JAK2V617F Mutation Research Articles

Highly Sensitive Blocker Displacement Amplification for Detection of Low-Level JAK2V617F Variant.

Key criteria in the diagnostic workup and risk stratification for myeloproliferative neoplasms (MPN) include molecular testing for JAK2V617F and other mutant alleles. Multiple methods for quantitatively detecting nucleotide sequence changes exist, but the lower limit of detection can limit identification of the low-level allele fraction of a variant. We evaluated a recently developed blocker displacement amplification (BDA)-based quantitative PCR platform for detection and quantitation of JAK2V617F variant allele fraction (VAF). Clinical samples were tested using BDA, next-generation sequencing (NGS), and droplet digital PCR (ddPCR) in a head-to-head comparison of sensitivity and specificity in detecting the JAK2V617F variant. In total, 112 human genomic DNA specimens previously tested for JAK2V617F gene mutation status with NGS were analyzed, including 12 samples with low-level variants with VAF ≤2%, 6 samples with VAF >2%, and 94 samples with no variant previously identified by NGS. BDA and ddPCR results correlated well across a range of VAFs, with both methods identifying the JAK2V617F variant down to at least 0.05% VAF. NGS of routine sequencing depth was less sensitive, identifying JAK2V617F only at 0.6% VAF. BDA can provide a cost-effective alternative means to identify low-level variants using instrumentation commonly found in laboratories.

Platelet function studies in myeloproliferative neoplasms patients with Calreticulin or JAK2V617F mutation

BackgroundJAK2V617F and Calreticulin (CALR) mutations are the most frequent molecular causes of Phi-negative myeloproliferative neoplasms (MPN). Patients with CALR mutations are at lower risk of thrombosis than patients with JAK2V617F. We hypothesized that CALR-mutated blood platelets would have platelet function defects that might explain why these patients are at lower risk of thrombosis. ObjectivesOur main objective was to explore and compare platelet function depending on the MPN molecular marker. MethodsWe analyzed platelet function in 16 patients with MPN with CALR mutations and 17 patients with JAK2V617F mutation and compared them with healthy controls. None of these patients was taking antiplatelet therapy. We performed an extensive analysis of platelet function and measured plasmatic soluble P-selectin and CD40L levels. ResultsWe observed significant defects in platelet aggregation, surface glycoprotein expression, fibrinogen binding, and granule content in platelets from patients with MPN compared with that in controls. Moreover, soluble CD40L and P-selectin levels were elevated in patients with MPN compared with that in controls, suggesting an in vivo platelet preactivation. Comparison of platelet function between patients with CALR and JAK2V617F MPN revealed only minor differences in platelets from patients with CALR. However, these results need to be interpreted within the context of absence of an inflammatory environment that could impact platelet function during MPN. ConclusionsThese results do not support the hypothesis that calreticulin-mutated platelets have platelet function defects that could explain the lower thrombotic risk of patients with CALR.

JAK2 Mutations Are Rare and Diverse in Myelodysplastic Syndromes: Case Series and Review of the Literature

To investigate and characterize JAK2 mutations in myelodysplastic syndrome (MDS), we present three cases with diverse JAK2 mutations and review the literature. The institutional SoftPath software was used to find MDS cases between January 2020 and April 2022. The cases with a diagnosis of a myelodysplastic/myeloproliferative overlap syndrome including MDS/MPN with ring sideroblasts and thrombocytosis were excluded. The cases with molecular data by next generation sequencing looking for gene aberrations commonly seen in myeloid neoplasms were reviewed for the detection of JAK2 mutations including variants. A literature review on the identification, characterization, and significance of JAK2 mutations in MDS was performed. Among 107 cases of the MDS reviewed, a JAK2 mutation was present in three cases, representing 2.8% of the overall cases. A JAK2 V617F mutation was found in one case representing slightly less than 1% of all the MDS cases. In addition, we found JAK2 R564L and JAK2 I670V point mutation variants to be associated with a myelodysplastic phenotype. JAK2 mutations in MDS are rare and represent less than 3% of cases. It appears that JAK2 variant mutations in MDS are diverse and further studies are needed to understand their role in the phenotype and prognosis of the disease.

GENETIC CHIMERISM IN MYELOPROLIFERATIVE NEOPLASMS: CLINICAL CASE OF COEXISTENCE OF JAK2V617F MUTATION AND BCR-ABL TRANSLOCATION

Essentialy, the diagnostics feature of myeloproliferative neoplasms (MPNs) is a genetic mutations. While bcr-abl translocation belongs to CML, Jak2V617F mutation is commonly associated with other MPNs. The recent decade has been clarified a data when a human blood presents bcr-abl translocation and Jak2V617F mutation both. This clinical case reports of bcr-abl translocation and Jak2V617F mutation when they were detected simultaneously by polymerase chain reaction (PCR) in a patient with myeloproliferative neoplasm, unclassifiable (MPN-U).

Mutation Status Defines Subtypes of Essential Thrombocythemia and Relation to Polycythemia Vera in Iraqi Patients

Background: Polycythemia vera (PV) and essential thrombocythemia (ET) are a part of the BCR-ABL1-negative myeloproliferative neoplasms (MPNs) that harbor mutation in Janus kinase 2 (JAK2), CALR, or MPL gene. Objectives: The objective of this study was to investigate the impact of JAK2 and CALR mutations on the clinical course and hematological phenotype of ET patients and to evaluate the biological and clinical features of ET and PV sharing the same type of mutation in JAK2V617F. Materials and Methods: This was a cross-sectional study that included 94 patients diagnosed with MPN, of them 47 had PV and 47 had ET. JAK2V617F mutation was assessed using either allele-specific PCR or JAK-2 quantitative real-time PCR kit. JAK2-negative patients were further assessed for the existence of CALR mutations using SNP biotechnology MPN screening kit. Results: JAK2 mutation was identified in 29 ET patients, whereas CALR mutations were confirmed in 18 patients. JAK2-mutated ET patients were significantly older than those with CALR mutations. Seventy-six were reported to have a mutation in JAKV617F, of them 47 were diagnosed as PV and 29 as ET. JAK2V617F-mutated PV patients had significantly higher levels of hemoglobin, hematocrit, and WBC than JAK2-mutated ET patients. On the other hand, JAK2-mutated PV patients exhibited lower platelet count than ET harboring the same mutation. Conclusion: JAK2-mutated ET represents a distinct clinical entity that has a hematological and clinical phenotype ranging between JAK2-mutated PV and CALR-mutated ET. The analysis of the mutational status is essential in discriminating subtypes of MPN and confirming the diagnosis in ET and PV patients.

Genetic and Clinical Characteristics of Patients with Philadelphia-Negative Myeloproliferative Neoplasm Carrying Concurrent Mutations in JAK2V617F, CALR, and MPL.

Simultaneous mutations in Janus kinase 2 (JAK2), calreticulin, and myeloproliferative leukemia (MPL) genes are generally not considered for characterizing Philadelphia-negative myeloproliferative neoplasms (MPNs), leading to misdiagnosis. Sanger sequencing and quantitative polymerase chain reaction were used to detect gene mutations in patients with MPN. We retrospectively screened the data of patients with double mutations in our center and from the PubMed database. Two patients tested positive for both JAK2V617F and CALR mutations (2/352 0.57%) in our center, while data of 35 patients from the PubMed database, including 26 patients with essential thrombocythemia (ET), 6 with primary myelofibrosis (PMF), 2 with unexplained thrombosis, and 1 with polycythemia vera were screened for double mutations. Among these mutations, co-mutation of JAKV617F-CALR constituted the majority (80.0%), when compared with JAKV617F-MPL (17.1%) and CALR-MPL (2.9%) mutations. Moreover, patients with concurrent mutational myeloproliferative neoplasm (MPN) were relatively older (P = .010) with significantly higher platelet counts than their counterparts with single gene mutations (P < .001). The occurrence of palpable splenomegaly (P < .001) and leukocyte count (P = .041) were also significantly different between patients with single and simultaneous gene mutations. These 4 risk factors also showed significant test effectiveness in the ET and PMF cohorts (P < .05). In terms of clinical characteristics of patients with ET, those with JAK2V617F-CALR mutation had higher but normal hemoglobin levels (P = .0151) than those carrying JAK2V617F-MPL mutation. From a clinical perspective, patients with multiple mutational MPN are different from those with single gene mutations. The poor treatment response by patients in our center and unfavorable indicators for patients with co-mutations in published literature indicate that customized treatment may be the best choice for patients with MPN carrying co-mutations.

The Sarawak Myelofibrosis (SaMy) experience: Demographics and outcome of myelofibrosis patients in Sarawak, Malaysia.

Introduction: Myelofibrosis is a rare disease. There is currently no published data reporting the demographics and outcome of myelofibrosis patients in Malaysia. We aimed to study the demographics, clinical characteristics, and outcome of our patients in Sarawak. Materials and methods: This non-interventional, retrospective, and multi-center study was conducted on secondary data of medical records collected at four Sarawak Public Hospitals. All adult myelofibrosis patients diagnosed between January 2001 and December 2021 were included. Results: A total of 63 patients (male 31) with myelofibrosis were included-47 (74.6%) primary and 16 (25.4%) secondary myelofibrosis. Eleven had antecedent polycythaemia vera, whereas five transformed from essential thrombocythaemia. The combined annual incidence rate was 0.182 per 100,000 population. The period prevalence per 100,000 population over the entire study duration was 2.502. The median age was 59.0 years (33.0-93.0). Majority had high-risk (34/63(54.0%)) and intermediate-2 risk disease (19/63(30.2%)). JAK2V617F mutation was identified in 52 patients (82.5%), followed by CALR mutation in 6 (9.5%) and negative for both mutations in 5 (7.9%). Hydroxyurea was used as first-line therapy in 41/63 (65.1%), followed by interferon (8/63(12.7%)) and ruxolitinib (4/63(6.3%)). Out of 46 patients who received second-line therapy, 18 (39.1%) were switched to ruxolitinib and 9 (19.6%) to interferon. The median age of survival for overall patients was 6.8 years. The use of ruxolitinib in myelofibrosis patients showed a better overall 5-year survival compared to the no ruxolitinib arm, despite no statistical significance (p = 0.34). Patients who had good performance status had lower hazard of death than patients who had poor performance status (high-risk (95% confidence intervals): 0.06(0.013-0.239), p < 0.001). Patients with intermediate risk disease had better overall survival compared to those in high-risk group (95% confidence intervals): 0.24(0.082-0.695), p = 0.009). Conclusion: This registry provides a real-world overview of myelofibrosis patients in our state and highlights the key insight into the unmet clinical need.

The Combination of JAK2V617F Allele Burden and WT1 Expression can Be Helpful in Distinguishing the Subtype of MPN Patients.

Classical Philadelphia-negative myeloproliferative neoplasm (MPN) includes Essential Thrombocythemia (ET), Polycythemia Vera (PV) and Primary Myelofibrosis (PMF). The JAK2V617F mutation is part of the major criteria for diagnosis of MPN. WT1 is reported to be highly overexpressed in most hematological malignancy. Our aim was to explore the combination value of JAK2V617F allele burden and WT1 expression in distinguishing the subtype of MPN patients. Allele specific real-time quantitative fluorescence PCR (AS-qPCR) was conducted to detect JAK2V617F allele burden. WT1 expression was assessed by RQ-PCR. Our study is a retrospective study. JAK2V617F allele burden and WT1 expression were different in MPN subgroups. The expression of WT1 in PMF and PV is higher than in ET. JAK2V617F allele burden in PMF and PV is also higher than in ET. ROC analysis indicated that combination of JAK2V617F allele burden and WT1 expression to discriminate ET and PV, ET and PMF, PV and PMF is 0.956, 0.871, 0.737 respectively. Furthermore, their ability to distinguish ET patients with high Hb levels from PV patients with high platelet counts is 0.891. Our data revealed that combination of JAK2V617F allele burden and WT1 expression is useful in distinguishing the subtype of MPN patients.

Esophagogastric varix caused by extrahepatic portal vein obstruction with essential thrombocythemia: A case report.

Extrahepatic portal vein obstruction (EHPVO) is a very rare disease-causing portal hypertension. Myeloproliferative neoplasm (MPN) including essential thrombocythemia (ET) is reported as a risk factor for EHPVO due to underlying persistent thrombophilia.A Japanese woman in her 40s was referred to our hospital with a one-month history of gastric variceal bleeding due to EHPVO. Laboratory investigation demonstrated thrombocytosis despite portal hypertension. She had a mutation of clonal marker JAK2V617F with EHPVO, which prompted us to consult a hematologist. Bone marrow biopsy revealed megakaryocyte lineage proliferation, leading to a diagnosis of ET.Esophagogastroduodenoscopy indicated esophagogastric varices (LsF2CbRC2, Lg-cF1RC1). Abdominal Computed Tomography and angiography revealed splenomegaly and portal vein thrombosis with cavernous transformation. These radiologic findings suggested EHPVO.The patient had a history of ruptured esophagogastric varices and required prophylaxis against further variceal bleeding prior to anti-thrombotic therapy for EHPVO with ET. We performed laparoscopic Hassab's operation followed by endoscopic variceal ligation (EVL) and hematological cytoreduction therapy.Laparoscopic Hassab's operation and three bi-monthly EVL improved the esophagogastric varix (LmF0RC0, Lg-f F0RC0) at 6 months after surgery. Platelet count decreased to 60.1 x104 /uL by cytoreduction therapy. She was very healthy at 7 months after surgery.Patients with EHPVO are traditionally referred to the gastroenterologist for abdominal pain, intestinal bleeding, or refractory ascites; however, hypercoagulative disease may be occult in such patients and require the attention of a hematologist. When encountering the patients with splanchnic thrombosis caused by EHPVO, the gastroenterologists should screen for hematological disease, including MPN.

Coexistence of JAK2V617F and CALR mutation in Tunisian cohort with Philadelphia-negative chronic myeloproliferative neoplasms

Coexistence of JAK2V617F and CALR mutation in Tunisian cohort with Philadelphia-negative chronic myeloproliferative neoplasms

Investigation of JAK2 V617F mutation prevalence in a sample of Iraqi patients with Beta thalassemia major

Investigation of JAK2 V617F mutation prevalence in a sample of Iraqi patients with Beta thalassemia major

Application of the Peptide Nucleic Acid Blocker to Improve the Sensitivity of Real-Time PCR for Quantitating JAK2 V617F Mutation

Application of the Peptide Nucleic Acid Blocker to Improve the Sensitivity of Real-Time PCR for Quantitating JAK2 V617F Mutation

Effects of Ruxolitinib on Myeloproliferative Neoplasms via the Negative Regulators.

We evaluated the JAK2V617F mutation and p-JAK2, SOCS-1, SHP-1 expression in JAK2V617F positive myeloproliferative neoplasms (MPNs) patients and the role of JAK/STAT pathway in human erythroleukemia (HEL) cells, which had JAK2V617F mutation. Protein expression of p-JAK2, SOCS-1, SHP-1 in bone marrow biopsies (BMBs) were detected by immunohistochemical staining methods. Cell apoptosis and cell cycle were detected by flow cytometry and Caspase 3/7 assay kits. 1. The p-JAK2, SOCS-1, and SHP-1 expressions were significantly different between JAK2V617F positive MPN and control patients (p < 0.01); 2. After being treated for 3 months, the p-JAK2, SOCS-1, and SHP-1 expressions were significantly different compared with newly diagnosed patients (p < 0.01). 3. HEL cell viabilities were significantly different after being treated with different concentrations of ruxolitinib. Ruxolitinib had a significant effect on the cell apoptosis, viability, and the protein activity of caspase-3 and -7 of HEL cells. 3. The mRNA and protein expressions of JAK2 and the protein expression of p-JAK2 were gradually decreased (p ＜ 0.01, p ＜ 0.05), while the mRNA and protein expressions of SOCS1 and SHP1 were gradually increased (all p ＜ 0.01).

Molecular prognostication in Ph-negative MPNs in 2022.

The application of genomic techniques, including cytogenetics and DNA sequencing, to decipher the molecular landscape of patients with myeloproliferative neoplasms (MPNs) has radically modified diagnostic approach and management through improved risk stratification. Three driver mutated genes (JAK2, MPL, CALR) are variably harbored by >80% of patients and associated with clinical characteristics, as well as major disease-related complications and different survival outcomes. Therefore, JAK2 V617F mutation is included in the revised International Prognosis Score of Thrombosis for Essential Thrombocythemia score for prediction of thrombosis in patients with essential thrombocythemia and prefibrotic primary myelofibrosis, while a CALR type 1 mutated genotype constitutes a favorable variable for survival in patients with myelofibrosis (MF). Novel, integrated clinical and cytogenetic/mutation scores (Mutation-Enhanced International Prognostic Score System for Transplantation-Age Patients with Primary Myelofibrosis [MIPSS70/v2], genetically inspired prognostic scoring system [GIPSS], Myelofibrosis Secondary to PV and ET- Prognostic Model [MYSEC-PM]) have been devised that guide selection of stem cell transplantation candidates with MF or help predict the risk associated with the transplant procedure (Myelofibrosis Transplant Scoring System), with greater performance compared with conventional scores based on hematologic and clinical variables only. On the other hand, several clinical needs remain unmet despite the great amount of molecular information available nowadays. These include the prediction of evolution to acute leukemia in a clinically actionable time frame, the identification of patients most likely to derive durable benefits from target agents, in primis JAK inhibitors, and, conversely, the significance of molecular responses that develop in patients receiving interferon or some novel agents. Here, we discuss briefly the significance and the role of genomic analysis for prognostication in patients with MPNs from a clinician's point of view, with the intent to provide how-to-use hints.

Reevaluation of cardiovascular risk factors for thrombotic events in 580 Japanese patients with essential thrombocythemia.

Risk-adapted therapy is recommended to prevent thrombosis in essential thrombocythemia (ET) patients. An advanced age, a history of thrombosis, and the presence of the JAK2V617F mutation are well-defined risk factors for thrombosis in ET; however, the impact of cardiovascular risk (CVR) factors on thrombosis in ET remains elusive. Therefore, we herein investigated the impact of CVR factors on thrombosis in 580 ET patients who met the 2017 World Health Organization Classification diagnostic criteria. A univariate analysis identified hypertriglyceridemia and multiple CVR factors as strong risk factors for thrombosis (hazard ratio [HR] 3.530, 95% confidence interval [CI] 1.630-7.643, P = 0.001 and HR 3.368, 95% CI 1.284-8.833, P = 0.014, respectively) and hyper-LDL cholesterolemia as a potential risk factor (HR 2.191, 95% CI 0.966-4.971, P = 0.061). A multivariate analysis revealed that hypertriglyceridemia was an independent risk factor for thrombosis (HR 3.364, 95% CI 1.541-7.346, P = 0.002). Furthermore, poor thrombosis-free survival was observed in patients with a serum triglyceride level ≥ 1.2mmol/L (HR = 2.592, P = 0.026 vs. < 1.2mmol/L) or two or more CVR factors (P = 0.011 vs. no CVR factors and P = 0.005 vs. one CVR factor). These results revealed the impact of CVR factors on thrombosis in ET. Since CVR factors are manageable, lifestyle interventions, such as the control of serum triglyceride levels, may effectively prevent thrombosis in ET patients.

Clinical characteristics and management of headache in patients with myeloproliferative neoplasms.

Headache is frequently reported as a neurological manifestation of myeloproliferative neoplasms (MPNs), including polycythemia vera and essential thrombocythaemia. This study sought to clarify the clinical characteristics and response to treatment of headaches in patients with MPNs. We prospectively studied 137 patients with MPNs. The following information was gathered to assess the features of headache at baseline and at follow-up (>6 months): (1) average duration of headache attacks, (2) number of headache days per month, (3) numerical rating scale (NRS), (4) Headache Impact Test-6 (HIT-6), and (5) Migraine Disability Assessment (MIDAS). We compared those parameters for headaches between the baseline and follow-up interviews according to the management. Thirty-seven (27.0%) patients had headache. The prevalence of headaches gradually decreased with increasing age (Age ≤ 49 years: 61.0%, 50-59 years: 38.5%, 60-69 years: 17.2%, 70-79 years: 5.1%, and ≥80 years: 0.0%, P < 0.001). Multiple logistic regression analysis showed that younger age, but not platelet counts or the JAK2 V617F mutation, was independently associated with headaches (Odds Ratios 2.004, 95% confidence intervals 1.293-3.108, P = 0.002). Scintillating scotomas were present in 22 (59.5%) of 37 patients with headaches, while four patients developed sudden headaches that lasted for only 0-10 min. Follow-up interviews were available for 31 (83.8%) of 37 patients with headaches. Twenty-one (67.7%) patients were treated with low-dose aspirin (100 mg once daily) [low-dose aspirin alone: n = 9; combined cytoreductive therapy: n = 12] for headache management. All parameters for headache [average duration of headache attacks, number of headache days per month, NRS score, HIT-6 score, and MIDAS score (all P < 0.001)] were significantly improved at follow-up in patients taking low-dose aspirin. However, there were no significant differences in these parameters of headaches in patients who did not receive low-dose aspirin. Headaches is common in patients with MPNs, particularly in younger patients. MPN-related headaches may be managed by using low-dose aspirin and controlling MPNs.

Essential Thrombocythemia: One-Center Data in a Changing Disease.

Introduction: Essential thrombocythemia is a chronic myeloproliferative neoplasm associated with thrombo-hemorrhagic events and the progression to myelofibrosis or acute myeloid leukemia. The purpose of this article is to present real-world data on ET cases diagnosed and managed between 1998 and 2020 in the largest, tertiary hematology reference center in Romania and to evaluate the impact of thrombotic events on survival. Methods: A real-world, retrospective cohort-type study was conducted. We collected and statistically analyzed data from 168 patients who met the 2016 WHO diagnostic criteria for ET and who were managed between 1998 and 2020 in our center. Results: The median age at diagnosis of ET was 51.8 years, with a female predominance (66.07%). The JAK2V617F mutation was detected in 60.71% of patients. Leukocytosis at diagnosis was associated with a higher risk of thrombosis, and JAK2V617F-positive cases exhibited a 1.5-fold higher risk of developing thrombotic events. The average survival in ET with major thrombosis was 14.5 years versus 20.6 years in ET cases without major thrombosis. Other predictors of survival were high-risk IPSET score and age >60 years. Conclusions: Romanian patients diagnosed with ET are generally younger than 60 years and are predominantly female. The occurrence of thrombotic events was influenced by gender, leukocyte count at diagnosis and JAK2V617F positivity. Survival was impacted by age, the presence of JAK2V617F mutation, hypertension, major thrombotic complications and IPSET score. Notably, these findings warrant careful interpretation and further confirmation in the setting of prospective studies.

Frequency of JAK2V617F, MPL and CALR driver mutations and associated clinical characteristics in a Norwegian patient cohort with myeloproliferative neoplasms

Myeloproliferative neoplasms are hematological disorders characterized by increased production in one or more myeloid cell lines, associated with driver mutations in JAK2-, MPL- and CALR-genes. The aims of this study were to investigate the prevalence of these driver mutations in a Norwegian patient cohort with myeloproliferative neoplasms, and to assess whether the different mutations were associated with different clinical presentation and natural history. Results from 820 patients in whom analysis for JAK2V617F-, CALR- and MPL had been performed at Haukeland University Hospital in the period 2014-2019 were retrieved and analyzed together with clinical variables related to diagnosis, hematological blood parameters and complications, obtained from patient records. We identified 182 cases of myeloproliferative neoplasms: 78 with JAK2V617F, 28 with CALR-mutations, two with MPL-mutations and 23 cases without a driver mutation. There was a lower prevalence of JAK2V617F mutation than expected in the polycythemia vera group, likely related to overdiagnosis. In patients with essential thrombocytosis, we found significantly higher levels of hemoglobin and erythrocyte volume fraction for JAK2V617F-mutated disease, and significantly higher levels of platelets and lactate dehydrogenase for CALR-mutated disease. Patients with JAK2V617F-mutated primary myelofibrosis had significantly higher levels of hemoglobin, and there was an increased number of smokers or former smokers in this group compared to patients with CALR-mutations. Except for a lower prevalence of JAK2V617F-mutation in polycythemia vera, the mutational distribution in our patient cohort was similar to previous findings in other populations. The novel finding of a higher prevalence of smokers in JAK2V617F-mutated primary myelofibrosis warrants further investigation.

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.

Establishment of isogenic induced pluripotent stem cells with or without pathogenic mutation for understanding the pathogenesis of myeloproliferative neoplasms

Identification and functional characterization of disease-associated genetic traits are crucial for understanding the pathogenesis of hematologic malignancies. Various in vitro and in vivo models, including cell lines, primary cells, and animal models, have been established to examine these genetic alterations. However, their nonphysiologic conditions, diverse genetic backgrounds, and species-specific differences often limit data interpretation. To evaluate somatic mutations in myeloproliferative neoplasms (MPNs), we used CRISPR/Cas9 combined with the piggyBac transposon system to establish isogenic induced pluripotent stem (iPS) cell lines with or without JAK2V617F mutation, a driver mutation of MPNs. We induced hematopoietic stem/progenitor cells (HSPCs) from these iPS cells and observed phenotypic differences during hematopoiesis using fluorescence-activated cell sorting analysis. HSPCs with pathogenic mutations exhibited cell-autonomous erythropoiesis and megakaryopoiesis, which are hallmarks in the bone marrow of patients with MPNs. Furthermore, we used these HSPCs as a model to validate therapeutic compounds and showed that interferon alpha selectively inhibited erythropoiesis and megakaryopoiesis in mutant HSPCs. These results demonstrate that genome editing is feasible for establishing isogenic iPS cells, studying genetic elements to understand the pathogenesis of MPNs, and evaluating therapeutic compounds against MPNs.