1. ¹Research Center for Traditional Chinese Medicine Complexity System, Shanghai University of Traditional Chinese Medicine, Shanghai, China
2. ²Department of Surgery, Shuguang Hospital, Shanghai, China
3. ³Department of Surgery, Second Military Medical University, Shanghai, China
4. ⁴Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA, USA
5. ⁵Department of Medical Microbiology and Immunology, Medical University of Ohio, Toledo, OH, USA
6. ⁶Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA, USA

Correspondence: Dr S Huang, Department of Biochemistry and Molecular Biology, Medical College of Georgia, 1459 Laney Walker Blvd., Augusta, GA 30912, USA. E-mail: shuang@mcg.edu

Received 18 December 2008; Revised 21 April 2009; Accepted 15 May 2009; Published online 22 June 2009.

Abstract

Proteinase-activated receptor 2 (PAR2) is a G protein-coupled receptor that is activated by trypsin-like proteinases. PAR2 is detected in breast tumor specimens; however, it is not clear how PAR2 level in breast cancer cell/tissues compares with normal cell/tissues. Here, we show the elevation of PAR2 protein level in 76 of 105 breast tumor specimens but only 5 of 24 normal breast tissues. PAR2 level is also higher in breast cancer cell lines than that in normal breast cells and non-cancerous breast cell lines. To determine the role of PAR2 in breast carcinogenesis, we examined the effect of PAR2 agonists on cell proliferation and migration. Our studies show that PAR2 agonists (PAR2-activating peptide and trypsin) are neither potent growth enhancers nor chemoattractants to breast cancer cells. Instead, PAR2 agonists induce significant chemokinesis. PAR2-mediated chemokinesis is G_i-dependent, and inhibiting Src kinase activity or silencing c-Src expression blocks PAR2-mediated chemokinesis. These results suggest that c-Src works downstream of G_i to mediate this PAR2 agonist-induced event. To characterize c-Src effector, we reveal that PAR2 agonists activate JNKs in a Src-dependent manner and that JNK activity is essential for PAR2-mediated chemokinesis. Moreover, PAR2 agonist stimulation leads to paxillin Ser¹⁷⁸ phosphorylation and paxillin(S178A) mutant inhibits PAR2-mediated chemokinesis. In conclusion, our studies show that PAR2 agonists facilitate breast cancer cell chemokinesis through the G_i-c-Src-JNK-paxillin signaling pathway.