An inherited gain-of-function risk allele in EPOR predisposes to familial JAK2V617F myeloproliferative neoplasms.

Myeloproliferative neoplasms (MPN) are mainly sporadic but inherited variants have been associated with higher risk development. Here, we identified an EPOR variant (EPORP488S ) in a large family diagnosed with JAK2V617F -positive polycythaemia vera (PV) or essential thrombocytosis (ET). We investigated its functional impact on JAK2V617F clonal amplification in patients and found that the variant allele fraction (VAF) was low in PV progenitors but increase strongly in mature cells. Moreover, we observed that EPORP488S alone induced a constitutive phosphorylation of STAT5 in cell lines or primary cells. Overall, this study points for searching inherited-risk alleles affecting the JAK2/STAT pathway in MPN.

Germ-line JAK2 mutations in the kinase domain are responsible for hereditary thrombocytosis and are resistant to JAK2 and HSP90 inhibitors.

The main molecular basis of essential thrombocythemia and hereditary thrombocytosis is acquired, and germ-line-activating mutations affect the thrombopoietin signaling axis. We have identified 2 families with hereditary thrombocytosis presenting novel heterozygous germ-line mutations of JAK2. One family carries the JAK2 R867Q mutation located in the kinase domain, whereas the other presents 2 JAK2 mutations, S755R/R938Q, located in cis in both the pseudokinase and kinase domains. Expression of Janus kinase 2 (JAK2) R867Q and S755R/R938Q induced spontaneous growth of Ba/F3-thrombopoietin receptor (MPL) but not of Ba/F3-human receptor of erythropoietin cells. Interestingly, both Ba/F3-MPL cells expressing the mutants and platelets from patients displayed thrombopoietin-independent phosphorylation of signal transducer and activator of transcription 1. The JAK2 R867Q and S755R/R938Q proteins had significantly longer half-lives compared with JAK2 V617F. The longer half-lives correlated with increased binding to the heat shock protein 90 (HSP90) chaperone and with higher MPL cell-surface expression. Moreover, these mutants were less sensitive to JAK2 and HSP90 inhibitors than JAK2 V617F. Our results suggest that the mutations in the kinase domain of JAK2 may confer a weak activation of signaling specifically dependent on MPL while inducing a decreased sensitivity to clinically available JAK2 inhibitors.

Long term follow up of 93 families with myeloproliferative neoplasms: life expectancy and implications of JAK2V617F in the occurrence of complications.

The long-term evolution of familial myeloproliferative neoplasms was studied in 93 families with 227 subjects including 97 with polycythemia vera (PV), 105 essential thrombocythemia (ET), 14 primary myelofibrosis (PMF) and 11 chronic myeloid leukemia (CML). In PV patients, with 12years of median follow-up, overall survival was 83% at 10years and 37% at 20years. A high JAK2(V617F) allele burden was correlated with the transformation to myelofibrosis (p<0.0001), but not with the transformation to acute leukemia. Among the 105 ET, with 8years of median follow-up, overall survival was 83% at 10years and 57% at 20years. Progression to acute leukemia and progression to myelofibrosis were 10% and 13%. There was a trend toward a more frequent evolution to myelofibrosis when the JAK2(V617F) mutated allele burden was >50% (p=0.09), but not to AML. Hematologic transformation of the MPN was responsible for 69% of the deaths, cerebral stroke for 7% and 4% died of myocardial infarction. Eleven JAK2(V617F) mutated patients developed 13 deep splanchnic thromboses in PV and ET. Finally whereas patients with familial PV and ET have a comparable prognosis to non-familial MPN, the JAK2(V617F) mutation was associated with a more frequent occurrence of thrombosis in the entire population.

Germline ATG2B/GSKIP-containing 14q32 duplication predisposes to early clonal hematopoiesis leading to myeloid neoplasms.

The germline predisposition associated with the autosomal dominant inheritance of the 14q32 duplication implicating ATG2B/GSKIP genes is characterized by a wide clinical spectrum of myeloid neoplasms. We analyzed 12 asymptomatic carriers and 52 patients aged 18-74 years from six families, by targeted sequencing of 41 genes commonly mutated in myeloid malignancies. We found that 75% of healthy carriers displayed early clonal hematopoiesis mainly driven by TET2 mutations. Molecular landscapes of patients revealed two distinct routes of clonal expansion and leukemogenesis. The first route is characterized by the clonal dominance of myeloproliferative neoplasms (MPN)-driver events associated with TET2 mutations in half of cases and mutations affecting splicing and/or the RAS pathway in one-third of cases, leading to the early development of MPN, mostly essential thrombocythemia, with a high risk of transformation (50% after 10 years). The second route is distinguished by the absence of MPN-driver mutations and leads to AML without prior MPN. These patients mostly harbored a genomic landscape specific to acute myeloid leukemia secondary to myelodysplastic syndrome. An unexpected result was the total absence of DNMT3A mutations in this cohort. Our results suggest that the germline duplication constitutively mimics hematopoiesis aging by favoring TET2 clonal hematopoiesis.

Analysis of the ten-eleven translocation 2 (TET2) gene in familial myeloproliferative neoplasms.

The JAK2(V617F) mutation does not elucidate the phenotypic variability observed in myeloproliferative neoplasm (MPN) families. A putative tumor suppressor gene, TET2, was recently implicated in MPN and myelodysplastic syndromes through the identification of acquired mutations affecting hematopoietic stem cells. The present study analyzed the TET2 gene in 61 MPN cases from 42 families. Fifteen distinct mutations were identified in 12 (20%) JAK2(V617F)-positive or -negative patients. In a patient with 2 TET2 mutations, the analysis of 5 blood samples at different phases of her disease showed the sequential occurrence of JAK2(V617F) and TET2 mutations concomitantly to the disease evolution. Analysis of familial segregation confirmed that TET2 mutations were not inherited but somatically acquired. TET2 mutations were mainly observed (10 of 12) in patients with primary myelofibrosis or patients with polycythemia vera or essential thrombocythemia who secondarily evolved toward myelofibrosis or acute myeloid leukemia.

Extent of hematopoietic involvement by TET2 mutations in JAK2V6¹7F polycythemia vera.

TET2 mutations are found in polycythemia vera and it was initially reported that there is a greater TET2 mutational burden than JAK2(V617F) in polycythemia vera stem cells and that TET2 mutations precede JAK2(V617F). We quantified the proportion of TET2, JAK2(V617F) mutations and X-chromosome allelic usage in polycythemia vera cells, BFU-Es and in vitro expanded erythroid progenitors and found clonal reticulocytes, granulocytes, platelets and CD34(+) cells. We found that TET2 mutations may also follow rather than precede JAK2(V617F) as recently reported by others. Only a fraction of clonal early hematopoietic precursors and largely polyclonal T cells carry the TET2 mutation. We showed that in vitro the concomitant presence of JAK2(V617F) and TET2 mutations favors clonal polycythemia vera erythroid progenitors in contrast with non-TET2 mutated progenitors. We conclude that loss-of-function TET2 mutations are not the polycythemia vera initiating events and that the acquisition of TET2 somatic mutations may increase the aggressivity of the polycythemia vera clone.

Germline duplication of ATG2B and GSKIP predisposes to familial myeloid malignancies.

No major predisposition gene for familial myeloproliferative neoplasms (MPN) has been identified. Here we demonstrate that the autosomal dominant transmission of a 700-kb duplication in four genetically related families predisposes to myeloid malignancies, including MPN, frequently progressing to leukemia. Using induced pluripotent stem cells and primary cells, we demonstrate that overexpression of ATG2B and GSKIP enhances hematopoietic progenitor differentiation, including of megakaryocytes, by increasing progenitor sensitivity to thrombopoietin (TPO). ATG2B and GSKIP cooperate with acquired JAK2, MPL and CALR mutations during MPN development. Thus, the germline duplication may change the fitness of cells harboring signaling pathway mutations and increases the probability of disease development.

Imatinib in combination with cytarabine for the treatment of Philadelphia-positive chronic myelogenous leukemia chronic-phase patients: rationale and design of phase I/II trials.

Imatinib (Gleevec) (formerly STI571) has been shown to selectively inhibit the tyrosine kinase domain of the oncogenic BCR-ABL fusion protein of chronic myelogenous leukemia (CML) cells. In recent phase I and II studies testing this new compound in patients who had failed to respond to interferon (IFN), hematological and cytogenetic responses were reported in most of those with chronic-phase CML. However, in some patients resistance has been associated with a single amino acid substitution in a threonine residue of the Abl kinase domain. In vitro studies examining the effects of imatinib plus cytarabine (Ara-C) using CML cell lines and colony-forming assays of CML patient samples have shown synergistic antiproliferative effects of this combination. Thus several groups decided to investigate this new combination with the hypothesis that cell resistance would be less frequent. The CML French Group performed a phase II trial to determine the safety and tolerability of a combination of imatinib and Ara-C for previously untreated patients with chronic-phase CML. Treatment was administered on 28-day cycles for 12 months. Patients were treated continuously with imatinib orally at a dose of 400 mg daily. Ara-C was given on days 14 to 28 of each cycle at an initial dose of 20 mg/m(2)/d via subcutaneous injection, hydroxyurea (HU) being stopped at least 7 days before imatinib. Recently, the Dutch group decided to explore a combination of high-dose Ara-C with imatinib in patients in chronic-phase CML. Preliminary results are encouraging. However, a long follow-up is required before concluding that these strategies will overcome cell resistance.

Spinal cord compression of dual etiology, multiple myeloma and spinal tuberculosis.

Spinal cord compression as an initial manifestation of multiple myeloma is a well-known phenomenon. We report for the first time a patient with spinal cord compression of dual etiology, multiple myeloma and spinal tuberculosis, treated successfully by local radiotherapy, chemotherapy and an antituberculous regimen.

Bcl-2 and immunoglobulin gene rearrangements in patients with malaria related chronic splenomegaly.

Two cases of malaria related chronic splenomegaly, one with tropical splenic lymphoma with villous lymphocytes (TSLVL) and the other with hyperreactive malarial splenomegaly (HMS) were analyzed by cytology, histology, karyotyping, immunophenotyping, and polymerase chain reaction (PCR) for detection of bcl-2/JH and FR3/JH rearrangements on blood and bone marrow samples, at diagnosis and 12 months after malarial prophylaxis. The reported data suggest that the detection of FR3/JH rearrangement might contribute to the diagnosis of TSLVL in patients with malaria related chronic splenomegaly, for whom bcl-2/JH rearrangement may be a common molecular event.

Genetic and clinical implications of the Val617Phe JAK2 mutation in 72 families with myeloproliferative disorders.

To study the prevalence of the Val617Phe JAK2 mutation in familial cases of myeloproliferative disorder (MPD) and its possible implication as a predisposing genetic factor, we analyzed 72 families including 174 patients (81 polycythemia vera [PV], 68 essential thrombocythemia [ET], 11 myelofibrosis with myeloid metaplasia [MMM], 12 chronic myeloid leukemia), 1 systemic mastocytosis, and 1 chronic myelomonocytic leukemia (CMML). The JAK2 mutation was found in three quarters of patients with PV and MMM and in half of patients with ET. Among 46 families with at least 2 cases of PV, ET, or MMM, the JAK2 mutation was absent in 6 families, heterogeneously distributed in 18, and present in all MPD patients in 22. Among these 22 families, the absence of the JAK2 mutation both in purified T and B cells in 13 unrelated patients and the observation of variable ratios of the JAK2 mutant allele in patient leucocytes indicated that the Val617Phe JAK2 mutation was acquired in familial MPDs. The JAK2 mutation was present in natural killer cells in two thirds of tested patients (27 of 40), suggesting its occurrence in a multipotent hematopoietic progenitor cell. The analysis of the hematologic profile showed that the homozygous JAK2 mutation confers a proliferative advantage and is associated with the progression of the hematologic disease.

Tandem autologous stem cell transplantation in high-risk de novo multiple myeloma: final results of the prospective and randomized IFM 99-04 protocol.

The combination of high levels of beta2-microglobulin (beta2-m) and chromosome 13 deletion allows identification of a high-risk subgroup of patients with de novo multiple myeloma (MM). In this population of patients, we have evaluated the impact of a murine anti-interleukin 6 (anti-IL-6) monoclonal antibody (BE-8) as part of the second conditioning regimen in a multicenter prospective randomized trial of tandem autologous stem cell transplantation (ASCT). Conditioning for the first ASCT was accomplished with melphalan 200 mg/m2 and for the second one with melphalan 220 mg/m2 plus dexamethasone with or without BE-8 infusion. This trial included 219 patients, of whom 166 were randomized, 85 without BE-8 (arm A) and 81 with BE-8 (arm B). The median overall survival (OS) and event-free survival (EFS) times of the whole group of patients were 41 and 30 months, respectively. Response rates, OS, and EFS were not different between the 2 arms of the trial. OS at 54 months was 46% in arm A and 51% in arm B (P = .90); median EFS was 35 months in arm A and 31 in arm B (P = .39). In high-risk patients the dose intensity of melphalan at 420 mg/m2 led to encouraging results, but the addition of anti-IL-6 monoclonal antibody to the second conditioning regimen did not improve either OS nor EFS.