F2R and cancer: To demonstrate the potential of our newly designed inhibitor of PAR1-activating proteinases present in the tumor microenvironment, we investigated its ability to inhibit PAR1 activation in PAR1-overexpressing cancer cells, and to block the migration and invasion of human melanoma cells lines that endogenously expresses PAR1 17, namely, WM3682 and the highly invasive line WM3314.