Strong evidence for up‐regulation of cyclooxygenase‐1 in head and neck cancer

BACKGROUND: Cyclooxygenase-1, in contrast to cyclooxygenase-2, is generally reported to be constitutively expressed as a housekeeping enzyme in many different tissues. A number of recently published reports, however, challenge the notion that cyclooxygenase-1 expression is invariably constitutive by demonstrating that this enzyme might be up-regulated under certain pathological conditions in, for example, breast or ovarian cancer cells. In this study we investigated the expression of cyclooxygenase-1 in head and neck tumours and compared it to the cyclooxygenase-1 expression levels in normal oropharyngeal epithelial cells. MATERIAL AND METHODS: Paraffin-embedded pretreatment biopsies were obtained from head and neck tumour patients (n = 35). In addition, samples of normal oropharyngeal mucosa were taken from patients (n = 12) undergoing routine tonsillectomy. Cyclooxygenase-1 expression levels were determined by immunohistochemistry, Western blotting and real-time RT-PCR in cancerous tissue versus normal mucosa. RESULTS: Immunohistochemistry revealed overexpression of cyclooxygenase-1 in tumour biopsies compared to normal mucosa. Cyclooxygenase-1 was highly synthesized in the cytoplasm of neoplastic cells while significantly lower levels were detectable in normal mucosal cells. Western blotting and real-time RT-PCR also demonstrated higher cyclooxygenase-1 levels in tumour specimens compared to normal tissue samples. CONCLUSION: In this study we show for the first time that cyclooxygenase-1 is overexpressed in head and neck cancer cells compared to epithelial cells of normal mucosa.