Fujimoto et al. BMC Cancer 2010, 10:443 http://www.biomedcentral.com/1471-2407/10/443 induced tyrosine phospholyration of EGFR in renal car- cinoma cells [20]. We also confirmed that the EGFR itself was elevated in response to PAR1 activation in gastric carcinoma cells (Figures 9, 10 &13). Since the EGF-like sequence repeats derived from TN-C can act as agonists for the EGFR in terms of MAPK activation [34], it is tempting to speculate that secreted TN-C might act as an autocrine activator of the EGFR to enhance the mitogenic effect of PAR1 activation. Further, the high-molecular-weight fractions recovered from the conditioned medium of a-thrombin-stimulated MKN45/PAR1 cultures were able to enhance the phos- phorylation of the EGFR (Figure 14 &15), in keeping with the hypothesis that the a-thrombin-stimulated cells can produce autocrine factors that can activate the EGFR. That TN-C itself represents that factor is an open question, since even the TN-C derived EGF repeat sequences do not significantly trigger EGFR autopho- sphorylation, although they do trigger EGFR-mediated activation of MAPK [34]. Further, it is not yet known if the EGF-like repeats in TN-C can activate the EGFR when present in the intact TN-C sequence. Notwith- standing, the high-molecular-weight fraction from the MKN45/PAR1 concentrates were able to induce EGFR phosphorylation, and the TN-C-targeted-neutralizing antibody significantly reduced that effect (Figure 14 &15). The data thus imply an autocrine role for TN-C in cancer cells that clearly merits further work to eluci- date the mechanism. TN-C, an adhesion modulatory extracellular matrix molecule, is implicated in signal transduction, proliferation and invasion in various can- cers [35-38]. Our results showed that TN-C was involved in the PAR1-mediated EGFR transactivation in cancer cells for the first time. Conclusion Finally, we showed that the signaling pathways that responded to PAR1 activation involving the activation of NF- B and transactivation of EGFR, which might be sti- mulated by TN-C, resulted in an increase in gastric can- cer cell proliferation and invasion. These data indicate that PAR1 is deeply associated with gastric cancer pro- gression, and thus a very attractive novel therapeutic target for blocking the progression of invasive and meta- static gastric cancers. Acknowledgements This study was supported in part by Grant-in-Aid 14770636 for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan to Y.H. Author details 1First Department of Surgery, Faculty of Medicine and Division of Bioresearch Laboratories, University of Fukui, Fukui, 910-1193, Japan. 2Centers for Advanced Research Support, University of Fukui, Fukui, 910-1193, Japan. 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