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+ = > 3 fmol/mg, PgR+ = > 5 fmol/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 micro g of RNA was 126 713 (range = 15 717-2 022 050). 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.