Celecoxib is a COX-2 inhibitor which has been demonstrated to exert antiproliferative effects on ER-positive and-negative human breast cancer cell lines in vitro and in vivo.37 Those published observations are similar to these findings demonstrating a time and dose dependence of cell growth inhibition of MCF-7 and MDA-MB-435 cells. This evidence concerns the gene PTGS2 and breast cancer.