Cyclooxygenase-2 Expression and Prostaglandin E2 Synthesis Are Up-Regulated in Carcinomas of the Cervix: A Possible Autocrine/Paracrine Regulation of Neoplastic Cell Function via EP2/EP4 Receptors

The prevalence of cervical cancer in South African women is reported as being the highest in the world, occurring, on the average, in 60 of every 100,000 women. Cervical cancer is thus considered an important clinical problem in sub-Saharan Africa. Recent studies have suggested that epithelial tumors may be regulated by cyclooxygenase (COX) enzyme products. The purpose of this study was to determine whether cyclooxygenase-2 (COX-2) expression and PGE2 synthesis are up-regulated in cervical cancers. Real-time quantitative RT-PCR and Western blot analysis confirmed COX-2 ribonucleic acid and protein expression in all cases of squamous cell carcinoma (n = 8) and adenocarcinoma (n = 2) investigated. In contrast, minimal expression of COX-2 was detected in histologically normal cervix (n = 5). Immunohistochemical analyses localized COX-2 expression and PGE2 synthesis to neoplastic epithelial cells of all squamous cell (n = 10) and adenocarcinomas (n = 10) studied. Immunoreactive COX-2 and PGE2 were also colocalized to endothelial cells lining the microvasculature. Minimal COX-2 and PGE2 immunoreactivity were detected in normal cervix (n = 5). To establish whether PGE2 has an autocrine/paracrine effect in cervical carcinomas, we investigated the expression of two subtypes of PGE2 receptors, namely EP2 and EP4, by real-time quantitative RT-PCR. Expression of EP2 and EP4 receptors was significantly higher in carcinoma tissue (n = 8) than in histologically normal cervix (n = 5; P< 0.01). Finally, the functionality of the EP2/EP4 receptors was assessed by investigating cAMP generation after in vitro culture of cervical cancer biopsies and normal cervix in the presence or absence of 300 nmol/L PGE2. cAMP production was detected in all carcinoma tissue after treatment with exogenous PGE2 and was significantly higher in carcinoma tissue (n = 7) than in normal cervix (n = 5; P < 0.05). The fold induction of cAMP in response to PGE2 was 51.1 ± 12.3 in cervical carcinoma tissue compared with 5.8 ± 2.74 in normal cervix. These results confirm that COX-2, EP2, and EP4 expression and PGE2 synthesis are up-regulated in cervical cancer tissue and suggest that PGE2 may regulate neoplastic cell function in cervical carcinoma in an autocrine/paracrine manner via the EP2/EP4 receptors.