Is JAK2 Inducible by Cytotoxic Chemotherapy?

Abstract Abstract 4979 Introduction The JAK2V617F mutation accounts for most cases of myeloproliferative neoplasms (MPN). Only a few case reports of MPN following cytotoxic chemotherapy have been reported, and all of them were published prior to the discovery of the JAK2V617F mutation. We report a series of 6 patients who developed a JAK2V617F positive MPN following cytotoxic chemotherapy. Patients From 2006 to 2009, 6 patients with a history of a hematologic or an oncologic malignancy who developed an MPN were identified and their medical records retrospectively reviewed. One patient had acute lymphoblastic leukemia, 1 had Hodgkin lymphoma, 1 had squamous cell carcinoma of the head and neck, 1 had cervical cancer, and 2 had breast cancer. All patients were in remission from their primary malignancies at the time the MPN was diagnosed. Five were females. The median age at diagnosis was 72 years. Median time to development of the myeloproliferative neoplasm was 14 years. Type of chemotherapy exposure, MPN diagnosis and time to MPN in each case is shown in the table below. The JAK2V617F mutation was detected either in the peripheral blood or the bone marrow of all patients. There was no predominance of any specific MPN diagnosis. Patients who received platinum-based chemotherapy developed the MPN sooner than those who received alkylators (6 vs 17.5 years respectively). Treatment consisted of phlebotomy, hydroxyurea, anagrelide, aspirin or a combination as deemed appropriate by the treating hematologist. Conclusion These findings lead us to hypothesize whether the development of JAK2V617F positive MPN may be related to prior exposure to cytotoxic chemotherapy. Exposure to platinum-based chemotherapy may cause the disorder to appear sooner compared with exposure to alkylators. Recently, JAK2V617F positive MPN was found to be strongly associated with a specific constitutional haplotype, 46/11 suggesting increased susceptibility to this mutation. Chromosomal analyses are planned to show whether any of the reported patients exhibit this haplotype. Ref: 1.Jones et al, Nat Genet. 2009 Apr;41(4):446-9. 2009 Mar 15. The authors have no relevant disclosure. Disclosures No relevant conflicts of interest to declare.

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Comparing Outcomes of Patients with Secondary AML: Treatment-Related MDS/AML, AML Secondary to Myeloproliferative Neoplasms (t-MPN), and AML with Prior Malignancies

Blood ◽

10.1182/blood.v120.21.3557.3557 ◽

2012 ◽

Vol 120 (21) ◽

pp. 3557-3557 ◽

Cited By ~ 2

Author(s):

Cecilia Y Arana Yi ◽

Hagop M. Kantarjian ◽

Guillermo Garcia-Manero ◽

William G. Wierda ◽

Gautam Borthakur ◽

...

Keyword(s):

Radiation Therapy ◽

Molecular Markers ◽

De Novo ◽

Conflicts Of Interest ◽

Myeloproliferative Neoplasms ◽

Myeloproliferative Neoplasm ◽

Secondary Aml ◽

Flt3 Mutations ◽

History Of ◽

De Novo Aml

Abstract Abstract 3557 Background: Secondary Acute Myeloid Leukemia (AML) accounts for approximately 10% of AML's and are often associated with adverse outcomes compared to de novo AML. In addition to cytogenetics, multiple gene mutations have been incorporated in the de novo AML risk stratification as independent prognostic and predictive factors. Little is known about these molecular markers in secondary AML. We analyzed the characteristics and outcomes of AML patients arising from myelodysplastic syndrome (MDS), myeloproliferative neoplasm (MPN), treatment-related AML (t-AML), or with prior history of cancer not treated with chemotherapy or radiation compared to de novo AML, and investigated the frequency and prognostic relevance of molecular markers among those groups. Patients and Methods: We analyzed the outcomes of adult patients with AML receiving induction chemotherapy at MDACC (n= 248) from 2010 to 2012. Median age was 67 years (range 17–82) and 142 (57.2 %) patients were >60 yrs. 108 (44%) were female. 146 (59 %) had de novo AML, 43 (17%) had t-AML, 23 (9%) had post-MDS, 16 (7%) post-MPN, and 20 (8%) AML with antecedent cancer not treated with chemotherapy and/or radiation therapy. Median white blood cell count (WBC) at diagnosis was 4.45 × 109/L (r: 0.4–186.5), and 82 (33%) pts had WBC >10 x109/L. Cytogenetics were diploid in 91 (37%), inv 16 in 16 (7%), t(8;21) in 12 (5%), trisomy 8 in 10 (4%), chromosome −5 and/or −7 in 60 (24%), 11q in 11 (4%), miscellaneous in 30 (12%), and insufficient metaphases on 18 (7%). 43(17%) had FLT3 mutations including 26 (10%) with FLT3-ITD, 14 (6%) FLT3-D835, and 3 (1%) double mutant. 32 (13 %) had NPM 1, 15 (6%) CBFb-MYH1, 10 (4%) ABL1/ETO, 6 (2%) JAK2, 34 (14 %) RAS, 1 (0.4%) cKIT, 18 (7%) CEBPA, 10 (4%) IDH1, and 8 (3.2%) IDH2. The pts were treated with several different induction chemotherapies. Idarubicin and cytarabine (IA)-based were more frequent in de novo and in 2nd cancer groups, while hypomethylating agents were more common in post-MDS and post-MPN groups. CR rates were higher in de novo AML than the rest of the groups, and early deaths were more common in the post-MPN group. The frequency of mutations was similar among groups with the exception of JAK 2 mutation, which was more frequent in post-MPN (Table 1). In pts with secondary AML, FLT3 mutations do not seem to further worsen their outcome (median survival 6.2 months for FLT3 wt and 6.4 for FLT3 ITD in 2nd AML; corresponding values for de novo AML are not reached and 13.3 months, respectively). (Figure 1) EFS and OS was worse in the post-MDS and post-MPN groups compared to de novo AML and second cancer group (p>0.001). Conclusion: In patients with secondary AML, antecedent of MDS or MPN are associated with unique molecular signatures (eg, rare FLT3-ITD in post MDS, frequent JAK2 in post-MPN) and have an inferior outcome. In contrast AML in pts with history of previous cancers not previously exposed to chemotherapy or radiation therapy survival outcomes are similar to de novo AML. Mutational status may not be as predictive of outcome among patients with secondary AML as it is for de novo AML. Disclosures: No relevant conflicts of interest to declare.

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Mixed phenotype acute leukemia and lineage switch from lymphoblastic leukemia to myeloid leukemia in the course of Philadelphia-negative myeloproliferative neoplasm – case reports and literature review

Acta Haematologica Polonica ◽

10.2478/ahp-2020-0021 ◽

2020 ◽

Vol 51 (2) ◽

pp. 112-118 ◽

Cited By ~ 1

Author(s):

Agnieszka Ożańska ◽

Marta Sobas ◽

Donata Szymczak ◽

Tomasz Wróbel

Keyword(s):

Acute Leukemia ◽

Myeloid Leukemia ◽

Myeloproliferative Neoplasms ◽

Case Reports ◽

Lymphoblastic Leukemia ◽

Myeloproliferative Neoplasm ◽

Primary Myelofibrosis ◽

Hematopoietic Stem ◽

Lineage Switch ◽

Mixed Phenotype

AbstractPhiladelphia-negative myeloproliferative neoplasms (Ph-neg MPNs) are characterized by clonal hematopoiesis derived from a mutated hematopoietic stem cell. Ph-neg MPNs rarely transforms into acute leukemia, and in most cases, the transformation leads to the development of acute myeloid leukemia (AML). The incidence of mixed-phenotype leukemia (MPAL) or acute lymphoblastic leukemia (ALL) with lineage switch is much rarer. The unidentified lineage of blast cells is due to the immaturity of their undifferentiated progenitors with co-expression of myeloid and lymphoid antigens. The prognosis of secondary acute leukemia transformed from Ph-neg MPN is very unfavorable, especially in MPAL or lineage switch from ALL to AML cases. Moreover, there are no therapeutic protocols for these specific leukemia subtypes. Therefore, we believe that all cases of MPAL or lineage switch leukemia should be reported. This article presents the case of a patient with JAK2-positive essential thrombocythemia (ET) transformed to MPAL, and a patient with triple-negative primary myelofibrosis (PMF) (negative for JAK2, CALR, and MPL) transformed to ALL with subsequent lineage switch to AML.

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Preclinical characterization of the selective JAK1/2 inhibitor INCB018424: therapeutic implications for the treatment of myeloproliferative neoplasms

Blood ◽

10.1182/blood-2009-04-214957 ◽

2010 ◽

Vol 115 (15) ◽

pp. 3109-3117 ◽

Cited By ~ 449

Author(s):

Alfonso Quintás-Cardama ◽

Kris Vaddi ◽

Phillip Liu ◽

Taghi Manshouri ◽

Jun Li ◽

...

Keyword(s):

Polycythemia Vera ◽

Interleukin 6 ◽

Myeloproliferative Neoplasms ◽

Primary Cultures ◽

Myeloproliferative Neoplasm ◽

Primary Myelofibrosis ◽

Experimental Models ◽

Jak2v617f Mutation ◽

Erythroid Progenitor ◽

Therapeutic Implications

AbstractConstitutive JAK2 activation in hematopoietic cells by the JAK2V617F mutation recapitulates myeloproliferative neoplasm (MPN) phenotypes in mice, establishing JAK2 inhibition as a potential therapeutic strategy. Although most polycythemia vera patients carry the JAK2V617F mutation, half of those with essential thrombocythemia or primary myelofibrosis do not, suggesting alternative mechanisms for constitutive JAK-STAT signaling in MPNs. Most patients with primary myelofibrosis have elevated levels of JAK-dependent proinflammatory cytokines (eg, interleukin-6) consistent with our observation of JAK1 hyperactivation. Accordingly, we evaluated the effectiveness of selective JAK1/2 inhibition in experimental models relevant to MPNs and report on the effects of INCB018424, the first potent, selective, oral JAK1/JAK2 inhibitor to enter the clinic. INCB018424 inhibited interleukin-6 signaling (50% inhibitory concentration [IC50] = 281nM), and proliferation of JAK2V617F+ Ba/F3 cells (IC50 = 127nM). In primary cultures, INCB018424 preferentially suppressed erythroid progenitor colony formation from JAK2V617F+ polycythemia vera patients (IC50 = 67nM) versus healthy donors (IC50 > 400nM). In a mouse model of JAK2V617F+ MPN, oral INCB018424 markedly reduced splenomegaly and circulating levels of inflammatory cytokines, and preferentially eliminated neoplastic cells, resulting in significantly prolonged survival without myelosuppressive or immunosuppressive effects. Preliminary clinical results support these preclinical data and establish INCB018424 as a promising oral agent for the treatment of MPNs.

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Aetiology of Myeloproliferative Neoplasms

Cancers ◽

10.3390/cancers12071810 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1810

Author(s):

Mary Frances McMullin ◽

Lesley Ann Anderson

Keyword(s):

Blood Donation ◽

Myeloproliferative Neoplasms ◽

Myeloproliferative Neoplasm ◽

Occupational Exposures ◽

Population Level ◽

Primary Myelofibrosis ◽

Epidemiological Studies ◽

Incidence Rates ◽

Autoimmune Conditions ◽

History Of

Myeloproliferative neoplasms (MPNs) have estimated annual incidence rates for polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis of 0.84, 1.03, and 0.47 per 100,000. Prevalence is much higher, particularly for PV and ET, as mortality rates are relatively low. Patients are often concerned about why they developed an MPN and epidemiological studies enable the identification of potential causative factors. Previous work in small heterogeneous studies has identified a variety of risk factors associated with MPNs including family history of MPN, autoimmune conditions, some occupational exposures, and blood donation. At a population level, germline predisposition factors in various populations have been associated with MPNs. The pilot MOSAICC (Myeloproliferative Neoplasm: An In-depth Case-Control) study is one of the largest epidemiological studies in MPN ever carried out to date. It demonstrated the most effective methods for carrying out a significant epidemiological study in this patient group including the best way of recruiting controls, as well as how to evaluate occupational and lifestyle exposures, evaluate symptoms, and collect biological samples. Significant results linked to MPNs in the pilot study of 106 patients included smoking, obesity, and childhood socioeconomic status. The methodology is now in place for a much larger ongoing MOSAICC study which should provide further insight into the potential causes of MPNs.

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Distinct Roles for the NF-κB Pathway In Myeloid and Lymphoid Transformation and Leukemogenesis by BCR-ABL.

Blood ◽

10.1182/blood.v116.21.1225.1225 ◽

2010 ◽

Vol 116 (21) ◽

pp. 1225-1225

Author(s):

Mo-Ying Hsieh ◽

Richard A. Van Etten

Keyword(s):

Stem Cells ◽

Bone Marrow Cells ◽

Conflicts Of Interest ◽

Lymphoblastic Leukemia ◽

Myeloproliferative Neoplasm ◽

Dominant Negative ◽

Lymphoid Cells ◽

Leukemic Cells ◽

Mutant Form ◽

B Lymphoid

Abstract Abstract 1225 The BCR-ABL tyrosine kinase, product of the t(9;22) Ph chromosome, activates multiple signaling pathways in leukemic cells from patients with chronic myeloid leukemia (CML) and Ph+ B-cell acute lymphoblastic leukemia (B-ALL). Previous studies have shown that NF-κB is activated in BCR-ABL-expressing cell lines and contributes to transformation of primary B-lymphoid cells by BCR-ABL (Reuther et al., Genes Dev. 1998;12:968), but the mechanism of activation has not been defined (Kirchner et al., Exp. Hematol. 2003;31:504), and importance of NF-kB to myeloid and lymphoid leukemogenesis by BCR-ABL is unknown. To interrogate the role of NF-κB in BCR-ABL-mediated transformation, we utilized a super-repressor mutant form of IκBα (IκBαSR), which has been used to block NF-κB nuclear localization and transactivation by constitutively sequestering NF-κB in the cytoplasm. Using retrovirus co-expressing BCR-ABL and IκBαSR, we found that IκBαSR blocked nuclear p65/RelA expression and inhibited the IL-3 independent growth of Ba/F3 cells and primary B-lymphoid cells transformed by BCR-ABL. The effect of NF-κB inhibition was primarily on proliferation rather than on cell survival, as there was no increase in apoptosis in cells expressing IκBαSR. When primary bone marrow cells were transduced and transplanted under conditions favoring induction of B-ALL or CML-like myeloproliferative neoplasm in recipient mice, co-expression of IκBαSR significantly attenuated disease development and prolonged survival of diseased mice. Molecular analysis of these leukemias demonstrated that NF-κB inhibition decreased the frequency of leukemia-initiating (“stem”) cells in the CML model, but not in the B-ALL model, and was associated with decreased expression of c-Myc, an NF-κB target. To clarify the mechanism of activation of NF-κB in BCR-ABL-expressing cells, we targeted two upstream kinases that negatively regulate IκBα, IKKα/IKK1 or IKKβ/IKK2. To accomplish this, we engineered retroviruses co-expressing BCR-ABL and kinase-inactive, dominant-negative mutants of IKK1 (IKK1KM) or IKK2 (IKK2KM). Co-expression of either IKK mutant inhibited both B-lymphoid transformation and leukemogenesis by BCR-ABL, as well as induction of CML-like MPN, with IKK1 inhibition more effective than IKK2. Together, these results demonstrate that NF-κB is activated in part through the canonical IKK pathway in BCR-ABL-expressing leukemia cells, and that NF-κB signaling plays distinct roles in the pathogenesis of myeloid and lymphoid leukemias induced by BCR-ABL. In CML, NF-κB may play a role for in generation and/or maintenance of leukemic stem cells. These results validate IKKs as targets for therapy in Ph+ leukemias, and motivate the evaluation of small molecule IKK inhibitors in these diseases. Disclosures: No relevant conflicts of interest to declare.

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Incidence of the JAK2V617F Mutation In Mexican Patients with Myeloproliferative Neoplasms (MPNs)

Blood ◽

10.1182/blood.v118.21.5180.5180 ◽

2011 ◽

Vol 118 (21) ◽

pp. 5180-5180

Author(s):

Gregorio Ignacio ◽

Rosa María Arana-Trejo ◽

Verónica Gónzalez ◽

Maria Paula Hérnandez ◽

Yolanda Lugo ◽

...

Keyword(s):

Conflicts Of Interest ◽

Myeloproliferative Neoplasms ◽

Direct Sequencing ◽

Jak2v617f Mutation ◽

Normal Blood ◽

Base Substitution ◽

Blood Samples ◽

Specific Pcr ◽

Dna And Rna ◽

Mexican Patients

Abstract Abstract 5180 Introduction: The V617F mutation in JAK2 gene has been described in approximately 50–90% of patients with ET, MF AND PV [essential trombocythaemia, idiopathic myelofibrosis and policithemia vera]; but has also been reported, albeit at a lower frequency, in patients with other myeloid malignancies such as atypical CML, CMML, AML, MDS, JMML and CNL. A single G>T base substitution in exon 12 results in the conversion of valine to a phenylalanine aminoacid at position 617 of the JAK2 gene. The identification in this study were using techniques such as allele-specific PCR, RFLP-PCR and direct sequencing; for to determine the incidence in Mexican patients with MPNs. Patients and Methods: The JAK2V617F mutation was determined in 88 patients and 5 normal blood samples for healthy individuals as controls. About the patients, 60 were cataloged like MPNs and 28 patients with features suggestive of MPNs vs CML. Samples for bone marrow or peripherical blood were taken either at time of diagnosis of MPNs or during treatment with cytoreductive or anti-thrombotic agents. DNA and RNA were extracted using the QIAamp DNA and RNeasy mini kit (Qiagen) and amplified by the three techniques mentioned for JAK2V617F and by nested RT-PCR for BCR/ABL. Results: The five normal blood samples for controls were negative for JAK2V617F mutation and to BCR/ABL. Patients had median age 65 years (47–85 years old), 46% male and 54% female. In de overall patients: 60 patients with MPNs all were BCR/ABL negative and 20 (33%) had JAK2V617F. In the 28 patients with likely MPNs vs CML, 23 were BCR/ABL positive/JAK2 negative, two had the coexistence of both genetics defects [BCR/ABL+ and JAK2V617F+] and 3 BCR/ABL and JAK2 negative. Finally the patiens with JAK2V617F+, were 12 ET, PV 1, MF 2, CML 2, and 5 continued like MPNs. Discussion: The incidence of the JAK2V617F in this study for MPNs patiens were 33% and the incidence varied between MPNs subtype. Less than ten cases of BCR/ABL+ CML with JAK2V617F have been published; we report two patients with the coexistence and we agree with previous reports that screening for JAK2V617F mutation should be considered in any BCR/ABL+ CML patients and the clinical outcome will be define in long period. Disclosures: No relevant conflicts of interest to declare.

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Loss of Wild-Type Jak2 Allele Enhances Myeloid Cell Expansion and Accelerates Myelofibrosis in Jak2V617F Knock-in Mice

Blood ◽

10.1182/blood.v120.21.809.809 ◽

2012 ◽

Vol 120 (21) ◽

pp. 809-809

Author(s):

Hajime Akada ◽

Saeko Akada ◽

Dongqing Yan ◽

Robert Hutchison ◽

Golam Mohi

Keyword(s):

Polycythemia Vera ◽

Cell Expansion ◽

Conflicts Of Interest ◽

Myeloproliferative Neoplasms ◽

Philadelphia Chromosome ◽

Myeloid Cell ◽

Negative Regulator ◽

Jak2v617f Mutation ◽

Common Mutation ◽

Wild Type

Abstract Abstract 809 The activating JAK2V617F mutation is the most common mutation found in Philadelphia chromosome (Ph)-negative myeloproliferative neoplasms (MPNs), which include polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). Although a majority of MPN patients carry heterozygous JAK2V617F mutation, loss of heterozygosity (LOH) on chromosome 9p involving JAK2 has been observed in ∼30% of patients with MPNs particularly in PV and PMF. JAK2V617F homozygosity through 9pLOH has been linked to more severe MPN phenotype. However, the contribution of 9pLOH in the pathogenesis of MPNs remains unclear. To investigate the role of wild-type JAK2 in MPNs induced by JAK2V617F, we have utilized conditional Jak2 knock-out and Jak2V617F knock-in alleles and generated heterozygous, hemizygous and homozygous Jak2V617F mice. Whereas heterozygous Jak2V617F expression results in a polycythemia vera-like disease in mice, loss of wild-type Jak2 allele in hemizygous or homozygous Jak2V617F mice results in a significantly greater increase in reticulocytes, white blood cells, neutrophils and platelets in the peripheral blood and larger spleen size. We also have found that hemizygous or homozygous Jak2V617F expression significantly increased megakaryocyte-erythroid progenitors in the bone marrow and spleens and marked infiltration of neutrophils in the liver compared with heterozygous Jak2V617F. More importantly, hemizygous or homozygous Jak2V617F mice show accelerated myelofibrosis compared with heterozygous Jak2V617F-expressing mice. Thus, loss of wild type Jak2 allele increases myeloid cell expansion and enhances the severity of the MPN. Together, these results suggest that wild-type Jak2 serves as a negative regulator of MPN induced by Jak2V617F. Disclosures: No relevant conflicts of interest to declare.

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Multiple Myeloma Associated GI Polyposis

Blood ◽

10.1182/blood.v120.21.5009.5009 ◽

2012 ◽

Vol 120 (21) ◽

pp. 5009-5009

Author(s):

Nassim Nabbout ◽

Mohamad El Hawari ◽

Thomas K. Schulz

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

Plasma Cells ◽

Conflicts Of Interest ◽

Case Reports ◽

Bone Marrow Failure ◽

Bone Lesions ◽

Rare Manifestation ◽

History Of ◽

Central Ulceration

Abstract Abstract 5009 Multiple myeloma is a neoplastic proliferation of monoclonal plasma cells that can result in osteolytic bone lesions, hypercalcemia, renal impairment, bone marrow failure, and the production of monoclonal gammopathy. The gastrointestinal tract is rarely involved in myeloma. GI polyposis is a rare manifestation of extra-medullary disease in multiple myeloma. Such cases usually present as gastrointestinal hemorrhage or intestinal obstruction. A 53-year-old African American male recently diagnosed with multiple myeloma presented with three-day history of rectal bleed and fatigue. EGD showed multiple raised, polypoid, rounded lesions with a superficial central ulceration in the stomach. Colonoscopy showed similar lesions in the ascending and transverse areas of the colon that ranged in size from 5 to 16 mm in diameter. Biopsies showed that these polyps were made of plasma cells. A bone marrow biopsy showed diffuse involvement (greater than 90%) of bone marrow with multiple myeloma with anaplastic features. The patient was started on bortezomib at diagnosis, however, he passed away a few weeks later. This type of metastatic disease has been described in isolated case reports in the literature, while solitary GI plasmacytoma has been reported more frequently. In rare cases, multiple myeloma can involve the GI tract which may lead to bleed or obstruction. This involvement is likely a marker of aggressivity. This example of extra-medullary disease in myeloma is an uncommon variant with features of poor prognosis and dedifferentiation. Disclosures: No relevant conflicts of interest to declare.

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Tet2 Loss Accelerates The Myeloproliferative Neoplasm (MPN) Phenotype Of Jak2V617F Knockin Mice But Is Insufficient To Cause Leukemic Transformation

Blood ◽

10.1182/blood.v122.21.4095.4095 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4095-4095

Author(s):

Edwin Chen ◽

Lawrence J Breyfogle ◽

Rebekka K. Schneider ◽

Luke Poveromo ◽

Ross L. Levine ◽

...

Keyword(s):

Gene Expression ◽

Bone Marrow ◽

Conflicts Of Interest ◽

Myeloproliferative Neoplasms ◽

Myeloproliferative Neoplasm ◽

Conditional Knockout ◽

The Other ◽

Myelogenous Leukemia ◽

Leukemic Transformation ◽

The Impact

Abstract TET2 mutations are early somatic events in the pathogenesis of acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and myeloproliferative neoplasms (MPN) and are one of the most common genetic lesions found in these diseases. In MPN, TET2 mutations are enriched within more advanced disease phenotypes such as myelofibrosis and leukemic transformation and often co-occur with the JAK2V617F mutation, which is present in the majority of MPN patients. We have developed and characterized a Jak2V617F conditional knockin mouse (Jak2VF/+), the phenotype of which closely recapitulates the features of human MPN. To determine the impact of Tet2 loss on Jak2V617F-mediated MPN, we crossed Tet2 conditional knockout mice with Jak2VF/+ knockin and Vav-Cre transgenic mice and backcrossed the compound mutant animals. We then characterized the effects of heterozygous and homozygous loss of Tet2 on the phenotype of Jak2VF/+ mice. We assessed peripheral blood counts, histopathology, hematopoietic differentiation using flow cytometry, colony formation and re-plating capacity. We also evaluated the effects of Tet2 loss on the transcriptome of the HSC compartment using gene expression microarrays and on HSC function using competitive bone marrow transplantation assays. Similar to Jak2VF/+/VavCre+ mice, Tet2+/-/Jak2VF/+/VavCre+ and Tet2-/-/Jak2VF/+/VavCre+ mice develop leukocytosis, elevated hematocrits (HCT) and thrombocytosis. Tet2-/-/Jak2VF/+/VavCre+ mice demonstrate enhanced leukocytosis and splenomegaly compared to the other groups. All groups demonstrate myeloid expansion, erythroid hyperplasia and megakaryocytic abnormalities consistent with MPN in the bone marrow and spleen, while more prominent myeloid expansion and megakaryocytic morphological abnormalities are observed in Tet2-/-/Jak2VF/+/VavCre+ mice as compared to the other groups. Notably, we do not see the development of acute myelogenous leukemia (AML) in Tet2-/-/Jak2VF/+/VavCre+ mice at 6 months. We see enhanced expansion of lineagelowSca1+cKithigh (LSK) cells (enriched for HSC) most prominently in the spleens of Tet2+/-/Jak2VF/+/VavCre+ and Tet2-/-/Jak2VF/+/VavCre+ mice as compared to Jak2VF/+/VavCre+ mice. In colony forming assays, we find that Tet2-/-/Jak2VF/+/VavCre+ LSK cells have enhanced re-plating activity compared to Jak2VF/+/VavCre+ LSK cells and that Tet2-/-/Jak2VF/+/VavCre+ LSK cells form more colonies that Tet2-/-/Jak2+/+/VavCre+ cells. Gene expression analysis demonstrates enrichment of a HSC self-renewal signature inTet2-/-/Jak2VF/+/VavCre+ LSK cells. Concordant with this, we find that Tet2-/-/Jak2VF/+/VavCre+ LSK cells have enhanced competitive repopulation at 16 weeks as compared to Jak2VF/+/VavCre+ and Tet2+/-/Jak2VF/+/VavCre+ LSK cells. In aggregate these findings demonstrate that Tet2 loss promotes disease progression in MPN but is insufficient to drive full leukemic transformation. Disclosures: No relevant conflicts of interest to declare.

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Latent Myeloproliferative Neoplasm May Underlie Retinal Vein Occlusion In Older Patients

Blood ◽

10.1182/blood.v122.21.5242.5242 ◽

2013 ◽

Vol 122 (21) ◽

pp. 5242-5242

Author(s):

Katerina Zoi ◽

Christine Zoi ◽

Andreas Giannopoulos ◽

Argyri Gialeraki ◽

Kassiani Giannaki ◽

...

Keyword(s):

Retinal Vein Occlusion ◽

Older Patients ◽

Conflicts Of Interest ◽

Myeloproliferative Neoplasms ◽

Significant Risk ◽

Jak2v617f Mutation ◽

Thrombotic Complication ◽

Allele Burden ◽

Vein Occlusion ◽

Increased Risk

Abstract Background Myeloproliferative neoplasms (MPNs) have been associated with a high incidence of thrombosis and bleeding episodes, which significantly contribute to disease-related morbidity and mortality. Clinical data indicate an association of the JAK2V617F mutation, seen in nearly all polycythemia vera (PV) cases and almost 60% of those with essential thrombocythemia (ET) and myelofibrosis (MF). The mutation is also seen in 37% of patients with in splachnic vein thrombosis (SVT) and its presence was associated with an increased risk for SVT. However, the prevalence of JAK2V617 seems to be low in patients with other thromboembolic events in unusual sites such as cerebral sinus, upper limb deep venous thrombosis (DVT). Additionally, activating mutations of MPL gene, seen in 3% of ET and 5% of MF patients, are considered as a significant risk factor for microvessel disturbances and have been associated with an increased risk of arterial thrombosis. Retinal vein occlusion (RVO) is a thrombotic complication in an uncommon site that may result in sight threatening disease. In this study we investigated the prevalence of JAK2V617F and MPLW515L/K mutations in a prospectively assembled cohort of patients with RVO, hypothesizing that some cases may be associated with an underlying undiagnosed MPN. Patients and Methods We studied 52 (23 males and 29 females) consecutive patients with no evidence of an underlying MPN who had been diagnosed with RVO confirmed with fluorangiography from January 2007 to September 2011. The mean age was 70 years (range: 49-85) Twenty eight patients (53.8%) presented with central RVO and 24 patients with branched RVO (46.5%). DNA was extracted from peripheral blood samples by standard procedures. The JAK2V617F mutation was detected using a tetra-primer amplification refractory mutation system (ARMS) polymerase chain reaction (PCR) assay with a sensitivity of 1% and the allele burden was estimated with a semi-quantitative method. MPLW515L/K were detected using allele-specific PCR (AS-PCR) assays with a sensitivity of 1%. Results Overall, MPN associated mutations were detected in 5/52 cases. JAK2V617F was detected in 2/52 cases (3.8%; 95%CI-1.4%-9%), while MPL exon 10 mutations were detected in 3/52 (5.7%; 95%CI-0.6%-12%). The JAK2V617F allele burden in the two positive patients was 45% and 52% respectively. Both patients who carried the JAK2V617F mutation were female. The first patient had been already diagnosed with ET according to the WHO criteria at the time of RVO screening. She was receiving hydroxyurea and aspirin and her platelet count was normal. The second patient who also carried the JAK2V617F mutation had a PLT count of 850.000/μl at the time of screening and was diagnosed with ET within the 3 following months. The patients with MPL mutations presented with normal blood counts. Conclusions Our findings indicate that a latent MPN could underlie RVO even in the absence of conventional diagnostic criteria. Our results represent the first report that MPL mutations could underlie RVO cases and suggest that routine screening of RVO cases for MPN mutations may be useful, especially in older patients. Disclosures: No relevant conflicts of interest to declare.

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