Cyclo-oxygenase-2 (COX-2) mRNA expression correlates with progesterone receptor positivity in human breast cancer

Background: We previously presented evidence showing that cyclo-oxygenase 2 (COX-2) plays an important role in mammary carcinogenesis and angiogenesis in human breast cancer The present study aims to compare COX-2 mRNA expression with hormone receptor status, S-phase fraction, telomerase activity, and DNA ploidy in human breast cancer. Methods: Total cellular RNA was extracted from frozen breast tissue samples according to standard methodology. The mRNA copy numbers for COX-2 were determined in 18 infiltrating carcinomas using quantitative RT-PCR and TaqMan methodology. The oestrogen receptor (ER) and progesterone receptor (PgR) status was determined using the ligand-binding technique (ER+ = >3fmol/mg, PgR+ = >5fmol/mg). We also determined DNA ploidy status (diploid or aneuploid), S-phase fraction (<6% = low, 6-10% = intermediate, > 10% = high), and telomerase activity (total protein generated by TRAP assay). Results: The median COX-2 mRNA copy number per mug of RNA was 126 713 (range = 15717-2022050). COX-2 expression was significantly associated with PgR positivity (p = 0.013). The association between COX-2 and DNA diploidy failed to reach a statistical significance (p = 0.085). No significant association was detected between COX-2 and S-phase fraction, ER status, or telomerase activity. Conclusions: COX-2 mRNA expression is associated with PgR positivity in human breast cancer. This observation is consistent with the hypothesis that COX-2 upregulates aromatase activity.