Figure 5

Growth inhibition of MDA-MB-468 cells was abrogated by exogenous prostaglandin (PG)E₂ addition. [³H]thymidine uptake assay was done to determine proliferation of (a) MDA-MB-231 and (b) MDA-MB-468 cells treated with 40 μmol/l celecoxib with or without varying amounts of exogenous PGE₂ (12.5–200 pg/ml). Cells were harvested after 96 hours in culture. In MDA-MB-231 cells, growth inhibition induced by 40 μmol/l celecoxib could not be restored by addition of exogenous PGE₂; however, addition of 200 pg/ml PGE₂ completely reversed the growth inhibition induced by 40 μmol/l celecoxib in the less invasive MDA-MB-468 cells. Average values of three experiments ± standard deviation is shown. P values represent significant differences between vehicle control and celecoxib treatment.