Suppressive effects of dabrafenib on endothelial protein C receptor shedding

Metformin inhibits multiple myeloma serum-induced endothelial cell thrombosis by down-regulating miR-532

OBJECTIVES

Thrombotic complications in multiple myeloma (MM) impairs the quality of life of 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 simultaneously. The expression of tissue factor (TF) in HUVECs was detected by flow cytometry and quantitative real-time PCR (qRT-PCR). QRT-PCR was also used to determine the expressions of endothelial protein C receptor (EPCR) and miR-532. The generation of thrombin and activated protein C was measured by thrombin generation and protein C activation assays. And EPCR, extracellular signal-regulated kinase (ERK) 1/2, p38 mitogen activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathway related protein expressions were detected by western blot.

RESULT

MM serum increased the expressions of TF, EPCR and miR-532, and induced thrombin generation and protein C activation in HUVECs. Based on the MM serum treatment, metformin decreased these expressions and inhibited the thrombin generation and protein C activation in HUVECs. However, miR-532 mimic reversed the effect of metformin and promoted the levels of thrombosis related indicators in HUVECs. Moreover, metformin activated the EPCR, ERK 1/2, p38 MAPK and NF-κB pathways but miR-532 mimic suppressed the activation of pathways.

CONCLUSION

Metformin played an inhibitory effect on MM serum-induced HUVEC thrombosis, suggesting that metformin could serve as a novel antithrombotic approach for MM patients.

The suppressive effect of dabrafenib, a therapeutic agent for metastatic melanoma, in IgE-mediated allergic inflammation

The functional inhibition of mast cells, which serve as a key effector cells in allergic reactions may be a specific target for treating immunoglobulin (Ig)E-mediated allergic reactions, which occur in various allergic diseases including anaphylaxis, asthma, and atopic dermatitis. In this study, we demonstrated the effects of dabrafenib, a therapeutic agent used to treat metastatic melanoma, with a focus on mast cell activation and local cutaneous anaphylaxis. In two types of mast cells (RBL-2H3 and mouse bone marrow-derived mast cells), dabrafenib (0.01, 0.1, 1 μM) pretreatment significantly decreased IgE-induced degranulation, intracellular calcium influx, and the activity of intracellular signaling molecules, such as Lyn, Syk, Akt, and PLCγ. Dabrafenib ameliorated mRNA and protein expression levels of interleukin-4 and tumor necrosis factor-α by the reduction of nuclear localization of nuclear factor-κB and nuclear factor of activated T-cells. In passive cutaneous anaphylaxis, oral administration of dabrafenib (0.1, 1, 10 mg/kg) reduced local pigmentation and ear thickness in a dose-dependent manner. Taken together, these results suggest that dabrafenib is a therapeutic drug candidate that controls IgE-mediated allergic inflammatory diseases through suppression of mast cell activity.