The role of plasmin in the pathogenesis of murine multiple myeloma.

Aside from a role in clot dissolution, the fibrinolytic factor, plasmin is implicated in tumorigenesis. Although abnormalities of coagulation and fibrinolysis have been reported in multiple myeloma patients, the biological roles of fibrinolytic factors in multiple myeloma (MM) using in vivo models have not been elucidated. In this study, we established a murine model of fulminant MM with bone marrow and extramedullar engraftment after intravenous injection of B53 cells. We found that the fibrinolytic factor expression pattern in murine B53 MM cells is similar to the expression pattern reported in primary human MM cells. Pharmacological targeting of plasmin using the plasmin inhibitors YO-2 did not change disease progression in MM cell bearing mice although systemic plasmin levels was suppressed. Our findings suggest that although plasmin has been suggested to be a driver for disease progression using clinical patient samples in MM using mostly in vitro studies, here we demonstrate that suppression of plasmin generation or inhibition of plasmin cannot alter MM progression in vivo.