Expression and functional activity of PAR-1 and PAR-2 in MDA-MB-231 cells. (A) MDA-MB-231 cells were probed with anti–PAR-1 (ATAP2) or anti–PAR-2 (SAM11) monoclonal antibodies, followed by FITC-labeled secondary antibody. FITC-labeled cells were analyzed by flow cytometry. Solid lines represent background fluorescence (control IgG), whereas dotted lines represent fluorescence shift attributable to PAR expression. (B) Intracellular calcium fluxes in response to PAR-1– and PAR-2–specific peptide agonists, or FVIIa. Fluo-4–loaded cells were exposed to a control medium, PAR-1–, or PAR-2–specific peptide agonists (50 μM) or FVIIa (100 nM). The resultant change in fluorescence at 520 nm after excitation at 485 nm is presented as relative fluorescence change compared with basal level fluorescence measured before the addition of compounds.