After 10 years of JAK2V617F: Disease biology and current management strategies in polycythaemia vera

Message in a platelet: decoding platelet transcriptomes in myeloproliferative neoplasms

Platelets are anucleate but contain a rich repertoire of mRNAs. In this issue of Cell Reports Medicine, Shen and colleagues1 present platelet transcriptomes from patients with myeloproliferative neoplasms to study disease mechanisms and generate a predictive algorithm for fibrotic progression.

Low-Risk Essential Thrombocythemia: A Comprehensive Review

Essential thrombocythemia (ET) is a chronic myeloproliferative neoplasm characterized by a persistently elevated platelet count in the absence of a secondary cause. The clinical consequences of uncontrolled thrombocytosis can include both thrombosis and hemorrhage. Patients with features conferring a “high risk” of vascular events benefit from reduction of the platelet count through cytoreductive therapy. The management of patients who lack such high-risk features has until recently been less well defined, but it is now apparent that many require minimal or even no intervention. In this review, we discuss the diagnostic pathway for younger patients with unexplained thrombocytosis, including screening molecular investigations, the role of bone marrow biopsy, and investigations in those patients negative for the classic myeloproliferative neoplasm driver mutations (JAK2, CALR, MPL). We discuss conventional and novel risk stratification methods in essential thrombocythemia and how these can be best applied in clinical practice, particularly in the era of more comprehensive genomic testing. The treatment approach for “low risk” patients is discussed including antiplatelets and the options for cytoreductive therapy, if indicated, together with areas of clinical need for future study.

The role of driver mutations in myeloproliferative neoplasms: insights from mouse models

High frequency of JAK2V617F or CALR exon 9 mutations is a main molecular feature of myeloproliferative neoplasms (MPNs). Analysis of mouse models driven by these mutations suggests that they are a direct cause of MPNs and that the expression levels of the mutated genes define the disease phenotype. The function of MPN-initiating cells has also been elucidated by these mouse models. Such mouse models also play an important role in modeling disease to investigate the effects and action mechanisms of therapeutic drugs, such as JAK2 inhibitors and interferon α, against MPNs. The mutation landscape of hematological tumors has already been clarified by next-generation sequencing technology, and the importance of functional analysis of mutant genes in vivo should increase further in the future.

STAT5 and STAT5 Inhibitors in Hematological Malignancies

The JAK-STAT pathway is an important physiologic regulator of different cellular functions including proliferation, apoptosis, differentiation, and immunological responses. Out of six different STAT proteins, STAT5 plays its main role in hematopoiesis and constitutive STAT5 activation seems to be a key event in the pathogenesis of several hematological malignancies. This has led many researchers to develop compounds capable of inhibiting STAT5 activation or interfering with its functions. Several anti-STAT5 molecules have shown potent STAT5 inhibitory activity in vitro. However, compared to the large amount of clinical studies with JAK inhibitors that are currently widely used in the clinics to treat myeloproliferative disorders, the clinical trials with STAT5 inhibitors are very limited. At present, a few STAT5 inhibitors are in phase I or II clinical trials for the treatment of leukemias and graft vs host disease. These studies seem to indicate that such compounds could be well tolerated and useful in reducing the occurrence of resistance to tyrosine kinase inhibitors in chronic myeloid leukemia. Of interest, STAT5 seems to play an important role in the regulation of hematopoietic stem cell self-renewal suggesting that combination therapies including STAT5 inhibitors can erode the cancer stem cell pool and possibly open the way for the complete cancer eradication. In this review, we discuss the implication of STAT5 in hematological malignancies and the results obtained with the novel STAT5 inhibitors.

Central Nervous System Lymphoma Harboring the JAK2 V617F Mutation That Developed after a 20-year History of Polycythemia Vera

A 78-year-old man who had a 20-year history of polycythemia vera (PV) with a JAK2 V617F mutation presented with gradually progressive disturbance of consciousness. Hyper-intense lesions in the peri-lateral ventricular area and left cerebellar hemisphere were observed by T2-weighted and fluid-attenuated inversion recovery magnetic resonance imaging. Cytologic and genetic analyses of the lymphoma cells obtained from his cerebrospinal fluid established the diagnosis of B-cell lymphoma. No lesions outside of the brain were recognized. Because of his poor general condition, he was not treated actively. A postmortem analysis revealed a JAK2 V617F mutation in the lymphoma cells, suggesting their origin was a PV clone.

Disease and treatment characteristics of polycythemia vera patients in Belgium: Results from a scientific survey

OBJECTIVE

The current survey aimed to gather predefined disease parameters and treatment strategies to characterize the polycythemia vera (PV) patient population in Belgium.

METHODS

Cross-sectional data from PV patients, seen at least once between May 2014 and May 2015 at 10 sites in Belgium, were collected in aggregated form and analyzed descriptively and quantitatively.

RESULTS

Data from 343 PV patients were collected. Of these, 174 (50.7%) were male and 256 (74.6%) were ≥60 years of age. Ninety-two (26.8%) had a prior history of thrombotic events. Considerable proportions of patients had increased hematological parameters (hematocrit > 45% [31.2%], leukocytes > 10 × 10⁹ /L [33.3%], and platelet > 400 × 10⁹ /L [38.2%]). Most patients had non-palpable spleen (284, 87.7%) and no phlebotomies during the past 6 months (197, 57.4%). Low-dose aspirin was given as thrombosis prophylaxis in 249 (72.6%) patients, while 232 (67.6%) received hydroxyurea (HU) as cytoreductive treatment. Forty-one patients (12.0%) were reported as resistant and/or intolerant to HU. Seventeen patients (5.0%) received ruxolitinib in the context of clinical trials.

CONCLUSION

This survey provides better insight into the characteristics of Belgian PV patients and currently used treatment strategies. It shows that 232 (67.6%) PV patients continue to receive HU despite being potentially HU-resistant.

Myeloproliferative neoplasms: from origins to outcomes

Substantial progress has been made in our understanding of the pathogenetic basis of myeloproliferative neoplasms. The discovery of mutations in JAK2 over a decade ago heralded a new age for patient care as a consequence of improved diagnosis and the development of therapeutic JAK inhibitors. The more recent identification of mutations in calreticulin brought with it a sense of completeness, with most patients with myeloproliferative neoplasm now having a biological basis for their excessive myeloproliferation. We are also beginning to understand the processes that lead to acquisition of somatic mutations and the factors that influence subsequent clonal expansion and emergence of disease. Extended genomic profiling has established a multitude of additional acquired mutations, particularly prevalent in myelofibrosis, where their presence carries prognostic implications. A major goal is to integrate genetic, clinical, and laboratory features to identify patients who share disease biology and clinical outcome, such that therapies, both existing and novel, can be better targeted.

Myeloproliferative neoplasms: from origins to outcomes

Substantial progress has been made in our understanding of the pathogenetic basis of myeloproliferative neoplasms. The discovery of mutations in JAK2 over a decade ago heralded a new age for patient care as a consequence of improved diagnosis and the development of therapeutic JAK inhibitors. The more recent identification of mutations in calreticulin brought with it a sense of completeness, with most patients with myeloproliferative neoplasm now having a biological basis for their excessive myeloproliferation. We are also beginning to understand the processes that lead to acquisition of somatic mutations and the factors that influence subsequent clonal expansion and emergence of disease. Extended genomic profiling has established a multitude of additional acquired mutations, particularly prevalent in myelofibrosis, where their presence carries prognostic implications. A major goal is to integrate genetic, clinical, and laboratory features to identify patients who share disease biology and clinical outcome, such that therapies, both existing and novel, can be better targeted.

The New Genomics: What Molecular Databases Can Tell Us About Human Population Variation and Endocrine Disease

Major recent advances in genetics and genomics present unique opportunities for enhancing our understanding of human physiology and disease predisposition. Here I demonstrate how analysis of genomic information can provide new insights into endocrine systems, using the human growth hormone (GH) signaling pathway as an illustrative example. GH is essential for normal postnatal growth in children, and plays important roles in other biological processes throughout life. GH actions are mediated by the GH receptor, primarily via the JAK2 protein tyrosine kinase and the STAT5B transcription factor, and inactivating mutations in this pathway all lead to impaired somatic growth. Variation in GH signaling genes has been evaluated using DNA sequence data from the Exome Aggregation Consortium, a compendium of information from >60,000 individuals. Results reveal many potential missense and other alterations in the coding regions of GH1, GHR, JAK2, and STAT5B, with most changes being uncommon. The total number of different alleles per gene varied by ~threefold, from 101 for GH1 to 338 for JAK2. Several known disease-linked mutations in GH1, GHR, and JAK2 were present but infrequent in the population; however, three amino acid changes in GHR were sufficiently prevalent (~4% to 44% of chromosomes) to suggest that they are not disease causing. Collectively, these data provide new opportunities to understand how genetically driven variability in GH signaling and action may modify human physiology and disease.

Investigational drugs in phase I and phase II clinical trials for thalassemia

INTRODUCTION

Regular transfusion and iron chelation are the current treatment of severe forms of thalassemia. As a consequence of this demanding supportive treatment, there are several unmet therapeutic needs. Due to a deeper understanding in the pathophysiology of thalassemia, new therapeutic strategies have been developed that are now in pre-clinical and clinical trials. Areas covered: Activin receptor ligand traps (luspatercept and sotatercept), drugs targeting ineffective erythropoiesis, showed encouraging results in Phase I and II clinical trials. A phase III clinical trial is currently ongoing. Ruxolitinib, a Jak2 inhibitor, has been tested to limit stress erythropoiesis in a phase II clinical trial. In addition, improvement in iron chelation has been developed. Moreover, several trials of gene therapy are currently active in different countries with different lentiviral vectors. Expert opinion: The most promising molecules are the activin receptor ligand traps. Together with gene therapy these could be an alternative to bone marrow transplant, aiming towards a curative strategy. The main limit to gene therapy seems to be the conditioning regimen, thus an in vivo gene therapy would be more suitable. At pre-clinical level gene editing is showing extremely encouraging results.