Cyclooxygenase-2 (COX-2) is one of the key enzymes for the catalytic conversion of arachidonic acid to prostanoids.37 Increased COX-2 expression was associated with a more malignant phenotype, partly due to an increase in the synthesisof angiogenic factors, and partly due to the suppression of immunological host responses.38 COX-2 expression was positively correlated with aromatase expression.39 Celecoxib is a COX-2 inhibitor which has been shown to inhibit proliferation of ER-positive and-negative human breast cancer cell lines.37 This evidence concerns the gene PTGS2 and breast cancer.