Induction of CXCR3 ligand release from breast cancer cells by unselective cyclooxygenase inhibitors. (a) Expression of COX-1 and COX-2 isoenzymes in MCF-7 and MDA-MB 231 cells. Representative western blots of lysates prepared from unstimulated and IFN-γ (10 ng/mL, 24 hours) exposed cells using monoclonal antibodies against the two COX isoenzymes. MCF-7 cells showed only weakly inducible COX-2 expression, whereas MDA-MB 231 cells expressed both COX-1 and COX-2, the latter one further induced by IFN-γ. In MCF-7 and in MDA-MB 231 cells, the COX-2 directed antibody shows two bands at 72 and 74 kDa which represent two different glycosylation states . (b to e) MCF-7 and MDA-MB 231 cells were preincubated with vehicle or various concentrations of ASA or indomethacin, 30 minutes before IFN-γ (50 ng/mL for MCF-7, 2.5 ng/mL for MDA-MB 231) was added. After 24 hours, cell supernatants were collected and CXCR3 ligand concentrations determined by ELISA. In both cell lines, both unselective COX inhibitors significantly enhance CXCL9 or CXCL10 secretion. (c and e) This effect was more pronounced for CXCL10, where the induction was about two- to three-fold of the control value. (b and d) For CXCL9, indomethacin was a more potent inducer than ASA. Asterisks mark significant differences compared with the control.