Myeloproliferative disorders

JAK2 and Beyond: Mutational Study of JAK2V617 in Myeloproliferative Disorders and Haematological Malignancies in Kashmiri population

BACKGROUND

Janus Tyrosine Kinase-2 (JAK2 V617F), a novel point mutation affecting the MPD'S is a somatic gain-of-function mutation. It alters a highly conserved amino acid valine in the negative regulatory JH2 domain to phenylalanine predicted to dysregulate kinase activity.

AIM

To evaluate the prevalence and clinical significance of JAK2 V617F mutation in various MPD's as well as in hematological malignancies.

SUBJECTS AND METHODS

JAK2 mutation was assessed in 90 patients with myeloproliferative disorders and 47 leukemic patients. In addition, peripheral blood samples from 90 healthy donors were also collected as control. We used a highly sensitive Allele-Specific polymerase chain reaction (AS-PCR) for the detection and confirmed the mutation further by direct sequencing.

RESULTS

Our results showed significant differences between various disorders with respect to either the proportion of positivity or that of mutant alleles. JAK2-V617F was detected in 67/90 MPD patients and 02/17 for AML,01/11 for ALL-L1,02/12 for ALL-L2 and 02/07 for CML and 90 healthy controls.

CONCLUSION

From the above findings it is evident that the JAK2 V617F mutation is widespread not only in MPD's but also in hematological malignancies, which might as well lead to the new classification of MPD'S. Our data also suggest that different genetic events may lead to JAK-STAT pathway activation in different malignancies.

The 5q deletion size in myeloid malignancies is correlated to additional chromosomal aberrations and to TP53 mutations

Deletions in the long arm of chromosome 5 (del(5q)) are recurrent abnormalities in myeloid malignancies. We analyzed del(5q) and accompanying molecular mutations in MDS, MPN and MDS/MPN cases. A high del(5q) frequency was revealed in MDS (1869/11398 cases; 16%), followed by MDS/MPN (37/1107; 3%) and MPN (97/6373; 2%). To investigate potential associations of the del(5q) size with the respective phenotypes, we applied array CGH analyses in selected cohorts of 61 MDS, 22 MDS/MPN and 23 MPN cases. The size varied between 16 and 119 Mb with no differences between the entities. However, MPN and MDS/MPN cases with del(5q) sole showed a significantly smaller del(5q) than cases with additional aberrations. Sequence analysis of 27 genes revealed ≥1 mutation in 91% of patients. The highest mutation frequencies in the total cohort were observed for TP53 (31%), JAK2 (23%) and DNMT3A (18%). The molecular mutation patterns in the del(5q) cohorts were different between the entities but resembled known patterns of cohorts not selected for del(5q). Further, TP53 mutations were significantly more frequent in cases with a larger deletion size (P = 0.003). The results suggest a correlation of large del(5q) with TP53 mutations and with additional chromosomal aberrations possibly contributing to more severe courses of these cases. © 2016 Wiley Periodicals, Inc.

JAK2 and genomic instability in the myeloproliferative neoplasms: a case of the chicken or the egg?

The myeloproliferative neoplasms (MPNs) are a particularly useful model for studying mutation accumulation in neoplastic cells, and the mechanisms underlying their acquisition. This review summarizes our current understanding of the molecular defects present in patients with an MPN, and the effects of mutations targeting Janus kinase 2 (JAK2)-mediated intracellular signaling on DNA damage and on the elimination of mutation-bearing cells by programmed cell death. Moreover, we discuss findings that suggest that the acquisition of disease-initiating mutations in hematopoietic stem cells of some MPN patients may be the consequence of an inherent genomic instability that was not previously appreciated.

Jumping translocation of chromosome 1q associated with good clinical outcome in a case of Burkitt leukemia

Acquired jumping translocations (JTs) are rare secondary aberrations occurring in various hematological malignancies. In Burkitt lymphoma/leukemia (BL) chromosome 1q abnormalities such as partial or whole arm duplications/translocations are frequently associated with the disease-specific t(8;14)(q24;q32). JTs of 1q are considered to have a bad prognostic impact in BL. We report clinical, conventional and molecular cytogenetic findings of a 12-year-old boy who presented with BL. In addition to the primary aberration, t(8;14)(q24;q32), JT of 1q onto chromosomes 21 and der(14) as well as the formation of isochromosome 1q could be detected in his bone marrow sample. Despite the expected poor prognostic outcome of these aberrations, the patient has been experiencing an event free survival of 7.5 years at the time of the present report, reflecting the excellent clinical outcome of the disease.

Molecular and genetic bases of myeloproliferative disorders: questions and perspectives

The discovery of the JAK2V617F mutation followed by the discovery of JAK2 exon 12 and MPLW515 mutations has completely modified the understanding, diagnosis, and management of the classic myeloproliferative disorders (MPDs), which include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Nonetheless, genetic defects have not yet been identified in about 40% of ET and PMF. There is now strong evidence that these mutations are the oncogenic events that drive these disorders and are responsible for most biologic and clinical abnormalities. In addition, there are convincing data indicating that the number of JAK2V617F copies (homozygosity vs. heterozygosity) is important in explaining how a single mutation can be associated with several disorders. However, it is still uncertain whether these mutations are sufficient to explain the full development, heterogeneity, and progression of MPD, or if other genetic or epigenetic events are also necessary. In this review, we discuss different hypothetical models of MPD pathogenesis supported by recent findings. Further characterization of the molecular events operating in these disorders will be essential in fully understanding their pathogenesis and in developing new therapeutic approaches.

Spinal myeloid sarcoma in two non-leukemic patients

Myeloid sarcoma, formerly termed granulocytic sarcoma or chloroma, consists of neoplastic granulocytic precursors and myeloblasts. Isolated chloromas (granulocytic sarcomas) are rare tumors. Spinal complications of chloromas, such as cord compression secondary to epidural tumor or cauda equine syndrome have been described but are rare. We herein report two cases with spinal granulocytic sarcomas in non-leukemic patients. The case of a previously healthy 22-year-old man diagnosed with multiple spinal granulocytic sarcomas with no evidence of bone marrow or other hematological involvement is described. And, a 43-year-old woman diagnosed cervical spinal granulocytic sarcoma with no evidence of bone marrow or other hematological involvement is described. The tumor was totally removed by microsurgery. The histopathological examination was consistent with granulocytic sarcoma. Granulocytic sarcoma should be considered in the differential diagnosis of an epidural mass in patients with or without acute leukemia, because early diagnosis followed by appropriate combined chemotherapy and radiation may obviate surgical intervention and eventually prevent leukemic transformation.

Age and hemoglobin level emerge as most important clinical prognostic parameters in patients with osteomyelofibrosis: introduction of a simplified prognostic score

The course of disease in patients with myelofibrosis is highly variable, with survival ranging from few months to many years. Several prognostic models have been established, with the LILLE score now most commonly used. However, in recent series, the latter scoring system repeatedly failed to discriminate patients with intermediate and poor prognosis. In the present study, we re-evaluated previous prognostic models in a separate patient population. We have studied 107 patients with myelofibrosis and correlated clinical parameters at the time of diagnosis with survival. Previous scoring systems were applied to allocate patients to subgroups with distinct prognosis. Most previous scoring systems failed to clearly discriminate an intermediate and poor prognostic group. By contrast, age and hemoglobin level emerged as most significant parameters in multivariate analysis. By allocating one risk point each for hemoglobin < 10 g/dl and age >60 years, three subgroups of patients with distinct prognosis could be identified in our cohort. The overall model and the difference between each of the subgroups were statistically significant in a training group, a test group, the overall cohort of patients and the group of patients with chronic idiopathic myelofibrosis. In summary, we propose an alternative prognostic model for patients with myelofibrosis that reliably identifies three groups of patients with highly different outcome. This is in contrast to previous prognostic scores, in which the poor prognosis group was often very small and/or could not be consistently differentiated from patients with an intermediate prognosis.

Quantitative assay for Janus kinase 2 (JAK2) mutation in Chinese patients with chronic myeloproliferative disorders

The Janus kinase 2 (JAK2) V617F mutation has considerably helped understanding of the molecular pathogenesis of chronic myeloproliferative disorders (MPD), hence this study investigated for the first time the mutational status and relative quantitation of JAK2 V617F mRNA in Chinese patients with chronic MPD. The study cohort comprised 123 chronic MPD patients (35 with polycythaemia vera [PV], 85 with essential thrombocythaemia [ET], three with idiopathic myelofibrosis [IMF]). Blood samples examined by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) and capillary electrophoresis showed that the prevalence of the JAK2 V617F mutation was 100%, 62.4% and 66.7% in PV, ET and IMF patients, respectively. The proportion of JAK2 V617F mutated mRNA was 89.5% in homozygotes and 57.9% in heterozygotes; 18 PV heterozygous patients showed significantly higher mutated JAK2 mRNA levels than 36 heterozygous ET patients. Six of 93 patients exhibited abnormal karyotypes, but specific chromosomal abnormality was not found. The combination of ARMS-PCR and capillary electrophoresis enables quantitative assay of JAK2 V617F mutation, which helps in chronic MPD diagnosis and estimation of minimal residual disease.

JAK2 stimulates homologous recombination and genetic instability: potential implication in the heterogeneity of myeloproliferative disorders

The JAK2V617F mutation is frequently observed in classical myeloproliferative disorders, and disease progression is associated with a biallelic acquisition of the mutation occurring by mitotic recombination. In this study, we examined whether JAK2 activation could lead to increased homologous recombination (HR) and genetic instability. In a Ba/F3 cell line expressing the erythropoietin (EPO) receptor, mutant JAK2V617F and, to a lesser extent, wild-type (wt) JAK2 induced an increase in HR activity in the presence of EPO without modifying nonhomologous end-joining efficiency. Moreover, a marked augmentation in HR activity was found in CD34+-derived cells isolated from patients with polycythemia vera or primitive myelofibrosis compared with control samples. This increase was associated with a spontaneous RAD51 foci formation. As a result, sister chromatid exchange was 50% augmented in JAK2V617F Ba/F3 cells compared with JAK2wt cells. Moreover, JAK2 activation increased centrosome and ploidy abnormalities. Finally, in JAK2V617F Ba/F3 cells, we found a 100-fold and 10-fold increase in mutagenesis at the HPRT and Na/K ATPase loci, respectively. Together, this work highlights a new molecular mechanism for HR regulation mediated by JAK2 and more efficiently by JAK2V617F. Our study might provide some keys to understand how a single mutation can give rise to different pathologies.

Minimal residual disease diagnostics in myeloid malignancies in the post transplant period

Allogeneic SCT is important in myelodysplastic syndrome, the BCR-ABL-negative chronic myeloproliferative diseases (CMPDs) and in poor-risk AML. Techniques to monitor the minimal residual disease, for example, by PCR or immunophenotyping gain increasing importance in the post transplantation period as basis for improved and earlier therapeutic interventions in impending relapse. Recent markers such as the NPM1 mutations in AML or the JAK2V617F mutation in the CMPD can be exactly quantified by real-time PCR and were evaluated for their prognostic value in the post transplantation phase and for their utility to plan adoptive immunotherapy in case of molecular relapse. With respect to chimerism, new and very sensitive methods were introduced, for example, quantitative assessment of genetic polymorphisms by real-time PCR, but also methods here are still highly individualized. Only in CML, where SCT focuses now on poor-risk cases or cases of tyrosine kinase inhibitor failure, follow-up schedules are standardized. Standardization of the different diagnostic techniques and of the intervals in the post transplantation period is urgently needed also in other myeloid malignancies and should be focus of future studies.

The diagnosis of BCR/ABL-negative chronic myeloproliferative diseases (CMPD): a comprehensive approach based on morphology, cytogenetics, and molecular markers

Recent years showed significant progress in the molecular characterization of the chronic myeloproliferative disorders (CMPD) which are classified according to the WHO classification of 2001 as polycythemia vera (PV), chronic idiopathic myelofibrosis (CIMF), essential thrombocythemia (ET), CMPD/unclassifiable (CMPD-U), chronic neutrophilic leukemia, and chronic eosinophilic leukemia (CEL)/hypereosinophilic syndrome, all to be delineated from BCR/ABL-positive chronic myeloid leukemia (CML). After 2001, the detection of the high frequency of the JAK2V617F mutation in PV, CIMF, and ET, and of the FIP1L1–PDGFRA fusion gene in CEL further added important information in the diagnosis of CMPD. These findings also enhanced the importance of tyrosine kinase mutations in CMPD and paved the way to a more detailed classification and to an improved definition of prognosis using also novel minimal residual disease (MRD) markers. Simultaneously, the broadening of therapeutic strategies in the CMPD, e.g., due to reduced intensity conditioning in allogeneic hematopoietic stem cell transplantation and the introduction of tyrosine kinase inhibitors in CML, in CEL, and in other ABL and PDGRFB rearrangements, increased the demands to diagnostics. Therefore, today, a multimodal diagnostic approach combining cytomorphology, cytogenetics, and individual molecular methods is needed in BCR/ABL-negative CMPD. A stringent diagnostic algorithm for characterization, choice of treatment, and monitoring of MRD will be proposed in this review.

A common 93-kb duplicated DNA sequence at 1q21.2 in acute lymphoblastic leukemia and Burkitt lymphoma

In three patients with acute lymphoblastic leukemia (ALL) and in another with Burkitt lymphoma (BL), conventional cytogenetics and fluorescence in situ hybridization (FISH), applied singly or in combination, showed 1q duplication in two cases of ALL with hyperdiploid karyotypes, 1q duplication resulting from an unbalanced translocation in a third case of ALL, and inv dup(1)(q) in a patient with BL. Centromeric or telomeric breakpoints and extension of the 1q duplicons varied in each case. FISH defined a minimal, common duplicated region of 93kb at band 1q21.2 corresponding to clone RP11-212K13. In this region three putative oncogenes or tumor suppressor genes have been mapped: SF3B4 (splicing factor 3b, subunit 4), OTUD7B (OTU domain containing 7B), and MTMR11 (myotubularin related protein 11). For the first time, a minimal common 1q21.2 duplicated sequence has been identified in lymphoid malignancies in a region where putative oncogenes or suppressor genes have been mapped. This finding elucidates the genomic background of ALL and BL with 1q duplication and provides the basis for molecular studies investigating which genes are involved in leukemogenesis or disease progression in these cases.

Cytogenetic and molecular aspects of Philadelphia negative chronic myeloproliferative disorders: clinical implications

Chronic myeloproliferative disorders (CMPD) are clonal disorders of the hematopoietic stem cell. The myeloid lineage shows increased proliferation with effective maturation, while peripheral leukocytosis, thrombocytosis or elevated red blood cell mass are found. In Philadelphia negative CMPD recurrent cytogenetic abnormalities occur, but no specific abnormality has been defined to date. The spectrum of cytogenetic aberrations is heterogeneous ranging from numerical gains and losses to structural changes including unbalanced translocations. The most common chromosomal abnormalities are 20q-, 13q-, 12p-, +8, +9, partial duplication of 1q, balanced translocations involving 8p11 and gains in 9p. Cytogenetic analysis of CMPD by conventional or molecular techniques has an important role in establishing the diagnosis of a malignant disease, adding also more information for disease outcome. Molecular studies may detect the possible role of candidate genes implicated in the neoplastic process, addressing new molecular target therapies. FIP1L1/PDGFRalpha rearrangements, as well as alterations of PDGFRbeta or FGFR1 gene have been found to be associated with specific types of CMPD. Recently, a novel somatic mutation, JAK2V617F, has been reported in most of the polycthemia vera (PV) patients, as well as in a lower percentage in essential thrombocythemia (ET) or idiopathic myelofibrosis (IMF) patients. This finding represents the most important advance in understanding of the molecular mechanisms underlined the pathogenesis of CMPD, contributing to the classification and management of patients.

Polycythaemia vera and essential thrombocythaemia: current treatment strategies

Polycythaemia vera (PV) and essential thrombocythaemia (ET) are classified as Philadelphia-negative chronic myeloproliferative diseases. Both PV and ET are rare diseases, but the prevalence is high. Patients who have not been treated for the diseases are at great risk of morbidity and mortality as a result of thrombohaemorrhagic events. However, if patients have been well treated, their prognosis is good and life-expectancy approaches normal. This article provides diagnostic tools and flowcharts for treatment of PV and ET. Treatment of PV and ET should be risk-adjusted and individualised. Low-dose aspirin is recommended as an antiaggregative drug in both diseases. For PV, phlebotomy to control a haematocrit at <0.45 is the cornerstone in treatment, and treatment with hydroxycarbamide (hydroxyurea) or interferon (IFN)-alpha is added to reduce hypermetabolic symptoms or splenomegaly becoming cytoreductive. In ET, hydroxycarbamide and anagrelide are the most used drugs, and anagrelide may also be added in PV to reduce thrombocytosis. IFNalpha is the only myelosuppressive treatment available during pregnancy. Current controversies regarding treatment illustrate the need for more randomised clinical trials. Demonstration of over expression of the PV-1 gene and in particular the JAK-2 mutation will be novel diagnostic criteria and may have an impact for future therapy of both PV and ET.

Global cytokine analysis in myeloproliferative disorders

Recently developed human cytokine array membranes combine the individual assets of enzyme-linked immunosorbent assay, enhanced chemiluminescence, and the high-throughput of microspot in order to detect multiple plasma cytokines simultaneously. We employed such a system to evaluate the presence and quantity of 79 different cytokines in the plasma of 20 patients with myeloproliferative disorders (MPDs) that were not on active therapy: 10 with primary myelofibrosis (PMF), 5 with polycythemia vera (PV), and 5 with essential thrombocythemia (ET). Compared to healthy controls, patients with PMF, but not those with either PV or ET, displayed significantly higher levels of tissue inhibitor of metalloproteinase (TIMP-1), macrophage inflammatory protein-1beta (MIP-1beta), and insulin-like growth factor binding factor-2 (IGFBP-2) (p=0.013, 0.028 and 0.02, respectively). These results constitute an important conformation for the pathogenetic role of these cytokines in PMF.

Recent advances in the bcr-abl negative chronic myeloproliferative diseases

The chronic myeloproliferative disorders are clonal hematopoietic stem cell disorders of unknown etiology. In one of these (chronic myeloid leukemia), there is an associated pathognomonic chromosomal abnormality known as the Philadelphia chromosome. This leads to constitutive tyrosine kinase activity which is responsible for the disease and is used as a target for effective therapy. This review concentrates on the search in the other conditions (polycythemia vera, essential thrombocythemia and idiopathic mylofibrosis) for a similar biological marker with therapeutic potential. There is no obvious chromosomal marker in these conditions and yet evidence of clonality can be obtained in females by the use of X-inactivation patterns. PRV-1mRNA over expression, raised vitamin B₁₂ levels and raised neutrophil alkaline phosphatase scores are evidence that cells in these conditions have received excessive signals for proliferation, maturation and reduced apoptosis. The ability of erythroid colonies to grow spontaneously without added external erythropoietin in some cases, provided a useful marker and a clue to this abnormal signaling. In the past year several important discoveries have been made which go a long way in elucidating the involved pathways. The recently discovered JAK2 V617F mutation which occurs in the majority of cases of polycythemia vera and in about half of the cases with the two other conditions, enables constitutive tyrosine kinase activity without the need for ligand binding to hematopoietic receptors. This mutation has become the biological marker for these conditions and has spurred the development of a specific therapy to neutralize its effects. The realization that inherited mutations in the thrombopoietin receptor (c-Mpl) can cause a phenotype of thrombocytosis such as in Mpl Baltimore (K39N) and in a Japanese family with S505A, has prompted the search for acquired mutations in this receptor in chronic myeloproliferative disease. Recently, two mutations have been found; W515L and W515K. These mutations have been evident in patients with essential thrombocythemia and idiopathic myelofibrosis but not in polycythemia vera. They presumably act by causing constitutional, activating conformational changes in the receptor. The discovery of JAK2 and Mpl mutations is leading to rapid advancements in understanding the pathophysiology and in the treatment of these diseases.

Myelodysplastic syndrome complicated with inflammatory intestinal ulcers: significance of trisomy 8

Three cases of myelodysplastic syndrome (MDS) complicated with inflammatory intestinal ulcers all had cytogenetic abnormalities with trisomy 8. The first two patients were diagnosed with intestinal Behçets disease and were successfully treated with salazosulphapiridine, and the third patient died after leukemic transformation. We review the reported cases of MDS complicated with Behçets disease. Most of these cases are Japanese, having intestinal involvement as well as cytogenetic abnormalities with trisomy 8. We discuss the significance of trisomy 8 in intestinal involvement in MDS.

Chromosomal Abnormalities and Molecular Markers in Myeloproliferative Disorders

The first possibly causative molecular aberration in patients with myeloproliferative disorders has recently been described. A point mutation in the Janus kinase 2 exchanging a valine for a phenylalanine at position 617 (JAK2 V617F) was found in 65% to 97% of polycythemia vera (PV) patients, as well as in approximately 50% of essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF) patients. In addition, a growing set of molecular and genetic markers, some possibly contributing to disease development, some more likely epiphenomena, has been characterized in these patients over the last few years. Compiling and synthesizing the increasing knowledge on the genetic changes observed in myeloproliferative disorder (MPD) patients will allow us to generate testable hypotheses on the molecular etiology of disease development. Therefore, this review will summarize the current knowledge on chromosomal aberrations, molecular markers, and gene expression studies in MPD patients. From these data, a model depicting our current understanding of the interplay between these markers is presented.

Gain of 9p due to an unbalanced rearrangement der(9;18): a recurrent clonal abnormality in chronic myeloproliferative disorders

Clonal aberrations leading to gain of 9p--mostly due to trisomy 9--are often reported in polycythemia vera. We report on four cases of chronic myeloproliferative disorders that demonstrated a new recurrent unbalanced rearrangement between chromosomes 9 and 18 leading to trisomy of 9p and a monosomy of 18p. This abnormality was confirmed with fluorescence in situ hybridization using chromosome painting and locus-specific probes. Three cases were diagnosed as polycythemia vera; one case presented with secondary acute myeloid leukemia following idiopathic osteomyelofibrosis. The prognostic impact of this unbalanced aberration and of gains of 9p in chronic myeloproliferative disorders remains to be clarified.

Molecular genetic analysis of haematological malignancies: I. Acute leukaemias and myeloproliferative disorders

Molecular genetic techniques are now routinely applied to haematological malignancies within a clinical laboratory setting. The detection of genetic rearrangements not only assists with diagnosis and treatment decisions, but also adds important prognostic information. In addition, genetic rearrangements associated with leukaemia can be used as molecular markers allowing the detection of low levels of residual disease. This review will concentrate on the application of molecular genetic techniques to the acute leukaemias and myeloprolferative disorders.

Impaired maturation of myeloid progenitors in mice lacking novel Polycomb group protein MBT-1

Polycomb group (PcG) proteins participate in DNA-binding complexes with gene-repressing activity, many of which have been highlighted for their involvement in hematopoiesis. We have identified a putative PcG protein, termed MBT-1, that is associated with Rnf2, an in vivo interactor of PcG proteins. MBT-1 structurally resembles the H-L(3)MBT protein, whose deletion is predicted to be responsible for myeloid hematopoietic malignancies. The human MBT-1 gene is located on chromosome 6q23, a region frequently deleted in leukemia cells, and shows a transient expression spike in response to maturation-inducing stimuli in myeloid leukemia cells. MBT-1(-/-) myeloid progenitor cells exhibit a maturational deficiency but maintain normal proliferative activities. This results in the accumulation of immature myeloid progenitors and hence, a marked decrease of mature myeloid blood cells, causing the MBT-1(-/-) mice to die of anemia during a late embryonic stage. Together, we conclude that MBT-1 specifically regulates the maturational advancement of myeloid progenitor cells during transitions between two developmental stages. We also show that MBT-1 appears to influence myelopoiesis by transiently enhancing p57(KIP2) expression levels.

Persistence of various chromosomal aberrations in recipient cells during complete remission after bone marrow transplantation followed by graft rejection

A 16-year-old boy in a second remission of acute lymphoblastic leukemia (ALL) had undergone transplantation of bone marrow from an unrelated donor. The conditioning regimen consisted of high-dose cytarabine, etoposide and 12 Gy of total-body irradiation. Although the donor marrow was rejected, hematopoiesis by the recipient himself recovered and he has remained in complete remission for more than 8 years after stem cell transplantation (SCT). Bone marrow karyotype analysis 1 month after SCT showed random chromosomal aberrations. Although complete remission was maintained, various chromosomal aberrations were detected in marrow cells, and in peripheral blood cells under phytohemagglutinin stimulation over 8 years. Moreover, a clone including del(20)(q11) appeared in marrow cells 7 months after SCT and thereafter was also detected 5 years later in the peripheral blood. This persistence of various chromosomal aberrations and a stable clone without evolution to myelodysplastic syndrome or leukemia support the multi step theory of leukemogenesis.

RARbeta2 is a candidate tumor suppressor gene in myelofibrosis with myeloid metaplasia

Myelofibrosis with myeloid metaplasia (MMM) is a clonal stem-cell disorder that leads to ineffective hematopoiesis, bone marrow fibrosis, and extramedullary hematopoiesis. The molecular mechanisms underlying the development of this myeloproliferative syndrome are currently unknown. In order to identify tumor suppressor genes that may be involved in the disease process, we performed an analysis for loss of heterozygosity (LOH) in CD34+ cells from 29 patients with MMM. We observed a frequency of allelic loss on chromosomal arm 3p in 24% of cases. Detailed mapping of 3p revealed a distinct region of deletion at 3p24. Among the genes known to map within this region is the retinoic acid receptor-beta (RARbeta2) gene. To determine whether RARbeta2 gene activity is diminished in this disease, we analysed its expression in CD34+ cells from 17 patients with MMM using quantitative PCR. Our results indicate that expression of RARbeta2 is significantly decreased in 100% of patient samples compared to that in CD34+ cells from 10 normal individuals. Since allelic loss at 3p24 occurs in <25% of patients, we investigated the contribution of epigenetic modifications to RARbeta2 inactivity. Using methylation-specific PCR, we found hypermethylation of RARbeta2 in 16 of 18 patients (89%), while the methylated form of the gene was absent in CD34+ cells from nine normal individuals. Our results suggest that RARbeta2 acts as a tumor suppressor gene in MMM and that epigenetic changes are the most significant determinants of RARbeta2 gene activity in these patients.

Is fluorescence in situ hybridization a useful method in diagnosis of polycythemia vera patients?

Polycythemia vera (PV) is a clonal stem cell disease with trilineage myeloid involvement, characterized by a growth factor-independent erythroid proliferation. At the time of diagnosis, the percentage of cytogenetic abnormalities using conventional cytogenetic techniques is less than 20% of all PV patients. In the present study, we compare the results between conventional cytogenetic methods and fluorescence in situ hybridization (FISH) probes in 31 untreated PV patients. The karyotypes of all 31 cases were obtained from 24-hour bone marrow cell cultures. The fixed material, proceeding from conventional cytogenetics cultures, was analyzed with FISH, using centromeric probes for chromosomes 8 and 9 and locus-specific probes for 13q14 and 20q12 regions. Five cases (17.8%) showed an abnormal karyotype with conventional cytogenetics. When FISH probes were used, three alterations not detected with conventional cytogenetics, were found: two cases with D20S108 deletions and one with a D13S319 deletion, increasing the percentage of abnormal karyotypes to 19.3%. We conclude that, probably, the application of FISH with the mentioned probes, is not very useful to detect cytogenetic aberrations in untreated PV patients.

Beyond chronic myelogenous leukemia

The myeloproliferative disorders (MPDs) are chronic malignant conditions originating from the clonal expansion of a multipotential hematopoietic stem cell. These diseases include polycythemia vera (PV), essential thrombocythenia, atypical chronic myeloid leukemia, idiopathic hypereosinophilic syndrome (HES), agnogenic myeloid metaplasia with myelofibrosis, and others. Receptor tyrosine kinases-the platelet-derived growth factor receptors (PDGFRs) and c-Kit-and their respective ligands have been implicated in the pathogenesis of MPDs. For example, a constitutively activated PDGFR fusion tyrosine kinase (FIP1L1-PDGFRA) was identified in some patients with HES, a disease characterized by sustained overproduction of eosinophils that has been classified by the World Health Organization as a chronic subtype of the MPDs. Imatinib is a selective inhibitor of PDGFRs, c-Kit, Abl and Arg protein-tyrosine kinases, as well as Bcr-Abl, the oncogenic tyrosine kinase that causes chronic myeloid leukemia. The efficacy of imatinib in treating HES, systemic mast cell disease, chronic myelomonocytic leukemia associated with PDGFRbeta fusion genes, and (to a lesser extent) PV and idiopathic myelofibrosis was reviewed from institutional experience and a review of the literature. In 3 studies that involved 11 patients with PV, 10 patients had reductions in phlebotomy with imatinib. Eight studies of 42 patients with HES indicated that 70% achieved complete hematologic remissions with imatinib. Four studies of 6 patients with MPD indicated responses with imatinib in 5 patients. Insight into the molecular pathogenesis of MPDs will improve the definitions of different disease categories and suggests that signal transduction inhibition is likely to be an increasingly important treatment option in the future.

Cytogenetics of chronic myeloproliferative disorders and related myelodysplastic syndromes

The only MPD associated with any specific chromosome anomaly is CML, which is linked with t(9;22)(q34;q11.2) or a variant of this anomaly. An association exists for del(13)(q12q14) and CIMF; t(5;12)(q33;p13) and CEL; and del(20q11), +8, and +9 and PV, but these anomalies can be seen in various hematologic malignancies. The most common chromosomal anomalies among MPD in order of frequency are t(9;22)(q34;q11.2), -Y, +8, +9, -7, del(20) (q11q13), del(13)(q12q14), del(5)(q13q33), and del(12)(p12). FISH techniques are useful for MPD to study inadequate bone marrow or blood specimens and to monitor disease status among patients with known chromosome anomalies, but they are not more sensitive than conventional chromosome studies.

Numbers of colony-forming progenitors in patients with systemic mastocytosis: potential diagnostic implications and comparison with myeloproliferative disorders

BACKGROUND

An increase in colony-forming progenitor cells (CFU) is typically seen in myeloproliferative disorders (MPD). Systemic mastocytosis (SM) is a haemopoietic neoplasm involving myeloid progenitors similar to MPD. In the present study, we measured the levels of peripheral blood (pb) and bone marrow (bm) CFU in patients with different categories of SM, and compared them with those obtained in MPD patients and healthy controls.

MATERIALS AND METHODS

Numbers of CFU (CFU-GM, BFU-E, CFU-GEMM) were measured in a colony assay in 25 patients with SM [indolent SM (ISM), n = 15; smouldering SM (SSM), n = 3; SM with an associated haematologic clonal non-mast cell lineage disease (SM-AHNMD), n = 5; aggressive SM (ASM), n = 1; mast cell leukaemia (MCL), n = 1] and 37 with MPD [chronic myeloid leukaemia (CML), n = 10; polycythemia vera (PV), n = 8; essential thrombocytosis (ET), n = 9; idiopathic myelofibrosis (IMF), n = 10].

RESULTS

In the patients with MPD, elevated numbers of pb CFU were detected in all groups when compared with healthy controls (P < 0.05). In most of the patients with ISM, circulating CFU levels (CFU-GM, BFU-E, and CFU-GEMM) were within the normal range. In SSM, pb CFU-GM levels were normal in two patients, and elevated in a third patient. In the "SM-AHNMD-group", CFU levels were found to reflect the nature of the AHNMD: in SM with concomitant acute myeloid leukaemia (SM-AML, n = 2), the levels of CFU were low or undetectable, whereas in SM with chronic myelomonocytic leukaemia (SM-CMML, n = 2), elevated numbers of pb CFU-GM were found.

CONCLUSION

The numbers of CFU are normal in patients with ISM, but elevated in some patients with SSM and SM-CMML. An elevated CFU level in SM should raise the suspicion of an associated MPD (CMML) or smouldering SM, a novel SM-subtype that shares several features with MPD and sometimes progresses to an overt SM-MPD.

The human L(3)MBT polycomb group protein is a transcriptional repressor and interacts physically and functionally with TEL (ETV6)

H-L(3)MBT, the human homolog of the Drosophila lethal(3)malignant brain tumor protein, is a member of the polycomb group (PcG) of proteins, which function as transcriptional regulators in large protein complexes. Homozygous mutations in the l(3)mbt gene cause brain tumors in Drosophila, identifying l(3)mbt as a tumor suppressor gene. The h-l(3)mbt gene maps to chromosome 20q12, within a common deleted region associated with myeloid hematopoietic malignancies. H-L(3)MBT contains three repeats of 100 residues called MBT repeats, whose function is unknown, and a C-terminal alpha-helical structure, the SPM (SCM, PH, MBT domain, which is structurally similar to the SAM (sterile alpha motif) protein-protein interaction domain, found in several ETS transcription factors, including TEL (translocation Ets leukemia). We report that H-L(3)MBT is a transcriptional repressor and that its activity is largely dependent on the presence of a region containing the three MBT repeats. H-L(3)MBT acts as a histone deacetylase-independent transcriptional repressor, based on its lack of sensitivity to trichostatin A. We found that H-L(3)MBT binds in vivo to TEL, and we have mapped the region of interaction to their respective SPM/SAM domains. We show that the ability of TEL to repress TEL-responsive promoters is enhanced by the presence of H-L(3)MBT, an effect dependent on the H-L(3)MBT and the TEL interacting domains. These experiments suggest that histone deacetylase-independent transcriptional repression by TEL depends on the recruitment of PcG proteins. We speculate that the interaction of TEL with H-L(3)MBT can direct a PcG complex to genes repressed by TEL, stabilizing their repressed state.

Concomitant primary polycythemia vera and follicle center cell non-Hodgkin lymphoma: a case report and review of the literature

The association of myeloproliferative and lymphoproliferative disorders is well known after cytotoxic drug or radiation exposure, while it is remarkably rare prior to therapy. We report on a patient simultaneously diagnosed as having polycythemia vera and II3A follicle center cell non-Hodgkin lymphoma (grade 1). At this timepoint, he is on 12-year follow-up, characterized by post-polycythemia myeloid metaplasia with myelofibrosis and persistent complete remission of lymphoma. The conventional marrow cytogenetic analysis performed during the course of the disease demonstrated an abnormal karyotype with deletion of the long arm of chromosome 20 and trisomy 8, while molecular analysis failed to detect BCR-ABL rearrangement in peripheral blood cells. To the best of our knowledge based on a computer-aided review of the literature (MED-LINE 1966-2002), this is the sixth case of concomitant primary polycythemia vera and lymphoma of non-Hodgkin type. Besides, there is a single literature report on polycythemia vera coexisting with the Hodgkin's lymphoma. In our case as well as in the recorded ones, two independent malignant clones of myeloid and lymphoid origin, respectively, seem to have arisen. Further reports, supported by chromosomal and molecular studies, could improve our knowledge on this extremely infrequent disease association.