Thrombotic characteristics of extracellular vesicles derived from prostate cancer cells.

BACKGROUND: Prostate cancer (PC) patients in advanced stages of the disease have high risk of blood coagulation complications. The procoagulant molecule Tissue factor (TF), and the fibrinolysis inhibitor plasminogen activator inhibitor-1 PAI-1 play important role in this complication. Extracellular vesicles (EV) shed from cancer cells may contribute to the regulation of TF and PAI-1. The procoagulant activity of EV can be associated with the oncogenic and metastatic characteristics of their cells.

METHODS: We have expressed EGFRvIII in DU145 cells to assess the role of this oncogene in the procoagulant activity of EV. The intercellular exchange of TF via EV was assessed by downregulating its expression in DU145 cells using shRNA vector, and determining the transfer of TF via EV enriched with the protein. Two PC cell lines with different metastatic potential were used to assess the correlation between the procoagulant activity of EV and the metastatic potential of PC cells. Photometric assays were used to determine FXa-activity and thrombin generation as indicators for the procoagulant activity of EV. Double-tagged proteinase-activated receptor 1(PAR-1) expressed in CHO cells to assess its activation by EV.

RESULTS: The expression of EGFRvIII in DU145 cells led to increased mRNA levels for TF and PAI-1, but the increase in these proteins expression was detected mostly in the EV. EV with enhanced levels of TF protein conferred higher TF procoagulant activity on the acceptor cells by intercellular exchange of this protein. Procoagulant activity of EV, assessed by FXa activity, and thrombin generation, was correlated with the oncogenic and metastatic potential of PC cells. The ability of EV to generate thrombin led to the activation of PAR-1, which was evident by the truncation of tagged-PAR-1.

CONCLUSION: The active oncogene EGFRvIII increases the concentration of TF and PAI-1 in EV. The procoagulant activity of EV is associated with the oncogenic and metastatic characteristics of their PC cells. Also, EV may contribute to the high procoagulant activity in the tumour microenvironment by the intercellular exchange of TF. Finally, through the generation of thrombin, EV can activate PAR-1, which evidently contributes to cancer progression, linking the coagulation system to tumor progression.