Systemic coagulation is activated in patients with meningioma and glioblastoma.

PURPOSE: Up to 30% of patients with glioblastoma (GBM) develop venous thromboembolism (VTE) over the course of the disease. Although not as high, the risk for VTE is also increased in patients with meningioma. Direct measurement of peak thrombin generation (TG) allows quantitative assessment of systemic coagulation activation in patients with GBM and meningioma. Our aim was to determine the extent of systemic coagulation activation induced by brain tumors, to measure the shift between pre- and post-operative peak TG in patients with GBM, and to assess the relationship between pre-surgical peak TG and pre-operative brain tumor volume on imaging. METHODS: Pre- and post-surgical plasma samples were obtained from successive patients with GBM and once from patients with meningioma and healthy age- and sex-matched blood donor controls. TG was measured using the calibrated automated thrombogram (CAT) assay, and tumor volumes were measured in pre-surgical MRI scans. RESULTS: Pre-surgical peak TG was higher in patients with GBM than in controls (288.6 ± 54.1 nM vs 187.1 ± 41.7 nM, respectively, P < 0.001), and, in the nine patients with GBM and paired data available, peak TG was significantly reduced after surgery (323 ± 38 nM vs 265 ± 52 nM, respectively, P = 0.007). Similarly, subjects with meningioma demonstrated higher peak TG compared to controls (242.2 ± 54.9 nM vs 177.7 ± 57.0 nM, respectively, P < 0.001). There was no association between peak TG and pre-operative tumor volume or overall survival. CONCLUSION: Our results indicate that systemic coagulation activation occurs with both meningioma and GBM, but to a greater degree in the latter. Preoperative peak TG did not correlate with tumor volume, but removal of GBM caused a significant decrease in coagulation activation.

Inhibition of protein phosphatase 2A (PP2A) prevents Mcl-1 protein dephosphorylation at the Thr-163/Ser-159 phosphodegron, dramatically reducing expression in Mcl-1-amplified lymphoma cells.

Abundant, sustained expression of prosurvival Mcl-1 is an important determinant of viability and drug resistance in cancer cells. The Mcl-1 protein contains PEST sequences (enriched in proline, glutamic acid, serine, and threonine) and is normally subject to rapid turnover via multiple different pathways. One of these pathways involves a phosphodegron in the PEST region, where Thr-163 phosphorylation primes for Ser-159 phosphorylation by glycogen synthase kinase-3. Turnover via this phosphodegron-targeted pathway is reduced in Mcl-1-overexpressing BL41-3 Burkitt lymphoma and other cancer cells; turnover is further slowed in the presence of phorbol ester-induced ERK activation, resulting in Mcl-1 stabilization and an exacerbation of chemoresistance. The present studies focused on Mcl-1 dephosphorylation, which was also found to profoundly influence turnover. Exposure of BL41-3 cells to an inhibitor of protein phosphatase 2A (PP2A), okadaic acid, resulted in a rapid increase in phosphorylation at Thr-163 and Ser-159, along with a precipitous decrease in Mcl-1 expression. The decline in Mcl-1 expression preceded the appearance of cell death markers and was not slowed in the presence of phorbol ester. Upon exposure to calyculin A, which also potently inhibits PP2A, versus tautomycin, which does not, only the former increased Thr-163/Ser-159 phosphorylation and decreased Mcl-1 expression. Mcl-1 co-immunoprecipitated with PP2A upon transfection into CHO cells, and PP2A/Aα knockdown recapitulated the increase in Mcl-1 phosphorylation and decrease in expression. In sum, inhibition of PP2A prevents Mcl-1 dephosphorylation and results in rapid loss of this prosurvival protein in chemoresistant cancer cells.

Molecular basis of purinergic signal metabolism by ectonucleotide pyrophosphatase/phosphodiesterases 4 and 1 and implications in stroke.

NPP4 is a type I extracellular membrane protein on brain vascular endothelium inducing platelet aggregation via the hydrolysis of Ap3A, whereas NPP1 is a type II extracellular membrane protein principally present on the surface of chondrocytes that regulates tissue mineralization. To understand the metabolism of purinergic signals resulting in the physiologic activities of the two enzymes, we report the high resolution crystal structure of human NPP4 and explore the molecular basis of its substrate specificity with NPP1. Both enzymes cleave Ap3A, but only NPP1 can hydrolyze ATP. Comparative structural analysis reveals a tripartite lysine claw in NPP1 that stabilizes the terminal phosphate of ATP, whereas the corresponding region of NPP4 contains features that hinder this binding orientation, thereby inhibiting ATP hydrolysis. Furthermore, we show that NPP1 is unable to induce platelet aggregation at physiologic concentrations reported in human blood, but it could stimulate platelet aggregation if localized at low nanomolar concentrations on vascular endothelium. The combined studies expand our understanding of NPP1 and NPP4 substrate specificity and range and provide a rational mechanism by which polymorphisms in NPP1 confer stroke resistance.

NPP4 is a procoagulant enzyme on the surface of vascular endothelium.

Ap3A is a platelet-dense granule component released into the extracellular space during the second wave of platelet aggregation on activation. Here, we identify an uncharacterized enzyme, nucleotide pyrophosphatase/phosphodiesterase-4 (NPP4), as a potent hydrolase of Ap3A capable of stimulating platelet aggregation and secretion. We demonstrate that NPP4 is present on the surface of vascular endothelium, where it hydrolyzes Ap3A into AMP and ADP, and Ap4A into AMP and ATP. Platelet aggregation assays with citrated platelet-rich plasma reveal that the primary and secondary waves of aggregation and dense granule release are strongly induced by nanomolar NPP4 in a concentration-dependent manner in the presence of Ap3A, while Ap3A alone initiates a primary wave of aggregation followed by rapid disaggregation. NPP2 and an active site NPP4 mutant, neither of which appreciably hydrolyzes Ap3A, have no effect on platelet aggregation and secretion. Finally, by using ADP receptor blockade we confirm that NPP4 mediates platelet aggregation via release of ADP from Ap3A and activation of ADP receptors. Collectively, these studies define the biologic and enzymatic basis for NPP4 and Ap3A activity in platelet aggregation in vitro and suggest that NPP4 promotes hemostasis in vivo by augmenting ADP-mediated platelet aggregation at the site of vascular injury.

Refractory heparin induced thrombocytopenia with thrombosis (HITT) treated with therapeutic plasma exchange and rituximab as adjuvant therapy.

We report a case of refractory heparin-induced thrombocytopenia with thrombosis (HITT) with prolonged thrombocytopenia and multiple thrombotic complications that failed to improve despite aggressive treatment. A 60 year old female with a prior history of venous thromboembolism was admitted with an acute pulmonary embolism, and developed HITT after several days on heparin therapy. She suffered multiple complications including bilateral venous limb gangrene, acute renal failure, and refractory thrombocytopenia, leading us to use multimodality therapy including therapeutic plasma exchange (TPE) and rituximab immunosuppression. The patient had transient improvements in her thrombocytopenia with TPE, and rituximab was added in an attempt to reduce antibody production. She eventually required bilateral limb amputation, and only after removal of the gangrenous limbs did her platelet count show sustained improvement. We discuss the possible contribution of infection to her prolonged course.

ABO incompatible platelets: risks versus benefit.

PURPOSE OF REVIEW: The importance of ABO blood group system compatibility in platelet transfusion is a subject of ongoing debate. Although there are theoretical advantages to pursuing a strict policy of providing exclusively ABO-compatible products, resource challenges may make this untenable for many transfusion services. Moreover, data supporting a net clinical benefit for this practice have been lacking. This review summarizes recent developments in the area of ABO compatibility and platelet transfusion and examines the risks and benefits associated with transfusion practices allowing for platelet ABO incompatibility. RECENT FINDINGS: ABO-major incompatible transfusions are associated with lower platelet count increments than either ABO identical or minor incompatible transfusions and may lead to decreased intervals between platelet transfusions in thrombocytopenic patients. ABO-minor incompatible transfusions may rarely result in acute hemolytic reactions that are not predicted by isohemagglutinin titers. Yet published evidence to date does not clearly demonstrate improvements in clinical outcomes for patients receiving ABO-identical or ABO-compatible platelets. Adherence to a strict policy of transfusing exclusively ABO-identical platelets may lead to an increase in product wastage and challenges in maintaining adequate platelet availability. SUMMARY: There is presently limited data and no consensus on the best approach for managing ABO compatibility in platelet transfusions. Well designed, sufficiently powered randomized clinical trials are urgently needed. These studies must examine not only safety and efficacy of various ABO matching strategies but also clinical benefit and resource utilization in order to identify optimal platelet transfusion strategies.

Plasma cell variant of Castleman lymphadenopathy presenting as an adrenal mass.

Adrenal masses are commonly found on radiographic studies performed for unrelated reasons. We report on a case of a non-functioning adrenal mass from which a needle biopsy showed a nonspecific infiltrate of polyclonal plasma cells and small lymphocytes. A definitive diagnosis of the plasma cell variant of Castleman lymphadenopathy was made only after surgical excision. While the hyaline vascular variant of Castleman lymphadenopathy has been identified in adrenal glands, this is the first report of the plasma cell variant in an adrenal mass. This case particularly underscores the importance of an excisional biopsy for proper diagnosis.

Severe acquired platelet dysfunction because of primary myelofibrosis with full functional and morphological recovery after allogeneic hematopoietic cell transplantation.

: Primary myelofibrosis (PMF) is a clonal hematopoietic stem cell disorder characterized by fibrosis of the marrow cavity, marked megakaryocyte atypia and progressive cytopenias. Although thrombosis predominates, bleeding is the primary manifestation in up to 20% of patients and may be life-threatening. In this report, we document restoration of megakaryocyte and platelet structure and function in PMF after allogeneic hematopoietic cell transplantation (HCT). A 59-year-old man presented with recurrent episodes of postoperative bleeding preceding a diagnosis of primary myelofibrosis (PMF). Platelet aggregation and secretion studies showed abnormal responses to all agonists tested (epinephrine, ADP, arachidonic acid, U46619, collagen, ristocetin) despite the presence of thrombocytosis. After an allogeneic HCT, platelet morphology and function studies were all normal. The pathophysiology of platelet dysfunction in myeloid neoplasia is not well understood but, as highlighted in our report, restoration of platelet function by HCT supports a clonal process involving an early hematopoietic progenitor cell.

Histopathologic and molecular aspects of CD56+ natural killer/ T-cell lymphoma of the testis.

Primary nasal-type natural killer/T-cell lymphoma of the testis is a rare malignancy. Although dissemination to the testis from other sites occurs somewhat more frequently than a primary presentation, even secondary testicular involvement is uncommon. In this article, the authors report on the comprehensive histopathologic, immunohistochemical, and molecular analysis of a case of primary testicular nasal-type natural killer/T-cell lymphoma, and review the features of 16 previously reported patients. The investigation carried out in this study indicates that the testicular nasal-type natural killer/T-cell lymphomas occur at a younger age than their B-cell counterparts, express cytoplasmic CD3 and surface CD56, and consistently show an infection by Epstein-Barr virus. These tumors have variable expression of T-cell antigens other than cytoplasmic CD3 and may show monoclonal rearrangement of T-cell receptor genes. Testicular natural killer/T-cell lymphomas of nasal type invariably follow an aggressive clinical course.

Association of factor V activity with risk of venous thromboembolism and atherothrombotic cardiovascular events: A retrospective population-based cohort study.

INTRODUCTION: Factor V (FV) deficiency is a rare inherited coagulation disorder associated with bleeding tendency. As a result, it has been postulated that decreased FV activity may confer protection against venous thromboembolism and atherothrombotic cardiovascular events. MATERIALS AND METHODS: Using the electronic database of the largest health care provider in Israel, we identified all adult individuals who were tested for FV activity between January 2004 and June 2017. Subjects with liver cirrhosis or FV Leiden mutation were excluded. FV activity was classified into three predefined categories; FV activity >50%, FV activity 30-50%, and FV activity ≤30%. Patients were followed from January 2004 to June 2017 for new atherothrombotic cardiovascular events (composite of myocardial infarction, stroke, and TIA) and venous thromboembolism (VTE). RESULTS: Overall 2021 individuals were included; 83.2% had FV activity >50%, 9.6% FV activity 30-50%, and 7.2% had FV activity ≤30%. Compared to individuals with FV activity >50% the adjusted HR for atherothrombotic cardiovascular events was 1.10 (95% CI, 0.63-1.90) in those with FV activity 30-50%, and 0.95 (0.49-1.8) in those with FV activity ≤30%. None of the patients with FV activity 30-50% had VTE during follow-up; therefore those with FV activity ≤50% were classified into one group. VTE incidence was lower in those with FV activity ≤50% compared to those with FV >50% activity; adjusted HR = 0.28 (0.09-0.91). CONCLUSION: This study suggests that decreased FV activity might be associated with decreased incidence of VTE. No significant association appears to exist between FV activity and atherothrombotic cardiovascular events.

Factor V Inhibitors: A Diagnostic and Therapeutic Challenge.

Historically, inhibitors to coagulation factor V (FV) most often have developed in patients treated with bovine thrombin, a topical hemostatic agent used during surgical procedures. With the advent of newer hemostatic agents, and the concurrent diminished use of bovine thrombin, the incidence of FV inhibitors has fallen. Nevertheless, FV inhibitors are occasionally seen on an idiopathic basis as well as in association with medications, malignancies, autoimmune disorders, pregnancy, and infections. Factor V inhibitors may present with life-threatening bleeding or thrombosis, or they may be discovered incidentally as a coagulation screening test abnormality. Management of patients with FV inhibitors is challenging and consists of control of bleeding and eradication of the inhibitor. In this short overview we review the role of platelet and plasma FV in hemostasis and discuss the unique characteristics, clinical features, diagnosis, treatment, and prognosis associated with FV inhibitors.

Fatal hemorrhage due to a spontaneous factor V inhibitor with lupus anticoagulant properties.

: Factor V inhibitors are rare and have varied clinical presentations. We report on a 76-year-old female admitted to the hospital for pneumonia and treated with multiple antibiotics. Her baseline prothrombin time was 15.6 s and the activated partial thromboplastin time was 35 s. On admission day 10, she developed arm weakness and brain imaging showed a subdural hematoma. The prothrombin time was now 59.1 s with an activated partial thromboplastin time of more than 160 s and a normal thrombin time. A mixing study did not correct the clotting times and coagulation factor assays showed a nonspecific inhibition pattern. Only factor V activity remained low with serial dilutions, however, and a 70 Bethesda Unit inhibitor was identified. Aggressive supportive care was initiated but the patient succumbed to the effects of the intracranial hemorrhage. Factor V inhibitors may display lupus anticoagulant properties and may cause catastrophic bleeding. Our case illustrates that these inhibitors can arise quickly and supports an association with antibiotics.