The pharmacotherapeutic management of patients with myelofibrosis: looking beyond JAK inhibitors

INTRODUCTION

The approach to myelofibrosis (MF) has been revolutionized in recent years, overcoming the traditional therapies, often not very effective. Janus kinase inhibitors (JAKi - from ruxolitinib up to momelotinib) were the first class of drugs with considerable results.

AREAS COVERED

Ongoing, new molecules are being tested that promise to give hope even to those patients not eligible for bone marrow transplants who become intolerant or are refractory to JAKi, for which therapeutic hopes are currently limited. Telomerase, murine double minute 2 (MDM2), phosphatidylinositol 3-kinase δ (PI3Kδ), BCL-2/xL, and bromodomain and extra-terminal motif (BET) inhibitors are the drugs with promising results in clinical trials and close to closure with consequent placing on the market, finally allowing JAK to look beyond. The novelty of the MF field was searched in the PubMed database, and the recently completed/ongoing trials are extrapolated from the ClinicalTrial website.

EXPERT OPINION

From this point of view, the use of new molecules widely described in this review, probably in association with JAKi, will represent the future treatment of choice in MF, leaving, in any case, the potential new approaches actually in an early stage of development, such as the use of immunotherapy in targeting CALR, which is coming soon.

Effect of hypoxia on HIF-1α and NOS3 expressions in CD34+ cells of JAK2V617F-positive myeloproliferative neoplasms

PURPOSE

Myeloproliferative neoplasms (MPN) are a heterogeneous group of hematopoietic stem-cell diseases with excessive proliferation of one or more blood cell lines. In this study, we evaluated the effect of different oxygen concentrations on HIF-1α and NOS3 gene expression to determine the effect of the bone marrow microenvironment on JAK2V617F positive Philadelphia chromosome negative (Ph-) MPNs.

PATIENTS AND METHODS

Peripheral blood mononuclear cells (MNC) of 12 patients with Ph- MPN were collected. The presence of JAK2V617F allele status was determined with allele-specific nested PCR analysis. MPN CD34+ and CD34depleted populations were isolated from MNC by magnetic beads. Separate cell cultures of CD34+/depleted populations were managed at different oxygen concentrations including anoxia (∼0%), hypoxia (∼3%), and normoxia (∼20%) conditions for 24 ​h. HIF-1α and NOS3 gene expression changes were examined in each population related to JAK2V617F status with real time RT-PCR.

RESULT

It was revealed that relative HIF-1α and NOS3 expressions were significantly increased in response to decreased oxygen concentration in all samples. Relative HIF-1α and NOS3 expressions were found to be higher especially in CD34+ and CD34depleted populations carrying JAK2V617F mutations compared to MPN patients carrying wild-type JAK2.

CONCLUSION

JAK2V617F might have specific role in HIF-1α and NOS3 regulations with respect to low oxygen concentrations in Ph- MPN. Further evaluations might reveal the effect of JAK2V617F on Ph- MPN pathogenesis in bone marrow microenvironment.

Transcriptomic comparison of bone marrow CD34 + cells and peripheral blood neutrophils from ET patients with JAK2 or CALR mutations

BACKGROUND

Essential thrombocythemia (ET) is one of the most common types of Ph-negative myeloproliferative neoplasms, an infrequent group of blood cancers that arise from a CD34 + hematopoietic stem cell (HSC) in the bone marrow (BM) primarily due to driver mutations in JAK2, CALR or MPL. These aberrations result in an overproduction of mature myeloid cells in peripheral blood (PB). To date, no targeted therapies have been approved for ET patients, so the study of the molecular mechanisms behind the disease and the identification of new therapeutic targets may be of interest. For this reason, in this study, we have compared the transcriptomic profile of undifferentiated CD34 + cells and mature myeloid cells from ET patients (CALR and JAK2-mutated) and healthy donors deposited in publicly available databases. The study of the similarities and differences between these samples might help to better understand the molecular mechanisms behind the disease according to the degree of maturation of the malignant clone and the type of mutation and ultimately help identify new therapeutic targets for these patients.

RESULTS

The results show that most of the altered hallmarks in neutrophils were also found in CD34 + cells. However, only a few genes showed a similar aberrant expression pattern in both types of cells. We have identified a signature of six genes common to patients with CALR and JAK2 mutations (BPI, CRISP3, LTF, MMP8, and PTGS1 upregulated, and PBXIP1 downregulated), a different signature of seven genes for patients with CALR mutations (BMP6, CEACAM8, ITK, LCN2, and PRG2 upregulated, and MAN1A1 and MME downregulated) and a signature of 13 genes for patients with JAK2 mutations (ARG1, CAST, CD177, CLEC5A, DAPP1, EPS15, IL18RAP, OLFM4, OLR1, RIOK3, SELP, and THBS1 upregulated, and IGHM downregulated).

CONCLUSIONS

Our results highlight transcriptomic similarities and differences in ET patients according to the degree of maturation of the malignant clone and the type of mutation. The genes and processes altered in both CD34 + cells and mature neutrophils may reveal altered sustained processes that could be studied as future therapeutic targets for ET patients.

Molecular diagnostic criteria of myeloproliferative neoplasms

INTRODUCTION

Myeloproliferative neoplasms (MPN) are a heterogeneous group of clonal hematopoietic stem cell neoplasms characterized by the driver mutations JAK2, CALR, and MPL. These mutations cause constitutive activation of JAK-STAT signaling, which is central to pathogenesis of MPNs. Next-generation sequencing has further expanded the molecular landscape allowing for improved diagnostics, prognostication, and targeted therapy.

AREAS COVERED

This review aims to address current understanding of the molecular diagnosis of MPN not only through improved awareness of the driver mutations but also the disease modifying mutations. In addition, other genetic factors such as clonal hematopoiesis of indeterminate potential (CHIP), order of mutation, and mutation co-occurrence are discussed and how these factors influence disease initiation and ultimately progression. How this molecular information is incorporated into risk stratification models allowing for earlier intervention and targeted therapy in the future will be addressed further.

EXPERT OPINION

The genomic landscape of the MPN has evolved in the last 15 years with integration of next-generation sequencing becoming the gold standard of MPN management. Although diagnostics and prognostication have become more personalized, additional studies are required to translate these molecular findings into targeted therapy therefore improving patient outcomes.

Clonal Hematopoiesis in Myeloproliferative Neoplasms Confers a Predisposition to both Thrombosis and Cancer

PURPOSE OF REVIEW

This review focuses on vascular complications associated with chronic myeloproliferative neoplasms (MPN) and more specifically aims to discuss the clinical and biological evidence supporting the existence of a link between clonal hematopoiesis, cardiovascular events (CVE), and solid cancer (SC).

RECENT FINDINGS

The MPN natural history is driven by uncontrolled clonal myeloproliferation sustained by acquired somatic mutations in driver (JAK2, CALR, and MPL) and non-driver genes, involving epigenetic (e.g., TET2, DNMT3A) regulators, chromatin regulator genes (e.g., ASXL1, EZH2), and splicing machinery genes (e.g., SF3B1). The genomic alterations and additional thrombosis acquired risk factors are determinants for CVE. There is evidence that clonal hematopoiesis can elicit a chronic and systemic inflammation status that acts as driving force for the development of thrombosis, MPN evolution, and second cancer (SC). This notion may explain the mechanism that links arterial thrombosis in MPN patients and subsequent solid tumors. In the last decade, clonal hematopoiesis of indeterminate potential (CHIP) has been detected in the general population particularly in the elderly and initially found in myocardial infarction and stroke, rising the hypothesis that the inflammatory status CHIP-associated could confer predisposition to both cardiovascular diseases and cancer. In summary, clonal hematopoiesis in MPN and CHIP confer a predisposition to cardiovascular events and cancer through chronic and systemic inflammation. This acquisition could open new avenues for antithrombotic therapy both in MPNs and in general population by targeting both clonal hematopoiesis and inflammation.

Portal vein thrombosis as the presenting manifestation of JAK2 positive myeloproliferative neoplasm

Deep venous thrombosis (DVT) is a complication of myeloproliferative neoplasms (MPNs). However, DVTs in unusual sites such as portal vein thrombosis (PVT) are rare and may be the first clinical manifestation of occult MPNs. There is a need for increasing awareness of such manifestations; so, here we discuss a patient who presented with new portal vein thrombosis, underwent further studies, was ultimately diagnosed with JAK2 positive MPN, and started on appropriate treatment with improvement of thrombosis and controlled hematocrit.

Atrial fibrillation and peripheral arterial disease define MPN patients with very high risk of thrombosis

Myeloproliferative neoplasms (MPNs) are associated with a high risk of thrombotic and hemorrhagic complications, especially in elderly patients. Atrial fibrillation (AF) and peripheral arterial disease (PAD), also frequently discovered in aging patients, are associated with similar complications. We analysed the incidence and complication rates of AF and PAD in a large cohort of MPN patients. In total, 289/1113 patients (26 %) suffered at least one of these diseases as follows: 179 (16.1 %) with AF alone, 81 with PAD alone (7.3 %) and 29 (2.6 %) with both conditions. Postdiagnosis thrombotic events were observed in 31.3 % of AF patients (p = 0.002, OR = 1.80 [1.23;2.61]), 35.8 % of PAD patients (p = 0.002, OR = 2.21[1.31;3.67]) and 62.1 % of AF/PAD patients (p < 0.0001, OR = 6.47 [2.83;15.46]) compared to 20.1 % of no-AF/no-PAD patients. Postdiagnosis hemorrhagic events were also identified in 17.9 %, 16 %, 24.1 % and 10.1 % of AF, PAD, AF/PAD, and no-AF/no-PAD patients, respectively (p = 0.003). This significantly higher risk of thrombosis/bleeding was also observed in patients <60 years old. AF and PAD were significant risk factors for both thrombotic and hemorrhagic risks in multivariate analysis. We identified AF and PAD as criteria for high risk of thrombosis, hemorrhage, and death, emphasizing the interest in early detection and efficient treatment of these conditions.

Pathological and genomic features of myeloproliferative neoplasms associated with splanchnic vein thrombosis in a single-center cohort

Here, we reviewed clinical-morphological data and investigated mutational profiles by NGS in a single-center series of 58 consecutive MPN-SVT patients admitted to our hospital between January 1979 and November 2021. We identified 15.5% of PV, 13.8% of ET, 34.5% of PMF, 8.6% of SMF and 27.6% of MPN-U. Most cases (84.5%) carried JAK2V617F mutation, while seven patients were characterized by other molecular markers, namely MPL in four and CALR mutations in three cases. NGS was performed in 54 (93.1%) cases: the most frequent additional mutations were found in TET2 (27.8%) and DNMT3A (16.7%) genes, whereas 25 (46.3%) patients had no additional mutation. Cases with JAK2V617F homozygosity had a higher median number of additional mutations than those with low allele burden. More importantly, all cases of leukemic evolution were characterized by a higher median number of co-mutations, and a co-mutational pattern of high-risk lesions, such as truncating mutations of ASXL1, bi-allelic TP53 loss, and CSMD1 mutations. Nevertheless, no difference was found between cases with and without additional somatic mutations regarding fibrotic progression, SVT recurrence, other thrombo-hemorrhagic complications, or death. After a median follow-up of 7.1 years, ten deaths were recorded; fibrotic progression/leukemic evolution was ascertained in one (1.7%) and six (10.3%) patients, respectively, while 22 (37.9%) patients suffered from recurrent thrombosis. In conclusion, our data underline the importance of using NGS analysis in the management of MPN-related SVT as it can support the MPN diagnosis, particularly in "triple-negative" cases, and provide additional information with potential consequences on prognosis and therapeutic strategies.

UPLC-MS/MS method development and application to pharmacokinetic study in rats and dogs of Flonoltinib Maleat

Flonoltinib Maleate (FM) is a novel selective inhibitor of Janus kinase 2/FMS-like tyrosine kinase 3 (JAK2/FLT3). In this study, we developed an ultra-high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method to measure the plasma concentrations of FM in rats and dogs for pharmacokinetic studies. For chromatographic separation, we used a BEH C18 column (2.1 × 50 mm, 1.7 μm particle size) in HPLC. The mobile phase A consisted of a water solution containing 0.1% formic acid (FA) and 2 mM NH₄OAc, mixed with acetonitrile (ACN) (V:V = 95:5). The mobile phase B was a water solution containing 0.1% FA and 2 mM NH₄OAc, mixed with ACN (V:V = 5:95), which was used for gradient elution. We used multiple reactive ion detection (MRM) mode and electrospray ionization positive (ESI+) mode for quantitative analysis. The standard curve was linear in the concentration range of 0.5 to 500 ng/ml in rat and dog plasma. The intra-batch and inter-batch precision (RSD%) of FM in rat and dog plasma was less than 15%. The intra-batch and inter-batch accuracy was 88.3-106.5% and 92.0-100.6% in rats, and 94.7-106.6% and 95.3-103.8% in dogs, respectively. The RSD (%) of matrix factors (MF) normalized to the internal standard (IS) of FM in rat and dog plasma was ≤5.6% and ≤3.0%, respectively. The extraction recovery and carryover were considered acceptable. When the sample concentration was higher than the upper limit of quantitation (ULOQ), the 10-fold dilution was reliable within the limits of acceptability. The UPLC-MS/MS method developed in this study was successfully applied in measuring the pharmacokinetic parameters of FM in rats and dogs after intravenous and oral administration, laying a foundation for the preclinical pharmacokinetic study of FM and providing a reference for clinical pharmacokinetic studies.

Budd-Chiari syndrome in myeloproliferative neoplasms: A review of literature

Myeloproliferative neoplasms (MPNs) are defined as clonal disorders of the hematopoietic stem cell in which an exaggerated production of terminally differentiated myeloid cells occurs. Classical, Philadelphia-negative MPNs, i.e., polycythemia vera, essential thrombocythemia and primary myelofibrosis, exhibit a propensity towards the development of thrombotic complications that can occur in unusual sites, e.g., portal, splanchnic or hepatic veins, the placenta or cerebral sinuses. The pathogenesis of thrombotic events in MPNs is complex and requires an intricate mechanism involving endothelial injury, stasis, elevated leukocyte adhesion, integrins, neutrophil extracellular traps, somatic mutations (e.g., the V617F point mutation in the JAK2 gene), microparticles, circulating endothelial cells, and other factors, to name a few. Herein, we review the available data on Budd-Chiari syndrome in Philadelphia-negative MPNs, with a particular focus on its epidemiology, pathogenesis, histopathology, risk factors, classification, clinical presentation, diagnosis, and management.

Prognostication in myeloproliferative neoplasms, including mutational abnormalities

Increasing knowledge of the molecular features of myeloproliferative neoplasms (MPNs) is being combined with existing prognostic models based on clinical, laboratory, and cytogenetic information. Mutation-enhanced international prognostic systems (MIPSS) for polycythemia vera (PV) and essential thrombocythemia (ET) have improved prognostic assessments. In the case of overt primary myelofibrosis (PMF), the MIPSS70 and its later revisions (MIPSS70+ and MIPSS70+ version 2.0) effectively predicted the overall survival (OS) of patients. Because post-PV and post-ET myelofibrosis have different biological and clinical courses compared to overt PMF, the myelofibrosis secondary to PV and ET-prognostic model was developed. Although these molecular-inspired prognostic models need to be further validated in future studies, they are expected to improve the prognostic power in patients with MPNs in the molecular era. Efforts are being made to predict survival after the use of specific drugs or allogeneic hematopoietic stem cell transplantation. These treatment outcome prediction models enable the establishment of personalized treatment strategies, thereby improving the OS of patients with MPNs.

[Clinical and genetic characteristics of young patients with myeloproliferative neoplasms]

Objectives: To investigate the clinical and genetic features of young Chinese patients with myeloproliferative neoplasms (MPN). Methods: In this cross-sectional study, anonymous questionnaires were distributed to patients with MPN patients nationwide. The respondents were divided into 3 groups based on their age at diagnosis: young (≤40 years) , middle-aged (41-60 years) , and elderly (>60 years) . We compared the clinical and genetic characteristics of three groups of MPN patients. Results: 1727 assessable questionnaires were collected. There were 453 (26.2%) young respondents with MPNs, including 274 with essential thrombocythemia (ET) , 80 with polycythemia vera (PV) , and 99 with myelofibrosis. Among the young group, 178 (39.3%) were male, and the median age was 31 (18-40) years. In comparison to middle-aged and elderly respondents, young respondents with MPN were more likely to present with a higher proportion of unmarried status (all P<0.001) , a higher education level (all P<0.001) , less comorbidity (ies) , fewer medications (all P<0.001) , and low-risk stratification (all P<0.001) . Younger respondents experienced headache (ET, P<0.001; PV, P=0.007; MF, P=0.001) at diagnosis, had splenomegaly at diagnosis (PV, P<0.001) , and survey (ET, P=0.052; PV, P=0.063) . Younger respondents had fewer thrombotic events at diagnosis (ET, P<0.001; PV, P=0.011) and during the survey (ET, P<0.001; PV, P=0.003) . JAK2 mutations were found in fewer young people (ET, P<0.001; PV, P<0.001; MF, P=0.013) ; however, CALR mutations were found in more young people (ET, P<0.001; MF, P=0.015) . Furthermore, mutations in non-driver genes (ET, P=0.042; PV, P=0.043; MF, P=0.004) and high-molecular risk mutations (ET, P=0.024; PV, P=0.023; MF, P=0.001) were found in fewer young respondents. Conclusion: Compared with middle-aged and elderly patients, young patients with MPN had unique clinical and genetic characteristics.

Predictors of increased risk of adverse cardiovascular outcomes among patients with myeloproliferative neoplasms and atrial fibrillation

BACKGROUND

Patients with myeloproliferative neoplasms (MPNs), essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF), have increased risk of cardiovascular (CV) disease. Atrial fibrillation (AF) is associated with adverse CV outcomes including arterial thrombosis, heart failure (HF), and CV death and coexists with MPN. Traditional risk scores (CHA2DS2-VASC and HAS-BLED) for estimating risks/benefits of anticoagulation to prevent thrombotic events in AF do not include MPN status. Therefore, we aimed to investigate CV outcomes in patients with MPN and AF and evaluate the predictive ability of traditional risk scores.

METHODS

We conducted a single-center, retrospective cohort study of patients with MPN and AF. Primary outcome was composite of CV death and arterial thromboembolism; secondary outcomes were bleeding requiring emergency department visit or hospitalization, hospitalization for HF, and all-cause death. Multivariable competing-risk and Cox proportional hazards regression models were used to estimate risk of outcomes. Receiver operating characteristic (ROC) curve used to evaluate predictive ability of CHA2DS2-VASC and HAS-BLED of composite outcome and bleeding, respectively.

RESULTS

A total 142 patients was included (62 ET, 54 PV, 26 MF). Composite outcome, bleeding, HF hospitalization and all-cause death occurred in 39 %, 30 %, 34 %, and 48 %, of patients respectively. After multivariable modeling, MF was associated with increased risk of composite outcome (SHR 2.70, 95 % CI 1.38-5.27) and all-cause mortality (HR 9.77, 95 % CI 4.88-19.54) but not bleeding (SHR 1.19, 95 % CI 0.51-2.80) or HF admissions (SHR 0.57, 95 % CI 0.19-1.72). CHA2DS2-VASC and HAS-BLED were poor predictors of composite outcome (C-statistic 0.52, 95 % CI 0.43-0.62) and bleeding (C-statistic 0.49, 95 % CI 0.40-0.58), respectively.

CONCLUSION

In patients with MPN and AF, MF is associated with increased risk of CV death and arterial thrombosis and traditional risk scores do not accurately predict outcomes in this patient population. Further investigation is needed to refine risk scores in this patient population.

Circulating CD133+/–CD34– Have Increased c-MYC Expression in Myeloproliferative Neoplasms

Objective

Myeloproliferative neoplasms (MPNs) are hematopoietic stem cell (HSC)-originated diseases with clonal myeloproliferation. The constitutive activation of the JAK/STAT pathway is frequently detected in patients with Philadelphia chromosome-negative (Ph–) MPNs with an acquired JAK2V617F mutation. The c-MYC proto-oncogene is associated with malignant growth and cellular transformation, and JAK2V617F was previously shown to induce constitutive expression of c-MYC. This study examines the expressional profile of c-MYC in Ph– MPNs with JAK2V617F and highlights its hierarchical level of activation in circulating hematopoietic stem/progenitor cell (HSPC) subgroups.

Materials and Methods

Mononuclear cells (MNCs) of Ph– MPNs were fluorochrome-labeled in situ with wild-type (wt) JAK2 or JAK2V617F mRNA gold nanoparticle technology and sorted simultaneously. Isolated populations of JAK2wt or JAK2V617F were evaluated for their c-MYC expressions. The MNCs of 14 Ph– MPNs were further isolated for the study of HSPC subgroups regarding their CD34 and CD133 expressions, evaluated for the presence of JAK2V617F, and compared to cord blood (CB) counterparts for the expression of c-MYC.

Results

The mRNA-labeled gold nanoparticle-treated MNCs were determined to have the highest ratio of c-MYC relative fold-change expression in the biallelic JAK2V617F compartment compared to JAK2wt. The relative c-MYC expression in MNCs of MPNs was significantly increased compared to CB (p=0.01). The circulating HSPCs of CD133^+/–CD34⁻ MPNs had statistically significantly elevated c-MYC expression compared to CB.

Conclusion

This is the first study of circulating CD133^+/–CD34⁻ cells in Ph– MPNs and it has revealed elevated c-MYC expression levels in HSCs/endothelial progenitor cells (HSCs/EPCs) and EPCs. Furthermore, the steady increase in the expression of c-MYC within MNCs carrying no mutations and monoallelic or biallelic JAK2V617F transcripts was notable. The presence of JAK2V617F with respect to c-MYC expression in the circulating HSCs/EPCs and EPCs of MPNs might provide some evidence for the initiation of JAK2V617F and propagation of disease. Further studies are needed to clarify the implications of increased c-MYC expression in such populations.

Chronic myeloid leukemia (CML) evolves from Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) with unexpected frequency

Myeloproliferative neoplasms (MPN) are chronic clonal disorders characterized by overproduction of myeloid-lineage blood cells and potential risk of evolution to acute myeloid leukemia (AML). Chronic myeloid leukemia (CML) is distinct from other MPNs in that its pathophysiology stems from the BCR-ABL fusion protein of the Philadelphia chromosome (Ph +). Though there are known cases of Ph- and Ph + MPNs coexisting in a single patient, overall prevalence has never been quantified in a prospective cohort. Here, we review our center's MPN registry, which shows 0.6% of Ph- MPN patients later developed CML. This development occurred no less than 10 and up to 36 years after Ph- MPN diagnosis. This rate of chronic transformation exceeds what is expected, as the incidence of CML in the United States is 2 per 100,000 people-years. The probability of this CML case rate in an average-risk population is less than 0.001%, suggesting there are shared risk factors between Ph- and Ph + MPNs. We speculate that these risk factors may include exposures, genetic predispositions, or be inherent to disease biology. Abrupt-onset leukocytosis heralded post-MPN CML in all cases here and suggests this salient clinical feature should trigger hematologists to consider this diagnosis and perform appropriate testing.

Patient-Reported Outcomes in Young Adults with Myeloproliferative Neoplasms

INTRODUCTION

Genetic landscape, disease characteristics, and clinical outcomes of young adults with myeloproliferative neoplasms (MPNs) were reported. However, data on patient-reported outcomes (PROs) in young adults with MPNs were rare.

METHODS

We conducted a multicenter, cross-sectional study to compare the PROs in respondents with thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF) by age at survey, including the young group (18-40 years), middle-aged group (41-60 years), and elderly group (>60 years).

RESULTS

Of the 1,664 respondents with MPNs, 349 (21.0%) were young including 244 (69.9%) with ET, 34 (9.7%) with PV, and 71 (20.3%) with MF. In multivariate analyses, the young groups with ET and MF were associated with the lowest MPN-10 scores among the 3 age groups; those with MF, highest proportion of reporting negative impact of disease and therapy on their daily life and work. The young groups with MPNs had the highest physical component summary scores but the lowest mental component summary scores in those with ET. The young groups with MPNs were most concerned about fertility; those with ET, treatment-related adverse events and long-term efficacy of treatment.

CONCLUSIONS

We concluded that young adults with MPNs have different PROs compared with middle-aged and elderly patients.

Novel JAK2 Exon 14 Mutations L611S or N622Y in cis with JAK2V617F Are Associated with Distinct Clinical Phenotype of Polycythemia Vera and Concurrent Eosinophilia

Eosinophilic phenotypes in polycythemia vera (PV) and essential thrombocythemia (ET) are rare and poorly characterized. Co-occurring JAK2 mutations in cis, specifically L611S or N622Y mutations, appear to result in a more aggressive clinical phenotype. PV/ET with eosinophilic phenotypes may require full next-generation sequencing to capture co-occurring mutations as opposed to more prevalent single-gene assays. These eosinophilic phenotypes are highly thrombotic and systemic symptoms appear responsive to early use of the janus kinase inhibitor ruxolitinib.

Novel modes of MPL activation in triple-negative myeloproliferative neoplasms

The identification of a somatic mutation associated with myeloid malignancy is of diagnostic importance in myeloproliferative neoplasms (MPNs). Individuals with no mutation detected in common screening tests for variants in JAK2, CALR, and MPL are described as 'triple-negative' and pose a diagnostic challenge if there is no other evidence of a clonal disorder. To identify potential drivers that might explain the clinical phenotype, we used an extended sequencing panel to characterise a cohort of 44 previously diagnosed triple-negative MPN patients for canonical mutations in JAK2, MPL and CALR at low variant allele frequency (found in 4/44 patients), less common variants in the JAK-STAT signalling pathway (12 patients), or other variants in recurrently mutated genes from myeloid malignancies (18 patients), including hotspot variants of potential clinical relevance in eight patients. In one patient with thrombocytosis we identified biallelic germline MPL variants. Neither MPL variant was activating in cell proliferation assays, and one of the variants was not expressed on the cell surface, yet co-expression of both variants led to thrombopoietin hypersensitivity. Our results highlight the clinical value of extended sequencing including germline variant analysis and illustrate the need for detailed functional assays to determine whether rare variants in JAK2 or MPL are pathogenic.

The indispensable role of the RNA helicase DDX5 in tumorigenesis induced by the myeloproliferative neoplasm-associated JAK2V617F mutant

A point mutation (V617F) in the Janus kinase 2 (JAK2) gene results in the production of disorderly activated tyrosine kinase, which causes myeloproliferative neoplasms (MPN). We herein demonstrated that the RNA helicase DDX5 was highly expressed at the mRNA and protein levels through the activation of signal transducer and activator of transcription 5 (STAT5) in Ba/F3 cells expressing a JAK2V617F mutant and erythropoietin receptor (V617F/EpoR cells) and MPN patient-derived HEL cells. A treatment with the JAK1/2 inhibitor, ruxolitinib and STAT5 inhibitor, pimozide significantly inhibited DDX5 mRNA expression and enhanced the degradation of DDX5 in these cells, suggesting that the JAK2V617F mutant positively regulates DDX5 mRNA expression and DDX5 protein stability by activating STAT5. The knockdown of DDX5 specifically inhibited the activation of mechanistic target of rapamycin (mTOR) in V617F/EpoR cells and HEL cells and significantly suppressed the proliferation of these cells. Furthermore, the knockdown of DDX5 markedly suppressed tumorigenesis, splenomegaly, and liver hypertrophy caused by an inoculation of V617F/EpoR cells in nude mice. Collectively, these results revealed that JAK2V617F exhibits transforming activity by inducing the expression of DDX5 in a STAT5-dependent manner, indicating the potential of the JAK2V617F/STAT5/DDX5 axis as a therapeutic target in the treatment of MPN.

[Novel therapeutics in myeloproliferative neoplasms: beyond JAK inhibitors]

The discovery of driver genes such as JAK2 in myeloproliferative neoplasms (MPN) led to a better understanding of MPN pathogenesis as a constitutive activation of the JAK/STAT signal. Following these findings, several types of JAK inhibitors have been developed. Ruxolitinib, a JAK1/2 inhibitor licensed for polycythemia vera and myelofibrosis, demonstrated efficacy in regulating hematocrit levels, lowering spleen volume, and relieving MPN-related symptoms. However, some patients with myelofibrosis are refractory to JAK inhibitors, and some are intolerant due to cytopenia. Furthermore, JAK inhibitors did not slow the progression of acute leukemia, indicating the need for new therapeutic methods for myelofibrosis. Novel medicines, including BCL inhibitor, MDM2 inhibitor, LSD1 inhibitor, PI3K inhibitor, BET inhibitor and telomerase inhibitor, are presently being evaluated in clinical studies for myelofibrosis with the potential to enhance clinical outcomes.

Clonal hematopoiesis and cardiovascular diseases: role of JAK2V617F

Bone marrow-derived hematopoietic and immune cells play important roles in the onset and progression of cardiovascular diseases. Recent genetic analyses have discovered that clonal expansion of bone marrow hematopoietic stem/progenitor cells carrying somatic gene mutations is common and is increasing with age in healthy individuals who do not show any hematologic disorders, termed as clonal hematopoiesis. It is emergingly recognized that clonal hematopoiesis is a significant risk factor for cardiovascular diseases rather than a cumulative incidence risk of blood cancers. JAK2V617F, a gain-of-function mutation, has been identified as one of the most important mutations in clonal hematopoiesis as well as the most frequent driver mutation in myeloproliferative neoplasms. Hematopoietic cell clones harboring JAK2V617F are causally associated with the pathogenesis of cardiovascular diseases. Here, we will review the key of JAK2V617F-mediated clonal hematopoiesis including identification, prevalence, and biological impacts, linking to cardiovascular diseases and the related mechanisms. Clonal hematopoiesis with JAK2V617F may be a novel therapeutic target for cardiovascular diseases, connected to precision medicines by detecting its presence.

Pulmonary hypertension is associated with poor cardiovascular and hematologic outcomes in patients with myeloproliferative neoplasms and cardiovascular disease

Cardiovascular events and hematologic progression to myelofibrosis or leukemia are leading causes of morbidity and mortality among patients with myeloproliferative neoplasms (MPN). Pulmonary hypertension (PH) is also associated with MPN and cardiovascular disease (CVD), though its prognostic significance in MPN is not well characterized. Our primary objective was to investigate the effect of PH, defined as right-ventricular systolic pressure (RVSP) ≥ 50 mmHg on echocardiogram or mean pulmonary artery pressure (mPAP) ≥ 20 on right heart catheterization, on cardiovascular and all-cause mortality and hematologic progression in patients with MPN and CVD (atrial fibrillation, heart failure hospitalization, and myocardial infarction after MPN diagnosis). Of the 197 patients included (86 ET, 80 PV, 31 PMF), 92 (47%) had PH and 98 (50%) were male. All-cause mortality (58 vs 37%, p = 0.004), cardiovascular death (35 vs 9%, p < 0.0001), and hematologic progression (23 vs 11%, p = 0.037) occurred more frequently in patients with PH. Multivariable competing-risk and proportional hazards regression showed that PH was associated with increased risk of all-cause death (adjusted hazard ratio [HR], 1.80, 95% CI 1.10-2.93), CV death (adjusted subdistribution HR 3.71, 95% CI 1.58-8.73), and hematologic progression (adjusted subdistribution HR 1.99, 95% CI 1.21-3.27).

Comparability of JAK2 p.V617F allele burden in peripheral blood and that in bone marrow in patients with suspected myeloproliferative neoplasms: a single-center prospective study

PURPOSE

To detect JAK2 p.V617F and measure allele burden in peripheral blood (PB) and bone marrow (BM) aspirates in patients with suspected myeloproliferative neoplasms (MPNs).

METHODS

Patients with suspected MPNs were prospectively enrolled between August 2017 and May 2019, and their PB and BM were collected during the same period. Quantitative fluorescence polymerase chain reaction (PCR) was used to detect the copy number of JAK2 wild type and the V617F mutant; the JAK2 V617F proportion was also calculated. The JAK2 p.V617F proportion in PB was compared to that in BM by Chi-square test.

RESULTS

Among 54 patients with suspected MPNs, 43 of them were eligible for analysis. The JAK2 p.V617F in PB had the same sensitivity and specificity as BM (all P>0.05). The Chi-square test suggested that the JAK2 p.V617F allele burden of PB was comparable to that of BM (Spearman Correlation =0.986; P=0.000).

CONCLUSION

PB could be used as an alternative to BM for JAK2 p.V617F measurement in patients with suspected MPNs.

[Allogeneic hematopoietic cell transplantation for myeloproliferative neoplasms]

The median survival duration of myelofibrosis is about 5 years and at present, allogeneic hematopoietic cell transplantation is the only curative treatment. Although myelofibrosis's clinical course and prognosis vary from patient to patient, the time and indication of transplantation should be determined in light of the likelihood of transplant-related death or long-term prognosis, as well as any information on each patient's gene mutation risk. Previous reports have demonstrated that allogeneic hematopoietic cell transplantation can be a curative treatment for myelofibrosis. However, the transplant-related mortality rate is as high as 30-50%, and the overall survival rate is only around 40%. Future research should clarify how to decide between JAK2 inhibitors and allogeneic hematopoietic cell transplantation, how to lower high transplant-related mortality, how to choose a stem cell source, how to create the best pretransplant treatment, and how to incorporate JAK2 inhibitors before transplantation.