Cytokine Profiling in Myeloproliferative Neoplasms: Overview on Phenotype Correlation, Outcome Prediction, and Role of Genetic Variants

Among hematologic malignancies, the classic Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) are considered a model of inflammation-related cancer development. In this context, the use of immune-modulating agents has recently expanded the MPN therapeutic scenario. Cytokines are key mediators of an auto-amplifying, detrimental cross-talk between the MPN clone and the tumor microenvironment represented by immune, stromal, and endothelial cells. This review focuses on recent advances in cytokine-profiling of MPN patients, analyzing different expression patterns among the three main Philadelphia-negative (Ph-negative) MPNs, as well as correlations with disease molecular profile, phenotype, progression, and outcome. The role of the megakaryocytic clone as the main source of cytokines, particularly in myelofibrosis, is also reviewed. Finally, we report emerging intriguing evidence on the contribution of host genetic variants to the chronic pro-inflammatory state that typifies MPNs.

Cytokine Profiling in Myeloproliferative Neoplasms: Overview on Phenotype Correlation, Outcome Prediction, and Role of Genetic Variants

Among hematologic malignancies, the classic Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) are considered a model of inflammation-related cancer development. In this context, the use of immune-modulating agents has recently expanded the MPN therapeutic scenario. Cytokines are key mediators of an auto-amplifying, detrimental cross-talk between the MPN clone and the tumor microenvironment represented by immune, stromal, and endothelial cells. This review focuses on recent advances in cytokine-profiling of MPN patients, analyzing different expression patterns among the three main Philadelphia-negative (Ph-negative) MPNs, as well as correlations with disease molecular profile, phenotype, progression, and outcome. The role of the megakaryocytic clone as the main source of cytokines, particularly in myelofibrosis, is also reviewed. Finally, we report emerging intriguing evidence on the contribution of host genetic variants to the chronic pro-inflammatory state that typifies MPNs.

Allogeneic Stem Cell Transplantation in Myelofibrosis

Myeloproliferative neoplasm (MPN) is a category in the World Health Organization classification of myeloid tumors. BCR-ABL1-negative MPN is a subcategory that includes primary myelofibrosis (MF), post-essential thrombocythemia MF, and post-polycythemia vera MF. These disorders are characterized by stem cell-derived clonal myeloproliferation. Clinically, these diseases present with anemia and splenomegaly and significant constitutional symptoms such as severe fatigue, symptoms associated with an enlarged spleen and liver, pruritus, fevers, night sweats, and bone pain. Multiple treatment options may provide symptom relief and improved survival; however, allogeneic stem cell transplantation (HCT) remains the only potentially curative option. The decision for a transplant is based on patient prognosis, age, comorbidities, and functional status. This review describes the recent data on various peritransplantation factors and their effect on outcomes of patients with MF and new therapeutic areas, such as the use and timing of Janus kinase inhibitors with HCT and gives overall conclusions from the available data in the published literature.

Allogeneic hematopoietic cell transplantation for advanced polycythemia vera and essential thrombocythemia

Allogeneic hematopoietic cell transplantation (HCT) is curative for selected patients with advanced essential thrombocythemia (ET) or polycythemia vera (PV). From 1990 to 2007, 75 patients with ET (median age 49 years) and 42 patients with PV (median age 53 years) underwent transplantations at the Fred Hutchinson Cancer Research Center (FHCRC; n = 43) or at other Center for International Blood and Marrow Transplant Research (CIBMTR) centers (n = 74). Thirty-eight percent of the patients had splenomegaly and 28% had a prior splenectomy. Most patients (69% for ET and 67% for PV) received a myeloablative (MA) conditioning regimen. Cumulative incidence of neutrophil engraftment at 28 days was 88% for ET patients and 90% for PV patients. Acute graft-versus-host disease (aGVHD) grades II to IV occurred in 57% and 50% of ET and PV patients, respectively. The 1-year treatment-related mortality (TRM) was 27% for ET and 22% for PV. The 5-year cumulative incidence of relapse was 13% for ET and 30% for PV. Five-year survival/progression-free survival (PFS) was 55%/47% and 71%/48% for ET and PV, respectively. Patients without splenomegaly had faster neutrophil and platelet engraftment, but there were no differences in TRM, survival, or PFS. Presence of myelofibrosis (MF) did not affect engraftment or TRM. Over 45% of the patients who undergo transplantations for ET and PV experience long-term PFS.

Evaluation of interleukin-23 plasma levels in patients with polycythemia vera and essential thrombocythemia

Essential thrombocythemia (ET), polycythemia vera (PV) and myelofibrosis share the same acquired genetic lesion, JAK2V617F. It is believed that cytokines participate in the activation of JAK2V617F. In this study, we analyzed the plasma levels of interleukin (IL)-23, IL-10 and IL-22 in patients with PV and ET. In the same subjects we also performed analysis of the JAK2(V617F) mutation, and evaluated a possible relationship between interleukin levels and thrombotic complications or with the symptom pruritus. Plasma levels of IL-23 were significantly increased in all patients with MPN in comparison to controls. Moreover, there was a significant difference between the levels of IL-23 in patients affected by PV and those measured in controls (8.57±3.69pg/mL vs. 6.55±4.125pg/mL; p<0.03). No difference was found between IL-23 levels in ET patients and controls. No statistically significant differences were found between the levels of IL-23, Il-22 or IL-10 in PV or ET subjects with or without thrombosis, in patients with or without pruritus, or according the JAK2V617F burden. In PV patients the JAK2 burden and Hb levels correlated with occurrence of pruritus. Our study seems to point out a possible involvement of IL-23 in the pathogenesis of PV.

Neutrophil-specific antigen HNA-2a, NB1 glycoprotein, and CD177

PURPOSE OF REVIEW

Several advances have been made in characterization of the molecule that carries human neutrophil antigen (HNA)-2a, NB1 glycoprotein, the gene that encodes NB1 glycoprotein, CD177, and the role of antibodies to HNA-2a in transfusion reactions.

RECENT FINDINGS

NB1 glycoprotein binds to the endothelial cell adhesion molecule, platelet endothelial cell adhesion molecule-1 (PECAM-1), and participates in neutrophil transmigration. The overexpression of neutrophil CD177 mRNA has become a useful, but nonspecific biomarker of myeloproliferative diseases, especially polycythemia vera. CD177 mRNA overexpression is also a biomarker of a subset of patients with essential thrombocythemia who are at increased risk of thromboembolic complications. In patients with myeloproliferative disorders CD177 mRNA overexpression is secondary to a gain-of-function mutation in JAK2, JAK2 V617F. NB1 glycoprotein is co-localized on neutrophil plasma membranes with proteinase 3 and a complex of NB1 glycoprotein and proteinase 3 may initiate the activation of neutrophils by antineutrophil cytoplasmic antibodies in patients with Wegener's granulomatosis. The inadvertent transfusion of antibodies to HNA-2a with blood components frequently causes pulmonary transfusion reactions.

SUMMARY

The expression of CD177 is an important biomarker of myeloproliferative diseases, NB1 glycoprotein is a ligand for PECAM-1 and it may have a role in Wegener's granulomatosis, and antibodies to HNA-2a frequently cause pulmonary transfusion reactions.

JAK2-V617F mutation analysis of granulocytes and platelets from patients with chronic myeloproliferative disorders: advantage of studying platelets

There have been conflicting reports over the JAK2-V617F mutation status of platelets in chronic myeloproliferative diseases (CMPDs). The aim of this study was to analyse JAK2-V617F status, not only in granulocytes but also in platelets. The JAK2-V617F mutation was analysed in both granulocytes and platelets in 115 patients with CMPDs using direct sequencing. JAK2-V617F was detected in granulocytes from 71 of those patients, all 71 of whom also had platelet JAK2-V617F expression. The remaining 44 patients showed negative JAK2-V617F expression on granulocytes, but positive JAK2-V617F expression was detected on the platelets from nine of the 33 essential thrombocythaemia (ET) patients, one of the eight polycythaemia vera patients, and two of the three primary myelofibrosis patients. When ET patients were divided into three groups according to granulocyte and platelet JAK2-V617F status (both-positive, platelets-only positive and both-negative), the both-positive and platelets-only positive groups shared the clinical features of higher white blood cell count and frequent thrombosis. These results suggest that analysis of platelets is a more sensitive approach for detecting JAK2-V617F in CMPD patients than analysis of granulocytes. They also suggest that previous reports of the incidence of JAK2-V617F in CMPD patients, obtained using only analysis of granulocytes, could be underestimations.

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.

Clonal granulocytes in polycythaemia vera and essential thrombocythaemia have shortened telomeres

Summary The purpose of this study was to evaluate telomere length in peripheral blood granulocytes and mononuclear cells collected from 22 women with polycythaemia vera (PV) and essential thrombocythaemia (ET). PV and ET are chronic myeloproliferative diseases whose heterogeneity of stem cell origin and clonal development has been established through analysis of X-chromosome inactivation patterns. The results from clonality assay and determination of telomere length show that only clonal granulocytes have shortened telomeres.

The contribution of Fc effector mechanisms in the efficacy of anti-CD154 immunotherapy depends on the nature of the immune challenge

Blockade of the CD154-CD40 co-stimulatory pathway with anti-CD154 mAbs has shown impressive efficacy in models of autoimmunity and allotransplantation. Clinical benefit was also demonstrated in systemic lupus erythematosus (SLE) and idiopathic thrombocytopenia patients with the humanized anti-CD154 mAb, 5C8 (hu5C8). However, thromboembolic complications that occurred during the course of the hu5C8 clinical trials have proven to be a major setback to the field and safe alternative therapeutics targeting the CD154-CD40 pathway are of great interest. Recently, effector mechanisms have been shown to play a part in anti-CD154 mAb-induced transplant acceptance in murine models, while this issue remains unresolved for humoral-mediated models. Herein, aglycosyl anti-CD154 mAbs with reduced binding to FcgammaR and complement were used as a novel means to test the role of effector mechanisms in non-human primate and murine models not amenable to gene knockout technology. While aglycosyl hu5C8 mAb was relatively ineffective in rhesus renal and islet allotransplantation, it inhibited primary and secondary humoral responses to a protein immunogen in cynomolgus monkeys. Moreover, an aglycosyl, chimeric MR1 mAb (muMR1) prolonged survival and inhibited pathogenic auto-antibody production in a murine model of SLE. Thus, the mechanisms required for efficacy of anti-CD154 mAbs depend on the nature of the immune challenge.

Patients with essential thrombocythaemia have an increased prevalence of antiphospholipid antibodies which may be associated with thrombosis

A significant proportion of patients with Essential Thrombocythaemia (ET) have thrombotic complications which have an important impact upon the quality, and duration of their life. We performed a retrospective cross sectional study of the prevalence of antiphospholipid antibodies (APA) in 68 ET patients. Compared to 200 "elderly" controls (>50 years) there was a significant increase in anticardiolipin IgM (p < 0.0001) and anti beta2 glycoprotein I (anti-beta2GPI) IgM (p < 0.0001) antibodies in ET. Thrombosis occurred in 10/20 with APA and 12/48 without, p = 0.04, relative risk 2.0 (95% confidence intervals 1.03-3.86): these patients did not differ in terms of other clinical features. The prevalence of thrombosis in patients with dual APA (6/7) was significant when compared to those with single APA (p = 0.02) and the remaining patients (p < 0.0002). Also anti-beta2GP1 IgM antibodies either alone, or in combination with another APA, were associated with thrombosis (p = 0.02). These results suggest that the prevalence of APA in ET and their influence upon thrombotic risk merit investigation in a larger study.

Typical essential thrombocythaemia does not express bcr-abelson fusion transcript

Essential thrombocythaemia (ET) is a chronic myeloproliferative disorder (MPD) characterized by an elevated platelet count and no identifiable underlying primary cause. According to the diagnostic criteria of the Polycythemia Vera Study Group (PVSG), ET lacks features diagnostic for other MPDs, including the Philadelphia chromosome (Ph) or bcr-abl rearrangement. Recently, some authors have reported bcr-abl transcript positivity in ET patients, but these findings remain controversial. The aim of this study was to investigate whether the bcr-abl transcript could be found in ET patients and to verify the hypothesis of a new ET variant. ET patients (n = 121) with a median age at diagnosis of 55 years were enrolled. The bcr-abl transcript status was examined by multiplex reverse transcription-polymerase chain reaction. Only two cases were positive for bcr-abl, one of which had the Ph at diagnosis. The positive bcr-abl transcript was associated, in both cases, with mild basophilia at diagnosis. After a median follow-up of 43 months (0-309 months), two patients in the bcr-abl-negative group developed Ph and bcr-abl-negative acute myeloid leukaemia (AML). In contrast, one of the two patients in the bcr-abl-positive group died from AML 13 years after diagnosis. In conclusion, our data on a large group of patients shows the rarity of the bcr-abl transcript in well-established ET. However, a subset of patients with apparent ET and basophilia may express the transcript and may constitute a novel entity intermediate between chronic myeloid leukaemia (CML) and typical ET. A prospective study is warranted in order to define better the clinical and biological characteristics of bcr-abl-expressing ET.

Leukemic transformation of essential thrombocythemia without previous cytoreductive treatment

Blastic transformation of essential thrombocythemia (ET) preceded by chemotherapy is occasionally described in the literature. In ET as well as in other myeloproliferative disorders the leukemogenic effect of alkylating agents and (32)P is well established, and recent reports also indicate a certain leukemogenic effect of hydroxyurea in these disorders. However, leukemic transformation in untreated ET seems to be a rare event. This is probably due to the fact that, at some time during their clinical course, most ET patients receive chemotherapy and are thereby exposed to leukemogenic challenge. We report on a woman with ET who had not received cytoreductive treatment prior to the development of acute myeloid leukemia, indicating that this transformation was a natural progression of her disorder.

Genetic lesions associated with blastic transformation of polycythemia vera and essential thrombocythemia

Polycythemia vera (PV) and essential thrombocythemia (ET) are chronic myeloproliferative disorders that may progress to acute leukemia in a subset of patients. This study aimed at investigating the genetic lesions associated with the blastic transformation of PV and ET. A panel of PV and ET cases at different stages of disease was analyzed for the presence of genetic alterations of TP53, NRAS, KRAS, and MDM2 by a combination of mutational analysis and Southern blot hybridization. The occurrence of microsatellite instability (MSI) was also tasted in selected cases. Samples of PV and ET analyzed in chronic phase disease were consistently devoid of all genetic lesions tested, suggesting that alterations of TP53, NRAS, KRAS, and MDM2 do not contribute significantly to development of chronic phase PV and ET. Conversely, mutations of TP53 were detected in 7/15 (46.6%) blastic phase cases, including 3/5 PV and 4/10 ET. In blastic phase patients for whom the corresponding chronic phase DNA was also available, it could be documented that the genetic lesion had arisen at the time of blastic transformation. In addition to TP53 mutations, cases of blastic phase PV and ET occasionally harbored mutations of NRAS (one case of blastic phase ET) or displayed MSI (one case of blastic phase PV). These data indicate that inactivation of TP53 is a relatively frequent event associated with the blastic transformation of PV and ET and may be responsible for the tumor progression of these disorders.

Spontaneous megakaryocyte colony formation in myeloproliferative disorders is not neutralizable by antibodies against IL3, IL6 and GM-CSF

Megakaryocyte progenitor growth in 42 patients with myeloproliferative disorders (MPD), including 23 essential thrombocythaemia (ET), eight polycythaemia vera (PV), six chronic myelogenous leukaemia (CML) and five primary myelofibrosis (PMF), was studied in vitro using plasma clot assay and serum-free agar culture. Spontaneous megakaryocyte colonies (CFU-MK) were found in 34/40 (80%) blood and 14/18 (77.8%) bone marrow plasma clot cultures, and also observed in 27/35 (77.1%) blood and 10/18 (55.6%) bone marrow serum-free agar cultures. In the blood of 27 patients with MPD (15 ET, four PV, four CML and four PMF) and the bone marrow of 10 patients (five ET, four CML and one PV), spontaneous colony formation was observed in both plasma clot and serum-free agar cultures. However, spontaneous CFU-MK was only found in plasma clot culture, but not in agar culture in two blood (one ET and one CML) and four bone marrow cultures (one ET, two PV, one CML). The colony numbers were greatly increased in the presence of aplastic anaemia serum (AAS) under both conditions. In 17 patients (12 ET, two CML and three PV) with spontaneous megakaryocyte colonies, anti-cytokine antibody neutralizing experiments were carried out in blood cultures. Anti-IL3, anti-IL6 and anti-GM-CSF antibody, alone or in combination, at different concentrations (1, 5 and 10 micrograms/ml), were added into plasma clot or agar cultures without exogenous stimulating growth factors. The results showed that the numbers of spontaneous megakaryocyte colonies were not significantly decreased in the presence of these monoclonal antibodies in the cultures. The data indicated that the megakaryocyte progenitor growth in MPD under in vitro conditions was heterogenous, and independent of exogenous stimulatory factors in most patients and that optimal megakaryocyte colony development in MPD still requires exogenous growth factors. Three possibilities are discussed with regard to the phenomenon that the spontaneous colony formation was not decreased with the addition of anti-IL3, anti-IL6 and anti-GM-CSF antibodies.

Cytoplasmic GpIIb-IIIa and cytokine secretion by blasts in a case of megakaryoblastic transformation of essential thrombocythemia

A 49-year-old woman with a four year history of therapy resistant essential thrombocythemia, progressed to acute leukemia that also proved refractory to chemotherapy. Blast cell features including immunophenotype, cytogenetics and in vitro cell cultures, suggested megakaryoblastic leukemia. In serum-free culture, blasts released GM-CSF and IL-6 which sustained autocrine growth and promoted normal myeloid and megakaryocytic colony formation.

Alpha interferon raises serum beta-2-microglobulin in patients treated for thrombocythaemia

Serum beta-2-microglobulin (b2m) levels were studied in 10 patients treated with alpha interferon (IFN) for thrombocythaemia associated with chronic myeloproliferative diseases. In eight patients the IFN treatment decreased the blood platelet level to < 600 x 10(9)/l. Serum b2m levels rose significantly and dose-dependently immediately after the onset of treatment, by a median maximal increase of 72% with IFN 3 MU every other day, and 95% with 3 MU daily. The b2m rise caused by IFN abolishes the value of serum b2m in states where b2m is used as an indicator of disease activity.

[Electro-optic method of recording antigen-antibody interactions in detection of antiplatelet antibodies in hemorrhagic thrombocytopathies]

A new electrooptic method was used to study the antiplatelet autoimmune process. Antiplatelet antibodies were assessed in 60 patients with idiopathic thrombocytopenic purpura and 60 ones with acquired hemorrhagic thrombocytopathies. The reference group consisted of 50 donors. The relationship between the autoimmune process intensity and the disease severity, as well as blood platelet counts over the course of corticosteroid therapy was studied.

Quantitative and functional studies of impaired natural killer (NK) cells in patients with myelofibrosis, essential thrombocythemia, and polycythemia vera. I. A potential role for platelet-derived growth factor in defective NK cytotoxicity

In view of the possibility that immunological dysfunctions may be involved in initiating or contributing to the pathogenesis of myeloproliferative disease, we investigated quantitative and functional activity of natural killer (NK) cells in patients with polycythemia vera, essential thrombocythemia and myelofibrosis, and have demonstrated, especially in myelofibrosis, a measurable cytotoxic defect in the ability of their peripheral blood mononuclear cells to efficiently kill the standard NK target, K-562. Furthermore, highly purified, FACS-sorted CD16+ lymphoid cells from patients with myelofibrosis were consistently defective in their ability to lyse K-562 targets, and could not be augmented substantially with recombinant interleukin (IL)-2. Only patients with myelofibrosis had significantly lower percentages and absolute numbers of CD16+ cells as compared to patients with essential thrombocythemia and polycythemia vera. Further experiments demonstrated that patients with myelofibrosis, although having fewer CD16+ NK cells, had a significantly increased proportion of CD16+ cells with detectable platelet-derived growth factor (PDGF) on their surface. In contrast, surface PDGF was barely detectable on CD16+ cells from patients with polycythemia vera and essential thrombocythemia, as well as from normal controls. Having previously reported that physiologic quantities of PDGF significantly inhibit human NK cell cytotoxicity, and that patients with myelofibrosis and essential thrombocythemia have significantly elevated circulating levels of plasma PDGF, we now have demonstrated that pretreatment of normal NK cells with concentrated, PDGF-containing, platelet-poor plasma from patients with these diseases significantly inhibits NK cytotoxicity. This inhibitory effect was reversed by neutralization of plasma PDGF with anti-PDGF (coupled to Sepharose resin). Both the NK defects demonstrated in this study, and the abnormal plasma PDGF results reported earlier, are most striking in myelofibrosis and least abnormal in polycythemia vera, with an intermediate degree of abnormality in essential thrombocythemia. Our new findings suggest a causal correlation between abnormal platelet release, plasma accumulation of PDGF, and the observed NK immunodeficiency in these myeloproliferative patients.

Quantitation of platelet glycoprotein IV (CD36) in healthy subjects and in patients with essential thrombocythemia using an immunocapture assay

Glycoprotein IV (GPIIb, CD36) is a major platelet membrane glycoprotein which is thought to participate in a number of adhesive reactions and to mediate signal transduction. In order to measure the total content of GPIV in human platelets, we have developed a simple and sensitive solid-phase radioimmunoassay based on the immunocapture of GPIV from Triton X-100-solubilized platelets. FA6-152, a monoclonal antibody to GPIV was coated on microtiter plates and bound antigen was quantified with a radiolabeled polyclonal antibody to GPIV. Using purified GPIV as a standard, the coefficients of variation of the assay were found to be less than 10% at concentrations of GPIV ranging from 0.15 to 0.75 micrograms/ml. The assay was validated by the parallelism obtained between purified GPIV dose-response curves and those obtained with platelet lysates, indicating a similar antigenic activity for GPIV in both samples. The level of GPIV in platelets from healthy donors was 0.23 +/- 0.05 (mean +/- SD, n = 15) micrograms per 100 micrograms of platelet proteins and a mean value of 27,440 +/- 6,200 (SD) molecules per platelet was calculated. The radioimmunoassay could be used to discriminate between the high level of platelet GPIV in patients with essential thrombocythemia (mean +/- SD = 81,850 +/- 27,780 molecules/platelet; n = 8) and the normal GPIV level in patients with secondary thrombocytosis (mean +/- SD = 26,810 +/- 4,030 molecules/platelet; n = 5), thereby demonstrating the clinical usefulness of the assay. The specific increase in platelet GPIV in patients with essential thrombocythemia was confirmed by immunoblot analysis whereas no increase in platelet GPIb or GPIIb-IIIa was observed by this technique.

In vitro inhibition of interferon alpha-2a antiproliferative activity by antibodies developed during treatment for essential thrombocythaemia

BACKGROUND

Various authors have reported the development of anti-interferon (IFN) antibodies following IFN-alpha treatment for haematological malignancies. So far the methods for detecting these antibodies have not considered the antiproliferative activity of this IFN, which is its most important property in anticancer therapy.

METHODS

In this in vitro study we evaluated the ability of anti-IFN alpha-2a neutralising antibodies to inhibit the antiproliferative activity of IFN alpha-2a and lymphoblastoid IFN alpha using megakaryocyte colony growth as the revelatory system. These antibodies were detected in two patients affected by essential thrombocythaemia (ET) who lost their haematological response to IFN alpha-2a, but responded to a subsequent treatment with lymphoblastoid IFN alpha.

RESULTS AND CONCLUSION

The results show that the inhibition of megakaryocyte colony growth induced by IFN alpha-2a was totally suppressed in the presence of the two ET patients' sera, whereas the inhibition induced by lymphoblastoid IFN alpha was not significantly affected. These in vitro data demonstrate the high specificity and activity of these antibodies on the antiproliferative effect of IFN alpha-2a.

α-interferon in hematological malignancies

Recent studies have generated data demonstrating significant clinical activity of alpha-interferon therapy in each of six hematological malignancies, chronic myeloid leukaemia, essential thrombocythemia, polycythemia rubra vera, non-Hodgkin's lymphomas, multiple myelomatosis and hairy cell leukaemia.

Elevated serum interleukin-6 levels in patients with reactive thrombocytosis

Interleukin-6 (IL-6) is known to promote megakaryocytopoiesis in vitro and raise platelet counts in vivo. To determine if there is a relationship between circulating IL-6 and thrombocytosis in man, we measured bioactive IL-6 in the serum of 13 patients with myeloproliferative disorders and 143 patients with reactive thrombocytosis having platelet counts greater than or equal to 600 x 10(9)/l. IL-6 activity was assayed using the IL-6-responsive B9 cell line. Seventy-one controls with normal platelet counts had a mean IL-6 level of 2.19 U/ml +/- 1.08 (SD). None of the 13 patients with myeloproliferative disorders had elevated IL-6 levels (1.56 U/ml +/- 1.2). In contrast, serum IL-6 levels of 143 patients (158 samples) with reactive thrombocytosis were significantly greater than controls (38.3 U/ml +/- 94.6; P less than 0.001), with 83% of the samples showing elevated serum IL-6. No significant correlation was observed between serum IL-6 levels and platelet counts in the reactive thrombocytosis group. We conclude that elevated IL-6 is associated with reactive thrombocytosis, and hypothesize that the increased platelet count in many cases is causally related to elevated IL-6.

Distribution of cell surface glycoprotein CD9 (P24) antigen on megakaryocyte lineage leukemias and cell lines

We herein describe CD9 (p24) antigen as existing on the cell surface of megakaryocyte lineage leukemias as well as megakaryocytic leukemia cell line, MEG-01 and HEL, by means of fluorescence-activated cell sorter (FACS IV) with a panel of monoclonal antibodies (Mabs). We found CD9 antigen expression on the cell surface of megakaryoblastic leukemias as well as MEG-01 and HEL cells. Furthermore, CD9 antigen expression increased while culturing these cells with phorbol esters, and was also found in the cytoplasm by means of indirect immunofluorescence test. These findings clearly showed that CD9 antigen exists on the cell surface of megakaryocytic cells which are capable of synthesizing the CD9.

Blastic transformation in essential thrombocythemia. In vitro differentiation of blast cells into granulocytic, erythroid, and megakaryocytic lineages

A 57-year-old man with essential thrombocythemia (ET) developed myelofibrosis, that progressed to a blastic transformation state. The characteristics of the blastic cells were serially studied both morphologically and phenotypically as well as in cell culture. The blastic cells that were first detected in peripheral blood had features of myeloid stem cells with slight differentiation toward megakaryocytic lineage. However, later in the course, most of the blastic cells were immature. During culture in the presence of human plasma-derived serum (PDS), some blastic cells obtained at the initial stage differentiated, mainly to both granulocytes and macrophages morphologically, but later tended to differentiate into both megakaryocytes and macrophages. Finally the blasts appeared to have lost their ability to differentiate morphologically. However, the blasts formed mixed colonies consisting of erythroblasts, granulocytes, macrophages, and immature blasts when cultured in methylcellulose with PHA-leukocyte conditioned medium. In addition, the blastic cells in suspension culture strongly expressed phenotypic features which are characteristic of erythroblasts, in the presence of both PDS and 12-0-tetradecanoylphorbol 13-acetate (TPA), whereas they expressed features of megakaryoblasts in the presence of PDS alone. These results suggest that essential thrombocythemia is of myeloid stem cell origin. This is the first case in the literature in which a clonal evolution in ET has been followed closely, essential events were identified serially, and the blastic cells, which appeared as a result of the progression of ET, were found to have the capability to differentiate toward the three myeloid lineages.

[Multi-phenotype leukemia in children. Apropos of 18 cases]

Eighteen cases of pediatric acute multi-phenotypic leukemia from 24 French centers investigated during 5 years are reported. The multi-phenotypic character of these cases was shown by the paradoxical presence of 2 or 3 associated membrane antigens which are normally lineage restricted. The following bi-phenotypic combinations were found: B/T lymphoid (n = 6), B/myeloid (n = 7) or T/myeloid (n = 2). Three cases of tri-phenotypic association were also observed [B/T/myeloid (n = 2), B/myeloid/megakaryoblastic (n = 1)]. Our findings suggest that combinations with a myeloid composant and the presence of cALLA (common acute lymphoid leukemia antigen) on less than 45% of cells seem to be related to a shorter survival.

The t(9;22) translocation in Philadelphia-positive essential thrombocythaemia does not involve the T lymphocyte lineage

A 42-year-old woman presented with clinical and haematological features of essential thrombocythaemia (ET). Cytogenetic investigation revealed a standard t(9;22) Philadelphia translocation in all evaluable metaphases which persisted throughout treatment. Gene probe analysis of the chromosome 22 breakpoint cluster region (bcr) locus revealed a breakpoint mapping between exons 1 and 3 of the bcr gene, consistent with a standard bcr-abl translocation as found in chronic myeloid leukaemia (CML). Moreover, in separate cell populations, the bcr breakpoint was demonstrable in DNA from granulocytes but not in T cells from either peripheral blood or bone marrow. Since ET is known to be a clonal disorder with a multipotential stem cell origin, these findings suggest that, as in CML, the bcr-abl hybrid gene arises through translocation in a multilineage stem cell which does not involve the T lymphocyte lineage.

An antibody to platelet membrane antigen associated with thrombotic events in essential thrombocythemia

A 71-year-old man with essential thrombocythemia presented with acute onset of thrombosis in his fingers. The platelet count at presentation was 752 x 10(9)/liter, and his PTT was within the normal range. Platelet aggregation was normal in response to ADP, decreased to epinephrine, and absent to collagen, with the patient receiving 1.2 g aspirin/day. Plasma vWF:Ag was 158 U/dl, VIII:C was 150 U/dl, and the vWF:Ag multimer pattern was normal. HLA antibodies were not detected in his serum, and the platelet-associated IgG was normal at 3.9 fg/platelet. Incubation of normal, unactivated platelets with the patient's plasma did not result in agglutination of the platelets. However, a serum antibody reacting against a platelet antigen with an apparent molecular weight of 45,000 could be demonstrated by Western blotting. This antibody also reacted with endothelial cells. The reactive pattern was similar to that of commercially obtained actin; the serum antibody could be removed by preincubation with actin. Platelet-plasmapheresis was carried out daily for 10 days, after which the serum still reacted weakly with the platelet antigen. By day 20, the band could still be identified on the electroblot, but 2 weeks later no band could be seen. Similar assay of sera from six other patients with myeloproliferative disorders and comparable thrombocytosis but without thrombotic manifestations did not show any such reactions. The data suggest a correlation between the presence of an antibody possibly directed against platelet and/or endothelial cell actin and the vascular events in this patient with essential thrombocythemia.

The role of apheresis in the support of life-threatening ITP relapse

A 14-year-old girl with chronic idiopathic thrombocytopenic purpura (ITP) presented in relapse with a platelet count of 1,000/microL and a high-level serum antiplatelet IgG antibody. She previously had been unresponsive to courses of therapy with steroids, vincristine, and splenectomy. When treatment with danazol and purified immunoglobulins was unsuccessful in controlling her rapidly progressive course, an 8-day plasma exchange procedure was initiated in combination with platelet transfusion therapy and immunosuppression with cyclophosphamide and vincristine. Within 2 days, her clinical state improved markedly, correlating with a drop in her serum antiplatelet antibody level. She continued to improve and was discharged on a regimen of cyclophosphamide and danazol. Her antiplatelet antibody level had fallen to within the normal range, despite a typical platelet count of 5,000/microL during the 8-day period. Two weeks later her platelet count rose to 65,000/microL. This case suggests that a course of therapeutic plasma exchange may have a temporizing role in the acute management of life-threatening chronic ITP relapse, generating time for the more definitive therapy of immunosuppression to take effect.

Acute myelofibrosis. Immunohistochemical study of four cases and comparison with acute megakaryocytic leukemia

Four cases of acute myelofibrosis are contrasted to three cases of acute megakaryocytic leukemia. The cases were clinically indistinguishable. Light microscopic examination of hematoxylin and eosin-stained bone marrow biopsy specimens from the cases of acute myelofibrosis showed a trilinear proliferation of mature and immature hematopoietic cells, increased numbers of mature magakaryocytes, and marked fibrosis. In contrast, the blast cells in the cases of acute megakaryocytic leukemia showed a continuous spectrum of differentiation from small blasts to megakaryoblasts. Immunoperoxidase staining showed the blast cells in all three cases of acute megakaryocytic leukemia to be strongly positive for Factor VIII, a marker of megakaryocytic differentiation. These same blasts did not stain with markers of myelomonocytic (lysozyme), lymphocytic (Hle), and myeloid (Leu-Ml) differentiation. In contrast, the blast cells in all four cases of acute myelofibrosis were Factor VIII, Hle, and Leu-Ml negative but did occasionally stain with anti-lysozyme.

Acute megakaryocytic leukemia with myeloid/monocytic differentiation

Acute megakaryocytic leukemia is a rare form of acute nonlymphocytic leukemia that occurs with increased frequency in patients with Down's syndrome. Herein, we report a child with Down's syndrome who presented with a large retroperitoneal mass due to acute megakaryocytic leukemia. Immunohistochemical stains of the tumor cells also demonstrated evidence of myeloid/monocytic differentiation, with positivity for alpha-1-antitrypsin, alpha-1-chymotrypsin, and lysozyme. The significance of this phenotypic heterogeneity is unclear and awaits further studies of similar cases.

Incomplete antigenic cross-reactivity between platelets and megakaryocytes: relevance to ITP

Immune thrombocytopenias are usually associated with normal or increased numbers of megakaryocytes in the marrow. Therefore, the mechanism(s) responsible for the destruction of circulating platelets may not affect megakaryocytes in the same way. One of the possibilities which could account for the differential effect on the cells would be the development of antibodies to components of platelet membranes which are not exposed on the surface of all megakaryocytes. To investigate this possibility, a rabbit antiserum specific for mouse platelets was tested against fresh and cultured mouse megakaryocytes by indirect immunofluorescence. This antiserum cross-reacted with 46% of fresh murine megakaryocytes and 54% of cultured megakaryocytes. Phase-contrast microscopy revealed the reacting megakaryocytes to be fully granulated with irregular contours and in the process of releasing platelets. Nonreactive megakaryocytes demonstrated smooth contours and lacked morphological evidence of thrombocytopoiesis. Electron microscopy showed that only in megakaryocytes (MK) with an irregular contour had the demarcation membrane system (DMS) reached continuity with the plasma membrane. Ultrastructural analysis of megakaryocytes from patients with ITP showed approximately 25% to 50% of megakaryocytes without evidence of injury, whereas 50% to 75% had extensive damage. In undamaged cells, platelet territories had not yet reached the peripheral zone. The DMS of damaged megakaryocytes opened to the exterior elaborating platelets. The observations suggested that some platelet antibodies react only with megakaryocytes which have reached the stage of thrombocytopoiesis. Relevant target antigens may not be exposed on all megakaryocytes before cytoplasmic fragmentation occurs.

Antigenic phenotype of myelomonocytic progenitors (CFU-GM) in chronic myeloproliferative disorders

The antigenic phenotype of myelomonocytic progenitors [colony-forming unit granulocyte-macrophage (CFU-GM)] from 33 patients with chronic myeloproliferative disorders was investigated using four cytotoxic monoclonal antibodies. Monoclonal antibodies S3-13, S8-6, and S16-144 which recognize normal hemopoietic progenitors of different lineages reacted with almost all CFU-GM. R1B-19 monoclonal antibody identified two subpopulations of myelomonocytic progenitors (type 1 and 2 CFU-GM), as reported previously in normal subjects. In 3 of 11 patients with chronic myelogenous leukemia, in 1 of 2 patients with chronic myelomonocytic leukemia, and in 2 of 4 patients with polycythemia vera, a higher proportion of the more immature CFU-GM (type 1) was detected in bone marrow cells. The more differentiated CFU-GM (type 2) is not detectable in normal peripheral blood. By contrast, in 14 of 15 chronic myelogenous leukemia patients, in 1 of 2 chronic myelomonocytic leukemia patients and in 3 of 8 patients with idiopathic myelofibrosis, it was present in high to very high proportions. It is clear from these findings that the antigens present on normal CFU-GM are expressed in chronic myeloproliferative disorders. The proportion and distribution of type 1 and 2 CFU-GM, on the other hand, are very different from those observed in the normal subjects.

Acute megakaryoblastic leukemia. Blast cell aggregates simulating metastatic tumor

Acute megakaryoblastic leukemia is a rare leukemia that can present diagnostic problems. We describe two children who have this disease and had clumps of blast cells in their bone marrow, a finding usually attributed to metastatic tumor. The megakaryocytic origin of the cells was supported by their cytochemical staining pattern (positive alpha-naphthyl acetate esterase resistant to sodium fluoride inhibition and negative alpha-naphthyl butyrate esterase) and by the presence of factor VIII-related antigen. Ultrastructural studies of blast cells from one patient demonstrated platelet peroxidase. The mechanism of blast cell clump formation in these cases is unknown; nevertheless, awareness that this feature can occur in acute megakaryoblastic leukemia may avoid a misdiagnosis of metastatic solid tumor.

An acute myeloproliferative disorder characterized by myelofibrosis and blast cells that express phenotypic properties associated with multiple hematopoietic lineages

The authors investigated the blast cells obtained from two patients with acute myelofibrosis with the use of recently developed immunochemical and ultrastructural markers. They intended to examine the expression of megakaryoblastic, erythroblastic, myeloblastic, and monoblastic properties in these cells. Respectively, 20% and 15% of the blasts from patient 1 and patient 2 expressed a megakaryoblastic phenotype as determined by reactivity with a polyclonal platelet glycoprotein antisera (PGP). However, 55% and 73% of these patients' blasts also exhibited myeloid/monocytic properties. Ultrastructural studies clearly demonstrated findings consistent with the presence of myeloblasts, monoblasts, and erythroblasts, as well as undifferentiated agranular blasts. These findings demonstrate the existence of a disorder in which blast cells simultaneously express properties associated with multiple hematopoietic lineages. This disorder is characterized by impaired terminal differentiation.

The value of immunoperoxidase studies in the diagnosis of 2 cases of acute leukaemia

2 cases of acute leukaemia in which the precise diagnosis was established using the immunoperoxidase technique on particle sections, a method not usually employed for acute leukaemias, are reported. Morphologically and cytochemically these cases were initially diagnosed as acute megakaryoblastic (case 1) and acute monocytic (case 2) leukaemia. Based on the immunoperoxidase studies, these diagnoses were corrected to DiGuglielmo's disease (case 1) and plasma cell leukaemia (case 2).

Megakaryocytic leukemia; identification utilizing anti-factor VIII immunoperoxidase

Coagulation Factor VIII is produced by endothelial cells and megakaryocytes. Antibody directed against Factor VIII or its associated antigens has been shown to be a sensitive marker for both normal and neoplastic endothelial cells. Its use to identify neoplastic megakaryocytes has not been described. We used immunoperoxidase localization of Factor VIII to identify megakaryocytes and immature megakaryocytic precursors in a case of megakaryocytic leukemia.