Metformin Inhibits Multiple Myeloma Serum-induced Endothelial Cell Thrombosis by Down-Regulating miR-532

Background: Thrombotic complications in multiple myeloma (MM) impairs the quality of life in patients. Metformin has a certain effect on anti-thrombosis, but its role and mechanism in MM -induced thrombosis are still uncovered. Therefore, this study evaluated the effect of metformin on MM-induced thrombosis.Methods: Human umbilical vein endothelial cells (HUVECs) were exposed to normal serum (15%), MM serum (15%), metformin (0.01 mmol/L), or MM serum, and metformin simulta-neously. The expression of tissue factor (TF) in HUVECs was detected by flow cytometry and quantitative real-time polymerase chain reaction PCR (qRT-PCR). QRT-PCR was also used to determine the expressions of endothelial protein C receptor (EPCR) and miR-532. The gen-eration of thrombin and activated protein C was measured by thrombin generation and protein C activation assays. EPCR, extracellular signal-regulated kinase (ERK) 1/2, p38 mitogen activated protein kinase (MAPK) and nuclear factor -KB (NF -KB) pathway related protein expressions were detected by western blot.Results: MM serum increased the expressions of TF and miR-532, induced thrombin genera-tion, inhibited EPCR and protein C activation in HUVECs. And metformin could reverse the effects of MM serum on the expressions of TF, EPCR and miR-532, thrombin generation, protein C activation in HUVECs. However, miR-532 mimic reversed the effects of metformin and pro-moted the levels of thrombosis-related indicators in HUVECs. Moreover, metformin activated the ERK 1/2, p38 MAPK, and NF -KB pathways but miR-532 mimic suppressed the pathway activation.Conclusions: Metformin played an inhibitory effect on MM serum-induced HUVEC thrombosis, suggesting that metformin could serve as a novel antithrombotic approach for MM patients.