Cyclooxygenase 1 and 2 mRNA and protein expression in the Gallus domesticus model of ovarian cancer

Abstract

Objective: Our purpose was to determine the mRNA and protein expression of cyclooxygenase 1 (COX-1) and cyclooxygenase 2 (COX-2) in ovarian tumors and normal ovaries of the hen, which is an excellent model for human ovarian cancer. Tissue concentrations of prostaglandin E(2) (PGE2) and PGE2 metabolites were also determined.

Methods: Tissue was obtained from ovarian tumor (n = 18) and normal ovary (n = 29) of 2- to 4-year old Single-comb White Leghorn hens. Quantitative real-time PCR with Sybr Green was used to quantify the mRNA expression of COX-1 and COX-2, using 18S expression as an internal control for COX normalization. Immunohistochemistry using antibodies for COX-1 and COX-2 was used to localize protein expression of each isoform in a subset of tumor (n = 5) and normal samples (n = 6). For determination of tissue prostaglandin concentration, tissue was obtained from ovarian tumor (n = 8) and normal ovary (n = 8). PGE2 and PGE2 metabolites were measured using competitive enzyme immunoassays (EIAs).

Results: Our results indicate that COX-1 mRNA expression is significantly higher (P < 0.05) in ovarian tumor samples compared to normal ovaries while there is no significant difference in expression of COX-2 between the samples. Immunohistochemistry results support this finding and show COX-1 expression only in tumor samples and COX-2 expression unchanged between normal ovary and tumor samples. PGE2 levels are significantly higher (P < 0.05) in tumor samples compared to normal ovaries, and there is no significant difference in PGE2 metabolite levels between the samples.

Conclusion: These findings may implicate COX-1 as a suitable target for the prevention or treatment of ovarian cancer.