Insights into JAK2-V617F mutation in CML

Co-occurrence of JAK2-V617 F mutation and BCR::ABL1 translocation in chronic myeloproliferative neoplasms: a potentially confounding genetic combination

Myeloproliferative neoplasms (MPNs) are classified into Philadelphia (Ph) chromosome-positive chronic myeloid leukemia (CML) and Ph-negative MPNs. BCR::ABL1 translocation is the key genetic event of CML, whereas JAK2/MPL/CALR mutations are molecular aberrations of Ph-negative MPNs. Despite initially considered mutually exclusive genetic aberrations, the co-occurrence of BCR::ABL1 and JAK2 has been reported in a limited number of cases. The two genetic alterations may be identified either at the same time or JAK2 aberration may be detected in patients with a previous CML treated with tyrosine kinase inhibitors or, finally, BCR::ABL1 translocation occurs in patients with a history of JAK2-positive MPN. This combination of genomic alterations is potentially confounding with clinical manifestations often misinterpreted either as disease progression or drug resistance, therefore leading to inappropriate patient's treatment. Our systematic review aims to improve hematologist and pathologist knowledge on this rare subset of patients. Starting from the presentation of two additional cases from our routine daily practice, we focus mainly on clinical, laboratory, and bone marrow histological findings, which may represent useful clues of BCR::ABL1 and JAK2 co-occurrence. The interaction between JAK2 and BCR::ABL1 clones during the disease course as well as therapy and outcome are presented.

BCR-ABL1 is a secondary event after JAK2V617F in a patient with essential thrombocythemia who develop chronic myeloid leukemia

Several cases such as myeloproliferative neoplasms (MPN) with the coexistence of JAK2 and BCR-ABL have been reported. However, cases of transformation of essential thrombocythemia (ET) into chronic myeloid leukemia (CML) during the disease progression were rarely reported. Here, we report the case of a patient with JAK2 V617F- positive ET who subsequently acquired BCR-ABL1, which transformed the disease into CML after 10 years from the initial diagnosis. In this study, we dynamically monitored JAK2 V617F and BCR-ABL and observed multiple gene mutations, including IDH2, IDH1, ASXL1, KRAS, and RUNX1. It is important to be aware of this potentially clone evolution in disease progression.

ASXL1 mutations predict inferior molecular response to nilotinib treatment in chronic myeloid leukemia

Gene mutations independent of BCR::ABL1 have been identified in newly diagnosed patients with chronic myeloid leukemia (CML) in chronic phase, whereby mutations in epigenetic modifier genes were most common. These findings prompted the systematic analysis of prevalence, dynamics, and prognostic significance of such mutations, in a clinically well-characterized patient population of 222 CML patients from the TIGER study (CML-V) by targeted next-generation sequencing covering 54 myeloid leukemia-associated genes. In total, 53/222 CML patients (24%) carried 60 mutations at diagnosis with ASXL1 being most commonly affected (n = 20). To study mutation dynamics, longitudinal deep sequencing analysis of serial samples was performed in 100 patients after 12, 24, and 36 months of therapy. Typical patterns of clonal evolution included eradication, persistence, and emergence of mutated clones. Patients carrying an ASXL1 mutation at diagnosis showed a less favorable molecular response to nilotinib treatment, as a major molecular response (MMR) was achieved less frequently at month 12, 18, and 24 compared to all other patients. Patients with ASXL1 mutations were also younger and more frequently found in the high risk category, suggesting a central role of clonal evolution associated with ASXL1 mutations in CML pathogenesis.

Concurrent JAK2-Positive Myeloproliferative Disorder and Chronic Myelogenous Leukemia: A Novel Entity? A Case Report With Review of the Literature

JAK2 V617F mutation and BCR-ABL translocation have been considered to be mutually exclusive. However, many cases where both hits coexisted have been reported. We have personally managed a case too. We believe this hybrid entity is underdiagnosed. Thus, we decided to shed light on this "double hit" disease to improve its diagnosis and optimize its treatment. We reviewed the English literature in PubMed since JAK2 discovery. We found 33 cases reported so far. We summarized patient characteristics and analyzed possible interactions between JAK2 and BCR-ABL clones.

Emergence of BCR-ABL1 Chronic Myeloid Leukemia in a JAK2-V617F Polycythemia Vera

Emergence of a new chronic myeloid neoplasm in the setting of a previous one, or their concomitant appearance seems to be a rare event, but plenty of cases have been reported. We describe the case of a patient with JAK2-V617F polycythemia vera, which looses JAK2 clone and develops overt BCR-ABL1 chronic myeloid leukemia after 6 years. Once treatment with tyrosine kinase inhibitors controls BCR-ABL1 clone, JAK2 clone arises again. In this report, we review the literature and discuss the clonal relationship of this event in light of the new molecular data.

The co-occurrence of driver mutations in chronic myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clonal disorders characterized by proliferation of one or more elements of the myeloid lineage. Key genetic aberrations include the BCR-ABL1 gene rearrangement in Philadelphia chromosome-positive chronic myelogenous leukemia (CML) and JAK2/MPL/CALR aberrations in Philadelphia chromosome-negative MPNs. While thought to be mutually exclusive, occasional isolated reports of coexistence of BCR-ABL1 and JAK2, and JAK2 with MPL or CALR aberrations have been described. Given the paucity of data, clinical characteristics and outcome of patients harboring concurrent Philadelphia-positive and Philadelphia-negative mutations or dual Philadelphia-negative driver mutations have not been systematically evaluated, and their clinical relevance is largely unknown. It is difficult to determine the true relevance of co-existing driver mutations on outcomes given the rarity of its occurrence. In this case series, we describe those patients who had dual driver mutations detected at any point during the course of their disease and characterized their clinical and laboratory features, bone marrow pathology, and overall disease course.

Myeloproliferative neoplasms with concurrent BCR-ABL1 translocation and JAK2 V617F mutation: a multi-institutional study from the bone marrow pathology group

Myeloproliferative neoplasms arise from hematopoietic stem cells with somatically altered tyrosine kinase signaling. Classification of myeloproliferative neoplasms is based on hematologic, histopathologic and molecular characteristics including the presence of the BCR-ABL1 and JAK2 V617F. Although thought to be mutually exclusive, a number of cases with co-occurring BCR-ABL1 and JAK2 V617F have been identified. To characterize the clinicopathologic features of myeloproliferative neoplasms with concomitant BCR-ABL1 and JAK2 V617F, and define the frequency of co-occurrence, we conducted a retrospective multi-institutional study. Cases were identified using a search of electronic databases over a decade at six major institutions. Of 1570 patients who were tested for both BCR-ABL1 and JAK2 V617F, six were positive for both. An additional five patients were identified via clinical records providing a total of 11 cases for detailed evaluation. For each case, clinical variables, hematologic and genetic data, and bone marrow histomorphologic features were analyzed. The sequence of identification of the genetic abnormalities varied: five patients were initially diagnosed with a JAK2 V617F+ myeloproliferative neoplasm, one patient initially had BCR-ABL1+ chronic myeloid leukemia, while both alterations were identified simultaneously in five patients. Classification of the BCR-ABL1-negative myeloproliferative neoplasms varied, and in some cases, features only became apparent following tyrosine kinase inhibitor therapy. Seven of the 11 patients showed myelofibrosis, in some cases before identification of the second genetic alteration. Our data, reflecting the largest reported study comprehensively detailing clinicopathologic features and response to therapy, show that the co-occurrence of BCR-ABL1 and JAK2 V617F is rare, with an estimated frequency of 0.4%, and most often reflects two distinct ('composite') myeloproliferative neoplasms. Although uncommon, it is important to be aware of this potentially confounding genetic combination, lest these features be misinterpreted to reflect resistance to therapy or disease progression, considerations that could lead to inappropriate management.

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

INTRODUCTION

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.

METHODS

The morphological, cytogenetic, and molecular genetic data from a retrospective analysis of 592 adult patients aged 18-86 years diagnosed with CML were analyzed.

RESULTS

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.

CONCLUSION

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.

Emergence of MPLW515 mutation in a patient with CALR deletion: Evidence of secondary acquisition of MPL mutation in the CALR clone

Myeloproliferative neoplasms are characterized by transduction pathway recognized as mutually exclusive molecular abnormalities such as BCR-ABL translocation, JAK2V617F or JAK2 exon 12 mutations, MPL w515, and CALR mutations. However, in some rare cases, associations of such mutations are found in 1 patient. This can be related to 2 pathologies (at least 2 different clones harboring 2 mutations) or associated mutations in 1 clone. We describe here such an association of CALR and MPL mutations in a patient harboring the second mutation in a subclone during the phenotypic evolution of the myeloproliferative neoplasms.

ASXL1 and JAK2V617F gene mutation screening in Iranian patients with chronic myeloid leukemia

AIM

In recent years, a few cases of chronic myeloid leukemia (CML) have been reported with both BCR-ABL and JAK2V617F mutations. Moreover, mutations in the additional sex comb-like 1 (ASXL1) gene were recently shown in various myeloid malignancies.There were no previous studies investigating the incidence of the ASXL1 and JAK2V617F mutations in Iranian patients with CML. Consequently, this study focuses on the analysis of these mutations in patients with CML.

METHODS

In total, 66 patients with a clinical diagnosis of CML were examined at the time of diagnosis. Thirty healthy subjects were checked as controls. Exon 12 of ASXL1 was amplified from genomic DNA and bidirectionally sequenced. We also performed JAK2V617F screening by amplification refractory mutation system-polymerase chain reaction and sequencing.

RESULTS

Mutations in the ASXL1 gene were found in five out of 66 CML patients (7.6%). We identified a novel variant (c.1968G > A, p.Asp656Asn) in one of the patients that has not been reported before. We also identified BCR-ABL and JAK2V617F mutations simultaneously in four patients (6%).

CONCLUSION

Our demonstration of ASXL1 mutation, a putative tumor suppressor gene, represents an important molecular abnormality in CML. We also showed that concomitant detection of BCR-ABL and JAK2V617F mutations has a relatively high incidence in Iranian patients.

Coexistence of JAK2 and BCR-ABL mutation in patient with myeloproliferative neoplasm

The World Health Organisation (WHO) classifies myeloproliferative neoplasm (MPN) into BCR-ABL positive chronic myeloid leukaemia (CML Ph(+)) and Ph(-) MPN. The JAK2 V617F mutation is specific for Ph(-) MPN and occurs in approximately 50% of primary myelofibrosis. Earlier reports suggest that the occurrence of JAK2 and BCR-ABL mutations are mutually exclusive. However, recent reports have documented the coexistence of BCR-ABL and JAK2 mutation in the same patient mostly following treatment with tyrosine kinase inhibitors (TKIs). We thus report a 60-year-old male with atypical clinical and laboratory features of MPN and the presence of both BCR-ABL and JAK2 Mutations.

Coexistence of JAK2V617F Mutation and BCR-ABL Translocation in a Pregnant Woman with Essential Thrombocythemia

In 2012, a 25-years-old pregnant woman presented with thromocytosis for 4 months, blood counts showed platelets 701 × 10(9)/L. Bone marrow examination disclosed a feature of hypercellular marrow in erythrocytic,granulocytic and megakaryocytic series. Cytogenetic analysis showed t(9;22)(q34;q11) in 100 % of metaphase. The percentage of BCR-ABL-positive FISH signals was 37 % in the peripheral blood. Molecular analysis showed the presence of the JAK2V617F mutation and BCR-ABL mRNA b3a2 transcript. A diagnosis of concomitant presence of essential thrombocythemia and chronic myelocytic leukemia was made. Based on this case and literatures reported before, it might be necessary to detect JAK2-V617F mutation and BCR-ABL fusion gene concomitantly in myeloproliferative neoplasms patients.

Frequency of JAK2 V617F mutation in patients with Philadelphia positive Chronic Myeloid Leukemia in Pakistan

Background and Objective: Co-existence of myeloproliferative disorders (MPD) and Janus associated kinase 2 mutation (JAK2 V617F) is a well-established fact. Only few case reports are available showing presence of JAK2 V617F mutation in chronic myeloid leukemia (CML). Purpose of this study was to determine the frequency of JAK2 V617F mutation in Philadelphia Chromosome positive (Ph ⁺) CML patients in Pakistan.

Methods: The study was conducted from August 2009 to July 2010 at Civil Hospital and Baqai Institute of Hematology (BIH) Karachi. Blood samples from 25 patients with CML were collected. Multiplex reverse transcription polymerase chain reaction (RT-PCR) was performed for Breakpoint Cluster Region – Abelson (BCR-ABL) rearrangement. Conventional PCR was performed for JAK2 V617F mutation on BCR-ABL positive samples.

Results: All 25 samples showed BCR-ABL rearrangement. Out of these 11 samples (44%) had JAK2 V617F mutation; the remaining 14 (56%) cases showed JAK2 617V wild type.

Conclusion: It is concluded that the co-existence of Ph ⁺CML and JAK2 V617F mutation is possible.

Impressive thrombocytosis evolving in a patient with a BCR-ABL positive CML in major molecular response during dasatinib treatment unmasks an additional JAK2V617F

We present a case of a 42-year old female with the rare diagnosis of a myeloproliferative syndrome harboring both a BCR-ABL transclocation and a JAK2V617F mutation.

Initially diagnosed with a CML, the patient underwent treatment with imatinib followed by dasatinib. Despite a major molecular response, the patient developed a thrombocytosis. Molecular analyses revealed a heterozygous JAK2V617F mutation, which was detected retrospectively in the bone marrow at the time of CML diagnosis.

This case underlines the complexity of MPS pathogenesis. For the clinician, a JAK2 mutational screening should be performed in CML patients without hematological response in the absence of BCR-ABL.

Simultaneous and sequential concurrent myeloproliferative and lymphoproliferative neoplasms

Concurrent manifestation of two chronic-stage myeloid and lymphoid/plasmacytoid neoplasms in one patient is rare and occurs in ≤1% of patients. There has been no systematic analysis of which combinations are frequent/infrequent and whether two concurrent diseases in one patient are clonally related or represent independent diseases. We therefore characterised a series of cases from our own archive (n = 65) and collected a large number of previously reported cases of patients in whom myeloid and lymphoid/plasmacytoid neoplasms co-occurred (n = 185). The most frequent combination was Philadelphia chromosome-negative myeloproliferative neoplasm with concurrent B cell chronic lymphocytic leukaemia, accounting for approximately 50% of double-disease patients. We compared the quantity of unsorted bone marrow cell-derived JAK2(V617F) and KIT(D816V) alleles with the quantity of the lymphoid/plasmacytoid compartment and analysed a subfraction of cases with fluorescence in situ hybridisation. Although a common aberrant progenitor has been reported in some cases in the literature, we found evidence of two independent chronic-stage myeloid and lymphoid/plasmacytoid neoplasms.

Concomitant BCR-ABL1 translocation and JAK2(V617F) mutation in three patients with myeloproliferative neoplasms

Chronic myeloproliferative neoplasms (MPN) are clonal disorders of hematopoietic stem cells, which fall into distinct categories based on a number of characteristics including the presence of the BCR-ABL1 gene fusion (chronic myelogenous leukemia) or the JAK2(V617F) mutation (polycythemia vera, primary myelofibrosis, and essential thrombocythemia). One of the criteria in the 2008 World Health Organization Classification divides MPN into different categories based on the presence of an underlying genetic abnormality, however the WHO does not currently address the classification of myeloproliferative neoplasms that have more than one genetic abnormality. The coexistence of a JAK2(V617F) mutation and BCR-ABL1 is rare, and to our knowledge, less than 25 cases have been reported in the literature. Our case series examines the clinical, histopathologic, and genetic features of 3 patients with myeloproliferative neoplasms characterized by concomitant BCR-ABL1 and JAK2(V617F). The implications for diagnosis and treatment of patients with concomitant BCR-ABL1 and JAK2(V617F) are discussed as well as how the BCR-ABL1 and JAK2(V617F)-positive clones may be related to one another.

New mutations and pathogenesis of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clonal disorders characterized by excessive production of mature blood cells. In the majority of classic MPN—polycythemia vera, essential thrombocythemia, and primitive myelofibrosis—driver oncogenic mutations affecting Janus kinase 2 (JAK2) or MPL lead to constitutive activation of cytokine-regulated intracellular signaling pathways. LNK, c-CBL, or SOCSs (all negative regulators of signaling pathways), although infrequently targeted, may either drive the disease or synergize with JAK2 and MPL mutations. IZF1 deletions or TP53 mutations are mainly found at transformation phases and are present at greater frequency than in de novo acute myeloid leukemias. Loss-of-function mutations in 3 genes involved in epigenetic regulation, TET2, ASXL1, and EZH2, may be early events preceding JAK2V617F but may also occur late during disease progression. They are more frequently observed in PMF than PV and ET and are also present in other types of malignant myeloid diseases. A likely hypothesis is that they facilitate clonal selection, allowing the dominance of the JAK2V617F subclone during the chronic phase and, together with cooperating mutations, promote blast crisis. Their precise roles in hematopoiesis and in the pathogenesis of MPN, as well as their prognostic impact and potential as a therapeutic target, are currently under investigation.

CBL, CBLB, TET2, ASXL1, and IDH1/2 mutations and additional chromosomal aberrations constitute molecular events in chronic myelogenous leukemia

Progression of chronic myelogenous leukemia (CML) to accelerated (AP) and blast phase (BP) is because of secondary molecular events, as well as additional cytogenetic abnormalities. On the basis of the detection of JAK2, CBL, CBLB, TET2, ASXL1, and IDH1/2 mutations in myelodysplastic/myeloproliferative neoplasms, we hypothesized that they may also contribute to progression in CML. We screened these genes for mutations in 54 cases with CML (14 with chronic phase, 14 with AP, 20 with myeloid, and 6 with nonmyeloid BP). We identified 1 CBLB and 2 TET2 mutations in AP, and 1 CBL, 1 CBLB, 4 TET2, 2 ASXL1, and 2 IDH family mutations in myeloid BP. However, none of these mutations were found in chronic phase. No cases with JAK2V617F mutations were found. In 2 cases, TET2 mutations were found concomitant with CBLB mutations. By single nucleotide polymorphism arrays, uniparental disomy on chromosome 5q, 8q, 11p, and 17p was found in AP and BP but not involving 4q24 (TET2) or 11q23 (CBL). Microdeletions on chromosomes 17q11.2 and 21q22.12 involved tumor associated genes NF1 and RUNX1, respectively. Our results indicate that CBL family, TET2, ASXL1, and IDH family mutations and additional cryptic karyotypic abnormalities can occur in advanced phase CML.

Emergence of chronic myelogenous leukemia from a background of myeloproliferative disorder: JAK2V617F as a potential risk factor for BCR-ABL translocation

We report the emergence of chronic myelogenous leukemia (CML) in a patient with JAK2V617F-positive polycythemia vera after 15 years of phlebotomy. The polycythemia vera clinical and molecular findings were suppressed at the time of CML diagnosis, only to re-emerge after the leukemia was successfully treated with imatinib. We explored the potential association between myeloproliferative disorders and CML in the context of the current literature and found a higher-than-expected coincidence based on known epidemiologic data for each specific condition. We hypothesize that myeloproliferative disorder (JAK2V617F or molecular events that cause JAK2V617F) is a risk factor for CML (BCR-ABL translocation). Because of therapeutic implications, clinicians should be aware that the conditions co-occur more frequently than once thought.

Chronic myelogenous leukemia, BCR-ABL1+

Session 1 of the 2007 Workshop of the Society for Hematopathology/European Association for Haematopathology focused on chronic myelogenous leukemia, BCR-ABL1+ (CML). CML is a myeloproliferative neoplasm arising at the level of a pluripotent stem cell and consistently associated with the BCR-ABL1 fusion gene. CML most commonly manifests in a chronic phase of the disease with neutrophilic leukocytosis, and the demonstration of the Philadelphia chromosome is the ultimate confirmation of the diagnosis. However, in select cases, the initial diagnosis remains challenging, and a number of issues pertaining to the manifestations and disease evolution remain unresolved. These issues have been illustrated by the cases submitted to our workshop and include unusual manifestations of CML, including manifestation in the accelerated and/or blast phase, and patterns of disease progression and therapy resistance in the era of protein tyrosine kinase inhibitor therapy.

A myeloproliferative disorder may hide another one

Chronic myeloproliferative disorders (MPDs) are divided into Philadelphia-positive chronic myeloid leukemia (CML) and Philadelphia-negative disorders including polycythemia vera, essential thrombocythemia and idiopathic myelofibrosis (IMF). Concomitance of a CML and another MPD is a rare event. We report here the case of a patient presenting initially with IMF who developed a Philadelphia-positive CML 7 years later. At the time of CML diagnosis, two distinct clones were present, one with a 13q deletion and one with a t(9;22). We raise the problem of a CML developing on an initial IMF, or two MPDs occurring from a common or two different stem cells.

JAKs in pathology: role of Janus kinases in hematopoietic malignancies and immunodeficiencies

The four mammalian Janus kinase (JAK) family members, JAK1, JAK2, JAK3 and TYK2, are non-receptor protein tyrosine kinases (PTKs) that are crucial for cytokine receptor signaling in blood formation and immune responses. Mutations and translocations in the JAK genes leading to constitutively active JAK proteins are associated with a variety of hematopoietic malignancies, including the myeloproliferative disorders (JAK2), acute lymphoblastic leukemia (JAK2), acute myeloid leukemia (JAK2, JAK1), acute megakaryoblastic leukemia (JAK2, JAK3) and T-cell precursor acute lymphoblastic leukemia (JAK1). In contrast, loss-of-function mutations of JAK3 and TYK2 lead to immunodeficiency. The role of JAKs as therapeutic targets is starting to expand, as more insights into their structure and activation mechanisms become available.

Emergence of therapy-unrelated CML on a background of BCR-ABL-negative JAK2V617F-positive chronic idiopathic myelofibrosis

We report the emergence of a chronic myeloid leukaemia (CML) during the course of a JAK2V617F-positive chronic idiopathic myelofibrosis (CIMF) in the absence of any myelosuppressive treatment. Although a response to imatinib was observed, the underlying myelofibrosis persisted after treatment and hydroxyurea was finally added to control the persistent thrombocytosis. Such rare patients with co-existing BCR-ABL translocation and JAK2V617F mutation must be identified in view of the possibility of targeted therapies. Moreover, the detection of BCR-ABL translocation appears to be crucial especially in the case of treated CIMF with an atypical course to identify CML before acute transformation.