Changes Of ADAMTS13Activity And VWF Antigen In Patients With Acute Myelogenous Leukemia; Clinical Significance Of Circulating Microparticles In Ph-myeloproliferative Neoplasms (MPN)

Part I Changes ofADAMTS13activity and VWF antigen inpatients with acute myelogenous leukemiaBackground and Objective:ADAMTS13is a plasma protease that specifically cleaves von Willebrand factor(vWF) in the A2domain and the deficiency of ADAMTS13leads to decreased degradationof ultralarge vWF multimers that which causes the formation of intravascular plateletthrombi in patients with thrombotic thrombocytopenic purpura(TTP). Recent studies haveshown that decreased ADAMTS13activity was associated with other thrombotic diseases,inflammation, malignancy disease and so on. However, the relevant of ADAMTS13andvWF in patients with acute leukemia remains unkown. This study aimed to investigate thechanges of ADAMTS13activity and vWF antigen in patients with acute myelogenousleukemia (AML) and evaluate their clinical significance.Methods:One hundred and sixteen AML patients who were newly diagnosed in our hospitalwere enrolled in the study. Among them, there were41cases of acute promyelocyticleukemia(APL) and75cases of non-APL patients. Patients were divided into infectiongroup and (n=57) and non-infection group (n=59) according to the presence of infection.Forty patients had complication with disseminated intravascular coagulation(DIC) while76patients without DIC. The sodium citrate anticoagulated plasma was collected before and after their induction chemotherapy and40healthy person were collected as controlgroup. Fluorescence resonance energy transfer substrate vWF73(FRETS-vWF73) assaywas used to detect the plasma ADAMTS13activity while vWF antigen level was measuredby ELISA.Results:(1) ADAMTS13activity in AML patients before induction chemotherapy wassignificantly lower than normal controls:(65.5±27.2)%vs (105.0±33.8)%(P<0.01),ADAMTS13activity increased to (95.7±38.2)%after induction chemotherapy in theperiod of complete remission phase, which was significantly higher than beforechemotherapy (P<0.01), and no significant difference was seen as compared with normalcontrols(P>0.05). VWF antigen in AML patients before induction chemotherapy[(238.9±119.6)%] was higher than normal controls [(116.6±43.4)%](P<0.01); afterchemotherapy, vWF antigen decreased to (147.1±86.4)%, which was significantly lowerthan before chemotherapy group (P<0.01) and still higher than normal controls (P<0.05).(2)ADAMTS13activity in AML patients complicated with infection was significantlylower than that without infection:(57.1±28.8)%vs (73.7±24.7)%(P<0.01); while vWFantigen was higher respectively:(265.7±128.1)%vs (213.2±105.6)%(P<0.05).(3) ADAMTS13activity in AML patients before induction chemotherapy complicatedwith DIC was significantly lower than those without DIC:(46.5±19.3)%vs (75.6±26.6)%(P<0.01), while vWF antigen was higher respectively:(281.5±119.1)%vs (216.6±114.4)%(P<0.05).(4) ADAMTS13activity in APL group was significantly lower than non-APL group:(53.8±23.5)%vs (72.0±28.3)%(P<0.01). In contrast, vWF antigen exhibited a higher level:(269.5±119.4)%vs (222.5±117.2)%(P<0.05).(5) ADAMTS13activity had negative correlation with vWF antigen in patients withAML (r=-0.23, P=0.02). Multiple linear regression analysis showed that DIC, infection andthrombin time were independent risk factors for decreased ADAMTS13while DIC andinfection were independent risk factors for vWF antigen. Conclusions:(1) ADAMTS13activity was significantly lower in AML patients before inductionchemotherapy than normal controls. ADAMTS13activity increased in the period ofcomplete remission phase after induction chemotherapy while vWF decreased.(2) APL patients were associated with lower ADAMTS13activity and higher vWFantigen as compared with otherAML patients.(3) AML patients with infection or DIC presented lower ADAMTS13activity andhigher vWF antigen. ADAMTS13and VWF may play a role in the development of AMLand the formation of infection and DIC. Part II Clinical significance of circulating microparticles inPh-myeloproliferative neoplasms (MPN)Background and Objective:Philadelphia chrosome-negative MPN (Ph-MPN) is a clonal disorder which consistsof polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis(PMF). JAK2V617F mutation has an important value for the pathogenesis of Ph-MPN.Thrombosis is common complication for Ph-MPN patients. Microparticles (MPs) aremembrane vesicles shedding from various cells and they are highly procoagulant. Studieshave shown that elevated MPs was involved in cancer patients and increase rates ofthrombotic complications, role of MPs in Ph-MPN patients is not fully known. Our studyaimed to explore the alterations of red blood cell MPs (RMPs), platelet-derived MPs(PMPs), endothelial MPs (EMPs) and tissue factor–positive MPs (TF+MPs) in the patientswith Ph-MPN and to evaluate their clinical significance.Methods:A total of92patients with Ph-MPN admitted to our hospital were enrolled for thisstudy between March2012and December2013. These patients included60essential thrombocythemia (ET),20polycythaemia vera (PV), and12primary myelofibrosis (PMF).There were52females and40males with a median age of52years old. Patients weredivided into thrombosis group and (n=23) and non-thrombosis group (n=69) according tothe presence of thrombosis complication. There were55patients have JAK2V617Fmutation while47patients without JAK2V617F mutation. Venous blood was collected inthe morning, anticoagulated with sodium citrate. Platelet-poor plasma was obtained bycentrifuged at3000r/min for15minutes and stored at-80℃until assayed. Using flowcytometry, plasma samples were measured for RMPs, PMPs, EMPs and TF+MPs withphycoerythrin (PE)-conjugated monoclonal antibodies CD235a, CD61, CD62E and CD142respectively.Results:(1) Levels of RMPs, PMPs, EMPs and TF+MPs in patients with Ph-MPN was(135.2±291.60)/μl,(960.7±1539.1)/μl,(808.8±1244.5)/μl and (103.2±303.6)/μlrespectively; they were all significantly higher than healthy controls (P<0.05). Moreover,levels of all four types of MPs in PMF group showed significantly higher than PV group(P<0.05), and RMPs in PMF group was significantly higher than ET group (P<0.05).(2) Ph-MPN patients with thrombosis complication showed higher levels of all fourtypes of MPs than those without thrombosis complication: RMPs (375.9±504.5)/μl vs(54.9±72.6)/μl (P<0.01); PMPs (1989.7±2023.7)/μl vs (617.7±1169.5)/μl (P<0.01); EMPs(2000.5±1851.7)/μl vs (411.6±568.2)/μl (P<0.01); TF+MPs (268.0±566.0)/μl vs(48.2±86.5)/μl (P<0.01).(3) Ph-MPN patients with splenomegaly showed higher levels of all four types of MPsthan those without splenomegaly: RMPs (190.0±371.0)/μl vs (70.0±127.3)/μl (P<0.01);PMPs (1447.5±1873.1)/μl vs (381.2±656.8)/μl (P<0.01); EMPs (1092.1±1518.9)/μl vs(471.6±682.4)/μl (P<0.01); TF+MPs (158.0±403.4)/μl vs (38.0±45.3)/μl (P<0.01).(4) PMPs in the JAK2V617F mutation group were higher than those patients withoutmutation (P<0.05), the other three MPs showed no statistical difference between twogroups. Conclusion:Ph-MPN patients showed higher levels of all four types of MPs than normal controls,especially in patients complicated with thrombosis complication or splenomegaly.Increased MPs in PMF patients was more obvious than PV and ET group. Patients withJAK2V617F mutation showed higher number of PMPs than that without JAK2V617Fmutation. Therefore, MPs play an important role in the pathogenesis of Ph-MPN, and therelease of the MPs may promote the formation of thrombosis.