F2RL1 and breast cancer: Moreover, blocking antibodies directed at PAR-2 but not PAR-1 were shown to attenuate tumor growth and metastasis in a breast xenograft model [6], and shRNA-mediated silencing of PAR-2 but not PAR-1 mRNA in breast cancer cells showed a specific role of PAR-2 in promoting the malignant cell phenotype [7].