Cooperation of tissue factor cytoplasmic domain and PAR2 signaling in breast cancer development

Constitutive expression of tissue factor (TF) by cancer cells triggers local activation of the coagulation cascade and promotes breast cancer progression through cell signaling involving protease activated receptor (PAR)2. In human breast cancer, TF and PAR2 are up-regulated and TF cytoplasmic domain phosphorylation is correlated with relapse. Here we show that cancer cell PAR2 signaling promotes angiogenesis independent of PAR2 phosphorylation at the recognized beta-arrestin recruitment site. Similar to PAR2(-/-) mice, TF cytoplasmic domain-deleted (TF Delta CT) mice have delayed spontaneous breast cancer development in the polyoma middle T model. Simultaneous deletion of PAR2 in TF Delta CT mice did not further delay tumor appearance, consistent with overlapping roles of TF and PAR2 in promoting the angiogenic switch in early stages of breast cancer. In advanced carcinomas, tumor-associated macrophages were reduced in TF Delta CT and TF Delta CT/PAR2(-/-) mice, and increased tumor vessel diameters of TF Delta CT mice were partially reversed by PAR2-deficiency, indicating that the TF cytoplasmic domain has additional roles that are interdependent with PAR2 signaling in regulating host angiogenic responses. These experiments demonstrate a crosstalk of tumor cell TF cytoplasmic domain and PAR2 signaling and provide a possible mechanism for the close correlation between TF phosphorylation and cancer recurrence of TF and PAR2-positive clinical breast cancer. (Blood. 2010; 116(26):6106-6113)