Proposed model of how coagulation protease activation of PAR-1 and PAR-2 regulates uPA and PAI-1 expression in mouse breast cancer cell lines. PAR-1 and PAR-2 can exist as individual receptors or in a complex. Cells, such as the 67NR cell line (left panel), express PAR-1 only whereas 4T1 cells express PAR-1 and a PAR-1/PAR-2 complex (right panel). The configuration of PAR-1 and PAR-2 determines the expression of uPA and PAI-1 in response to different coagulation proteases.