PTGS2 and breast cancer: We found that celecoxib treatment at concentrations of 40 and 60 μmol/l was able to reduce significantly the formation of channels in both breast cancer cell lines in a dose-dependent manner, as compared with vehicle treated cells (P < 0.001 for MDA-MB-231 cells and P < 0.001 for MDA-MB-468 cells; Fig. 6a), suggesting a role for COX-2 in channel formation.