of radiotherapy, which is the primary treatment for NPC.

Abbreviations: COX, cyclooxygenase; EBV, Epstein-Barr virus; MVD, microvessel density; NPC, nasopharyngeal carcinoma

Keywords: nasopharyngeal carcinoma; cyclooxygenase; head and neck; undifferentiated carcinoma; upper aerodigestive tract

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