Evidence for the involvement of B lymphoid cells in polycythemia vera and essential thrombocythemia

A Rare Coexistence of Multiple Myeloma and Polycythemia Vera

Multiple myeloma (MM) is classically associated with organ dysfunction leading to hypercalcemia, renal insufficiency, anemia and bone disease, known as the CRAB criteria. More than 70% of patients with MM present with anemia. Few rare case reports, however, have demonstrated the presentation of MM associated with polycythemia. We present an interesting case of a 65-year-old female who was initially diagnosed with monoclonal gammopathy of undetermined significance (MGUS) which progressed to smoldering myeloma and later developed into MM. The patient also had coexisting polycythemia vera (PCV). We discuss the typical patient presentations as well as the expanded diagnostic criteria for MM. The pathophysiology explaining the coexistence of polycythemia and MM will be explored as well.

Development of multiple myeloma after 15 years of treatment for polycythemia vera and successful treatment using bortezomib: A case report

Multiple myeloma (MM) and polycythemia vera (PV) rarely coexist; the clinical manifestations and treatment of this coexistence have not been described. An 81-year-old woman developed MM 15 years after undergoing PV treatment and was successfully treated using bortezomib. Herein, we share our experience of treating MM under such unusual conditions.

CALR-positive myeloproliferative disorder in a patient with Ph-positive chronic myeloid leukemia in durable treatment-free remission: a case report

Current diagnostic criteria for Philadelphia-negative myeloproliferative neoplasia (MPN) have been redefined by the discovery of Janus kinase 2 (JAK2), myeloproliferative leukemia (MPL) and calreticulin (CALR) genetic alterations. Only few cases of coexistence of CALR-mutated MPN and Philadelphia-positive chronic myeloid leukemia (CML) have been described so far. Here we report the case of a patient with CML diagnosed in 2001, treated with imatinib and pegylated interferon (IFN) frontline. She reached complete molecular remission (CMR) and discontinued imatinib, maintaining treatment free remission. Due to persistent thrombocytosis, we repeated bone marrow (BM) analysis and diagnosed CARL-mutated essential thrombocythemia (ET). A CALR-positive clone was found to be present since 2001, and was unaffected by imatinib treatment, possibly representing a molecular abnormality arising at stem cell level.

MPN patients harbor recurrent truncating mutations in transcription factor NF-E2

The molecular etiology of myeloproliferative neoplasms (MPNs) remains incompletely understood, despite recent advances incurred through the discovery of several different mutations in MPN patients. We have recently described overexpression of the transcription factor NF-E2 in MPN patients and shown that elevated NF-E2 levels in vivo cause an MPN phenotype and predispose to leukemic transformation in transgenic mice. We report the presence of acquired insertion and deletion mutations in the NF-E2 gene in MPN patients. These result in truncated NF-E2 proteins that enhance wild-type (WT) NF-E2 function and cause erythrocytosis and thrombocytosis in a murine model. NF-E2 mutant cells acquire a proliferative advantage, witnessed by clonal dominance over WT NF-E2 cells in MPN patients. Our data underscore the role of increased NF-E2 activity in the pathophysiology of MPNs.

No evidence for JAK2(V617F) mutation in monoclonal B cells in 2 patients with polycythaemia vera and concurrent monoclonal B cell disorder

Occurrence of Philadelphia chromosome-negative myeloproliferative neoplasms (Ph(-) MPN) and lymphoproliferative disorders, like B cell chronic lymphocytic leukaemia (B-CLL), in the same patient is rare. JAK2(V617F) mutation was recently introduced as a powerful diagnostic tool for Ph(-) MPN. JAK2(V617F) mutation is not present in B-CLL. In 4 previously reported patients with JAK2(V617F)-positive Ph(-) MPN and B-CLL there was no definitive proof of JAK2(V617F) mutation in B-CLL cells, although this was suggested in 1 patient. We present 2 patients with JAK2(V617F)-positive polycythaemia vera who subsequently developed a monoclonal B cell disorder. The granulocytes were separated from the mononuclear cells by centrifugation on density gradient. Using an ARIA-SORP sorter, the CD20+/CD5+ B cells were separated from the CD20+/CD5- B cells, T cells, NK cells and monocytes. On each of the fractions JAK2(V617F) mutation was analysed by allele-specific competitive blocker-PCR. In both patients JAK2(V617F) mutation was present in granulocytes confirming the clinical diagnosis of polycythaemia vera. We did not detect the JAK2(V617F) mutation in the CD20+/CD5+ B cells but detected it in CD20+/CD5- B cells, T and NK cells, indicating a lymphoid subdifferentiation of the JAK2(V617F) MPN clonality. JAK2(V617F) MPN and monoclonal B cell disorder can coexist but there is no evidence that the proliferative behaviour of these B cells is mediated through the JAK2(V617F) mutation.

Coexistence of plasma cell dyscrasia with prefibrotic stage of primary myelofibrosis: a case report

Introduction. Coexistence of myeloproliferative neoplasms with lymphoproliferative syndromes has been described in the past, whereas plasma cell dyscrasias seem to be the most common cases. Case Presentation. We present a case of a 59-year-old Caucasian female of Greek origin who presented with thrombocytosis. Clinical and laboratory investigation disclosed the presence of a smoldering myeloma with coexisting histological and molecular characteristics of primary myelofibrosis. The patient had the acquired point mutation V617F in the JAK2 gene but not the bcr-abl rearrangement and was treated for myelofibrosis with subsequent improvement of all haematological parameters without evidence of myelomatic evolution. Conclusion. We present the first case in the literature of a smoldering myeloma coexisting with primary myelofibrosis. The underlying pathogenetic mechanism could be either related to the presence of a pluripotent neoplastic stem cell capable to differentiate into both lymphoid and myeloid cells or be related to two separate nosologic entities.

Mutations with epigenetic effects in myeloproliferative neoplasms and recent progress in treatment: Proceedings from the 5th International Post-ASH Symposium

Immediately following the 2010 annual American Society of Hematology (ASH) meeting, the 5th International Post-ASH Symposium on Chronic Myelogenous Leukemia and BCR-ABL1-Negative Myeloproliferative Neoplasms (MPNs) took place on 7–8 December 2010 in Orlando, Florida, USA. During this meeting, the most recent advances in laboratory research and clinical practice, including those that were presented at the 2010 ASH meeting, were discussed among recognized authorities in the field. The current paper summarizes the proceedings of this meeting in BCR-ABL1-negative MPN. We provide a detailed overview of new mutations with putative epigenetic effects (TET oncogene family member 2 (TET2), additional sex comb-like 1 (ASXL1), isocitrate dehydrogenase (IDH) and enhancer of zeste homolog 2 (EZH2)) and an update on treatment with Janus kinase (JAK) inhibitors, pomalidomide, everolimus, interferon-α, midostaurin and cladribine. In addition, the new ‘Dynamic International Prognostic Scoring System (DIPSS)-plus' prognostic model for primary myelofibrosis (PMF) and the clinical relevance of distinguishing essential thrombocythemia from prefibrotic PMF are discussed.

Involvement of mast cells by the malignant process in patients with Philadelphia chromosome negative myeloproliferative neoplasms

The Philadelphia chromosome negative myeloproliferative neoplasms (MPNs) are clonal hematologic malignancies frequently characterized by a mutation in JAK2 (JAK2V617F). Peripheral blood (PB) CD34(+) cells from patients with polycythemia vera (PV) and primary myelofibrosis (PMF) generated in vitro significantly fewer mast cells (MCs) than normal PB CD34(+) cells. The numbers of MC progenitors assayed from MPN CD34(+) cells were, however, similar to that assayed from normal CD34(+) cells. A higher percentage of the cultured MPN MCs expressed FcvarepsilonRIalpha, CD63 and CD69 than normal MCs, suggesting that cultured MPN MCs are associated with an increased state of MC activation. Further analysis showed that a higher proportion of cultured PV and PMF MCs underwent apoptosis in vitro. By using JAK2V617F, MplW515L and chromosomal abnormalities as clonality markers, we showed that the malignant process involved MPN MCs. JAK2V617F-positive MC colonies were assayable from the PB CD34(+) cells of each of the 17 JAK2V617F positive MPN patients studied. Furthermore, erlotinib, a JAK2 inhibitor, was able to inhibit JAK2V617F-positive PV MC progenitor cells, indicating that malignant MC progenitor cells are a potential cellular target for such JAK2 inhibitor-directed therapy.

Zap-70 positive chronic lymphocytic leukemia co-existing with Jak 2 V671F positive essential thrombocythemia: a common defective stem cell?

Essential thrombocythemia (ET) co-existing with chronic lymphocytic leukemia (CLL) is extremely rare. We report two cases of ET with Jak 2 V617F in Zap-70+ CLL. ET is a myeloproliferative stem cell disease. Zap-70 expression in CLL correlates with non-mutated immunoglobulin genes. The occurrence of a less mature CLL in patients with a pluripotential stem cell disease raises the possibility that an initial "trigger hit" occurred in a pre-Jak 2 common early progenitor in these patients. Subsequent additional molecular events accumulated independently following myeloid and lymphoid differentiation, leading to the development of two diseases of likely identical origin but different lineages.

The JAK2V617F mutation in polycythemia vera and other myeloproliferative disorders: one mutation for three diseases?

The discovery of the JAK2V617F mutation has made the diagnosis of polycythemia vera (PV) much easier, but the pathogenesis of PV is still incompletely understood. In particular, it is not yet elucidated how a single mutation can be found in multiple myeloproliferative disorders (MPD) and myelodysplastic syndromes with ring sideroblasts and whether the sole JAK2V617F is sufficient to induce a MPD in humans. Several hypotheses are under investigation such as differences in the targeted hematopoietic stem cells (HSC), host modifier polymorphisms, intensity of JAK2V617F signaling, presence of other somatic mutations, or the presence of a pre-JAK2 event that may vary according to the MPD phenotype. Multiple studies have provided some evidence for and against each hypothesis, but it now seems possible to reconcile these hypotheses into a model that will need to be tested using newly developed tools. Recent investigations have also led to new treatment modalities that could benefit patients with PV.

The history of myeloproliferative disorders: before and after Dameshek

In 1951, William Dameshek described the concept of 'myeloproliferative disorders (MPDs)' by grouping together chronic myelogenous leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF) and erythroleukemia; he reasoned that a self-perpetuating trilineage myeloproliferation underlined their pathogenesis. Pre-Dameshek luminaries who laid the foundation for this unifying concept include Bennett, Virchow, Heuck, Vaquez, Osler, Di Guglielmo and Epstein. In 1960, Nowell and Hungerford discovered the Philadelphia (Ph) chromosome in CML. In 1967, Fialkow and colleagues used X-linked polymorphisms to establish CML as a clonal stem cell disease. Also in 1967, the PV Study Group was summoned by Louis Wasserman to study the natural history of PV and conduct large-scale clinical trials. In 1972, Janet Rowley deciphered the Ph chromosome as a reciprocal translocation between chromosomes 9 and 22, thus paving the way for its subsequent characterization as an oncogenic BCR-ABL mutation. In 1996, Brian Druker discovered imatinib-a small molecule ABL inhibitor with exceptional therapeutic activity in CML. In 2005, a gain-of-function JAK2 mutation (JAK2V617F) was described in BCR-ABL-negative MPDs, raising the prospect of a CML-like treatment strategy in PV, ET and PMF. The current review considers these and other landmark events in the history of MPDs.

T cells from patients with polycythemia vera elaborate growth factors which contribute to endogenous erythroid and megakaryocyte colony formation

In the present study, we report that media conditioned by polycythemia vera (PV) CD3+ cells promote BFU-E and CFU-Mk colony formation by both cord blood and PV peripheral blood CD34+ cells in the absence of exogenous cytokines and promoting megakaryocyte proplatelet formation. CD3+ cells constitutively produce elevated levels of IL-11, while stimulation with the addition of phytohemagglutinin (PHA) increased GM-CSF levels in most of the patients with PV. Anti-IL-11-neutralizing antibody partially inhibited the formation of BFU-E and CFU-Mk colonies promoted by PV CD3+ cell-conditioned media. Although IL-11 is not produced by normal T cells, real-time PCR and flow cytometric analysis showed that IL-11 was upregulated in the CD3+ cells of most PV patients as compared to normal CD3+ cells. In addition, a greater percentage of BFU-E colonies formed by PV CD34+ cells in the presence of PV CD3+ cell-conditioned media alone were JAK2V617F-positive as compared with that induced by EPO. We conclude that dysregulated production of soluble growth factor(s), including IL-11 and GM-CSF by PV T cells, contributes to the in vitro formation of erythroid colonies in the absence of exogenous cytokines by PV CD34+ cells and likely plays a role in sustaining hematopoiesis in PV.

The JAK2 V617F mutation involves B- and T-lymphocyte lineages in a subgroup of patients with Philadelphia-chromosome negative chronic myeloproliferative disorders

The JAK2 V617F mutation is a frequent genetic event in the three classical Philadelphia-chromosome negative chronic myeloproliferative disorders (Ph(neg.)-CMPD), polycythemia vera (PV), essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF). Its occurrence varies in frequency in regards to phenotype. The mutation is found in the majority of patients with PV and about half of the patients with ET and IMF. These diseases are clonal stem cell disorders arising in an early stem cell progenitor. The level in the stem cell hierarchy on which the initiating genetic events and the JAK2 V617F mutation occurs is not known. The mutation has so far been detected in all cells of the myeloid lineage, whereas the potential clonal involvement of the lymphoid lineage is controversial. In this study, we detected the JAK2 V617F mutation by real-time quantitative PCR (qPCR) in both B-lymphocytes and T-lymphocytes in a subgroup of patients with Ph(neg.)-CMPDs. These results demonstrate the origin of the JAK2 V617F positive disorders in an early stem cell with both lymphoid and myeloid differentiation potential.

JAK-2 mutations and their relevance to myeloproliferative disease

PURPOSE OF REVIEW

The identification of the JAK2V617F allele greatly improved our understanding of the molecular pathogenesis of myeloproliferative disorders. This review focuses on recent studies offering new genetic, biochemical, and functional insight into the role of JAK2V617F in the pathogenesis of these disorders.

RECENT FINDINGS

JAK2V617F mutations are present in almost all patients with polycythemia vera, and in approximately half of those with essential thrombocytosis and myelofibrosis. JAK2V617F has constitutive tyrosine kinase activity, and is able to transform hematopoietic cells and activate JAK-STAT signaling when co-expressed with homodimeric type I cytokine receptors. Murine bone marrow transplant experiments demonstrate that JAK2V617F is sufficient for the development of polycythemia vera in recipient mice. These results suggested that JAK-STAT pathway activation might contribute to the pathogenesis of JAK2-negative myeloproliferative disorders, and led to the discovery of an activating mutation in the thrombopoietin receptor in JAK2-negative myelofibrosis and essential thrombocytosis.

SUMMARY

The discovery of the JAK2V617F allele represents an important advance in our understanding of the molecular pathogenesis of myeloproliferative disorders, though many questions remain regarding the role of a single allele in three clinically distinct disorders, the mechanism of activation of JAK2V617F, and the pathogenesis of JAK2-negative myeloproliferative disorders.

Chronic neutrophilic leukemia and chronic myelomonocytic leukemia: WHO defined

The World Health Organization (WHO) classification of myeloid disorders has provided updated parameters for the consistent diagnosis of two previously less than optimally defined chronic myeloid disorders, CNL and CMML. The classification of these disorders, which had been controversial, is now better defined and provides more clinically and biologically relevant disease definitions to enable uniform diagnosis and a framework to evaluate natural history and therapeutic interventions. CNL is now recognized as a distinct entity among the chronic myeloproliferative disorders and CMML is included within the new category of 'myelodysplastic/myeloproliferative diseases' (MDS/MPD). Predominant neutrophilia defines CNL whereas CMML is defined by predominant and monocytosis. In each case these defining features must be distinguished from reactive causes for the same in the absence of clear evidence of myeloid clonality (CNL and CMML) or dysplasia (CMML). The exclusion of underlying bcr/abl-driven oncogenesis is an essential component in the diagnosis of these chronic leukemic processes. The optimal therapy for both CNL and CMML remains uncertain. Current management decisions are based on small studies or extrapolated from therapeutic strategies that are effective in similar chronic, clonal myeloid disorders. Given the potential for evolution to acute leukemia or progressive refractory leucocytosis or cytopenias, allogeneic stem cell transplantation might be appropriate for younger patients. Continued reporting and investigation of specific therapeutic strategies and responses must be encouraged.

Classification of chronic myeloid disorders: From Dameshek towards a semi-molecular system

Hematological malignancies are phenotypically organized into lymphoid and myeloid disorders, although such a distinction might not be precise from the standpoint of lineage clonality. In turn, myeloid malignancies are broadly categorized into either acute myeloid leukemia (AML) or chronic myeloid disorder (CMD), depending on the presence or absence, respectively, of AML-defining cytomorphologic and cytogenetic features. The CMD are traditionally classified by their morphologic appearances into discrete clinicopathologic entities based primarily on subjective technologies. It has now become evident that most CMD represent clonal stem cell processes where the primary oncogenic event has been characterized in certain instances; Bcr/Abl in chronic myeloid leukemia, FIP1L1-PDGFRA or c-kit(D816V) in systemic mastocytosis, rearrangements of PDGFRB in chronic eosinophilic leukemia, and rearrangements of FGFR1 in stem cell leukemia/lymphoma syndrome. In addition, Bcr/Abl-negative classic myeloproliferative disorders are characterized by recurrent JAK2(V617F) mutations, whereas other mutations affecting the RAS signaling pathway molecules have been associated with juvenile myelomonocytic leukemia. Such progress is paving the way for a transition from a histologic to a semi-molecular classification system that preserves conventional terminology, while incorporating new information on molecular pathogenesis.

Involvement of various hematopoietic-cell lineages by the JAK2V617F mutation in polycythemia vera

The JAK2(V617F) mutation has been shown to occur in the overwhelming majority of patients with polycythemia vera (PV). To study the role of the mutation in the excessive production of differentiated hematopoietic cells in PV, CD19+, CD3+, CD34+, CD33+, and glycophorin A+ cells and granulocytes were isolated from the peripheral blood (PB) of 8 patients with PV and 3 healthy donors mobilized with G-CSF, and the percentage of JAK2(V617F) mutant allele was determined by quantitative real-time polymerase chain reaction (PCR). The JAK2(V617F) mutation was present in cells belonging to each of the myeloid lineages and was also present in B and T lymphocytes in a subpopulation of patients with PV. The proportion of hematopoietic cells expressing the JAK2(V617F) mutation decreased after differentiation of CD34+ cells in vitro in the presence of optimal concentrations of SCF, IL-3, IL-6, and Epo. These data suggest that the JAK2(V617F) mutation may not provide a proliferative and/or survival advantage for the abnormal PV clone. Although the JAK2(V617F) mutation plays an important role in the biologic origins of PV, it is likely not the sole event leading to PV.

The JAK2V617F tyrosine kinase mutation in myeloproliferative disorders: status report and immediate implications for disease classification and diagnosis

Janus kinase 2 (JAK2) is a cytoplasmic protein-tyrosine kinase that catalyzes the transfer of the gamma-phosphate group of adenosine triphosphate to the hydroxyl groups of specific tyrosine residues in signal transduction molecules. JAK2 mediates signaling downstream of cytokine receptors after ligand-induced autophosphorylation of both receptor and enzyme. The main downstream effectors of JAK2 are a family of transcription factors known as signal transducers and activators of transcription (STAT) proteins. The myeloproliferative disorders (MPD), a subgroup of myeloid malignancies, are clonal stem cell diseases characterized by an expansion of morphologically mature granulocyte, erythroid, megakaryocyte, or monocyte lineage cells. Among the traditionally classified MPD, the disease-causing mutation has been delineated, thus far, for only chronic myeloid leukemia (ie, bcr/abl). In the past 3 months, 7 different studies have Independently described a close association between an activating JAK2 mutation (JAK2V617F) and the classic bcr/abi-negative MPD (ie, polycythemia vera, essential thrombocythemia, myelofibrosis with myeloid metaplasia) as well as the less frequent occurrence of the same mutation in both atypical MPD and the myelodysplastic syndrome. The particular finding is consistent with previous observations that have implicated the JAK/STAT signal transduction pathway in the pathogenesis of bcr/abl-negative MPD, Including the phenotype of growth factor independence and/or hypersensitivity. The current article summarizes this new information and discusses its implications for both classification and diagnosis of MPD.

Molecular markers for the diagnosis of Philadelphia chromosome negative myeloproliferative disorders

Polycythemia vera, essential thrombocythemia, idiopathic myelofibrosis and chronic myelogenous leukemia have been collectively termed the myeloproliferative disorders due to similarities in their clinical presentation. With the exception of chronic myelogenous leukemia, which is characterized by the presence of the Philadelphia chromosome, the myeloproliferative disorders display no consistent cytogenetic abnormalities. Hence, the diagnosis of Polycythemia vera, essential thrombocythemia and idiopathic myelofibrosis to date relies on clinical criteria. However, several molecular aberrations have been described, which can be used as molecular markers for the diagnosis of these clinical entities. This review outlines the diagnostic assays developed and highlights the advantages and disadvantages of the following markers: (1). Endogenous Erythroid Colonies, (2). Clonality, (3). Reduced c-Mpl protein expression and (4). PRV-1 mRNA over expression.

The chronic myeloproliferative disorders: Clonality and clinical heterogeneity

The chronic myeloproliferative disorders (MPD), polycythemia vera (PV), chronic idiopathic myelofibrosis (IMF), essential thrombocytosis (ET), and chronic myelogenous leukemia (CML), are thought to be clonal disorders arising in a multipotent hematopoietic progenitor cell. However, establishing the diagnosis of an MPD other than CML is problematic due to a lack of clinically applicable clonal markers. Furthermore, in some patients, in whom a classical MPD phenotype is present, the hematopoietic stem cells appear to be polyclonal, suggesting that the chronic MPD other than CML may actually be a genetically heterogeneous group of disorders. Furthermore, since the aberrant clone is believed to arise from a multipotent hematopoietic stem cell, the non-CML chronic MPD-ET, PV, and IMF-could be related. Additional unresolved issues regarding the MPD include: identification of the multipotent hematopoietic progenitor cell involved, the molecular basis for the clinical heterogeneity amongst the individual MPD, the clinical significance of clonality in non-CML MPD, and reconciliation of therapy with the clonal and clinical heterogeneity of these disorders. Determination of clonality has largely been carried out using X chromosome-linked polymorphisms, but such studies are limited to women and with increasing patient age are compromised by skewing of allelic expression in both neutrophils and T lymphocytes, making the results difficult to interpret. X chromosome-linked polymorphism studies have indicated that in PV the target stem cell is one that gives rise to both lymphoid and myeloid progenitors. Recently, two epigenetic markers have been identified in the MPD: impaired expression of the thrombopoietin receptor, Mpl, in platelets and megakaryocytes, and overexpression in neutrophils of the mRNA of a gene designated polycythemia rubra vera-1 (PRV-1). The role of these epigenetic abnormalities in the diagnosis of the MPD remains to be established. Currently, given the unresolved issues with respect to the clinical and clonal heterogeneity of the MPD, treatment needs to be tailored individually in patients with an MPD.

Propensity for hemorrhage and thrombosis in chronic myeloproliferative disorders

Polycythemia vera (PV) and essential thrombocythemia (ET) are two myeloproliferative disorders (MPDs) with frequent thrombotic and hemorrhagic complications. Thrombosis is often the cause of mortality in PV and ET; hemorrhage occurs more commonly in idiopathic myelofibrosis patients, but is rarely fatal. Thromboses may occur in arteries or veins. Splanchnic, portal, hepatic, and splenic vein thromboses are not uncommon and thrombosis is also thought to cause placental vascular insufficiency and fetal wastage during pregnancies in MPD patients. These complications may result because of altered interactions between platelets, white blood cells, or endothelial cells, due to either altered receptor expression, receptor-ligand interactions, or signaling events. Age, leukocytosis, increased hematocrit, and a history of thrombotic events are risk factors for thrombosis. In determining a link between clonality and thrombosis using X-chromosome inactivation patterns in patients with ET, those who were polyclonal were less likely to experience thromboses. The search for hypercoagulability in these patients led to identification of changes in the expression patterns of coagulation proteins from the coagulation cascade. Mutations in factor V Leiden were examined and the incidence of mutations did not vary between normal and MPD patients. However, mutations in factor V Leiden were found to be risk factors for venous thrombotic events. Similarly, presence of a prothrombin gene mutation showed a higher risk for venous thromboembolic events. Proteolyzed thrombospondin appeared to contribute to hypercoagulability, and acquired von Willebrand factor disorder gave rise to hemorrhagic complications. These findings provide several potential reasons for thrombotic and hemorrhagic complications in MPD patients. Therefore, the best therapy for these patients is reduction of their platelet counts to less than 450,000/microL and close regulation of their hematocrits. The role of leukocytosis in bleeding or hemorrhage in this population remains to be elucidated.

Molecular markers in myeloproliferative disorders: from classification to prognosis?

The recent description of molecular markers in patients with myeloproliferative disorders (MPDs) has raised several questions: does the presence of multiple markers coincide in individual patients or can a patient acquire some markers selectively? Do the markers distinguish molecular categories of MPDs? Do these categories coincide with the clinically defined subgroups of MPDs: PV, ET and IMF? If not, which system of categorization is more useful to the patient and his physician, the molecular one or the clinical one, and why? The present review will summarize the current knowledge of molecular markers in MPDs and discuss today's answers to the above questions. Since our knowledge of the molecular basis of MPDs is rapidly expanding, it is my hope that this review will soon be outdated.

Both B and T lymphocytes may be clonally involved in myelofibrosis with myeloid metaplasia

A combination of magnetic cell sorting (MACS) and fluorescent in situ hybridization (FISH) techniques was used to detect clonal cytogenetic markers in different myeloid and lymphoid cell types of the peripheral blood from 4 patients with myelofibrosis with myeloid metaplasia (MMM) that was associated with either a 13q- or a 20q- karyotypic abnormality. Interphase cytogenetics studies demonstrated abnormal clonal FISH signal patterns in neutrophil, myeloid, erythroid, megakaryocyte, and B- and T-cell preparations in 3 of the 4 patients. In one patient, FISH results were within normal limits in T cells and slightly abnormal in B cells. In general, the percentage of abnormal nuclei was variable in both lymphocyte populations but always higher in B lymphocytes compared with T lymphocytes. The current study provides direct evidence for the clonal involvement of both B and T lymphocytes in MMM. A larger study is needed to clarify the relevance of the observed interpatient heterogeneity in clonal constitution.

Polycythemia vera: a comprehensive review and clinical recommendations

More than a century has elapsed since the appearance of the modern descriptions of polycythemia vera (PV). During this time, much has been learned regarding disease pathogenesis and PV-associated molecular aberrations. New information has allowed amendments to traditional diagnostic criteria. Phlebotomy remains the cornerstone treatment of PV, whereas myelosuppressive agents may augment the benefit of using phlebotomy for thrombosis prevention in high-risk patients. Excessive aspirin use is contraindicated in PV, although the use of lower-dose aspirin has been shown to be safe and effective in alleviating microvascular symptoms including erythromelalgia and headaches. Recent studies have shown the utility of selective serotonin receptor antagonists for treating PV-associated pruritus. Nevertheless, many questions remain unanswered. What is the specific genetic mutation or altered molecular pathway that is causally related to the disease? In the absence of a specific molecular marker, how is a working diagnosis of PV made? What evidence supports current practice in the management of PV? This article summarizes both old and new information on PV; proposes a modern diagnostic algorithm to formulate a working diagnosis; and provides recommendations for patient management, relying whenever possible on an evidence-based approach.

Exploring polycythaemia vera with fluorescence in situ hybridization: additional cryptic 9p is the most frequent abnormality detected

Between 1986 and 2001, 220 patients with polycythaemia vera (PV) were studied using conventional cytogenetics. Of 204 evaluable patients, 52 (25.4%) had clonal abnormalities. The recurrent chromosomal rearrangements were those of chromosome 9 (21.1%), del(20q) (19.2%), trisomy 8 (19.2%), rearrangements of 13q (13.4%), abnormalities of 1q (11.5%), and of chromosomes 5 and 7 (9.6%). Subsequent analysis of 32 patients, performed at follow-up of up to 14.8 years, revealed new clonal abnormalities in five patients and the disappearance of an abnormal clone in four. Eleven patients remained normal up to 11.5 years and seven patients maintained an abnormality for over 10 years. Fifty-three patients were studied retrospectively using interphase fluorescence in situ hybridization (I-FISH), utilizing probes for centromere enumeration of chromosomes 8 and 9, and for 13q14 and 20q12 loci. Conventional cytogenetics demonstrated clonal chromosome abnormalities in 23% of these 53 patients. The addition of I-FISH increased the detection of abnormalities to 29% and permitted clarification of chromosome 9 rearrangements in an additional 5.6% of patients. FISH uncovered rearrangements of chromosome 9 in 53% of patients with an abnormal FISH pattern, which represented the most frequent genomic alteration in this series.

Leukemogenic risk of hydroxyurea therapy as a single agent in polycythemia vera and essential thrombocythemia: N- and K-ras mutations and microsatellite instability in chromosomes 5 and 7 in 69 patients

Polycythemia vera (PV) and essential thrombocythemia (ET) are chronic myeloproliferative diseases that carry intrinsically the potential for leukemic transformation. The aims of this study were (1) to detect involvement of N- and K-ras mutations in codons 12 and 13 in the pathogenesis of the chronic and blastic phases of PV and ET, (2) to study the occurrence of microsatellite instability (MSI) in chromosomes 5 and 7 during the chronic phase and blastic transformation of the disease, and (3) to examine the incidence of leukemia in patients treated with hydroxyurea (HU). Samples of PV and ET patients were analyzed with a polymerase chain reaction. No N- or K-ras mutations were detected. A positive score for MSI in chromosome 7 was found in 1 patient with PV during leukemic transformation. Three of 69 patients developed acute myelogenous leukemia, 2 with PV and 1 with ET. As of this report, the overall incidence of leukemic transformation is 5.7% (2/35 patients) in PV and 3.3% (1/30 patients) in ET patients treated with HU. These results indicate that (1) MSI is a genetic marker that can be detected, even in a small group of patients, at the blastic phase of the disease and (2) no increased leukemogenicity was noted in this group of patients treated with HU.

Current opinion in essential thrombocythemia: pathogenesis, diagnosis, and management

A working diagnosis of essential thrombocythemia (ET) is made in the presence of nonreactive thrombocytosis and after the exclusion of another chronic myeloid disorder that may mimic ET in its presentation. Clinically, ET is characterized by vasomotor symptoms, thrombohemorrhagic complications, recurrent fetal loss, and transformation of the disease into either myelofibrosis with myeloid metaplasia or acute myeloid leukemia. Median survival in the majority of patients is close to that of an age-adjusted normal population, and current therapy has not been shown to either retard or hasten leukemic transformation, which is reported to occur in 1% to 20% of patients. The use of hydroxyurea in high-risk patients with ET has reduced the incidence of thrombosis, and recent studies have suggested the value of keeping the platelet count below 400 x 10(9)/L in such cases. The incidence of thrombosis in low-risk patients may not be high enough to warrant the use of cytoreductive therapy. Although effective in controlling vasomotor symptoms, aspirin therapy has not been shown to influence the risk of either recurrent thrombosis or first-trimester miscarriage in ET. Recent laboratory studies have suggested that hematopoiesis in ET may not always be clonal. Similarly, there is substantial heterogeneity in both megakaryocyte/platelet surface expression of the thrombopoietin receptor (c-Mpl) and bone marrow microvessel density. Clinicopathologic correlates to these biologic parameters are currently being defined.

Clonal hemopoiesis and risk of thrombosis in young female patients with essential thrombocythemia

OBJECTIVE

Several studies demonstrated a high prevalence of nonrandom X-chromosome inactivation pattern (X-CIP) in essential thrombocythemia (ET). This study explored the incidence of clonal hemopoiesis in myeloid precursors and endogenous erythroid colonies (EECs) in ET patients and its correlation with thrombotic manifestations.

MATERIALS AND METHODS

Clonal analysis of hemopoiesis using X-CIP was performed in 40 female patients with ET. Median age was 40.5 years (range 20-64), and median platelet count at testing time was 700 x 10(9)/L (range 220-1300 x 10(9)/L). Patients older than 65 years were excluded to reduce age-related skewing. Clonality was assessed on neutrophils, platelets, EECs, and bone marrow CD34(+) cells.

RESULTS

Eight (20%) of 40 patients developed thrombosis mainly at diagnosis. Clonal hemopoiesis was found in 17 (42.5%) patients, 15 (37.5%) had polyclonal hemopoiesis, and 8 (20%) were considered uninterpretable due to constitutive skewing. Clonality was confirmed on purified CD34(+) subpopulations from bone marrow, documenting that clonality does not appear lineage-restricted. There were no statistical differences in age at diagnosis, median platelet count at testing time, and length of follow-up. Thrombotic episodes were significantly more frequent in the monoclonal group (p = 0.04, Fisher exact test).

CONCLUSIONS

Young female patients with ET exhibiting a clonal pattern of hemopoiesis by X-CIP analysis are at higher risk for thrombosis. X-CIP analysis may contribute to defining the individual risk leading to appropriate treatment. X-CIP will allow a correct diagnosis in patients with latent myeloproliferative disorders and thrombosis in unusual sites. Clonal hemopoiesis is easily recognized by X-CIP, but its applicability is limited to the female sex and is hampered by the presence of age-related or constitutive skewing.

Recent progress in the pathogenesis and management of essential thrombocythemia

In the last decade, the diagnosis of essential thrombocythemia (ET) has been refined by appreciation of the occurrence of karyotypically occult but molecularly evident chronic myelogenous leukemia and morphologically subtle myelodysplastic syndrome (MDS) and cellular-phase agnogenic myeloid metaplasia (AMM). Although ET continues to be defined by the presence of nonreactive thrombocythemia that is not accounted for by another chronic myeloid disorder, recent studies of clonality and other laboratory parameters have suggested clinically relevant biologic heterogeneity among affected patients. Furthermore, randomized, prospective, and controlled retrospective data have provided additional clinical information that has resulted in the development of risk categories and risk-adjusted treatment recommendations.

The Pathogenesis of Chronic Myeloproliferative Diseases

Chronic myeloproliferative disorders are operationally classified to include essential thrombocythemia, polycythemia vera, and agnogenic myeloid metaplasia. In most cases, clonal hematopoiesis, involving all 3 myeloid lineages, can be demonstrated. However, the underlying molecular lesions that are responsible for disease initiation and progression remain elusive. There are ongoing efforts to clarify the pathogenetic role of cytokines, bone marrow stromal cells and molecules, and intracellular aberrations in either signal transduction or apoptosis. This review discusses some of the current and past observations regarding the pathogenesis of chronic myeloproliferative disorders.

Towards a molecular understanding of polycythemia rubra vera

Polycythemia rubra vera (PV) is one of four diseases collectively called the myeloproliferative disorders (MPDs). Each disorder leads to an increased production of one or several hematopoietic cell lineages. MPDs arise from acquired mutations in a pluripotent hematopoietic stem cell. However, the molecular mechanisms leading to the development of these diseases are poorly understood. This review will summarize and evaluate recent advances in our understanding of one particular MPD, PV.

Acute lymphoid leukemia following polycythemia vera

The tendency to evolve into acute leukemia is a well-known characteristic of polycythemia vera (PV), which is shared with the remaining chronic myeloproliferative disorders and increases after the administration of cytotoxic agents. Acute transformation is usually of myeloid phenotype, whereas acute lymphoid leukemia (ALL) following PV is seldom observed. A 63-year-old woman is described who developed ALL at 6 years from the initial diagnosis of PV, for which she had received radioactive phosphorus and hydroxyurea. The ALL was of B-cell type, corresponding to the L-3 subtype of the FAB classification. Despite the administration of combination chemotherapy the patient died shortly after the diagnosis of acute leukemia. The present case adds to seven previously described patients with the above association, all of whom had received cytotoxic therapy for PV. Median interval from PV to ALL diagnosis was 10 years, and there was a predominance of the B-cell phenotype. The prognosis was poor since all but one of the patients had a short survival after ALL diagnosis. The possible etiological and pathogenetic link between PV and the subsequent ALL is discussed.

Clonality markers in polycythaemia and primary thrombocythaemia

Our current understanding of the pathogenesis of the myeloproliferative disorders is based on the assumption that they represent a clonal disorder resulting from transformation of a haematopoietic stem cell. Clonality assays exploit the fact that female cells have only one active X-chromosome. Methods for determining X chromosome inactivation have been devised at the protein (G6PD isoenzymes); DNA (HUMARA; phosphoglycerate kinase (PGK); hypoxanthine-phosphoribosyl transferase (HPRT) and RNA (G6PD; P55; IDS) levels. In this type of RNA assay the product of the active X chromosome is quantified by studying polymorphisms present in mRNA. The presence of skewed lyonization in normal females is a potential limitation to the method, although the use of T cells as a control makes it possible to distinguish clonal haematopoiesis from skewed lyonization. However, the phenomenon of acquired skewing in normal elderly women means that X-inactivation patterns in elderly patients must be interpreted with caution. Clonality studies have been conducted in polycythaemia vera (PV) and essential thrombocythaemia (ET) patients. They usually demonstrate a clonal X-inactivation pattern in granulocytes and/or platelets but a polyclonal pattern in T cells. However, in both ET and PV a significant minority of patients exhibit polyclonal haematopoiesis with polyclonal patterns in granulocytes/platelets. Female patients with polyclonal haematopoiesis differ from those with clonal haematopoiesis in terms of age and platelet count and possibly in their requirements for treatment. This new technology for the investigation of the MPD seems promising for understanding certain clinical aspects of these diseases and may be introduced for evaluation of new modalities of treatment.

Impaired platelet binding of fibrinogen due to a lower number of GPIIB/IIIA receptors in polycythemia vera

We have previously described a stimulus-specific defect in platelet aggregation in polycythaemia vera (PV) after stimulation with surface receptor dependent agonists such as platelet activating factor (PAF). In contrast, responses to phorbol myristate acetate (PMA) were normal. We now report that after PAF stimulation, using flow cytometry, the amount of fibrinogen bound to its receptor was significantly lower in PV platelets with a median MFI of 6.0 (range 4.1-17.3) compared to controls, 12.8 (range 8-21.3; n=11; p<0.01). We found no evidence of preactivation of PV platelets. Quantitative analysis of GPIIIa gave a significantly lower number of GPIIIa on resting PV platelets, 14300 subunits of GPIIIa (range 8500-15500) vs. 19800 for controls (range 13400-26800; n=12; p<0.01). Both patients and controls increased their number of receptors on the cell surface after stimulation with PAF and PMA, but the significant difference in the number of receptors per cell remained. Indirect evaluation of PAF receptor function showed that activation of CD 62 did not differ in PV and controls after PAF stimulation. Additionally, although the basal level of serotonin in platelet-rich plasma was significantly lower in PV, there was a threefold increase of the basal level after stimulation with PAF for both PV and control platelets, also indicating a normal interaction of PAF with its receptor. Although our results indicate both an impaired PAF induced aggregation in PV and a lower number of GPIIb/IIIa complexes on single platelets, whether these phenomena are related remains uncertain.

Clonality analysis of hematopoiesis and thrombopoietin levels in patients with essential thrombocythemia

Essential thrombocythemia (ET) is a myeloproliferative disorder, characterized by sustained thrombocytosis. Diagnosis requires the elimination of all known causes of thrombocytosis. ET is believed to be a clonal disorder, and we investigated the frequency of a clonal hematopoiesis in this disease with the aim of using this as a positive diagnostic criterion. However, a non-random inactivation pattern can be encountered in normal females which mimics clonal hematopoiesis. In addition, the percentage of normal females with skewed lyonization seems higher using techniques based on the difference in DNA methylation, compared to G6PD enzyme polymorphism. Recently, new techniques based on transcript analysis have been developed. We report here the results of clonality studies of hematopoiesis in 53 ET patients using two different techniques based on DNA and RNA polymorphisms, and T-lymphocytes as a control tissue of lyonization. The majority of ET patients showed monoclonal hematopoiesis in the presence of polyclonality of T-lymphocytes. Because all ET patients did not show the same clonal pattern of hematopoiesis, we searched for inappropriate secretion of thrombopoietin (TPO) in patients with polyclonal disease. This assay was performed in 48 patients, of whom 9 showed polyclonal hematopoiesis and 27 monoclonal hematopoiesis. We found no difference in TPO levels between ET patients and normal controls, nor between patients with polyclonal hematopoiesis and those with monoclonal hematopoiesis. Our results confirm the high frequency of monoclonal hematopoiesis in ET, the usefulness of RNA markers, and the possibility of using T-lymphocytes as a control tissue for X-chromosome inactivation patterns. On the other hand, TPO levels are not decreased even in ET patients with high platelet counts, suggesting an increased production or decreased clearance of TPO in this disease.

Pathogenesis of polycythaemia vera

Polycythaemia vera (PV) is thought to result from clonal expansion of a transformed multipotent stem cell. Progenitors from patients with PV display abnormal responses to several growth factors, suggesting the presence of a defect in a signalling pathway common to different growth factors. A number of approaches are now focused on defining the molecular lesion or lesions. Identification of causal genes will be of considerable interest both to clinicians, who currently lack a specific and sensitive diagnostic test, and to scientists interested in fundamental issues of stem cell behaviour.

No evidence for an altered mRNA expression or protein level of haematopoietic cell phosphatase in CD34+ bone marrow progenitor cells or mature peripheral blood cells in polycythaemia vera

Polycythaemia vera (PV) is a myeloproliferative disorder characterized by haematopoietic progenitor cells being hypersensitive to cytokines such as erythropoietin, interleukin-3, stem cell factor and insulin-like growth factor 1, which results in an increased production of mature blood cells. The pathogenetic cellular mechanism(s) behind this hypersensitivity to cytokines is unknown, but the number of cytokine receptors and the interaction between ligand and receptor are normal in PV. Interest has therefore focused on post-receptor mechanism(s). Haematopoietic cell phosphatase (HCP) is an intracellular tyrosine phosphatase that has been demonstrated to regulate proliferative signals negatively induced by the cytokines mentioned above. Moreover, motheaten mice that genetically lack HCP have an increased amount of erythroid progenitors that are hypersensitive to Epo, and patients with familial polycythaemia have been shown to exhibit a mutation of the Epo receptor gene that includes the docking site for HCP. We therefore studied mRNA expression of HCP in pure populations of CD34+ cells, granulocytes, platelets and lymphocytes from patients with PV, chronic myeloid leukaemia (CML) or essential thrombocythemia (ET), as well as healthy controls. Using a polymerase chain reaction analysis employing specific primers for HCP, we failed to detect any abnormalities of HCP expression in PV in any of the cell populations that were examined. Moreover, HCP mRNA expression was similar in ET and CML compared to controls. Finally, Western blot analysis revealed a normal HCP protein content in PV granulocytes and platelets. We therefore conclude that neither an impaired expression of the HCP gene nor a defect in HCP protein synthesis is present in PV, and does not seem to play a role in the aetiology of this disorder.

Megakaryocytes and platelets in myeloproliferative disorders

Increased megakaryocyte (MK) proliferation in bone marrow is a feature common to the three Ph-negative myeloproliferative disorders (MPDs), i.e. essential thrombocythaemia (ET), polycythaemia vera (PV), and myelofibrosis with splenic myeloid metaplasia (MMM), and to chronic myelocytic leukaemia (CML). Enlarged MKs with multilobulated nuclei and cell clustering in close proximity are the hallmark of all the Ph negative MPDs. Clonality of haematopoietic cells, based on X chromosome inactivation, can now be studied in a majority of female patients in all nucleated cell fractions as well as in platelets. Cytofluorometric studies have demonstrated a shift towards higher ploidy classes in PV and ET MKs which may be useful in discriminating between both primary and reactive thrombocytosis and CML patients which show a significant shift to lower MK ploidy values. The role of MK proliferation on the evolution of myelofibrosis common to MPDs has been firmly established. Implication of platelet-derived growth factor (PDGF) in myelofibrosis has already been demonstrated. More recently transforming growth factor beta (TGF beta) synthesized and secreted by MK has been implicated in fibroblasts stimulation. A significant increase in circulating colony-forming units of MKs (CFU-MK) has been repeatedly observed in MPDs as well as a spontaneous MK colony formation in a majority of ET patients. Hypersensitivity to thrombopoietin (TPO) in relation to a functional defect of the TPO-MPL pathway may play a major role in spontaneous MK growth. There is no currently available test of platelet functions able to predict the risk of occurrence of thrombotic or haemorrhagic complications in MPD patients. However, the role of platelet activation in the pathogenesis of ischaemic erythromelalgia has been established and a correlation between presenting haemorrhagic manifestations and platelet counts in excess of 1000 x 10(9)/l has been found.

Clonality Analysis of Hematopoiesis in Essential Thrombocythemia: Advantages of Studying T Lymphocytes and Platelets

Essential thrombocythemia (ET) is a myeloproliferative disorder characterized by a sustained elevation of the platelet count in the absence of other causes of thrombocytosis. ET is difficult to diagnose, and the demonstration of clonal hematopoiesis may be of value. However, clonality analysis of hematopoietic cells based on the study of the X-chromosome inactivation pattern is complicated by the observation that some normal females present skewed lyonization. Moreover, DNA methylation of X-linked genes in hematopoietic cells may differ from that in other tissues. Appropriate controls for skewed lyonization are therefore critical for the study of clonality. We developed two techniques based on X-chromosome inactivation and polymerase chain reaction (PCR) analysis of polymorphisms, to study clonality in ET patients. Reverse transcriptase-PCR analysis of IDS, P55, and G6PD mRNAs was used to examine the different hematopoietic cell lineages including platelets in patients heterozygous for these polymorphisms and analysis of the HUMARA gene methylation pattern permitted us to study clonality in all nucleated cell fractions of the other patients. Using both types of assay and T lymphocytes as a control tissue for lyonization, clonal hematopoiesis was demonstrated in 28 patients. In 14 patients, the granulocytes were polyclonal; among these patients, platelets were monoclonal in 3 cases, polyclonal in 7 cases, and in the remaining 4 cases this fraction could not be studied because the patients were homozygotes for all RNA markers. No conclusion about clonality could be drawn in 6 cases. Polyclonal hematopoiesis was found in all the cases of reactive thrombocytosis. These findings confirm the high frequency of monoclonal hematopoiesis in ET, the utility of studying platelets, and the possibility of using T lymphocytes as a control tissue for X-chromosome inactivation patterns.

Clonality Analysis of Hematopoiesis in Essential Thrombocythemia: Advantages of Studying T Lymphocytes and Platelets

Essential thrombocythemia (ET) is a myeloproliferative disorder characterized by a sustained elevation of the platelet count in the absence of other causes of thrombocytosis. ET is difficult to diagnose, and the demonstration of clonal hematopoiesis may be of value. However, clonality analysis of hematopoietic cells based on the study of the X-chromosome inactivation pattern is complicated by the observation that some normal females present skewed lyonization. Moreover, DNA methylation of X-linked genes in hematopoietic cells may differ from that in other tissues. Appropriate controls for skewed lyonization are therefore critical for the study of clonality. We developed two techniques based on X-chromosome inactivation and polymerase chain reaction (PCR) analysis of polymorphisms, to study clonality in ET patients. Reverse transcriptase-PCR analysis of IDS, P55, and G6PD mRNAs was used to examine the different hematopoietic cell lineages including platelets in patients heterozygous for these polymorphisms and analysis of the HUMARA gene methylation pattern permitted us to study clonality in all nucleated cell fractions of the other patients. Using both types of assay and T lymphocytes as a control tissue for lyonization, clonal hematopoiesis was demonstrated in 28 patients. In 14 patients, the granulocytes were polyclonal; among these patients, platelets were monoclonal in 3 cases, polyclonal in 7 cases, and in the remaining 4 cases this fraction could not be studied because the patients were homozygotes for all RNA markers. No conclusion about clonality could be drawn in 6 cases. Polyclonal hematopoiesis was found in all the cases of reactive thrombocytosis. These findings confirm the high frequency of monoclonal hematopoiesis in ET, the utility of studying platelets, and the possibility of using T lymphocytes as a control tissue for X-chromosome inactivation patterns.

Clonality assays and megakaryocyte culture techniques in essential thrombocythemia

The development of techniques permitting in vitro growth of human megakaryocytes progenitors and more recently identification of the proto oncogene c-mpl (Mpl-R) and its ligand (Mpl-L) have created new opportunities for studying pathophysiology of E.T. Plasma or serum of E.T. patients was unable to overestimulate MK colony formation by normal bone marrow cells. Significant increases in circulating CFU MK in E.T. patients have been repeatedly observed while in E.T. marrow, due to inappropriate sampling, colony number was not significantly different from normal. Spontaneous colony formation is observed in approximately 100% bone marrow and 85% blood from E.T. patients. Spontaneous colony formation persisted in plasma clot assay without added plasma or serum and in serum free agar cultures but only at a slightly lower rate than in plasma clot. Spontaneous colony formation in culture condition without plasma and serum were never observed with normal bone marrow and blood. Spontaneous MK growth was observed in a higher proportion of E.T. patients than erythroid colony formation but both phenomenon can occur in about 50% of the patients. CFU MK colony formation disappeared in serum free cultures using highly purified CD 34 cells. MK development is not completely independent of regular control. An hypersensitivity of E.T. MK progenitors to growth factors known to stimulate normal hematopoiesis (IL3.IL6, GM CSF, has been shown as well as a decreased sensitivity to negative regulators (TGF beta), has been suggested. The number of spontaneous MK colonies was not significantly decreased by added anti IL3, IL6 or anti GM CSF, antibodies in culture medium. Pre incubation of blood non adherent mononuclear cells of E.T. patients with antisense oligonucleotides to c-mpl significantly decreased the cloning efficiency of spontaneous megakaryocyte growth as compared to the introduction of scrambled oligomers. Finally m RNA expression of the Mpl-L (TPO) was not formed in MK spontaneously grown in serum free liquid cultures after 12 days. These results suggest that human c-mpl proto oncogene may be implicated in the pathway of spontaneous megakaryocytopoiesis in MPD but an absence of autocrine-stimulation by TPO of spontaneous growth in MPD. Analysis of peripheral blood cell clonality was performed in 55 E.T. patients using either the DNA methylation pattern of the androgen receptor (AR) gene or mRNA transcripts of G6PD or IDS genes. 51 out of 55 patients were informative. Non random X inactivation was found on unfractioned blood in 73% as compared with 23% in normal females (skewed Lyonisation). In 12 patients monoclonality of hematopoiesis was definitely confirmed by recording polyclonality of the mononuclear fraction or of T lymphocytes. In 4 patients monoclonal hematopoiesis was limited to platelets, 7 patients remained polyclonal in whole blood and all cellular fractions studied. MK colony formation (provided that the serum free agar culture system is clearly standardised) and clonality studies on whole blood or granulocyte, T lymphocyte and platelet fractions may be proposed as positive criteria for diagnosis of E.T.

Multiple myeloma following essential thrombocythemia

The association of essential thrombocythemia (ET) and multiple myeloma (MM) is exceedingly rare, with only four such cases reported in the literature until now. In this paper, a patient is reported who developed IgA-lambda MM more than five years after the diagnosis of ET, for which she had received alpha interferon and radioactive phosphor (32P). She died shortly afterwards despite melphalan and prednisone therapy. In four of the five patients in whom the above association has been reported, including the present one, MM appeared some time after ET was initially recognized, with three of them having received alkylating drugs as their treatment for ET. MM was heterogeneous with respect to the M--component type and the clinical course. The possible etiological & pathogenetic link between both these entities is discussed.

Impaired activation of phospholipase D in polycythaemia vera-implications for the pathogenesis of the disease?

A series of studies have demonstrated a stimulus-specific defect in PMN oxidative metabolism after stimulation with surface receptor dependent stimuli such as fMLP, leukotriene B4 and platelet activating factor (PAF), whereas the response to phorbol myristate acetate was normal. Having discovered this defect, studies of the stimulus response coupling for oxidative responses were performed showing a normal interaction of fMLP with it's receptor, as well as an intact activation of phospholipase C, as measured by the generation of 1,4,5-inositoltrisphosphate, and the subsequent rise of intracellular calcium. In contrast, the formation of diacylglycerol and phosphatidylethanol was decreased in PV PMN, denoting an impaired activation of phospholipase D (PLD). It was shown by flow cytometry analyses that the hampered oxidative response was present both in single PMN and monocytes. Moreover, platelets from PV patients, whose PMN exhibit a lower oxidative response to PAF, also have a diminished aggregatory response to PAF. Thus three different cell lineages in PV have been revealed to respond abnormally to surface receptor dependent stimuli, indicating that the proposed impairment of PLD might be relevant for changes in the malignant stem cell clone. Since phosphatidic acid, produced as a result of PLD activation, may be implicated in the regulation of several oncogenes, perturbations of the PLD system could theoretically be important for the development of PV.

Characterization of 20q deletions in patients with myeloproliferative disorders or myelodysplastic syndromes

Deletions of the long arm of chromosome 20 are associated with several myeloid malignancies. We have analyzed the structure of the del(20q) in 30 patients and two cell lines. Twenty-one of the patients presented with a myeloproliferative disorder and nine with a myelodysplastic syndrome. Two categories of deletions were identified. Eighteen patients had a large deletion with loss of both G(+) bands from the long arm of chromosome 20. Twelve patients had small deletions with loss of one G(+) band from the long arm of chromosome 20. A chromosome paint was generated from a del 20q marker carrying a small deletion. This probe was hybridized to normal metaphases (reverse chromosome painting) and also to metaphases from patients with a del 20q (comparative reverse chromosome painting). All six small deletions analyzed were characterized by loss of the proximal G(+) band (q12) and retention of the distal G(+) band (q13.2). These data define a minimal deleted region extending from 20q11.2-20q13.1.

Stimulus-specific defect in platelet aggregation in polycythemia vera

We have previously reported that polymorphonuclear granulocyte (PMN) and monocyte oxidative metabolism is reduced in polycythemia vera (PV) patients compared to healthy control subjects, after stimulation with cell surface receptor-dependent stimuli such as n-formyl-methionyl-leucyl-phenylalanine, leukotriene B4 and platelet-activating factor (PAF). In contrast, the oxidative response to phorbol myristate acetate (PMA) is normal. We now show that, in PV patients exhibiting significantly reduced PMN chemiluminescence after PAF stimulation, PAF induced platelet aggregation was also reduced--40 +/- 3% compared to 50 +/- 2% in controls (p < 0.01). The defective aggregatory response to PAF in PV remained over a wide range of stimuli concentrations. Platelet aggregation induced by PMA and ADP, however, was similar in PV and controls. In contrast, platelet aggregation induced by PAF (or by ADP and PMA) was not significantly reduced in patients with chronic myeloid leukemia, essential thrombocythemia and multiple myeloma. Furthermore, the release of beta-thromboglobulin was slightly but not significantly higher after PAF stimulation in PV and this argues against an abnormal PAF receptor as the cause of the defective function. Thus, not only PV neutrophils, but also PV platelets show a discrete defect of the stimulus response coupling for PAF, indicating a disease-specific abnormality that appears to be of clonal origin.

Issues in the diagnosis and management of essential thrombocythemia

OBJECTIVE

To summarize the current trends in the diagnosis and management of essential thrombocythemia (ET) and to discuss the treatment of young and pregnant patients with ET.

DESIGN

We review our experiences in the diagnosis and management of ET.

MATERIAL AND METHODS

A definitive diagnosis of ET at initial examination is seldom possible because of the low incidences of associated clonal cytogenetic abnormalities and palpable splenomegaly. The criteria of the Polycythemia Vera Study Group for the diagnosis of ET are provided, as are the clinical and laboratory features that help to distinguish ET from reactive thrombocytosis.

RESULTS

Patients with ET have an almost normal life expectancy if thrombohemorrhagic complications are controlled. Although a previous history of thrombosis is an established risk factor for further episodes, the adverse effects of extreme thrombocytosis and age are less well defined. Determining which patients require therapy is controversial. The management of young or pregnant patients necessitates special considerations.

CONCLUSION

Until additional data become available, no strong recommendations can be given in support of or against specific therapy for asymptomatic young patients. We favor treatment in asymptomatic patients with cardiovascular risk factors but not in asymptomatic women who are pregnant or are of childbearing age.