The JAK2V617 mutation induces constitutive activation and agonist hypersensitivity in basophils from patients with polycythemia vera

The JAK1/JAK2 inhibitor ruxolitinib inhibits mediator release from human basophils and mast cells

Introduction

The Janus kinase (JAK) family includes four cytoplasmic tyrosine kinases (JAK1, JAK2, JAK3, and TYK2) constitutively bound to several cytokine receptors. JAKs phosphorylate downstream signal transducers and activators of transcription (STAT). JAK-STAT5 pathways play a critical role in basophil and mast cell activation. Previous studies have demonstrated that inhibitors of JAK-STAT pathway blocked the activation of mast cells and basophils.

Methods

In this study, we investigated the in vitro effects of ruxolitinib, a JAK1/2 inhibitor, on IgE- and IL-3-mediated release of mediators from human basophils, as well as substance P-induced mediator release from skin mast cells (HSMCs).

Results

Ruxolitinib concentration-dependently inhibited IgE-mediated release of preformed (histamine) and de novo synthesized mediators (leukotriene C4) from human basophils. Ruxolitinib also inhibited anti-IgE- and IL-3-mediated cytokine (IL-4 and IL-13) release from basophils, as well as the secretion of preformed mediators (histamine, tryptase, and chymase) from substance P-activated HSMCs.

Discussion

These results indicate that ruxolitinib, inhibiting the release of several mediators from human basophils and mast cells, is a potential candidate for the treatment of inflammatory disorders.

Association of JAK2V617F allele burden and clinical correlates in polycythemia vera: a systematic review and meta-analysis

Janus kinase 2 (JAK2) V617F mutation is present in most patients with polycythemia vera (PV). One persistently puzzling aspect unresolved is the association between JAK2V617F allele burden (also known as variant allele frequency) and the relevant clinical characteristics. Numerous studies have reported associations between allele burden and both hematologic and clinical features. While there are strong indications linking high allele burden in PV patients with symptoms and clinical characteristics, not all associations are definitive, and disparate and contradictory findings have been reported. Hence, this study aimed to synthesize existing data from the literature to better understand the association between JAK2V617F allele burden and relevant clinical correlates. Out of the 1,851 studies identified, 39 studies provided evidence related to the association between JAK2V617F allele burden and clinical correlates, and 21 studies were included in meta-analyses. Meta-analyses of correlation demonstrated that leucocyte and erythrocyte counts were significantly and positively correlated with JAK2V617F allele burden, whereas platelet count was not. Meta-analyses of standardized mean difference demonstrated that leucocyte and hematocrit were significantly higher in patients with higher JAK2V617F allele burden, whereas platelet count was significantly lower. Meta-analyses of odds ratio demonstrated that patients who had higher JAK2V617F allele burden had a significantly greater odds ratio for developing pruritus, splenomegaly, thrombosis, myelofibrosis, and acute myeloid leukemia. Our study integrates data from approximately 5,462 patients, contributing insights into the association between JAK2V617F allele burden and various hematological parameters, symptomatic manifestations, and complications. However, varied methods of data presentation and statistical analyses prevented the execution of high-quality meta-analyses.

Real-World Electronic Medical Records Data Identify Risk Factors for Myelofibrosis and Can Be Used to Validate Established Prognostic Scores

Myelofibrosis (MF) is a myeloproliferative neoplasia arising de novo as primary myelofibrosis (PMF) or secondary to polycythemia vera or essential thrombocythemia. Patients experience a high symptom burden and a marked reduction in life expectancy. Despite progress in molecular understanding and treatment, the clinical and prognostic heterogeneity of MF complicates treatment decisions. The International Prognostic Scoring System (IPSS) integrates clinical factors for risk stratification in MF. This study leverages the TriNetX database with more than 64,000 MF patients to assess the impact of accessible parameters on survival and complicating events, including AML transformation, cachexia, increased systemic inflammation, thrombosis and hemorrhage. Age over 65 years correlated with increased risks of death, AML transformation, thrombosis and hemorrhage. Anemia (Hb < 10 g/dL), leukocytosis (>25 × 103/µL) and thrombocytopenia (<150 × 103/µL) reduced survival and increased risks across all assessed events. Monocytosis is associated with decreased survival, whereas eosinophilia and basophilia were linked to improved survival. Further, as proof of concept for the applicability of TriNetX for clinical scores, we devised a simplified IPSS, and confirmed its value in predicting outcomes. This comprehensive study underscores the importance of age, anemia, leukocytosis and thrombocytopenia in predicting disease trajectory and contributes to refining prognostic models, addressing the challenges posed by the disease's heterogeneity.

Basophils from allergy to cancer

Human basophils, first identified over 140 years ago, account for just 0.5-1% of circulating leukocytes. While this scarcity long hampered basophil studies, innovations during the past 30 years, beginning with their isolation and more recently in the development of mouse models, have markedly advanced our understanding of these cells. Although dissimilarities between human and mouse basophils persist, the overall findings highlight the growing importance of these cells in health and disease. Indeed, studies continue to support basophils as key participants in IgE-mediated reactions, where they infiltrate inflammatory lesions, release pro-inflammatory mediators (histamine, leukotriene C₄: LTC₄) and regulatory cytokines (IL-4, IL-13) central to the pathogenesis of allergic diseases. Studies now report basophils infiltrating various human cancers where they play diverse roles, either promoting or hampering tumorigenesis. Likewise, this activity bears remarkable similarity to the mounting evidence that basophils facilitate wound healing. In fact, both activities appear linked to the capacity of basophils to secrete IL-4/IL-13, with these cytokines polarizing macrophages toward the M2 phenotype. Basophils also secrete several angiogenic factors (vascular endothelial growth factor: VEGF-A, amphiregulin) consistent with these activities. In this review, we feature these newfound properties with the goal of unraveling the increasing importance of basophils in these diverse pathobiological processes.

Automated analysers underestimate atypical basophil count in myeloid neoplasms

INTRODUCTION

Recent data suggest basophils can adopt an atypical appearance in myeloid disorders including myeloproliferative neoplasms (MPNs) and myeloproliferative/myelodysplastic disease. We hypothesized that automated analysers may not accurately quantitate basophils in myeloid neoplasms based on scatter properties. This study examined basophil counts and properties in myeloid disorders by automated cell analyser, manual differential, and flow cytometry.

METHODS

Patients with myeloid neoplasms and control patients with no myeloid disorder diagnosis at a tertiary care centre were identified. Basophil percentage was compared for automated analyser counts (Sysmex XN9000), manual differential, and flow cytometry. Basophil scatter properties in MPNs were examined using flow cytometry.

RESULTS

Thirty-one patients with myeloid neoplasms were included: 58% were male, mean age was 70.2 (±20.7) years, 32% had a diagnosis of chronic myeloid leukaemia with the remaining patients divided among various other forms of myeloid disease (including: essential thrombocythemia, polycythemia vera, unclassifiable MPN, myelodysplastic syndromes). For these patients, mean basophil percentage by automated analyser was significantly lower than manual differential (2.7 ± 2.9 vs. 7.1 ± 4.6, respectively, p < 0.001). No significant difference was found between automated versus manual differential for basophils in control subjects (p = 0.373). For myeloid neoplasm patients, mean basophil percentage was not significantly different between manual differential and flow cytometry (p = 0.116); mean basophil percentage by automated analyser was significantly lower than flow cytometry (2.7 ± 2.9 vs. 5.3 ± 3.7, respectively, p = 0.003).

CONCLUSION

Automated analysers underestimate basophil counts in patients with myeloid neoplasms. Manual differential and flow cytometry are recommended for more accurate quantitation and characterization of aberrant basophils.

Behind the scenes with basophils: an emerging therapeutic target

Though basophils were originally viewed as redundant blood ‘mast cells’, the implementation of flow cytometry has established basophils as unique leukocytes with critical immunomodulatory functions. Basophils play an active role in allergic inflammation, autoimmunity, and hematological malignancies. They are distinguishable from other leukocytes by their characteristic metachromatic deep-purple cytoplasmic, round granules. Mature basophils are phenotypically characterized by surface expression of IL-3Rα (CD123); IL-3 drives basophil differentiation, degranulation, and synthesis of inflammatory mediators including type 2 cytokines. Basophil degranulation is the predominant source of histamine in peripheral blood, promoting allergic responses. Basophils serve as a bridge between innate and adaptive immunity by secreting IL-4 which supports eosinophil migration, monocyte differentiation into macrophages, B-cell activation, and CD4 T-cell differentiation into Th2 cells. Further, basophilia is a key phenomenon in myeloid neoplasms, especially chronic myeloid leukemia (CML) for which it is a diagnostic criterion. Increased circulating basophils, often with aberrant immunophenotype, have been detected in patients with CML and other myeloproliferative neoplasms (MPNs). The significance of basophils’ immunoregulatory functions in malignant and non-malignant diseases is an active area of research. Ongoing and future research can inform the development of immunotherapies that target basophils to impact allergic, autoimmune, and malignant disease states. This review article aims to provide an overview of basophil biology, identification strategies, and roles and dysregulation in diseases.

Is There a Role for Basophils in Cancer?

Basophils were identified in human peripheral blood by Paul Ehrlich over 140 years ago. Human basophils represent <1% of peripheral blood leukocytes. During the last decades, basophils have been described also in mice, guinea pigs, rabbits, and monkeys. There are many similarities, but also several immunological differences between human and mouse basophils. There are currently several strains of mice with profound constitutive or inducible basophil deficiency useful to prove that these cells have specific roles in vivo. However, none of these mice are solely and completely devoid of all basophils. Therefore, the relevance of these findings to humans remains to be established. It has been known for some time that basophils have the propensity to migrate into the site of inflammation. Recent observations indicate that tissue resident basophils contribute to lung development and locally promote M2 polarization of macrophages. Moreover, there is increasing evidence that lung-resident basophils exhibit a specific phenotype, different from circulating basophils. Activated human and mouse basophils synthesize restricted and distinct profiles of cytokines. Human basophils produce several canonical (e.g., VEGFs, angiopoietin 1) and non-canonical (i.e., cysteinyl leukotriene C₄) angiogenic factors. Activated human and mouse basophils release extracellular DNA traps that may have multiple effects in cancer. Hyperresponsiveness of basophils has been demonstrated in patients with JAK2^V617F-positive polycythemia vera. Basophils are present in the immune landscape of human lung adenocarcinoma and pancreatic cancer and can promote inflammation-driven skin tumor growth. The few studies conducted thus far using different models of basophil-deficient mice have provided informative results on the roles of these cells in tumorigenesis. Much more remains to be discovered before we unravel the hitherto mysterious roles of basophils in human and experimental cancers.

Aquagener Pruritus als Warnzeichen eines inneren Tumorleidens – eine Fallvorstellung und Literaturübersicht

Aquagener Pruritus (AP), d. h. Jucken, Kribbeln, Brennen nach Wasserkontakt, ist ein häufiges Symptom bei Polycythaemia vera und anderen myeloproliferativen Neoplasien, kann aber auch unabhängig davon auftreten. Wie andere Formen des Pruritus schränkt AP die Lebensqualität der Betroffenen häufig ein und kann zu einem hohen Leidensdruck führen. Zur Pathogenese existieren unterschiedliche Erklärungsansätze, jedoch kein einheitliches Konzept. Passend dazu sprechen Patienten auch nur zum Teil auf vorhandene Therapien an, die überwiegend off label sind. In dieser Literaturübersicht zum AP werden beschriebene Pathomechanismen diskutiert und mögliche Therapieformen genannt. Ein verbessertes Verständnis von AP soll dazu beitragen, dieses Symptom zu erkennen und an mögliche zugrunde liegende Erkrankungen, insbesondere an ein inneres Tumorleiden, zu denken.

Key Role of Inflammation in Myeloproliferative Neoplasms: Instigator of Disease Initiation, Progression. and Symptoms

PURPOSE OF REVIEW

Chronic inflammation is a characteristic feature of myeloproliferative neoplasm (MPN) and impacts many aspects of the disease including initiation, progression, and symptomatology.

RECENT FINDINGS

The chronic inflammatory state of MPN results from disruption of immune signaling pathways leading to overproduction of inflammatory cytokines by both the neoplastic clones and bystander immune cells. This chronic inflammation may allow for the neoplastic clone to gain a selective advantage. The symptomatic burden felt by MPN patients may be a result of the chronic inflammation associated with MPN, as several cytokines have been linked with different symptoms. Pharmacologic as well as nonpharmacologic treatments of the inflammatory component of this disease may lead to decreased symptomatic burden, prevention of disease progression, and improvement in overall disease trajectory. Inflammation plays a key role in the pathogenesis of MPN and represents an important therapeutic target.

Polycythemia vera: the current status of preclinical models and therapeutic targets

INTRODUCTION

Polycythemia vera (PV) is the most common myeloproliferative neoplasm (MPN). PV is characterized by erythrocytosis, leukocytosis, thrombocytosis, increased hematocrit, and hemoglobin in the peripheral blood. Splenomegaly and myelofibrosis often occur in PV patients. Almost all PV patients harbor a mutation in the JAK2 gene, mainly represented by the JAK2^V617F point mutation.

AREAS COVERED

This article examines the recent in vitro and in vivo available models of PV and moreover, it offers insights on emerging biomarkers and therapeutic targets. The evidence from mouse models, resembling a PV-like phenotype generated by different technical approaches, is discussed. The authors searched PubMed, books, and clinicaltrials.gov for original and review articles and drugs development status including the terms Myeloproliferative Neoplasms, Polycythemia Vera, erythrocytosis, hematocrit, splenomegaly, bone marrow fibrosis, JAK2^V617F, Hematopoietic Stem Cells, MPN cytoreductive therapy, JAK2 inhibitor, histone deacetylase inhibitor, PV-like phenotype, JAK2^V617F BMT, transgenic JAK2^V617F mouse, JAK2 physiologic promoter.

EXPERT OPINION

Preclinical models of PV are valuable tools for enabling an understanding of the pathophysiology and the molecular mechanisms of the disease. These models provide new biological insights on the contribution of concomitant mutations and the efficacy of novel drugs in a 'more faithful' setting. This may facilitate an enhanced understanding of pathogenetic mechanisms and targeted therapy.

How I investigate basophilia in daily practice

Basophilia is a rare disorder of the complete blood count (CBC) and its management in daily practice remains unclear. Two main factors explain this situation. On the one hand, the reliability of the basophil count is insufficient, whether it is performed by a microscopic slide examination or by a hematology analyser. On the other hand, our knowledge of conditions associated with basophilia is largely based on few case reports and on reviews that refer to older reviews. The association between basophilia and myeloid neoplasm, especially chronic myeloid neoplasm, is well established. Conversely, there are conflicting data on some benign medical conditions and it remains unclear where basophilia may be present. In this review, we have investigated the medical literature to define which medical conditions can lead to basophilia and which cannot, and we propose a practical approach to manage basophilia divided into 3 steps. First, we have to check the real existence of the basophilia by getting rid of spurious basophilia. Then, we have to look for symptoms that suggest reactive basophilia and for clue of a neoplastic cause. Finally, in case of suspicion of a myeloid neoplasm or persistence of the basophilia in the absence of a reactive cause, we have to decide which examinations need to be prescribed to confirm a neoplastic basophilia.

Aquagenic pruritus in essential thrombocythemia is associated with a higher risk of thrombosis

BACKGROUND

Thromboses and phenotypic evolutions (leukemia, myelofibrosis) are the most frequent complications in polycythemia vera (PV) and essential thrombocythemia (ET). Aquagenic pruritus (AP) is not only PV symptom, but is also present in ET. The presence of pruritus in PV is associated with a lower risk of arterial thrombosis.

AIMS

To date, no equivalent study has been done to analyse the impact of AP for ET patients.

MATERIALS & METHODS

We used the data from our cohort of patients with myeloproliferative neoplasms seen in our institution (OBENE database, NCT02897297). We collect information at diagnosis, presence or not of AP and all types of complications during their follow-up. To avoid masked PV, all JAK2 positive cases were tested isotopic red mass cell if appropriate.

RESULTS

Among 396 ET patients, presence of AP was found in 42 (10.6%). ET patients with AP were more proliferative, more symptomatic at diagnosis and more difficult to treat. Furthermore, they presented increased risk of thromboses (30.9 versus 17%, P = .03; OR = 2.2 [1.01;4.66]) and phenotypic evolutions (33.3 versus 13.3%, P = .0007; OR = 3.2 [1.44;6.77]), during follow-up.

DISCUSSION

Aquagenic pruritus is classically associated to PV. But we confirmed here that AP is also present in ET and characterizes patients with higher risk of morbidity (thrombotic events and phenotypic evolutions).

CONCLUSIONS

The systematic determination of the presence of AP in ET patients should permit us to better identify these high-risk patients for better management and follow-up.

Polycythemia Vera-Associated Complications: Pathogenesis, Clinical Manifestations, And Effects On Outcomes

Polycythemia vera is a Philadelphia-negative chronic myeloproliferative neoplasm, characterized by erythrocytosis, which is unique, compared to essential thrombocytosis and primary myelofibrosis. Though longevity can usually be expected, vascular morbidity is associated with this condition, as well as a propensity to evolve into myelofibrosis (post-PV MF) and acute myeloid leukemia. In addition, patients can have a pronounced symptom burden. Herein, contributors to the symptomatic burden, as well as the thrombotic and transformative tendencies are reviewed. From a symptom perspective, some are explained by cytokine release, others by microvascular complications, whereas certain symptoms can herald disease evolution. Thrombosis has multifactorial contributors, including but not limited to gender, and inflammatory stress; investigators have recently hypothesized that microparticles and Neutrophil Extracellular Trap Formations may add to thrombotic burden. Finally, we examine the progression to post-PV MF as well as leukemic transformation, highlighting well-established risk factors including age and leukocytosis, certain treatments, and the presence of “non-driver” mutations.

Possible roles of basophils in chronic itch

Basophils are blood granulocytes and normally constitute <1% of blood peripheral leucocytes. Basophils share some morphological and functional similarities with mast cells, and basophils were once regarded as redundant and negligible circulating mast cells. However, recent studies reveal the indispensable roles of basophils in various diseases, including allergic and pruritic diseases. Basophils may be involved in itch through the mediation of a Th2 immune response, interaction with other cells in the skin and secretion of a wide variety of itch-related mediators, for example histamine, cytokines and chemokines (IL-4, IL-13, IL-31 and TSLP), proteases (cathepsin S), prostaglandins (PGE2 and PGD2), substance P and platelet-activating factor. Not only pruritic skin diseases (eg, atopic dermatitis, irritant contact dermatitis, chronic urticaria, prurigo, papulo-erythroderma of Ofuji, eosinophilic pustular folliculitis, scabies, tick bites and bullous pemphigoid) but also pruritic systemic diseases (eg, primary sclerosing cholangitis and polycythemia vera) may be affected by basophils.

Serum chitotriosidase: a circulating biomarker in polycythemia vera

OBJECTIVES

Serum chitotriosidase activity (CHIT1) is a biomarker of macrophage activation with an important role in inflammation-induced tissue remodeling and fibrosis. Macrophages have been described to play a crucial role in regulating pathological erythropoiesis in polycythemia vera (PV). The aim of this study was to evaluate CHIT1 in patients diagnosed with Philadelphia-negative myeloproliferative neoplasms (MPNs).

METHODS

Using fluorometric assay, we measured CHIT1 in 28 PV, 27 essential thrombocythemia (ET), 17 primary myelofibrosis (PMF), 19 patients with secondary myelofibrosis and in 25 healthy controls.

RESULTS

CHIT1 was significantly higher in PV (p < .001) and post-PV myelofibrosis (MF) transformation (post-PV MF) (p = .020), but not in ET (p = .080), post-ET MF transformation (p = .086), and PMF patients (p = .287), when compared to healthy controls. CHIT1 in PV was positively correlated with hemoglobin (p = .026), hematocrit (p = .012), absolute basophil count (p = .030) and the presence of reticulin fibrosis in the bone marrow (p = .023).

DISCUSSION

A positive correlation between CHIT1 and these distinct laboratory PV features might imply macrophages closely related to clonal erythropoiesis as cells of CHIT1 origin. In addition, a positive association between CHIT1 and reticulin fibrosis might indicate its potential role in PV progression.

CONCLUSION

CHIT1 might be considered as a circulating biomarker in PV. Additional studies are needed to clarify the role of CHIT1 in promoting disease progression and bone marrow fibrosis in PV.

A spotlight on the management of complications associated with myeloproliferative neoplasms: a clinician's perspective

INTRODUCTION

Myeloproliferative neoplasms (MPNs) are associated with a variety of symptoms and signs which cause major morbidity for the patients. The disorders are associated with increased incidence of thromboembolic and hemorrhagic events which can lead to complications and shortened life expectancy. Areas covered: Using systematic literature review and expert clinical and research experience the authors discuss strategies for the management of symptoms and signs including pruritus, fatigue, splenomegaly, and cytopenia. Cytoreduction including treatments to inhibit the JAK/STAT pathway are considered. Pathogenesis and prevention and treatment of thrombotic and hemorrhagic events and their management is addressed and the suggested management of the special situations such as surgery and pregnancy are discussed. Expert commentary: Management of disease has traditionally focused on symptom treatment and complication prevention but the discovery of driver mutations has led to treatments aiming to eliminate the clone, which should be the ultimate goal of therapy. A future challenge is to develop safe and effective MPN therapy and to personalize therapy.

Management of symptoms in polycythemia vera and essential thrombocythemia patients

The BCR-ABL-negative myeloproliferative neoplasms (MPNs) are clonal stem cell derived malignancies, which include polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF). The MPNs are characterized by dysregulated JAK-STAT signaling pathways. PV and ET are associated with an increased risk of thrombo-hemorrhagic complications, risk of progression to MF and leukemia. Presentation of patients with PV and ET is variable and usually as a result of abnormal full blood count indices (raised hemoglobin and hematocrit, leukocytosis, and thrombocytosis). Presentation with thrombosis or splenomegaly occurs in ∼30% of patients. Historically thought of as indolent compared with MF, patients with PV and ET have significant disease symptom burden which does not directly correlate to the current clinical prognostic classifications. The mainstay of therapy is reserved for patients with high-risk disease and thus excludes a population of patients with significant symptom related morbidity impacting their quality-of-life and survival. Recent treatment strategies have aimed to incorporate disease burden assessment into the selection of therapeutic interventions such as JAK2 inhibitors and HDAC inhibitors. We will review the advances in the field of MPN symptom assessment and symptom burden experienced by ET and PV patients. We will also discuss the risk-stratified management of ET and PV patients alongside symptom assessment and the impact of potential novel therapies, for patients who fail to respond to conventional treatment.

Impact of Inflammation on Myeloproliferative Neoplasm Symptom Development

Myeloproliferative neoplasms (essential thrombocythemia, ET; polycythemia vera, PV; myelofibrosis, MF) are monoclonal malignancies associated with genomic instability, dysregulated signaling pathways, and subsequent overproduction of inflammatory markers. Acknowledged for their debilitating symptom profiles, recent investigations have aimed to determine the identity of these markers, the upstream sources stimulating their development, their prevalence within the MPN population, and the role they play in symptom development. Creation of dedicated Patient Reported Outcome (PRO) tools, in combination with expanded access to cytokine analysis technology, has resulted in a surge of investigations evaluating the potential associations between symptoms and inflammation. Emerging data demonstrates clear relationships between individual MPN symptoms (fatigue, abdominal complaints, microvascular symptoms, and constitutional symptoms) and cytokines, particularly IL-1, IL-6, IL-8, and TNF-α. Information is also compiling on the role symptoms paradoxically play in the development of cytokines, as in the case of fatigue-driven sedentary lifestyles. In this paper, we explore the symptoms inherent to the MPN disorders and the potential role inflammation plays in their development.

Pruritus in Systemic Diseases: A Review of Etiological Factors and New Treatment Modalities

Pruritus is the most frequently described symptom in dermatology and can significantly impair the patient's quality of life. In 10–50% of adults with persistent pruritus, it can be an important dermatologic clue for the presence of a significant underlying systemic disease such as renal insufficiency, cholestasis, hematologic disorder, or malignancy (Etter and Myers, 2002; Zirwas and Seraly, 2001). This review describes the presence of pruritus in different systemic diseases. It is quite important to discover the cause of pruritus for providing relief for the patients experiencing substantial morbidity caused by this condition.

Tyrosine Kinase 2-mediated Signal Transduction in T Lymphocytes Is Blocked by Pharmacological Stabilization of Its Pseudokinase Domain

Inhibition of signal transduction downstream of the IL-23 receptor represents an intriguing approach to the treatment of autoimmunity. Using a chemogenomics approach marrying kinome-wide inhibitory profiles of a compound library with the cellular activity against an IL-23-stimulated transcriptional response in T lymphocytes, a class of inhibitors was identified that bind to and stabilize the pseudokinase domain of the Janus kinase tyrosine kinase 2 (Tyk2), resulting in blockade of receptor-mediated activation of the adjacent catalytic domain. These Tyk2 pseudokinase domain stabilizers were also shown to inhibit Tyk2-dependent signaling through the Type I interferon receptor but not Tyk2-independent signaling and transcriptional cellular assays, including stimulation through the receptors for IL-2 (JAK1- and JAK3-dependent) and thrombopoietin (JAK2-dependent), demonstrating the high functional selectivity of this approach. A crystal structure of the pseudokinase domain liganded with a representative example showed the compound bound to a site analogous to the ATP-binding site in catalytic kinases with features consistent with high ligand selectivity. The results support a model where the pseudokinase domain regulates activation of the catalytic domain by forming receptor-regulated inhibitory interactions. Tyk2 pseudokinase stabilizers, therefore, represent a novel approach to the design of potent and selective agents for the treatment of autoimmunity.

Aquagenic pruritus induced by clomipramine

OBJECTIVE

Aquagenic pruritus is the development of severe, prickling-like skin discomfort without observable skin lesions that is evoked by contact with water at any temperature.

METHOD

This is a case report of a man presenting with aquagenic pruritus after starting clomipramine treatment for anxiety and depression.

RESULTS

The patient's aquagenic pruritus resolved after discontinuing the clomipramine but reemerged when treatment was restarted.

CONCLUSIONS

A greater awareness and knowledge about aquagenic pruritus among physicians could help improve the clinical recognition and management of this clinical entity.

Polycythemia vera: current pharmacotherapy and future directions

INTRODUCTION

In the past, management of polycythemia vera (PV) was built upon a cornerstone of control over erythrocytosis, through therapeutic phlebotomy, as well as the use of low-dose aspirin. Historically, selected patients were managed with additional cytoreductive therapies to decrease the risk of vascular events, with the recognition that these therapies likely did not impede progression.

AREAS COVERED

Recent clinical trials have demonstrated, in a randomized fashion, that optimal control of the hematocrit to target levels < 45% are important for decreasing the risk of vascular events. We are identifying that our historical set of cytoreductive agents, such as hydroxyurea, may be replaced in the future. The first candidate is pegylated interferon alpha-2a, which is demonstrating the ability to control vascular events and control extended hematopoiesis, while potentially having impact on fibrotic progression and Janus kinase 2 (JAK2) V1617F mutant allele burden. Ruxolitinib, as well as other JAK2 inhibitors in development, are demonstrating that this class of agents is making a very meaningful impact on the risk of vascular events in PV, controlling expanded hematopoiesis, as well as helping with symptomatic burden.

EXPERT OPINION

Future goals include attaining a better understanding of the specific roles of JAK inhibitor therapy and whether their use in combination with standard therapies offers greater efficacy than single agents alone.

Aquagenic pruritus in polycythemia vera: characteristics and influence on quality of life in 441 patients

Aquagenic pruritus (AP) is a symptom typical for polycythemia vera, but very little is known about its exact frequency, characteristics, influence on quality of life, and proper treatment. Therefore, we investigated these aspects in a large cohort of German patients with polycythemia vera using a patient directed questionnaire. Our analysis revealed that 301 of 441 analyzed patients suffered from AP. In 64.8%, AP occurred on average 2.9 years prior to diagnosis of polycythemia vera. Only in 15.4% did this lead to a hematological investigation. AP occurs primarily on the trunk and proximal parts of the extremities. Most patients complain about itching (71.8%), the remainder about tickling, stinging, or burning sensations. Forty-four patients (14.6%) classified the pruritus as "unbearable." Patients with AP reported reduced global health status and higher fatigue, pain, and dyspnea. Only 24% of patients received pruritus specific treatment for pruritus consisting mostly of histamine antagonists, which ameliorated symptoms in about half of the patients. In 5.6% of patients, polycythemia vera directed therapy (phlebotomy/cytoreduction) resolved the symptoms. In summary, AP is a serious symptom in patients with polycythemia vera, which until recently was difficult to treat. The advent of the novel JAK2 inhibitors, however, may open new ways for therapy.

Itch pathophysiology may differ among ethnic groups

The prevalence of itch is higher in individuals with darker skin types. In this paper, we review the systems involved in the physiology of itch and how they may differ across the races. Current data point out that the differences may be explained by barrier function, mast cell physiology, and itch receptor polymorphisms.

BCR-ABL1-negative chronic myeloid neoplasms: an update on management techniques

Recent discoveries concerning mutations associated with chronic myeloproliferative neoplasms have modified our understanding of the biology of these incurable diseases and guided us to the development of inhibitors active on the constitutively activated JAK-STAT pathway. Concurrently, numerous studies dealt with clinical issues; it led to a revised WHO classification; clarified the role of mutated JAK2 and leukocytosis in the pathogenesis of cardiovascular events; allowed the development of risk prognostic scores and tools for monitoring response to therapy; and resulted in completion of Phase III trials with JAK2 inhibitor in myelofibrosis. All these results hold the promise of improving patient prognostication and therapeutic approach, with the aim of efficiently preventing disease-associated complications and, hopefully, to improve the dismal survival associated with myelofibrosis. This review discusses how to manage, according to current clinical practice, the steps of diagnosis, prognostication and therapeutic choices in myeloproliferative neoplasm patients.

Evaluation of interleukin-23 plasma levels in patients with polycythemia vera and essential thrombocythemia

Essential thrombocythemia (ET), polycythemia vera (PV) and myelofibrosis share the same acquired genetic lesion, JAK2V617F. It is believed that cytokines participate in the activation of JAK2V617F. In this study, we analyzed the plasma levels of interleukin (IL)-23, IL-10 and IL-22 in patients with PV and ET. In the same subjects we also performed analysis of the JAK2(V617F) mutation, and evaluated a possible relationship between interleukin levels and thrombotic complications or with the symptom pruritus. Plasma levels of IL-23 were significantly increased in all patients with MPN in comparison to controls. Moreover, there was a significant difference between the levels of IL-23 in patients affected by PV and those measured in controls (8.57±3.69pg/mL vs. 6.55±4.125pg/mL; p<0.03). No difference was found between IL-23 levels in ET patients and controls. No statistically significant differences were found between the levels of IL-23, Il-22 or IL-10 in PV or ET subjects with or without thrombosis, in patients with or without pruritus, or according the JAK2V617F burden. In PV patients the JAK2 burden and Hb levels correlated with occurrence of pruritus. Our study seems to point out a possible involvement of IL-23 in the pathogenesis of PV.

The itchy scalp--scratching for an explanation

Scalp pruritus is a common complaint that is considered a diagnostically and therapeutically challenging situation. Scalp skin has a unique neural structure that contains densely innervated hair follicles and dermal vasculature. In spite of the recent advances in our understanding of itch pathophysiology, scalp itching has not been studied as yet. In this review, we summarize the current knowledge on the neurobiology of scalp and hair follicles as well as itch mediators and provide a putative mechanism for scalp itch with special emphasis on neuroanatomy and pathophysiology.

Pruritus in primary myelofibrosis: clinical and laboratory correlates

Recent clinical trials with JAK or mammalian target of rapamycin (mTOR) inhibitors in primary myelofibrosis (PMF) have identified pruritus as one of the most treatment-responsive disease traits. However, little is known about the prevalence of pruritus in PMF or its clinical and laboratory correlates. Among 566 consecutive patients with PMF seen at our institution, the presence or absence of pruritus was documented in 90 (16%) and 146 (26%) patients, respectively. Patients with pruritus were less likely to express MPLW515 (0% vs. 10%; P = 0.02) or leukopenia (8% vs. 24%; P = 0.002). The latter association was more pronounced in the absence of JAK2 or MPL mutations. Pruritus also clustered with marked leukocytosis (23% vs. 11%; P = 0.01) and JAK2V617F (71% vs. 59%; P = 0.08). Pruritus did not correlate with karyotype (P = 0.33), risk category per the Dynamic International Prognostic Scoring System (DIPSS)-plus (P = 0.37), DIPSS-plus-adjusted survival (P = 0.41), or leukemic transformation (P = 0.13). Plasma levels of 20 cytokines, which are known to be abnormally expressed in PMF, including IL-1b, IL-2R, IL-6, IL-8, and VEGF, were measured in 63 informative cases and showed no correlations with history of pruritus. We conclude that pruritus is relatively frequent in PMF and is prognostically irrelevant. The pathogenesis of PMF-associated pruritus is not necessarily linked to proinflammatory cytokines but may instead involve molecules that are either granulocyte-derived or influence granulopoiesis. The apparently differential effect of MPL vs. JAK2 mutations on pruritus requires further investigation.

Special issues in myeloproliferative neoplasms

Special issues in myeloproliferative neoplasms (MPN) comprise clinical conditions with high relevance for the duration and quality of the patient's life, but with limited evidence to support sound diagnostic and therapeutic recommendations and a low probability of being solved by the current standard of clinical research. These issues include MPN in pregnancy and in children, abdominal vein thrombosis, bleeding complications, surgery, pruritus, and leukemic transformation. Practical suggestions to guide clinical decisions in these settings remain largely empirical, but recently developed guidelines based on experts' consensus may help to tackle these problems. This article reviews the state of the art regarding these issues, with special emphasis on experts' consensus recommendations.

Philadelphia-negative classical myeloproliferative neoplasms: critical concepts and management recommendations from European LeukemiaNet

We present a review of critical concepts and produce recommendations on the management of Philadelphia-negative classical myeloproliferative neoplasms, including monitoring, response definition, first- and second-line therapy, and therapy for special issues. Key questions were selected according the criterion of clinical relevance. Statements were produced using a Delphi process, and two consensus conferences involving a panel of 21 experts appointed by the European LeukemiaNet (ELN) were convened. Patients with polycythemia vera (PV) and essential thrombocythemia (ET) should be defined as high risk if age is greater than 60 years or there is a history of previous thrombosis. Risk stratification in primary myelofibrosis (PMF) should start with the International Prognostic Scoring System (IPSS) for newly diagnosed patients and dynamic IPSS for patients being seen during their disease course, with the addition of cytogenetics evaluation and transfusion status. High-risk patients with PV should be managed with phlebotomy, low-dose aspirin, and cytoreduction, with either hydroxyurea or interferon at any age. High-risk patients with ET should be managed with cytoreduction, using hydroxyurea at any age. Monitoring response in PV and ET should use the ELN clinicohematologic criteria. Corticosteroids, androgens, erythropoiesis-stimulating agents, and immunomodulators are recommended to treat anemia of PMF, whereas hydroxyurea is the first-line treatment of PMF-associated splenomegaly. Indications for splenectomy include symptomatic portal hypertension, drug-refractory painful splenomegaly, and frequent RBC transfusions. The risk of allogeneic stem-cell transplantation-related complications is justified in transplantation-eligible patients whose median survival time is expected to be less than 5 years.

Polycythemia vera

The diagnostic approach to a patient with polycythemia has been greatly simplified by the introduction of new genetic testing in addition to traditional tests, such as measurement of red cell mass and serum erythropoietin (Epo) level. Clonal erythrocytosis, which is the diagnostic feature of polycythemia vera (PV), is almost always associated with a JAK2 mutation (JAK2V617F or exon 12). Therefore, in a patient with acquired erythrocytosis, it is reasonable to begin the diagnostic work-up with JAK2 mutation analysis to distinguish PV from secondary erythrocytosis. The clinical course of PV is marked by a high incidence of thrombotic complications that represent the main cause of morbidity and mortality in these patients. Blood hyperviscosity as well as platelet and leukocyte quantitative, and qualitative abnormalities play a major role in the pathogenesis of thrombophilia. Prevention of vascular events and minimizing the risk of disease transition into acute leukaemia are the main targets of the whole PV treatment strategy. This can rely on the use of low-dose aspirin in most patients, while the choice of the optimal cytoreductive strategy is based on the individual vascular risk. Phlebotomy is still the preferred treatment in subjects at low risk, while hydroxyurea or pipobroman is usually administered to most elderly subjects or subjects with a previous vascular history. The use of pegylated interferon, imatinib, and JAK2 inhibitors is currently being evaluated.

Polycythemia vera-associated pruritus and its management

BACKGROUND

Pruritus is a defining feature of polycythemia vera (PV) and is seen in approximately 40% of patients. In most cases, the pruritus is characteristically triggered by contact with water (aquagenic) at any temperature.

MATERIALS AND METHODS

A detailed MEDLINE search for all English language articles related to PV, PV-associated pruritus and aquagenic pruritus that were published from 1965 till date was carried out.

RESULTS

Many different treatment options have been tried over the past several decades, including antihistamines, antidepressants, interferon alpha, phlebotomy, phototherapy, iron supplements and myelosuppressive medications, all demonstrating mixed results. Recently, agents that target JAK2 and mammalian target of rapamycin (mTOR) have shown impressive clinical benefit.

CONCLUSION

PV-associated pruritus is a major cause of morbidity amongst patients with PV. Antidepressant medications interfering with serotonin uptake are somewhat efficacious. Cytoreductive therapy is reserved for refractory cases. Targeted therapy with JAK2 and mTOR inhibitors offers renewed hope.