Quantitative analysis of breast cancer tissue microarrays shows high Cox-2 expression is associated with poor outcome

Epidemiologic and preclinical studies suggest that cyclooxygenase-2 ( Cox-2) may promote tumor growth and spread by affecting angiogenesis and apoptosis in breast cancer. Using a tissue microarray ( TMA), we analyzed the expression and subcellular localization of Cox- 2 by AQUA and X-tile, our algorithms for quantitative analysis of protein expression and determination of optimal cutpoints. Our TMA consisted of 669 Stage I - III primary breast cancers. The total tumor and subcellular expression of Cox- 2 were then correlated with clinicopathologic factors and with survival. Cox- 2 expression appeared higher in malignant than in benign tissue and was predominantly membrane/cytoplasmic ( i.e. non-nuclear). X-tile determines an optimum cutpoint on a training set then uses this cutpoint on a validation set. This cutpoint was 19.3 ( top 44 percent defined as positive) with high nonnuclear Cox- 2 expressers having significantly worse survival. Cox- 2 expression also was inversely associated with estrogen receptor ( ER) and progesterone receptor ( PR), and directly associated with nuclear grade. Multivariate analysis showed that Cox- 2 remained a significant prognostic factor for survival independent of tumor size, nodal status, ER, Her2/neu, and grade. In summary, Cox- 2 is overexpressed in breast neoplasms, is associated with other markers of poor prognosis, and is significantly associated with worse survival independent of known prognostic factors. Furthermore, AQUA and X-tile analysis suggest an optimal cutpoint that may be helpful in future investigations of Cox- 2 and specifically, in studies looking at its expression as a predictive biomarker in clinical trials of Cox- 2 inhibitors in breast cancer.