Silencing PAR-1 and PAR-2 in 4T1 cells. (A-B) Real-time PCR analysis of PAR-1 (A) and PAR-2 (B) mRNA expression in 4T1^ΔPAR-1 and 4T1^ΔPAR-2 cells expressed as a percentage of the 4T1^GFP control. PAR-1 and PAR-2 levels were normalized to HPRT mRNA. uPA protein (C) and PAI-1 protein (D) were measured by ELISA after 24 hour incubation with FXa (125nM) or thrombin (20nM). Results are shown as mean ± SEM of 3 independent experiments. *P ≤ .05 and **P ≤ .001 (4T1^GFP versus 4T1^ΔPAR-1), ^¶P ≤ .05 and ^¶¶P ≤ .001 (4T1^GFP versus 4T1^ΔPAR-2), ^§P ≤ .05 and ^§§P ≤ .001 (4T1^ΔPAR-1 versus 4T1^ΔPAR-2).