Abstract 3022: PAR-2 activation is required for cancer stem cells maintenance through upregulation of POSTN

Abstract

Abstract Backgrounds: PARs are seven transmembrane-spanning domain G-protein coupled receptors (GPCRs) which act as targets of certain serine proteinases, such as thrombin and trypsin. PAR2 is the only member in the family which cannot be activated by thrombin. The studies in knockout mice revealed that PAR2 plays more important roles in tumor formation compared to other PARs. Aims: To investigate the roles of PAR2 activation in cancer stem cell maintenance and possible mechanisms. Methods and Results: In human colorectal cancer samples, PAR2 was significantly correlated with CD133 at mRNA level measured with real time PCR. With six colorectal cancer cell lines, it was found that the cell line with higher level of PAR2 expression presents higher rate of CD133+ cells and vice versa. To test whether PAR2 is required for cancer stem cell, we developed cell lines with knock down of PAR2 stablely. It was found that inhibition of PAR2 expression in cancer cells not only reduced the level of CD133 but also significantly blocked the ability of sphere formation in vitro. In addition, we found that PAR2 activation induced the expression of POSTN, which is a well established secreted protein related to cancer stem cell maintenance. Deficiency of PAR2 in cancer cell also reduced the level of POSTN. More importantly, recombinant POSTN protein was able to restore the ability of sphere formation decreased by PAR2 deficiency in cancer cells. Furthermore, Activation of PAR2 caused TGFβ activation without affecting levels of total TGFβ. Given that TGFβ(5ng/ml) only could stimulate POSTN expression, it is very possible that PAR2 stimulates POSTN expression through TGFβ-related pathway. Finally, to test the role of PAR2-induced POSTN in cancer stem cell maintenance in vivo, we measured the correlation of PAR2 and POSTN in paired primary and metastatic ovarian cancer samples. Not surprisingly, significant correlation of PAR2 and POSTN expression was only observed in metastatic ovarian cancer group, which express significant higher level of cancer stem cell-related genes compared with primary group. Conclusion: Our study strongly indicated that PAR2 activation was involved in cancer stem cell maintenance through TGFβ- mediated POSTN expression. Citation Format: Yiming Ma, Hongying Wang. PAR-2 activation is required for cancer stem cells maintenance through upregulation of POSTN. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3022. doi:10.1158/1538-7445.AM2014-3022