Growth inhibition of breast cancer cells by celecoxib

Overexpression of cyclooxygenase-2 (COX-2) has been found in several tumor types including colorectal, lung, and head and neck cancers. Previously we have shown that COX-2 is expressed in 87% of primary breast tumors. The purpose of this study was to assess the affect of selective COX-2 inhibitor celecoxib on in vitro breast cancer cell growth. Methods: Breast cancer cell line MDA-MB-231, a cell line with constitutive COX-2 expression, was plated 1×10³cells/well in 96-well plates, in duplicate. Cells were allowed to attach for 24 hours, and then cultured in the absence or presence of 12.5-50 mM celecoxib. After 48 hours of exposure, the effect on cell growth was studied by 3[H] thymidine incorporation assay and MTT assay, in the presence of appropriate concentrations of celecoxib. The treated groups were compared to control cells with a Student t-test (2-tailed). A p value less than 0.05 was considered significant. Results: Celecoxib had a dose-dependent inhibitory effect on cell proliferation as determined by 3[H] thymidine incorporation assay. This inhibition was statistically significant for all doses of celecoxib tested, and was as high as 20-fold. The MTT assay demonstrated a 56% decrease in viable cells in the 50 mM-treated group compared with the control group (p=0.006). Conclusions: Our preliminary studies suggest that celecoxib has a growth inhibitory effect on COX-2 expressing breast cancer cells in vitro. The role of selective COX-2 inhibitors in breast cancer therapy, alone or in combination with other cytotoxic agents and its role in chemoprevention of breast cancer needs to be further explored.