V617F-positive Myeloproliferative Neoplasms Research Articles

PPIL2 Is a Target of the JAK2-STAT5 Pathway and Mediates p53 Polyubiquitination and Degradation

The activated JAK2-STAT pathway is characteristic of myeloproliferative neoplasms (MPNs). We previously revealed that Plek2, a downstream target of the JAK2/STAT5 pathway, functions as a scaffold protein to activate Akt and plays an important role in the pathogenesis of JAK2 V617F-induced MPNs. To further explore the mechanisms of the Plek2 signalosome, we performed a comprehensive proteomic analysis of Plek2 interacting proteins and found peptidylprolyl isomerase-like 2 (PPIL2) as a potential novel effector of the signalosome. As a U-box E3 ubiquitin ligase, PPIL2 was reported to be involved in cancer metastasis. However, its role in normal and malignant hematopoiesis remains unknown. We found that PPIL2 is required for human and murine erythropoiesis in vitro. Knockout of PPIL2 through CRISPR/Cas9 significantly reduced cell proliferation and differentiation and led to marked apoptosis. Mechanistically, PPIL2 interacts with and catalyzes p53 polyubiquitination at lysine 24 to promote proteosome-mediated p53 degradation, thereby preventing p53-dependent cell cycle inhibition and apoptosis. We further revealed that PPIL2 is a downstream target of the JAK2/STAT5 pathway and is upregulated in a JAK2 V617F-positive MPN mouse model and in patients with MPNs. Loss of Ppil2 ameliorated JAK2 V617F-induced myeloproliferative phenotypes including erythrocytosis, neutrophilia, thrombocytosis, and splenomegaly in JAK2 V617F-knockin mice. The same findings were also observed when the JAK2 V617F-knockin mice were treated with cyclosporin A, an inhibitor of PPIL2. Our findings reveal PPIL2 as an effector of the JAK2/STAT5 pathway and Plek2 signalosome. PPIL2 plays an important role in normal erythropoiesis and the pathogenesis of JAK2 V617F-induced MPNs by degrading p53, pointing to PPIL2 as a potential therapeutic target for the treatment of MPNs.

Modulation of human thrombopoietin receptor conformations uncouples JAK2 V617F-driven activation from cytokine-induced stimulation

AbstractThe thrombopoietin receptor (TpoR) plays a central role in myeloproliferative neoplasms (MPNs). Mutations in JAK2, calreticulin, or TpoR itself drive the constitutive activation of TpoR and uncontrolled proliferation and differentiation of hematopoietic stem cells and progenitors. The JAK2 V617F mutation is responsible for most MPNs, and all driver mutants induce pathologic TpoR activation. Existing therapeutic strategies have focused on JAK2 kinase inhibitors that are unable to differentiate between the mutated MPN clone and healthy cells. Surprisingly, the targeting of TpoR itself has remained poorly explored despite its central role in pathology. Here, we performed a comprehensive characterization of human TpoR activation under physiological and pathological conditions, focusing on the JAK2 V617F mutant. Using a system of controlled dimerization of the transmembrane and cytosolic domains of TpoR, we discovered that human TpoR (hTpoR) adopts different dimeric conformations upon Tpo-induced vs JAK2 V617F–mediated activation. We identified the amino acids and specific dimeric conformation of hTpoR responsible for activation in complex with JAK2 V617F and confirmed our findings in the full-length receptor context in hematopoietic cell lines and primary bone marrow cells. Remarkably, we found that the modulation of hTpoR conformations by point mutations allowed for specific inhibition of JAK2 V617F–driven activation without affecting Tpo-induced signaling. Our results demonstrate that modulation of the hTpoR conformation is a viable therapeutic strategy for JAK2 V617F–positive MPNs and set the path for novel drug development by identifying precise residues of hTpoR involved in JAK2 V617F–specific activation.

Exploration of the role of NKG2D ligands MICA and MICB in JAK2 V617F-positive myeloproliferative neoplasms.

JAK2 V617F-driven myeloproliferative neoplasms (MPNs) can escape immune surveillance through PD-L1 up-regulation and HLA class I pathway down-regulation. To complement these data we assessed the role of major histocompatibility complex class I-related genes (MICA and MICB) in JAK2 V617F+ MPNs. Using high resolution genotyping we identified two protective alleles, MICA*008:01 and MICA*016. MPN patients had significantly higher levels of soluble sMICA molecules. Peripheral blood JAK2 V617F+ granulocytes had higher surface expression of MICB but did not differ in the amount of MICA and MICB transcripts from normal granulocytes. MICA and MICB genes were significantly down-regulated in JAK2 V617F+ CD34+ cells from primary myelofibrosis patients in comparison to normal CD34+ hematopoietic stem cells. These data suggest minor but significant role of MICA and MICB genes in the pathogenesis of MPNs. It is also possible that MICA targeting approaches could be of clinical benefit for some of those patients.

Calreticulin Mutations in Myeloproliferative Neoplasms Patients Diagnosed in UKM Medical Centre

Introduction: Calreticulin (CALR) mutations are one of the molecular markers that has been incorporated for the diagnosis of myeloproliferative neoplasms (MPN) in the revised 2017 WHO Classification of Haematopoietic and Lymphoid Tumors. This study was performed to determine the prevalence of CALR mutations in patients with MPN diagnosed in UKMMC and to compare their demographics plus laboratory features with other MPN patients. Meth- ods: A total of 59 MPN patients who tested negative for JAK2V617Fmutation were selected and 21 MPN patients positive for JAK2V617F were included as controls. Screening for CALR exon 9 was done by multiplex polymerase chain reaction (PCR) followed by Sanger sequencing. Results: A total of six JAK2 V617F negative MPN samples were found to be positive for CALR mutations. Out of these six, three patients with CALR mutations were of type I mutation, two were type II while one was a mutation in the stretch III region. None of the twenty one JAK2 V617F positive MPN samples were positive for CALR mutation. Clinical phenotypes for those positive for CALR were restricted to Essential Thrombocythemia (ET), Primary Myelofibrosis (PMF) and one case of atypical Chronic Myeloid Leukaemia (CML). Conclusion: CALR mutations constituted 10.16% from the MPN patients who were negative for JAK2V617F mutation with no significant differences in platelet counts, hemoglobin (Hb), hematocrit and white cell counts as compared to MPN patients with JAK2 V617F mutations. Testing for CALR mutations among those who are negative for JAK2V617F within Malaysian population maybe worthwhile and require larger scale studies.

Ropegiterferon Alfa-2b-Njft for Treatment Myeloproliferative Neoplasms: A Single Institution Experience

Background: While interferon alfa has been used for decades as a cytoreductive agent in myeloproliferative neoplasms (MPNs), tolerability and need for frequent parenteral administration have limited its widespread adoption. Ropeginterferon Alfa-2b-njft (ropeg) is monopegylated extended half-life interferon alpha product that received FDA approval for treatment of polycythemia vera (PV) in November 2021. A phase III clinical trial has demonstrated efficacy and tolerability of this novel agent as compared to hydroxyurea (HU) in PV patients with indication for cytoreductive therapy. Real-world experience (RWE) assessment of a newly available pharmaceutical can yield important insights regarding barriers to access, clinical feasibility, and usage in populations not yet evaluated in clinical trial. In this single institution cohort, we report the first RWE using ropeg for patients with MPNs, including essential thrombocythemia (ET), in the United States. Methods: Patients presenting to an MPN clinic at an academic medical center were evaluated for initiation of ropeg based individualized assessment, with patients engaged in shared decision-making regarding risks and benefits. Patients were screened for autoimmune, neuropsychiatric, or endocrine disorder on basis of history and limited laboratory investigation as appropriate, including thyroid stimulating hormone, triglycerides, and anti-nuclear antibody testing. The treating physician and pharmacist provided pre-treatment counseling including review of potential toxicities, administration teaching, and financial considerations. Patients on HU were started on a dose 50mcg every 2 weeks via subcutaneous injection with subsequent HU tapering; patients not on HU were started 100mcg every 2 weeks. Ropeg dosing was increased to target hematologic response. Complete blood counts and comprehensive metabolic panels were ordered every 2 weeks until hematologic response achieved, with less frequent monitoring thereafter. Results: Between December 2021 to June 2022, 13 patients with JAK2 V617F positive MPNs have been started on ropeg. Four patients were unable to start ropeg due to payor denial of coverage and ineligibility for manufacturer patient assistance programs. Patients were predominantly female (10/13, 77%) with average age of 60.9 years (range 36-73 years). Seven patients had PV (transformed from ET in 2 cases), 5 patients had ET, and 1 patient had post-ET myelofibrosis. Mean pre-treatment hematocrit, platelet count, and WBC were 42.5% (range 34.3% - 51.5%), 630 *109/L (range 127-2065*109/L), and 7.0*109/L (range 2.5 - 13*109/L) respectively. At treatment start, 7 patients were on HU (either alone or in combination with therapeutic phlebotomy (TP)), 1 was on TP alone, 1 was on ruxolitinib, 1 was on peginterferon alfa-2a, and 3 were on no cytoreductive treatment. Reasons for switching to ropeg included poor tolerance or efficacy of prior therapy (6/13, 46%), patient interest in potential disease modifying properties of interferon (6/13, 46%), and, in the case of patient on peginterferon alfa-2a, ease of administration (1/13, 7.6%). Patients received medication through insurance approval with copay assistance (11/13, 85%) or through the manufacturer patient assistance program (2/13, 15%). Average time to receipt of medication from prescription submission was 25 days. At mean follow-up time of 12.9 weeks, all patients remain on treatment. One patient required treatment interruption due to severe fatigue, two patients deferred scheduled doses due to cold-like symptoms. While efficacy data is immature, one patient with PV and 2 patients with ET obtained a hematologic response (hematocrit <45% without phlebotomy in 3 months and platelet count <450), with mean response time 6.9 weeks (range 5.7 -7.7). Two patients experienced rebound in hematocrit after HU stop and are requiring TP as bridging therapy. Conclusions: Medication access, patient counseling, and symptom and laboratory monitoring must be addressed in translating clinical trial findings to clinical practice with ongoing evaluation of drug efficacy and safety. In a single institution analysis, 13 patients with MPNs, including 5 patients with ET, were started on ropeg with good initial tolerance at mean follow-up of 12.9 weeks. Lengthy insurance approval process and payor coverage denials limit medication access.

Study of the Janus kinase 2 (JAK2) gene haplotype 46/1 association with driver mutations of chronic Ph-negative myeloproliferative neoplasms

Introduction. Haplotype JAK2 46/1 is associated with more frequent development of Ph-negative myeloproliferative neoplasms (MPN) and with an increased detection rate of the JAK2 V617F mutation. At the same time, the molecular mechanisms of such associations remain unclear. Previously, there were no studies of regional, age and gender aspects of the predictive value of carriage of the 46/1 JAK2 haplotype, which could assess this relationship in some observations.Aim — to analyze the degree of association between 46/1 haplotype and the V617F mutation of the JAK2 gene depending on the sex, age, and place of residence of patients examined for suspected MPN.Methods. The study included 949 DNA samples from patients with suspected MPN. Samples of 150 volunteers and blood donors were included in the control group. Haplotype 46/1 (rs10974944), V617F mutation in the JAK2 gene, mutations in the CALR gene (type 1: c.1092_1143del; L367fs*46, COSV57116546; type 2: c.1154_1155insTTGTC; K385fs*47, COSV57116551) and in the MPL gene (W515K, W515L) were determined for all samples using real-time polymerase chain reaction (PCR-RT).Results. The 46/1 JAK2 haplotype were shown to be associated with a clinically significant level (&gt; 2 %) of the allelic burden of the JAK2 V617F mutation. The odds ratio of the risk of developing a V617F positive MPN when carrying this haplotype variant did not depend on the main place of residence of the patients and was found to be most pronounced in men under 50 years of age. The odds ratio of the risk did not depend on the age of the examined women.Conclusion. The association of 46/1 haplotype with the presence of other drivers of MPN mutations in the CALR or MPL genes was also statistically significant, which confirms the hypothesis of “favorable soil” rather than “hypermutability” of the JAK2 gene.

Study of Tumor Necrosis Factor-Alpha-Induced Protein 3 Gene Single-Nucleotide Variants in JAK2 V617F-Positive Myeloproliferative Disorders: A Case–Control Study

Background and Objectives: Myeloproliferative neoplasms (MPNs) are Philadelphia negative disorders involving polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF). Although JAK2 mutation is almost involved, other several mutations are linked to MPNs risk and prognosis. TNFAIP3 genetic mutations are related to several cancers and autoimmune diseases. Our study aimed to demonstrate the effects of rs2230926_T/G &amp; rs5029939_C/G SNVs of TNFAIP3 gene on the risk and prognosis of JAK2 V617F positive MPNs.&#x0D; Methods: Matched 2 groups in age, sex and race were enrolled in our research; 80 MPNs cases group and 130 normal healthy controls group with follow up of MPNs cases for 3 years. Taqman assay probes involved in real time polymerase chain reaction (PCR) were utilized for variants analysis.&#x0D; Results: The rs2230926 &amp; rs5029939 SNVs were in modest linkage disequilibrium (LD) in MPNs cases. The observed frequencies of G allele and its genotypes of both variants were more prevalent in MPNs patients than normal controls. The bleeding symptoms and the presence of splenomegaly were more existent in the heterozygous genotype and the combined G involved genotypes respectively. The overall survival (OS) was lower in G containing genotypes of both variants but the progression free survival (PFS) was affected only in rs5029939 SNV.&#x0D; Conclusion: Our study revealed the association of G containing genotypes of both rs2230926 &amp; rs5029939 SNVs to the increased MPNs incidence as well to poor clinical course and prognosis of JAK2 V617F positive MPNs disorders in Egyptian ethnic.

Germline ERBB2 Variants Associate with Myeloproliferative Neoplasms

Background: The myeloproliferative neoplasms (MPN) and myelodysplastic syndrome (MDS) are usually sporadic diseases, however, familial cases are well-described. Approximately 10% of MPN cases display familial clustering, and there is a 5-7 fold increased risk of developing an MPN among first degree relatives of MPN patients. While familial MDS appears to be less common, identification of multiple predisposition genes has led to the incorporation of this entity into the most recent WHO classification of myeloid neoplasms. Identification of predisposing germline mutations in the myeloid malignancies has led to a better understanding of the pathophysiology of these diseases and improved clinical care. However, many familial MDS and MPN cases exist in which the inherited genetic lesion is unknown. Our recent investigation of a multigenerational family with inherited MDS/AML marked by erythroid hyperplasia identified a missense variant in ERBB3 that co-segregated with the disease phenotype (1). In this study, we investigated a kindred with an autosomal dominant familial cancer syndrome characterized by both MPN and solid tumor malignancies.Methods: Whole exome sequencing was performed via the Baylor-Hopkins Center for Mendelian Genomics at Center for Inherited Disease Research at Johns Hopkins University. Saliva or peripheral blood samples were used as source DNA. Sequence analysis and variant calling/filtering was performed as previously described (1). Targeted sequencing of the ERBB genes was performed via MiSeq using an Illumina TruSeq Custom Amplicon (v1.5) designed to sequence the entire open reading frame of selected genes. Analysis was performed using Illumina BaseSpace TruSeq applications. Germline variants were identified via variant allele frequency and heterozygous, nonsynonymous variants with a minor allele frequency < 0.01 and a depth > 40x were prioritized.Results: The proband was diagnosed with a JAK2 V617F positive MPN at age 37. Subsequent personal cancer history included melanoma and renal carcinoma. Family history was significant for ovarian cancer and melanoma in her mother, MPN and melanoma in her maternal aunt, and bladder cancer in her maternal uncle (Figure 1A). Exome sequencing of the three family members affected with melanoma was performed in order to identify the predisposing inherited variant in this family. Sequence analysis produced 71 candidate rare, heterozygous, nonsynonymous single nucleotide variants (SNV), including one in the gene ERBB2 . Genotyping of 2 additional family members for the ERBB2 c.3182T>C;p.L1061P SNV established that it co-segregates with disease (Figure 1A). To further investigate the prevalence of rare germline ERBB2 and ERBB3 variants in both MPN and MDS, we performed targeted sequencing of these genes in two discovery cohorts: 1) 96 cases of MPN, of which 63 had a 1st or 2nd degree relative with a family history of MPN and 2) 19 cases of erythroid MDS/AML. Five out of 96 (5.2%) cases of MPN were found to have ERBB2 variants, while 3 of 96 (3.1%) had ERBB3 variants. Of the 19 erythroid MDS/AML cases, no ERBB2 variants were identified, while 1 had an ERBB3 variant. Further, one MPN case with a germline ERBB2 c.G3250T:p.D1084Y variant had a family history of breast cancer in her mother, who also carried this variant (Figure 1B). We analyzed a validation cohort of 630 cases of hematologic malignancies (approximately 20% MPN) sequenced as part of their clinical evaluation at the Sidney Kimmel Cancer Center. Similar to the findings in our discovery cohorts, rare germline ERBB2 variants were enriched in MPN, found in approximately 5% of MPN compared to only 1.8% of all other myeloid disorder diagnoses. In contrast, germline ERBB3 variants were present in 1.6% of MPN compared to 1.8% of the other myeloid disorders (Table).Conclusions: We have identified germline ERBB2 variants that co-segregate with disease in two kindreds with familial cancer syndromes manifesting as a mixed MPN and solid tumor phenotype. In addition, we show that germline ERBB2 and ERBB3 variants are present in patients with hematologic malignancies at a higher incidence than expected in the general population, and ERBB2 variants are associated with an MPN phenotype. Together, these data implicate these genes in the predisposition to myeloid malignancy as well as other familial cancer syndromes. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

High Risk Janus Kinase 2 V617F Allele Burden in a Seven-Year Cohort of Patients with Myeloproliferative Neoplasms.

JAK2 V617F is the most common somatic mutation associated with the classical Philadelphia (Ph) chromosome negative myeloproliferative neoplasms (MPNs), which include essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF). JAK2 V617F allele burden may be used for establishing the diagnosis, determining prognosis, and monitoring progression in these diseases. Limited data is available regarding the epidemiology of MPNs in Africa, and there is paucity of data on demographic, laboratory, and clinical features of MPNs in South Africa. This study determined the JAK2 V617F allele burden in a seven-year retrospective cohort of patients diagnosed with MPNs and described the characteristics of these diseases in a South African setting. A laboratory database search was performed to identify patients diagnosed with ET, PV or PMF and a positive JAK2 V617F mutation, diagnosed qualitatively on Fluorescence Resonance Energy Transfer (FRET) real-time PCR and melting curve analysis. The allele burden for these patients was measured on archived residual DNA samples using a quantitative allele specific amplification (QUASA) assay. Demographic data and relevant laboratory results at presentation were analyzed. The search identified 87 patients who tested positive for JAK2 V617F mutation and fulfilled the diagnostic criteria for ET, PV or PMF from 2012 to 2018. Median age at diagnosis was 64 years with a male: female ratio of 1.2:1. ET, PV and PMF accounted for 11.5%, 44.8%, and 43.7% of the MPNs, respectively. Median allele burden for ET, PV, and PMF was 24.9%, 71.1%, and 55.8%, respectively. Allele burden was significantly lower in ET compared to PV (p = 0.0003) and PMF (p = 0.0023) and correlated with leukocytosis, neutrophilia, eosinophilia, and low erythrocyte mean cell volume (p < 0.05). JAK2 V617F-positive MPNs occurred predominantly in older patients with approximately equal gender ratio. ET was the least common MPN and there was a higher proportion of PMF cases than described in studies in Europe and America. Allele burden was also relatively high for all three subtypes of MPNs when compared to other published data, which may predispose to poorer prognosis.

Ectopic PD-L1 expression in JAK2 (V617F) myeloproliferative neoplasm patients is mediated via increased activation of STAT3 and STAT5.

Escalated PD-L1 expression has been identified during malignant transformation in a number of cancer types and helps cancer cells escape an effective anti-tumor immune response. The mechanisms underlying escalated production of PD-L1 in many cancers, however, are still far from clear. We studied PD-L1, STAT3 and STAT5 mRNA expression using qRT-PCR in 72 BCR/ABL1 negative myeloproliferative neoplasm (MPN) patients (39 polycythemia vera and 33 essential thrombocythemia). Furthermore, phosphorylation status of STAT3 and STAT5 was studied using immunoblotting in the same patients. All MPN patients were first screened for JAK2 (V617F) mutation by tetra-primer ARMS-PCR, followed by quantification of JAK2 (V617F) mutation burden in all V617F positive MPN patients by ASO-PCR. Patients were screened for BCR/ABL1 fusion gene transcripts to rule out Ph positive status. Our findings showed that mRNA levels of PD-L1 and STAT3 were significantly higher in JAK2 (V617F) MPN patients, while as STAT5 was insignificantly upregulated. STAT3 and STAT5 phosphorylation was seen to be higher in JAK2 (V617F) MPN patients compared to the JAK2 (WT) patients. Upregulation of PD-L1, STAT3 and STAT5 was significantly associated with JAK2 (V617F) percentage in MPN patients. PD-L1, STAT3 and STAT5 expression significantly and positively correlated with JAK2 (V617F) allele burden. In addition, significant coexpression of PD-L1 with STAT3 and STAT5 was observed in MPN patients. In summary, JAK2 (V617F) mutation is accompanied by increased PD-L1 expression and this PD-L1 over expression is mediated by JAK2 (V617F) mainly through STAT3, while as STAT5 may play a minor role.

SH2B3 (LNK) rs3184504 polymorphism is correlated with JAK2 V617F-positive myeloproliferative neoplasms

Abstract Background: Pathogenesis and phenotypic diversity in myeloproliferative neoplasms (MPN) cannot be fully explained by the currently known acquired mutations alone. Some susceptible germline variants of different genes have been proved to be associated with the development of these diseases. The goal of our study was to evaluate the association between the rs3184504 polymorphism of SH2B3 (LNK) gene (p.R262W, c.784T&gt;C) and the risk of developing the four typical MPN - polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF), and chronic myeloid leukemia (CML). Material and methods: We investigated the SH2B3 rs3184504 T&gt;C polymorphism by real-time PCR in 1901 MPN patients (575 with PV, 798 with ET, 251 with PMF, and 277 with CML), all of them harboring one of the specific driver mutations - JAK2 V617F or CALR in case of PV, ET and PMF, or BCR-ABL1 in case of CML, and 359 controls. Results: Overall, the TT homozygous genotype was significantly associated with BCR-ABL1-negative MPN (OR = 1.34; 95% CI = 1.03-1.74; crude p-value = 0.02; adjusted p-value = 0.04). The most significant association was seen in case of PV (OR = 1.54; 95% CI = 1.14-2.06; crude p-value = 0.004; adjusted p-value = 0.024). Also, SH2B3 rs3184504 correlated significantly with JAK2 V617F-positive MPN (OR = 1.36; 95% CI = 1.04-1.77; crude p-value = 0.02; adjusted p-value = 0.08), but not with those CALR-positive. ET (regardless of molecular subtype) and CML were not correlated with SH2B3 rs3184504. Conclusions: The SH2B3 rs3184504 polymorphism is associated with risk of MPN development, especially PV. This effect is restricted to JAK2 V617F-positive PV and PMF only.

TERT and JAK2 polymorphisms define genetic predisposition to myeloproliferative neoplasms in Japanese patients.

Myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), are often characterized by specific somatic mutations in any of the three genes: JAK2, CALR, or MPL. A single nucleotide polymorphism (SNP), rs2736100, in the reverse transcriptase gene (TERT) and a germline JAK2 46/1 haplotype have been associated with MPNs in North American and European patients. We examined 201 Japanese MPN patients, including 52 with PV, 131 with ET, and 18 with PMF, as well as 366 control individuals for TERT rs2736100 and JAK2 rs10974944, a tagging SNP of the 46/1 haplotype. Furthermore, correlations between the JAK2 V617F allele burden at diagnosis and TERT rs2736100 or JAK2 rs10974944 were evaluated using a digital PCR assay for accurate quantitation. The JAK2 46/1 haplotype, but not the TERT rs2736100 SNP, was correlated to the JAK2 V617F mutant allele burden in JAK2 V617F-positive MPN patients. In conclusion, we demonstrated that both TERT rs2736100_C and JAK2 46/1 haplotype are predisposing factors for MPNs in Japanese patients. While TERT rs2736100_C tended to have a more general, non-specific effect on all MPNs, the JAK2 46/1 haplotype was essentially predisposed to the JAK2 V617F-positive MPNs.

Splanchnic venous thrombosis in JAK2 V617F mutation positive myeloproliferative neoplasms \u2013 long term follow-up of a regional case series

BackgroundSplanchnic Vein Thrombosis (SVT) is strongly associated with underlying JAK2 V617F positive myeloproliferative neoplasms (MPN).MethodsPatients attending the tertiary haematology service in Northern Ireland with SVT and underlying JAK2 V617F MPN were identified by consultant staff. A retrospective audit was undertaken to examine therapeutic interventions and relevant outcomes. Descriptive statistics were used for qualitative data whilst students t-test allowed comparison of quantitative data.ResultsWe report on the medium to long term follow-up of fourteen patients presenting with SVT on the basis of JAK2 V617F positive MPN. Females comprised 78.5% of the patients and there was an average age of 47.3 years at time of diagnosis. There was significant morbidity evident at diagnosis with liver transplantation attempted in all patients with Budd Chiari (n = 3), oesophageal varices present in 57.1%, ascites present in 42.8% and splenomegaly evident in 71.4%. 42.8% of patients did not exhibit classical phenotypic blood count findings for MPN at time of diagnosis. Over a median follow-up of 88.5 months (range = 8–211 months) recurrence of SVT was only documented in the setting of interventional liver procedure. Major haemorrhagic complications were recorded in 35.7% of patients and there was an association with dual anticoagulation and antiplatelet use. Recurrent thrombosis outside of the splanchnic venous system occurred in 28.5% of patients, predominantly occurring off therapeutic anticoagulation. No deaths were recorded and one transformation to myelofibrosis was seen during follow-up. Cytoreduction therapies were routinely used but had a high discontinuation rate due to cytopenias and intolerance.ConclusionThis analysis highlights the complexities of management of this group of patients over a period of long follow-up with a focus on the evidence behind therapeutic options.

Januskinase-2 V617F Positive Myeloproliferative Neoplasms and Haemostatic Disorders: Importance of Obesity in Prediction of Thrombotic Events

Introduction: Myeloproliferative neoplasms (MPN), namely polycythaemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) have been associated with an increased risk of thrombotic and haemorrhagic events, mainly when januskinase-2 (JAK 2) V617F mutation is detected1. This association is higher for thrombotic events (TE) contributing for overall mortality in MPN patients, although the pathophysiological mechanisms remain unclear. Although age and history of thrombosis have been considered the most important factors for thrombosis risk assessment, cardiovascular risk factors have recently been included in prognostic scores for thrombosis in individuals with MPN.Aim: The primary end-point of this study was to evaluate the prevalence of thrombotic and haemorrhagic events in a population with MPN (PV, ET, PMF) harbouring the JAK-2 V617F mutation. A secondary end-point was to identify possible risk factors for these events.Methods: We retrospectively analysed the records of MPN patients with JAK-2 V617F mutation, identified between January 2010 and September 2013. Variables analysed included blood counts, gender, age at diagnosis, therapy, vascular events and cardiovascular risk (body mass index obesity-defined (WHO), diabetes, dyslipidemia, hypertension and smoking status). Multiple linear regression analysis was performed to identify the variables that best predict thrombosis after controlling for potential confounders. Variables significant in the univariate analysis were included in the regression. Analysis was performed using the SPSS version 22.0 (SPSS, Chicago, IL, USA). p-value lower than .05 was considered significant.Results: Excluding blood counts, MPN subgroups did not differ considering the studied variables, namely, thrombotic and bleeding events. In this MPN JAK-2 V617F mutated population (N=99; PV:38, ET:56, PMF:5), the prevalence of thrombotic and bleeding events was 35.4% (PV: 42.1%; ET: 30.4%; PMF: 40%) and 19.2% (PV: 15.8%; ET: 17.9%; PMF: 60%), respectively. With patients having more than one TE (1-5), there were 49 episodes, presented in either arterial (53.1%) or venous (46.9%) territories. The commonest sites of arterial thrombosis (N=26) were cerebral (50%), coronary (15.4%), peripheral arteries (15.4%) and ophthalmic (11.5%); venous thrombosis locations (N=23) were deep venous thrombosis (31.1%), superficial venous thrombosis (21.7%), pulmonary embolism (17.4%) and splanchnic (17.4%) (3 portal and 1 splenic). Prediction of TE was explained in 75% by a model including the number of thrombosis and obesity [R2 =.747; F (2, 36) = 53.255; p<.001; β (number of TE) = .410; β (obesity) = -.198]. The group with thrombosis showed lower number of platelets in comparison with the counterpart [F (1, 94) = 4.836; p= .030; η2 = .05]. None of other studied parameters differed significantly between groups with and without thrombosis.Bleeding episodes (N=28) occurred mostly under antiplatelet and/or anticoagulant therapy (N=22) and local/traumatic causes were identified in 42.9% of the events. In 2 haemorrhagic cases platelet blood count was >1x106/mL. The commonest affected sites were gastrointestinal tract (21.4%), nasal (21.4%), subdural (14.3%).In our study population, mortality was associated to older age (p= .002), male gender (p=.026), smoking (p=.007) and number of TE (p=.029). Mortality was found to be correlated with venous but not with arterial thrombosis (r=0.232, p=.021; r=0.105, p=.299, respectively).Conclusions and Discussion: In this MPN JAK-2 V617F mutated population we found higher prevalence of thrombotic events then bleeding episodes. The prediction of TE was explained in 75% by a model that includes the number of thrombosis episodes and obesity. Since JAK-2 V617F is a driver mutation in MPN acting through JAK/STAT inflammatory pathway and the finding of a TE prediction model that includes obesity, a chronic inflammatory condition, the present study underlies: 1) the importance of inflammation in the pathophysiology of thrombosis-MPN associated; 2) the relevance of the recent inclusion of cardiovascular risk factors as variables in prognostic scores for thrombosis in individuals with MPN.ReferencesFalchi L, Kantarjian HM, Verstovsek S (2017). Assessing the thrombotic risk of patients with essential thrombocythemia in the genomic era. Leukemia 31, 1845-1854. DisclosuresSilva:Gilead Sciences: Research Funding; Abbvie, Gilead Sciences, Janssen, BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche, Janssen, Celgene: Other: Travel Support; Roche, Janssen: Other: Institution's payment for consultancy.

JAK2 R1063H Variant Enhances V617F Constitutive Signaling and Favors Development of Essential Thrombocythemia with Increased Hemoglobin and Neutrophils

The clinical consequences of the highly prevalent JAK2 V617F mutation in Ph-negative myeloproliferative neoplasms (MPNs) are well studied. However, the impact on the MPN phenotype of co-occurring JAK2 variants is less well characterized. In this study, we focused on JAK2 R1063H, a variant previously reported in a pediatric case of hereditary erythrocytosis (Kapralova et al, Blood 2016) and in 3 out of 93 polycythemia vera patients that were JAK2 V617F-positive (Levine et al, Cancer Cell 2005). It has been described as a very rare polymorphism in population (frequency 0.004377).In order to gain insight into the clinical and functional relevance of coexisting JAK2 mutations, we tested a cohort of 390 JAK2 V617F-positive MPN patients for JAK2 R1063H and identified 14 carriers of both mutations. From the clinical perspective, the double-positive patients exhibited predominantly an essential thrombocythemia phenotype that was accompanied by significantly higher neutrophil granulocyte counts and hemoglobin values, when compared to those harboring only JAK2 V617F mutation. By employing targeted NGS for genes known to be involved in myeloid malignancies we found that the mutational profile and the number of additional somatic mutations in double-mutant patients seemed to be comparable to previous studies of JAK2 V617F-positive MPNs.Next, we used digital droplet PCR (ddPCR) for JAK2 R1063H and JAK2 V617F allele burden assessment. Quantification of JAK2 R1063H allele indicated that in 8 patients the variant was heterozygous, likely inherited (the percentage of the mutant allele being around 50%). In 3 patients with a high JAK2 V617F allelic burden a nearly homozygous status for R1063H was identified (a fractional abundance >80%) suggesting that one R1063H allele was inherited and the second one was acquired by uniparental disomy, as a result of mitotic recombination. In 3 other patients, the JAK2 R1063H mutation was most likely acquired due to the low percentage of the mutant allele (between 20.7% and 31.5%). For cis/trans configuration analysis of JAK2 V617F and R1063H mutations, we performed single-colony sequencing of subcloned JAK2 cDNA from 9 out of 14 patients. A cis configuration of the mutations was detected in 7 and a trans configuration in 2 cases. In one patient, the cis configuration of JAK2 mutations combined with results obtained by ddPCR (the allele burdens for R1063H and V617F were 31.5% and 52.8%, respectively) suggested that R1063H was acquired, following V617F acquisition.To assess the effect on JAK2 signaling of coexisting JAK2 V617F and R1063H mutations in cis or trans, we created human cDNA JAK2 mutants (V617F, R1063H and V617F/R1063H). STAT5 transcriptional activity of the JAK2 WT and JAK2 mutants in the presence of myeloid dimeric cytokine receptors (EPOR, given the higher hemoglobin levels, G-CSFR, given the observed neutrophilia in patients carrying JAK2 V617F and R1063H, and TPOR) measured in JAK2-deficient γ-2A cells by dual luciferase assay revealed a significantly higher constitutive activity of JAK2 V617F/R1063H (cis mutant) compared to that of JAK2 V617F, in both homozygous and heterozygous configurations and with either of the dimeric myeloid cytokine receptors. In the trans configuration of JAK2 V617F and JAK2 R1063H, we did not observe a significant difference compared to combination of JAK2 V617F and JAK2 WT. Western blot analysis assessing activated phosphorylated forms of JAK2, STAT5 and ERK1/2 demonstrated a higher level of constitutive activation of JAK2 and STAT5 generated by the double V617F/R1063H mutant versus JAK2 V617F and similar effect was shown also for ERK1/2 signaling.Our results suggest that either an acquisition of V617F in cis on a germline R1063H allele or a gain of additional JAK2 R1063H on JAK2 V617F will lead to an increase in downstream signaling by the driver JAK2 V617F. The oncogenic signaling of JAK2 V617F enhanced by the R1063H mutation has a clinical effect, leading to a significantly increased number of neutrophilic granulocytes and hemoglobin values, in agreement with higher levels of signaling via EPOR and G-CSFR.The work was supported by projects COP A1.1.4. ID: P_37_798, Contract 149/26.10.2016, (MySMIS2014+: 106774), MyeloAL, WELBIO F 44/8/5-MCF/UIG-10955, ARC: N° 16/21-073, by Ludwig Institute for Cancer Research, Salus Sanguinis Foundation, Fondation Les avions de Sébastien, Belgium and by GACR 17-05988S and MSMT LTAUSA17142. DisclosuresNo relevant conflicts of interest to declare.

Coexistence of JAK2 or CALR mutation is a rare but clinically important event in chronic myeloid leukemia patients treated with tyrosine kinase inhibitors.

There are 7 designated conditions under the category of myeloproliferative neoplasms (MPN), including chronic myelogenous leukemia (CML) and classical MPN, that is, polycythemia vera (PV), essential thrombocythaemia (ET), and primary myelofibrosis (PMF). Recently, reports about Philadelphia and JAK2 V617F-positive MPN cases have been described in literature. The coexistence of different molecular defects may change the clinical and laboratory manifestation of MPN and may result in an inappropriate interpretation of the response to treatment with tyrosine kinase inhibitors in CML patients. The morphological, cytogenetic, and molecular genetic data from a retrospective analysis of 592 adult patients aged 18-86years diagnosed with CML were analyzed. In 5 CML patients, the presence of JAK2 V617F or CALR mutation was confirmed. Three of 4 TKI-treated patients did not reach complete hematologic response due to the persistence of thrombocytosis and/or splenomegaly. In all of them (in 3 with JAK2 V617F mutation and 1 with CALR mutation), thrombocytosis was present at the time when complete cytogenetic response was documented. In 3 out of 4 reported CML patients, thrombocytosis and/or splenomegaly were still present even at the time when deep molecular response was reached. In our opinion, a detailed evaluation and appropriate interpretation of clinical and laboratory data in such a category of patients seem to be extremely important, especially when a decision about the TKI change due to therapy failure is considered.

Loss of p53 induces leukemic transformation in a murine model of Jak2 V617F-driven polycythemia vera.

As leukemic transformation of myeloproliferative neoplasms (MPNs) worsens the clinical outcome, reducing the inherent risk of the critical event in MPN cases could be beneficial. Among genetic alterations concerning the transformation, the frequent one is TP53 mutation. Here we show that retroviral overexpression of Jak2 V617F mutant into wild-type p53 murine bone marrow cells induced polycythemia vera (PV) in the recipient mice, whereas Jak2 V617F-transduced p53-null mice developed lethal leukemia after the preceding PV phase. The leukemic mice had severe anemia, hepatosplenomegaly, pulmonary hemorrhage and expansion of dysplastic erythroid progenitors. Primitive leukemia cells (c-kit+Sca1+Lin- (KSL) and CD34-CD16/32-c-kit+Sca1-Lin- (megakaryocyte-erythroid progenitor; MEP)) and erythroid progenitors (CD71+) from Jak2 V617F-transduced p53-null leukemic mice had leukemia-initiating capacity, however, myeloid differentiated populations (Mac-1+) could not recapitulate the disease. Interestingly, recipients transplanted with CD71+ cells rapidly developed erythroid leukemia, which was in sharp contrast to leukemic KSL cells to cause lethal leukemia after the polycythemic state. The leukemic CD71+ cells were more sensitive to INCB18424, a potent JAK inhibitor, than KSL cells. p53 restoration could ameliorate Jak2 V617F-transduced p53-null erythroleukemia. Taken together, our results show that p53 loss is sufficient for inducing leukemic transformation in Jak2 V617F-positive MPN.

Complex Anomalous Hepatic Venous Circulation Presenting with Budd-Chiari Syndrome in Patient with Janus Kinase 2 V617F Positive Myeloproliferative Neoplasm

Complex Anomalous Hepatic Venous Circulation Presenting with Budd-Chiari Syndrome in Patient with Janus Kinase 2 V617F Positive Myeloproliferative Neoplasm

Germ line variants predispose to both JAK2 V617F clonal hematopoiesis and myeloproliferative neoplasms

AbstractWe conducted a genome-wide association study (GWAS) to identify novel predisposition alleles associated with Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) and JAK2 V617F clonal hematopoiesis in the general population. We recruited a web-based cohort of 726 individuals with polycythemia vera, essential thrombocythemia, and myelofibrosis and 252 637 population controls unselected for hematologic phenotypes. Using a single-nucleotide polymorphism (SNP) array platform with custom probes for the JAK2 V617F mutation (V617F), we identified 497 individuals (0.2%) among the population controls who were V617F carriers. We performed a combined GWAS of the MPN cases plus V617F carriers in the control population (n = 1223) vs the remaining controls who were noncarriers for V617F (n = 252 140). For these MPN cases plus V617F carriers, we replicated the germ line JAK2 46/1 haplotype (rs59384377: odds ratio [OR] = 2.4, P = 6.6 × 10−89), previously associated with V617F-positive MPN. We also identified genome-wide significant associations in the TERT gene (rs7705526: OR = 1.8, P = 1.1 × 10−32), in SH2B3 (rs7310615: OR = 1.4, P = 3.1 × 10−14), and upstream of TET2 (rs1548483: OR = 2.0, P = 2.0 × 10−9). These associations were confirmed in a separate replication cohort of 446 V617F carriers vs 169 021 noncarriers. In a joint analysis of the combined GWAS and replication results, we identified additional genome-wide significant predisposition alleles associated with CHEK2, ATM, PINT, and GFI1B. All SNP ORs were similar for MPN patients and controls who were V617F carriers. These data indicate that the same germ line variants endow individuals with a predisposition not only to MPN, but also to JAK2 V617F clonal hematopoiesis, a more common phenomenon that may foreshadow the development of an overt neoplasm.

TERT rs2736100 A>C SNP and JAK2 46/1 haplotype significantly contribute to the occurrence of JAK2 V617F and CALR mutated myeloproliferative neoplasms - a multicentric study on 529 patients.

Polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF) represent typical myeloproliferative neoplasms (MPN), usually characterized by specific somatic driver mutations (JAK2 V617F, CALR and MPL). JAK2 46/1 haplotype and telomerase reverse transcriptase gene (TERT) rs2736100 A>C single nucleotide polymorphism (SNP) could represent a large fraction of the genetic predisposition seen in MPN. The rs10974944 C>G SNP, tagging the JAK2 46/1 haplotype, and the TERT rs2736100 A>C SNP were genotyped in 529 MPN patients with known JAK2 V617F, CALR and MPL status, and 433 controls. JAK2 46/1 haplotype strongly correlated to JAK2 V617F-positive MPN and, to a lesser extent, CALR-positive MPN. The TERT rs2736100 A>C SNP strongly correlated to all MPN, regardless of the phenotype (PV, ET or PMF) and major molecular subtype (JAK2 V617F- or CALR-positive). While both variants have a significant contribution, they have nuanced consequences, with JAK2 46/1 predisposing essentially to JAK2 V617F-positive MPN, and TERT rs2736100 A>C having a more general, non-specific effect on all MPN, regardless of phenotype or major molecular subtype.