Induction of CXCR3 binding ligands in human breast cancer cell lines by inflammatory cytokines. MCF-7 and MDA-MB 231 breast cancer cells were starved in serum-free medium for 24 hours and then exposed for another 24 hours to the IFN-γ and TNF-α concentrations indicated. Supernatants were harvested, and CXCL9 and CXCL10 concentrations determined by ELISA. Results from at least three independent experiments are presented. (a to d) In each experiment cells in at least six different wells were stimulated in parallel. IFN-γ induced both chemokines in a dose-dependent manner. (c and d) In contrast, TNF-α had a measurable effect on CXCL10 only. (a to d) Addition of TNF-α to IFN-γ potentiates the interferon effect. This is more pronounced in MCF-7 than in MDA-MB 231 cells. Statistical significance was defined as * P≤0.05, ** P≤0.005, or *** P≤0.0005.