Pattern of Coagulation Activation in Patients with Myeloproliferative Neoplasms

Background: Myeloproliferative neoplasms (MPN), comprising essential thrombocythemia (ET), polycythemia vera (PV) and myelofibrosis (MF), are associated with a high incidence of venous thromboembolism (VTE), especially splanchnic vein thrombosis (SVT), but the etiology of a hypercoagulable state in MPN remains elusive. JAK2^V617F-associated development of acquired protein C (APC) resistance has been reported, suggesting an alteration of the thrombin-protein C (PC) axis.

Methods: To further study the impact of the thrombin-PC axis on hypercoagulability in MPN, plasma levels of thrombin and APC were measured using oligonucleotide-based enzyme capture assays (OECA) in prospectively collected samples from 21 MPN patients (10 females) with a history of VTE (thereof 17 with SVT) and 24 MPN patients (13 females) without VTE. In addition to the OECA, markers of coagulation and fibrinolysis were measured including prothrombin activation fragment F1+2, D-dimer, plasmin-α2-antiplasmin complex (PAP), and thrombin-antithrombin-complex (TAT). All but one patient with prior VTE and 21 patients (88%) without prior thrombosis were positive for the JAK2^V617F or the CALR mutation. Due to repeated study visits over a period of 21 months, a total of 35 samples from patients with a history of thrombosis and 46 from patients without VTE were available for analysis. Another comparison was performed between patients under anticoagulant treatment (17 patients, 27 samples) vs no anticoagulant treatment (28 patients, 54 samples). Furthermore, the results obtained in MPN patients were compared to those in 43 healthy subjects (22 females) who acted as a control group.

Results: All biomarkers were significantly increased in MPN patients compared to healthy controls (Table 1). ANOVA neither revealed a difference between the disease subgroups of MF, PV, and ET nor between MPN patients with and without a history of VTE. In both patients with and without prior VTE APC, D-Dimer, F1+2, and PAP were significantly increased: Plasma levels of APC (median, IQR) of 0.078 (0.033-0.146) ng/mL, D-Dimer of 0.45 (0.29-0.67) mg/L, F1+2 of 0.219 (0.138-0.499) nmol/L, and PAP of 195 (118-453) ng/mL were measured in MPN patients with prior VTE. In patients without a history of thrombosis APC was 0.063 (0.026-0.108) ng/mL, D-dimer 0.33 (0.27-0.54) mg/L, F1+2 0.247 (0.146-0.381) nmol/L, and PAP 321 (175-526) ng/mL. The same pattern was observed in samples from patients without anticoagulant treatment, whereas in MPN patients under anticoagulants only APC (0.103, 0.027-0.137 ng/mL, p=0.0014), D-dimer (0.35, 0.23-0.60 mg/L, p=0.0022) and PAP (202, 144-423 ng/mL, p=0.0108), but not F1+2 (0.152, 0.098-0.219 nmol/L) were increased in comparison to the healthy control group. Consistent with these findings, F1+2 was the only biomarker, that differed significantly (p=0.0021) between MPN patients with anticoagulant therapy and patients not receiving anticoagulant medication (0.296, 0.185-0.502 nmol/l).

Conclusion: The obtained data indicate, that MPN-induced thrombin formation, as demonstrated by increased levels of F1+2, causes activation of the anticoagulant PC system. In addition, the increase of PAP indicates activation of fibrinolysis which might contribute to elevated plasma levels of D-dimer. Thus, F1+2 might be better suited than D-dimer to monitor the effect of anticoagulant therapy in MPN.

View largeDownload slide

View largeDownload slide

Close modal