Platelet Function, Role in Thrombosis, Inflammation, and Consequences in Chronic Myeloproliferative Disorders.

Platelets are conventionally defined as playing a vital role in homeostasis and thrombosis. This role has over the years transformed as knowledge regarding platelets has expanded to include inflammation, cancer progression, and metastasis. Upon platelet activation and subsequent aggregation, platelets release a host of various factors, including numerous pro-inflammatory factors. These pro-inflammatory factors are recruiters and activators of leukocytes, aiding in platelets' immune regulating function and inflammatory function. These various platelet functions are interrelated; activation of the inflammatory function results in thrombosis and, moreover, in various disease conditions, can result in worsened or chronic pathogenesis, including cancer. The role and contribution of platelets in a multitude of pathophysiological events during hemostasis, thrombosis, inflammation, cancer progression, and metastasis is an important focus for ongoing research. Platelet activation as discussed here is present in all platelet functionalities and can result in a multitude of factors and signaling pathways being activated. The cross-talk between inflammation, cancer, and platelets is therefore an ideal target for research and treatment strategies through antiplatelet therapy. Despite the knowledge implicating platelets in these mentioned processes, there is, nevertheless, limited literature available on the involvement and impact of platelets in many diseases, including myeloproliferative neoplasms. The extensive role platelets play in the processes discussed here is irrefutable, yet we do not fully understand the complete interrelation and extent of these processes.

Lymphopenia in hospitalized patients and its relationship with severity of illness and mortality.

BACKGROUND: Lymphopenia is associated with various pathologies such as sepsis, burns, trauma, general anesthesia and major surgeries. All these pathologies are clinically expressed by the so-called Systemic Inflammatory Response Syndrome which does not include lymphopenia into defining criteria. The main objective of this work was to analyze the diagnosis of patients admitted to a hospital related to lymphopenia during hospital stay. In addition, we investigated the relationship of lymphopenia with the four levels of the Severity of Illness (SOI) and the Risk of Mortality (ROM). METHOD AND FINDINGS: Lymphopenia was defined as Absolute Lymphocyte Count (ALC) <1.0 x109/L. ALC were analyzed every day since admission. The four levels (minor, moderate, major and extreme risk) of both SOI and ROM were assessed. A total of 58,260 hospital admissions were analyzed. More than 41% of the patients had lymphopenia during hospital stay. The mean time to death was shorter among patients with lymphopenia on admission 65.6 days (CI95%, 57.3-73.8) vs 89.9 (CI95%, 82.4-97.4), P<0.001. Also, patients with lymphopenia during hospital stay had a shorter time to the mortality, 67.5 (CI95%, 61.1-73.9) vs 96.9 (CI95%, 92.6-101.2), P<0.001. CONCLUSIONS: Lymphopenia had a high prevalence in hospitalized patients with greater relevance in infectious pathologies. Lymphopenia was related and clearly predicts SOI and ROM at the time of admission, and should be considered as clinical diagnostic criteria to define SIRS.

Molecular pathogenesis of the myeloproliferative neoplasms.

The Philadelphia negative myeloproliferative neoplasms (MPN) compromise a heterogeneous group of clonal myeloid stem cell disorders comprising polycythaemia vera, essential thrombocythaemia and primary myelofibrosis. Despite distinct clinical entities, these disorders are linked by morphological similarities and propensity to thrombotic complications and leukaemic transformation. Current therapeutic options are limited in disease-modifying activity with a focus on the prevention of thrombus formation. Constitutive activation of the JAK/STAT signalling pathway is a hallmark of pathogenesis across the disease spectrum with driving mutations in JAK2, CALR and MPL identified in the majority of patients. Co-occurring somatic mutations in genes associated with epigenetic regulation, transcriptional control and splicing of RNA are variably but recurrently identified across the MPN disease spectrum, whilst epigenetic contributors to disease are increasingly recognised. The prognostic implications of one MPN diagnosis may significantly limit life expectancy, whilst another may have limited impact depending on the disease phenotype, genotype and other external factors. The genetic and clinical similarities and differences in these disorders have provided a unique opportunity to understand the relative contributions to MPN, myeloid and cancer biology generally from specific genetic and epigenetic changes. This review provides a comprehensive overview of the molecular pathophysiology of MPN exploring the role of driver mutations, co-occurring mutations, dysregulation of intrinsic cell signalling, epigenetic regulation and genetic predisposing factors highlighting important areas for future consideration.

Current Concepts of Pathogenesis and Treatment of Philadelphia Chromosome-Negative Myeloproliferative Neoplasms.

Philadelphia chromosome-negative myeloproliferative neoplasms are hematopoietic stem cell disorders characterized by dysregulated proliferation of mature myeloid blood cells. They can present as polycythemia vera, essential thrombocythemia, or myelofibrosis and are characterized by constitutive activation of JAK2 signaling. They share a propensity for thrombo-hemorrhagic complications and the risk of progression to acute myeloid leukemia. Attention has also been drawn to JAK2 mutant clonal hematopoiesis of indeterminate potential as a possible precursor state of MPN. Insight into the pathogenesis as well as options for the treatment of MPN has increased in the last years thanks to modern sequencing technologies and functional studies. Mutational analysis provides information on the oncogenic driver mutations in JAK2, CALR, or MPL in the majority of MPN patients. In addition, molecular markers enable more detailed prognostication and provide guidance for therapeutic decisions. While JAK2 inhibitors represent a standard of care for MF and resistant/refractory PV, allogeneic hematopoietic stem cell transplantation remains the only therapy with a curative potential in MPN so far but is reserved to a subset of patients. Thus, novel concepts for therapy are an important need, particularly in MF. Novel JAK2 inhibitors, combination therapy approaches with ruxolitinib, as well as therapeutic approaches addressing new molecular targets are in development. Current standards and recent advantages are discussed in this review.

Current clinical strategies and emergent treatment landscapes in leukemic transformation of Philadelphia-negative myeloproliferative neoplasms.

Introduction: Transformation to acute myeloid leukemia (AML) of Philadelphia chromosome-negative (Ph-) chronic myeloproliferative neoplasms (MPN) represents a challenging medical concern and an unmet clinical need, since it charts a very poor outcome and a low rate of response to standard treatments with the exception of allogeneic hematopoietic stem cell transplantation (HSCT). Recent novel insights into the molecular disease pathways and the genomic features characterizing the transformation of Ph-MPN have led to new therapeutic individualized approaches with the potential to modify the clinical management of these difficult-to-treat patients. Areas covered: Literature review (MeSH headings/PubMed) of risk factors of MPNs progression and treatment options for transformed disease with traditional standard approaches, and novel and investigational agents was performed. One or combinations of related subject headings like transformed MPN, epigenetics, molecular alterations, HSCT, ruxolitinib, azacytidine, decitabine, gliterinib, novel agents, personalized therapy was screened. Informative papers were selected by the appropriate actual evidence and suggesting strategies for improving outcomes in the future. Expert opinion: Current and emerging treatments for transformed Ph-MPN, are presented. Novel targeted or experimental agents to be used both before HSCT, to induce blast-free state, or to modify the disease prognosis and improve survival and quality of life are critically reviewed.

Clinical course and short-term outcome of postsplenectomy reactive thrombocytosis in children without myeloproliferative disorders: A single institutional experience from a developing country.

OBJECTIVES: To evaluate the clinical outcome and complications in the pediatric population who had splenectomy at our institution, emphasizing the incidence of postplenectomy reactive thrombocytosis (RT) and its clinical significance in children without underlying hematological malignancies. MATERIALS AND METHODS: The medical records of pediatric patients undergoing splenectomy were retrospectively reviewed for the period 1999-2018. The following variables were analyzed: Demographic parameters (age, sex), indications for surgery, operative procedures, preoperative and postoperative platelet count (postplenectomy RT), the use of anticoagulant therapy, and postoperative complications. The patients were divided into two groups according to indications for splenectomy: The non-neoplastic hematology group and the non-hematology group (splenectomy for trauma or other spleen non-hematological pathology). RESULTS: Fifty-two pediatric (37 male and 15 female) patients who underwent splenectomy at our institution were reviewed. Thirty-four patients (65%) were in the non-hematological group (splenic rupture, cysts, and abscess) and 18 patients (35%) in the non-neoplastic hematological group (hereditary spherocytosis and immune thrombocytopenia). The two groups did not differ significantly in regards to the patients' age, sex, and preoperative platelet count (P>0.05 for all variables). Forty-nine patients (94.2%) developed postplenectomy RT. The percentages of mild, moderate and extreme thrombocytosis were 48.9%, 30.7%, and 20.4%, respectively. The comparisons of RT patients between the non-neoplastic hematology and the non-hematology group revealed no significant differences in regards to the patients' age, sex, preoperative and postoperative platelet counts, preoperative and postoperative leukocyte counts, and the average length of hospital stay (P>0.05 for all variables). None of the patients from the cohort was affected by any thrombotic or hemorrhagic complications. CONCLUSIONS: We confirm that RT is a very common event following splenectomy, but in this study it was not associated with clinically evident thrombotic or hemorrhagic complications in children undergoing splenectomy for trauma, structural lesions or non-neoplastic hematological disorders.

Global dynamics of healthy and cancer cells competing in the hematopoietic system.

Stem cells in the bone marrow differentiate to ultimately become mature, functioning blood cells through a tightly regulated process (hematopoiesis) including a stem cell niche interaction and feedback through the immune system. Mutations in a hematopoietic stem cell can create a cancer stem cell leading to a less controlled production of malfunctioning cells in the hematopoietic system. This was mathematically modelled by Andersen et al. (2017) including the dynamic variables: healthy and cancer stem cells and mature cells, dead cells and an immune system response. Here, we apply a quasi steady state approximation to this model to construct a two dimensional model with four algebraic equations denoted the simple cancitis model. The two dynamic variables are the clinically available quantities JAK2V617F allele burden and the number of white blood cells. The simple cancitis model represents the original model very well. Complete phase space analysis of the simple cancitis model is performed, including proving the existence and location of globally attracting steady states. Hence, parameter values from compartments of stem cells, mature cells and immune cells are directly linked to disease and treatment prognosis, showing the crucial importance of early intervention. The simple cancitis model allows for a complete analysis of the long term evolution of trajectories. In particular, the value of the self renewal of the hematopoietic stem cells divided by the self renewal of the cancer stem cells is found to be an important diagnostic marker and perturbing this parameter value at intervention allows the model to reproduce clinical data. Treatment at low cancer cell numbers allows returning to healthy blood production while the same intervention at a later disease stage can lead to eradication of healthy blood producing cells. Assuming the total number of white blood cells is constant in the early cancer phase while the allele burden increases, a one dimensional model is suggested and explicitly solved, including parameters from all original compartments. The solution explicitly shows that exogenous inflammation promotes blood cancer when cancer stem cells reproduce more efficiently than hematopoietic stem cells.

Erythrocyte-derived microvesicles induce arterial spasms in JAK2V617F myeloproliferative neoplasm.

Arterial cardiovascular events are the leading cause of death in patients with JAK2V617F myeloproliferative neoplasms (MPNs). However, their mechanisms are poorly understood. The high prevalence of myocardial infarction without significant coronary stenosis or atherosclerosis in patients with MPNs suggests that vascular function is altered. The consequences of JAK2V617F mutation on vascular reactivity are unknown. We observe here increased responses to vasoconstrictors in arteries from Jak2V617F mice resulting from a disturbed endothelial NO pathway and increased endothelial oxidative stress. This response was reproduced in WT mice by circulating microvesicles isolated from patients carrying JAK2V617F and by erythrocyte-derived microvesicles from transgenic mice. Microvesicles of other cellular origins had no effect. This effect was observed ex vivo on isolated aortas, but also in vivo on femoral arteries. Proteomic analysis of microvesicles derived from JAK2V617F erythrocytes identified increased expression of myeloperoxidase as the likely mechanism accounting for their effect. Myeloperoxidase inhibition in microvesicles derived from JAK2V617F erythrocytes suppressed their effect on oxidative stress. Antioxidants such as simvastatin and N-acetyl cysteine improved arterial dysfunction in Jak2V617F mice. In conclusion, JAK2V617F MPNs are characterized by exacerbated vasoconstrictor responses resulting from increased endothelial oxidative stress caused by circulating erythrocyte-derived microvesicles. Simvastatin appears to be a promising therapeutic strategy in this setting.

[Thrombosis and platelet dysfunction in myeloproliferative neoplasms]. / Thromboses et thrombopathies dans les syndromes myéloprolifératifs.

Myeloproliferative neoplasms are acquired hematological malignancies, mainly affecting the adult and whose morbidity and mortality stems from haemostasis disorders. The most frequently encountered complications include thrombosis, affecting preferentially the arterial territory, but also atypical locations such as splanchnic vein thrombosis. The pathophysiology of these thromboses is complex and involves different actors: blood cells, endothelium and flow conditions. Numerous studies have been conducted to identify risk factors for thrombosis. To date, only two risk factors have been validated through prospective studies (age over 60 years old, history of thrombotic events) and allow classification of patients as "low risk" and "high risk" as the basis for current treatment recommendations. Haemorrhagic manifestations, less frequent than thrombosis, are mainly related to an alteration of primary haemostasis and are therefore manifested by mucocutaneous bleeding. In these patients, platelet dysfunctions and/or acquired Willebrand syndromes can be found. The pathophysiology of thrombosis and platelet dysfunction during myeloproliferative neoplasms remains to date partially unknown. In this review, we offer to focus on physiopathological mechanisms as well as the latest advances in their understanding.

The Spectrum of Aggressive Mastocytosis: A Workshop Report and Literature Review.

Most cases of mastocytosis are indolent, usually cutaneous mastocytosis or indolent systemic mastocytosis (SM). Aggressive mast cell (MC) diseases are very rare and often fatal. They can develop de novo or due to progression of indolent forms and can present in different ways; either as MC sarcoma or as advanced SM which includes aggressive SM, MC leukemia, and SM with an associated hematological neoplasm. This review will describe these different aggressive forms of mastocytosis, illustrated by cases submitted to the workshop of the 18th Meeting of the European Association for Haematopathology, Basel 2016, organized by the European Bone Marrow Working Group. In addition, the diagnostic criteria for identifying myelomastocytic leukemia, an aggressive myeloid neoplasm with partial MC differentiation that falls short of the criteria for SM, and disease progression in patients with established mastocytosis are discussed.

A rare cause of acute coronary syndromes in young adults - myeloproliferative neoplasms: A case series.

INTRODUCTION: Acute coronary syndromes (ACS) mostly occur in patients with traditional risk factors. Especially in young adults without major cardiovascular (CV) risk factors, one of the less common causes of ACS is myeloproliferative neoplasms (MPNs). METHODS: We retrospectively collected data on 11 consecutive patients (nine men, two women, mean age 40.18±8.4 years) with a diagnosis of MPN who presented with ACS. The demographic characteristics of the study population, type of MPN, clinical manifestations, location of myocardial infarction (MI), coronary angiography findings, complete blood count and other related findings, and treatment strategy before and after diagnosis were analyzed. RESULTS: Six patients were diagnosed with polycythemia vera, four with essential thrombocytosis and one with primary myelofibrosis. A JAK2 mutation was found in nine patients. Mean time to diagnosis of MPN was 2.81 years after presenting ACS and mean age at first MI was 32.9±6 years. Six patients had no major CV risk factors. Ten patients had anterior MI and one had inferior MI. After initiation of specific treatment for MPN, no recurrent thrombotic events were observed in a mean follow-up of 4±2.44 years. CONCLUSIONS: In young adults presenting with ACS, MPNs should be considered, especially in the absence of atherosclerotic coronary artery lesions. It is also important to pay attention to blood cell count abnormalities seen in intracoronary thrombotic events. Early diagnosis and treatment of MPNs is essential to prevent recurrence of thrombotic events and may reduce mortality and morbidity related to thrombotic complications.

Mathematical analysis of the Cancitis model and the role of inflammation in blood cancer progression.

Recently, a tight coupling has been observed between inflammation and blood cancer such as the Myeloproliferative Neoplasms (MPNs). A mechanism based six-dimensional model-the Cancitis model-describing the progression of blood cancer coupled to the inflammatory system is analyzed. An analytical investigation provides criteria for the existence of physiological steady states, trivial, hematopoietic, malignant and co-existing steady states. The classification of steady states is explicitly done in terms of the inflammatory stimuli. Several parameters are crucial in determining the attracting steady state(s). In particular, increasing inflammatory stimuli may transform a healthy state into a malignant state under certain circumstances. In contrast for the co-existing steady state, increasing inflammatory stimuli may reduce the malignant cell burden. The model provides an overview of the possible dynamics which may inform clinical practice such as whether to use inflammatory inhibitors during treatment.

Experimental Modeling of Myeloproliferative Neoplasms.

Myeloproliferative neoplasms (MPN) are genetically very complex and heterogeneous diseases in which the acquisition of a somatic driver mutation triggers three main myeloid cytokine receptors, and phenotypically expresses as polycythemia vera (PV), essential thrombocytosis (ET), and primary myelofibrosis (PMF). The course of the diseases may be influenced by germline predispositions, modifying mutations, their order of acquisition and environmental factors such as aging and inflammation. Deciphering these contributory elements, their mutual interrelationships, and their contribution to MPN pathogenesis brings important insights into the diseases. Animal models (mainly mouse and zebrafish) have already significantly contributed to understanding the role of several acquired and germline mutations in MPN oncogenic signaling. Novel technologies such as induced pluripotent stem cells (iPSCs) and precise genome editing (using CRISPR/Cas9) contribute to the emerging understanding of MPN pathogenesis and clonal architecture, and form a convenient platform for evaluating drug efficacy. In this overview, the genetic landscape of MPN is briefly described, with an attempt to cover the main discoveries of the last 15 years. Mouse and zebrafish models of the driver mutations are discussed and followed by a review of recent progress in modeling MPN with patient-derived iPSCs and CRISPR/Cas9 gene editing.

[Pathogenesis of thrombosis in JAK2V617F myeloproliferative neoplasms]. / La thrombose au cours des néoplasies myéloprolifératives - Influence de la mutation JAK2V617F.

BCR-ABL negative myeloproliferative neoplasms are acquired hematologic diseases characterized by blood cell proliferation and that include polycythemia vera (PV), essential thrombocytemia (ET) and primary myelofibrosis (PMF). Occurring of venous and arterial thrombosis is the main complication of these diseases. Risk factors for thrombosis are individuals older than 60 and history of thrombosis. The mechanisms leading to thrombosis are complex and involve several blood compartments, plasmatic factors and endothelial cells. Over the last years, new actors of thrombosis have been discovered.

TITLE: La thrombose au cours des néoplasies myéloprolifératives - Influence de la mutation JAK2V617F. ABSTRACT: Les néoplasies myéloprolifératives (NMP) sans translocation de Philadelphie sont des maladies hématologiques acquises caractérisées par la prolifération d'une ou plusieurs lignées sanguines. Elles regroupent la polyglobulie de Vaquez (PV), la thrombocytémie essentielle (TE) et la myélofibrose primitive (MFP). La survenue de thromboses artérielles ou veineuses est un risque majeur au cours de ces maladies. Les facteurs de risque reconnus actuellement sont un âge supérieur à 60 ans et un antécédent de thrombose. Les mécanismes concourant à ce risque pro-thrombotique augmenté sont cependant multiples et complexes, impliquant l'ensemble des cellules sanguines, des facteurs plasmatiques et le compartiment endothélial. Ces dernières années, de nouveaux mécanismes physiopathologiques ont été révélés.

Thrombosis in the Philadelphia Chromosome-Negative Myeloproliferative Neoplasms.

The myeloproliferative neoplasms (MPNs) are clonal stem cell-derived diseases. This chapter focuses on the subcategory of Philadelphia (Ph) chromosome-negative classical MPNs, polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF). These MPNs are associated with both microvascular and macrovascular thrombosis, which may occur in the venous and arterial circulation. Erythrocytosis, leukocytosis, and increased JAK2V617F allele burden are known to be risk factors. In this chapter, we review the thrombotic and hemostatic manifestations of the Philadelphia (Ph) chromosome-negative classical MPNs, including the clinical manifestations, the pathophysiology, as well as management.

The effectiveness of exercise-based rehabilitation to patients with myeloproliferative neoplasms-An explorative study.

The aim of the study was to determine the impact of an interdisciplinary exercise-based rehabilitation intervention on fatigue and quality of life (QOL) in patients with Philadelphia-negative myeloproliferative neoplasms (MPNs). At the Danish Knowledge Centre for Rehabilitation and Palliative Care, a 5-day interdisciplinary exercise-based rehabilitation intervention was carried out on 48 patients with MPN. It was followed by 12 weeks of self-exercising prior to follow-up. Initially and at follow-up, participants filled out validated questionnaires; Brief Fatigue Inventory, Multidimensional Fatigue Inventory, European Organization for Research and Treatment of Cancer Quality-of-Life questionnaire, Myeloproliferative Neoplasm Symptom Assessment Form and Hospital Anxiety and Depression Scale. Maximal oxygen uptake and muscular strength were tested as well. Paired t test was used to compare scores between baseline and follow-up. In total, 45 participants (94%) completed the follow-up. No significant differences were observed on fatigue or QOL when comparing baseline and follow-up. Mean maximal oxygen uptake increased from 27.2 to 33.6 ml O2 · kg-1  ·min-1 (p < 0.001). Handgrip strength (p = 0.01) and the 30-s chair-stand test (p < 0.001) improved as well. No changes were found regarding levels of fatigue and QOL. However, we observed a significant increase in the physical capacity. Our observations call for further studies investigating the effects of non-pharmacological approaches in patients with MPN.

Current approaches to challenging scenarios in myeloproliferative neoplasms.

INTRODUCTION: The Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) including polycythemia vera, essential thrombocythemia and primary myelofibrosis are clonal hematological malignancies that originate at the level of the hematopoietic stem cell, and are characterized by excessive proliferation of cells belonging to one or more of the myeloid lineages. Central to the pathogenesis of the MPNs is constitutive activation of the JAK/STAT signaling pathway due to a family of driver mutations affecting JAK2, CALR or MPL. These disorders share common clinical and laboratory features, a significant burden of systemic symptoms, increased risk of developing arterial and venous thrombotic events, and the potential to progress to myelofibrosis and acute leukemia. Areas covered: We identified four clinical situations which represent challenging management dilemmas for patients with MPNs. Our conclusions and recommendations are based on a literature search using MEDLINE and recent meeting abstracts using the keywords, focusing on publications directly addressing these scenarios and on recent contributions to the field. Expert commentary: Multi-center efforts to study large cohorts of MPN patients have led to more uniform and evidence-based approaches to key aspects in MPN management. However, treatment strategies to deal with specific clinical scenarios are lacking.