Molecular basis of the diagnosis and treatment of polycythemia vera and essential thrombocythemia

JAK2V617F mutation in patients with splanchnic vein thrombosis

BACKGROUND

Splanchnic vein thrombosis can be the presenting manifestation of myeloproliferative neoplasms. However, the diagnosis of a myeloproliferative neoplasm in these patients is often problematic, and more objective criteria are needed.

AIM

To determine the frequency of the mutation JAK2V617F in patients with splanchnic vein thromboses.

METHODS

A consecutive series of 108 adult patients with portal vein thrombosis (n = 77) and Budd-Chiari syndrome (n = 31) referred for hemostasis evaluation was retrospectively studied, with a median follow-up of 51 months (1-104).

RESULTS

One or more prothrombotic risk factors were present in 63% of the patients. Twenty-four (22%) out of the 108 patients presented the JAK2V617F, including 2 cirrhotic patients. Most had a low mutated allele burden (median 16.5%). JAK2V617F was present in all four patients with a previous diagnosis of a myeloproliferative neoplasm. In nine JAK2V617F-positive patients, the diagnosis of a myeloproliferative neoplasm was made at the thrombosis work-up, during follow-up or after JAK2V617F detection. Among the other 11 patients carrying the mutation, 2 patients have died, 4 had no evidence suggesting a myeloproliferative neoplasm, 1 had a normal bone marrow biopsy, and the other 4 could not be persuaded to undergo a biopsy. Among the patients without an overt myeloproliferative neoplasm, 15 out of 99 (15%) presented the JAK2V617F mutation. None of the JAK2V617F-negative patients have developed signs of a myeloproliferative neoplasm during follow-up.

CONCLUSIONS

Our findings suggest that JAK2V617F occurs in a high proportion of patients with splanchnic vein thrombosis, and reinforces the diagnostic utility of JAK2V617F testing in this setting.

Is the absence of JAK2 mutation a risk factor for bleeding in essential thrombocythemia? An analysis of 106 patients

BACKGROUND

JAK2(V617F) mutation has been recognized as a possible thrombotic risk factor in essential thrombocythaemia (ET). It's role is probably due to an increased myeloid proliferation and white blood cells (WBC) activation. Only few data are available about the effect of JAK2(V617F) on hemorrhagic risk. The aim of our study was to evaluate the influence of the mutational status on hemorrhagic complication.

METHODS

We retrospectively analysed laboratory and clinical findings of 106 consecutive patients with ET to evaluate possible relationships between thrombosis, abnormal bleeding, peripheral blood count, overexpression of PRV1 and JAK2(V617F) mutational status.

RESULTS

ON UNIVARIATE ANALYSIS WE FOUND: an association between JAK2(V617F) mutation and thrombotic events before or at diagnosis (p<0.003, OR=4.44, 95% CI=1.74-12.4); no statistical correlation between the median value of JAK2(V617F) burden and an increased risk of thrombosis (p=0.4, 95% CI= -22.8-10.4); significant relationships between mutated status and higher haematocrit, high WBC count and low platelet count; and a strong correlation between JAK2(V617F) and PRV1 overexpression (p<0.0001). Moreover, the presence of the JAK2(V617F) mutation and a WBC count greater than 8.4 x 10(9)/L were found to be independent factors related to thrombotic complications in multivariable analysis (p<0.006, OR=3.85, 95% CI=1.3-11.9; and p<0.002, OR=2.8, 95% CI=1.08-7.03, respectively). The prognostic impact of JAK2 mutation status and WBC count on thrombosis was evaluated in the whole cohort. Only new cases occurring in patients without previous thrombotic events were recorded for the analysis. The multivariable analysis showed a statistical correlation between the presence of the mutation and a WBC count greater than 8.12 x 10(6)/L and an increased risk of thrombosis if no cytoreductive treatment was started at diagnosis (JAK2(V617F) p=0.02; WBC p=0.02; OR=4.97; 95% CI=1.04-23.8). Finally, wild-type JAK2 was associated with a higher haemorrhagic risk (p=0.02) in univariate analysis but only a platelet count greater than 1,022 x 10(9)/L was associated with an increased risk of bleeding in the multivariable analysis.

CONCLUSION

Our data confirm the role of both JAK2(V617F) as factor associated with an increased risk of thrombosis at the diagnosis and during follow-up in no treated patients. Moreover a WBC count over 8.4 x 10(9)/L1 was also strictly associated to an increased risk of thrombosis. Regarding bleedings, our statistical analysis allows to exclude the mutation protective role on haemorrhage.

Therapeutic potential of Janus-activated kinase-2 inhibitors for the management of myelofibrosis

Myelofibrosis (either primary or postpolycythemia vera/essential thrombocythemia) is a chronic and debilitating myeloproliferative neoplasm for which there is no well-accepted standard of care. Clinical manifestations of this disease (e.g., cytopenias, splenomegaly, bone marrow fibrosis) and constitutional symptoms (e.g., hypercatabolic state, fatigue, night sweats, fever) create significant treatment challenges. For example, progressive splenomegaly increases the risk for more serious clinical sequelae (e.g., portal hypertension, splenic infarction). Myelofibrosis arises from hematopoietic stem cells or early progenitor cells. However, the molecular mechanisms underlying its pathogenesis and clinical presentation are poorly understood, delaying the development of effective and targeted treatments. Recent studies have implicated mutations that directly or indirectly lead to the deregulated activation of Janus-activated kinase 2 (JAK2). Appreciation for the activation of JAK2 and the importance of increased levels of circulating proinflammatory cytokines in the pathogenesis and clinical manifestations of myelofibrosis has led to novel therapeutic agents targeting JAKs. This review will briefly discuss the origins of the JAK2 hypothesis, the clinical relevance of JAK2 mutations in myelofibrosis, and recent clinical progress in targeting JAKs as a therapeutic intervention for patients with this chronic and debilitating disease.

The contribution of cyclooxygenase-1 and -2 to persistent thromboxane biosynthesis in aspirin-treated essential thrombocythemia: implications for antiplatelet therapy

We tested whether cyclooxygenase 2 (COX-2) expression and unacetylated COX-1 in newly formed platelets might contribute to persistent thromboxane (TX) biosynthesis in aspirin-treated essential thrombocythemia (ET). Forty-one patients on chronic aspirin (100 mg/day) and 24 healthy subjects were studied. Platelet COX-2 expression was significantly increased in patients and correlated with thiazole orange–positive platelets (r = 0.71, P < .001). The rate of TXA2 biosynthesis in vivo, as reflected by urinary 11-dehydro-TXB2 (TXM) excretion, and the maximal biosynthetic capacity of platelets, as reflected by serum TXB2, were higher in patients compared with aspirin-treated healthy volunteers. Serum TXB2 was significantly reduced by the selective COX-2 inhibitor NS-398 added in vitro. Patients were randomized to adding the selective COX-2 inhibitor, etoricoxib, or continuing aspirin for 7 days. Etoricoxib significantly reduced by approximately 25% TXM excretion and serum TXB2. Fourteen of the 41 patients were studied again 21 (± 7) months after the first visit. Serum TXB2 was consistently reduced by approximately 30% by adding NS398 in vitro, while it was completely suppressed with 50μM aspirin. Accelerated platelet regeneration in most aspirin-treated ET patients may explain aspirin-persistent TXA2 biosynthesis through enhanced COX-2 activity and faster renewal of unacetylated COX-1. These findings may help in reassessing the optimal antiplatelet strategy in ET.

[50-year-old woman with elevated haemoglobin and iron deficiency]

BACKGROUND

Elevated haemoglobin and erythrocytosis are frequent causes for investigation.

MATERIAL AND METHODS

A 50-year-old woman with elevated haemoglobin and erythrocytosis was referred to our hospital for investigation.

RESULTS AND INTERPRETATION

She had elevated serum erythropoietin and iron deficiency. Mutational status of the JAK2 gene was negative with respect to polycythemia vera, and no secondary reasons for polycythemia - including tumours - were revealed. A bone marrow biopsy and bone marrow smear showed a moderately increased number of lambda- positive monoclonal plasma cells, and small amounts of lambda light chains were detected in the urine. Serum electrophoreses showed no gammopathy. The reason for her elevated haemoglobin could be an erythropoietin-producing tumour or an idiopathic erythrocytosis based on a mutation in exon 12 of the JAK2 gene. Investigation of her plasma cells revealed a 10-fold increase in erythropoietin mRNA expression, indicating the reason for her elevated serum erythropoietin and haemoglobin values.

The role of the Platelet Function Analyzer (PFA)-100 and platelet aggregometry in the differentiation of essential thrombocythemia from reactive thrombocytosis

INTRODUCTION

The most crucial component of all diagnostic criteria for essential thrombocythemia (ET) has been the exclusion of reactive thrombocytosis (RT). Our aim was to evaluate the diagnostic performance of the PFA-100 collagen-epinephrine (CEPI) cartridge test and epinephrine-induced aggregometry individually, but mainly combined, in the differentiation of ET from RT.

MATERIALS AND METHODS

26 patients with ET and 25 with RT were studied. Platelet function was analyzed by the PFA-100 and by light transmission aggregometry with epinephrine and ADP. The JAK2 mutational status was identified and hematological parameters, plasma von Willebrand factor antigen and activity levels were also assessed.

RESULTS

The sensitivity (Se), specificity (Sp), positive predictive value (PPV), and the negative predictive value (NPV) of PFA-100 CEPI vs epinephrine-induced aggregometry in the differentiation of ET from RT were estimated as follows: Se (%): 78.9 vs 84.6, Sp (%): 92.0 vs 96.0, PPV (%): 88.2 vs 95.7, NPV (%): 85.2 vs 85.7, respectively. When both of these methods were combined, a lower sensitivity of 68.4%, but a specificity of 100% was attained. The PPV observed with this double abnormal combination was 100% and the NPV 80.6%. Lastly, when we assessed the abnormality for either CEPI CT or epinephrine-induced aggregometry, the sensitivity was 100%, the specificity 88.0%, PPV 86.4% and NPV 100%. Thus, an abnormal combination was strongly suggestive of ET, while normal results with both methods excluded ET.

CONCLUSIONS

If our results are replicated by further studies, these two methods could be used very effectively as adjunct markers in the differentiation between ET and RT.

Enrichment of Sca1+ hematopoietic progenitors in polycythemic mice inhibits leukemogenesis

Polycythemia vera (PV) is a myeloproliferative disorder characterized by a pronounced increase in the number of erythroid cells. However, despite this aberrant proliferation, the incidence of erythroleukemia is paradoxically rare in PV patients. In this study, we show that the progression of Friend virus-induced erythroleukemia is delayed in a mouse model of primary familial congenital polycythemia in which the wild-type Epo-receptor (EpoR) gene is replaced with a truncated human EPOR gene. Herein, we show that these mice exhibit enrichment of Sca1(+)/cKit(-) progenitors and several mature immune cells, such as dendritic cells and macrophages. In cotransplantation experiments, Sca1(+)/cKit(-) progenitors inhibit the tumorigenicity of Sca1(-)/cKit(+) erythroleukemic cells. A cell line established from Sca1(+)/cKit(-) progenitors is also capable of inhibiting leukemic proliferation in culture and in mice. This phenomenon of leukemic inhibition, also detected in the serum of PV patients, is partially attributed to increased nitric oxide secretion. In addition, the administration of erythropoietin into leukemic mice induces a polycythemia-like state associated with the expansion of Sca1(+)/cKit(-) progenitors and derivative immune cells, thereby inhibiting leukemia progression. This study indicates that a combination therapy incorporating the enrichment of Sca1(+)/cKit(-) progenitors may serve as a novel approach for the treatment of leukemia.

What is the significance of thrombocytosis in patients with trauma?

BACKGROUND

The incidence and risk factors for the development of thrombocytosis after trauma have not been well established. Although it has been suggested that the occurrence of this sequela may be associated with adverse events, there are also limited data regarding outcomes of patients developing posttraumatic thrombocytosis. The objective of this study was to determine the incidence of, risk factors for, and sequela of posttraumatic thrombocytosis.

METHODS

A retrospective review of all trauma intensive care unit (ICU) admissions between July 1998 and December 2005 identified patients with early (< or = 7 days), late, and no thrombocytosis. Bivariate analysis was used to compare the clinical and demographic characteristics with outcomes between the three patient groups.

RESULTS

A total of 3,484 patients were admitted to the ICU during the 7-year study period. After exclusions, the study population consisted of 3,286 patients. The overall incidence of thrombocytosis was 18.7%; early thrombocytosis was found in 72 patients, and late thrombocytosis was identified in 542 patients. All complications examined were significantly higher in patients with thrombocytosis. Overall, the venous thromboembolic rate was 2.4%; for patients with thrombocytosis it was 4.6% compared with 1.9% in patients without thrombocytosis. Overall mortality was 15.4%, but was significantly lower in patients with thrombocytosis (3.8% vs. 18.1%, p < 0.0001). Independent risk factors for the development of thrombocytosis included obesity, laparotomy, blunt injury, Injury Severity Score > 16, mechanical ventilation, Chest Abbreviated Injury Score > 3, and tachycardia.

CONCLUSION

Thrombocytosis is a common finding among patients with trauma admitted to the ICU. The occurrence of both early and late thrombocytosis is associated with significantly higher rates of complications, particularly venous thromboembolism. However, patients developing posttraumatic thrombocytosis may have a significantly lower mortality compared with those without this sequela of injury.

The granulocyte-macrophage colony-stimulating factor receptor: linking its structure to cell signaling and its role in disease

Already 20 years have passed since the cloning of the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor alpha-chain, the first member of the GM-CSF/interleukin (IL)-3/IL-5 family of hemopoietic cytokine receptors to be molecularly characterized. The intervening 2 decades have uncovered a plethora of biologic functions transduced by the GM-CSF receptor (pleiotropy) and revealed distinct signaling networks that couple the receptor to biologic outcomes. Unlike other hemopoietin receptors, the GM-CSF receptor has a significant nonredundant role in myeloid hematologic malignancies, macrophage-mediated acute and chronic inflammation, pulmonary homeostasis, and allergic disease. The molecular mechanisms underlying GM-CSF receptor activation have recently been revealed by the crystal structure of the GM-CSF receptor complexed to GM-CSF, which shows an unexpected higher order assembly. Emerging evidence also suggests the existence of intracellular signosomes that are recruited in a concentration-dependent fashion to selectively control cell survival, proliferation, and differentiation by GM-CSF. These findings begin to unravel the mystery of cytokine receptor pleiotropy and are likely to also apply to the related IL-3 and IL-5 receptors as well as other heterodimeric cytokine receptors. The new insights in GM-CSF receptor activation have clinical significance as the structural and signaling nuances can be harnessed for the development of new treatments for malignant and inflammatory diseases.

JAK2 V617F mutation in essential thrombocythemia: correlation with clinical characteristics, response to therapy and long-term outcome in a cohort of 275 patients

The JAK2(V617F) mutation occurs in 50% of patients with essential thrombocythemia (ET). We investigated the correlation between the JAK2(V617F) mutation and clinical and laboratory characteristics, thrombohemorrhagic risk and incidence of disease evolution in 275 patients with ET followed for a median follow-up of 7 years. JAK2(V617F) mutation was detected in 175 patients (64%), of whom 173 were heterozygous. Patients with the mutation were older and displayed higher hemoglobin and hematocrit levels, but lower platelet count. Cytotoxic treatment requirement was similar in the two groups, but patients with the mutation showed better responses. Incidence of thrombosis and disease evolution was comparable. JAK2 mutational status assessment was valuable to distinguish two populations of patients with ET, showing distinctive hematologic and clinical features.

Association of V617F Jak2 mutation with the risk of thrombosis among patients with essential thrombocythaemia or idiopathic myelofibrosis: a systematic review

INTRODUCTION

Many studies evaluated the association of V617F Jak-2 with the risk of thrombosis in patients with essential thrombocythaemia, but the results of these studies were inconsistent. Few studies evaluated the association of V617F Jak-2 mutation with the risk of thrombosis in patients with idiopathic myelofibrosis. Therefore, we performed a systematic review of the studies that assessed the risk of thrombosis associated with V617F Jak-2 in patients with ET or IM.

MATERIALS AND METHODS

We searched MEDLINE and EMBASE databases and reference lists of retrieved articles. Odds ratios (ORs) and 95% confidence intervals (CI) were calculated for each trial and pooled.

RESULTS

We included 21 studies involving patients with essential thrombocythaemia and 6 studies patients with idiopathic myelofibrosis. In essential thrombocythaemia patients, V617F Jak-2 was associated with a significant increased risk of thrombosis (OR 1.92, 95% CI 1.45-2.53), both of venous (OR 2.49, 95% CI 1.71-3.61) and arterial (OR 1.77, 95% CI 1.29-2.43) vessels. In idiopathic myelofibrosis patients, the risk of thrombosis associated with V617F Jak-2 tended to be increased (OR 1.76, 95% CI 0.91-3.41).

CONCLUSIONS

Our systematic review suggests that V617F Jak-2 increases the risk of thrombosis in essential thrombocythaemia patients by about two fold while its role in idiopathic myelofibrosis patients is uncertain.

JAK2V617F and prothrombin G20210A gene mutations in a patient with Budd-Chiari syndrome and essential thrombocythemia

Myeloproliferative disorders and the inherited thrombophilias have been described as the main causes underlying the Budd-Chiari syndrome. Moreover, the presence of the JAK2V617F was associated with a higher frequency of Budd-Chiari syndrome in patients who have overt or even latent myeloproliferative disorder. We herein describe a 28-year-old woman who was diagnosed with Budd-Chiari syndrome and later developed an overt myeloproliferative disorder. The patient was found to carry both the JAK2V617F and the prothrombin G20210A mutation in the heterozygous form. The significance of the chronology of diagnosis is highlighted.

Automated JAK2V617F quantification using a magnetic filtration system and sequence-specific primer-single molecule fluorescence detection

We established an automated mutational analysis detection system using magnetic filtration and the sequence-specific primer-single molecule fluorescence detection (SSP-SMFD) assay to identify the janus activating kinase-2 (JAK2)(V617F). DNA was extracted from 100 microL of whole blood automatically by a magnetic filtration system. The JAK2 1849G-->T mutation occurs in chronic myeloproliferative disorder (CMPD), and the detection of this change has diagnostic potential. To detect and semiquantitate this mutation, we used two artificial oligonucleotides (wild-type specific and mutated-type specific) and performed the SSP-SMFD assay using an automated fluorescence cell sorter measuring device. The SSP-SMFD assay can detect the presence of a minimum of 5% of the mutated artificial oligonucleotide, thus indicating that this technique is available in detecting contamination of at least 5% cells with the homozygous JAK2(V617F) mutation. Based on this technique, we analyzed 94 patients with CMPD and compared with the results obtained by the polymerase chain reaction (PCR)-direct sequence. Two homozygous JAK2(V617F) patients were identified as heterozygous JAK2(V617F) by the PCR-direct sequence, and four patients judged as wild-type JAK2 by the PCR-direct sequence were identified as heterozygous JAK2(V617F) by the SSP-SMFD method. Our automated system is simple and suitable for high-throughput analysis in detecting JAK2(V617F) with a threshold detection limit of 5%.

Advances in hemorrhagic stroke therapy: conventional and novel approaches

Treatments for spontaneous intracerebral, thrombolytic-induced and intraventricular hemorrhages (IVH) are still at the preclinical or early clinical investigational stages. There has been some renewed interest in the use of surgical evacuation surgery or thrombolytics to remove hematomas, but these techniques can be used only for specific types of brain bleeding. The STICH (Surgical Trial in Intracerebral Haemorrhage) clinical trials should provide some insight into the potential for such techniques to counteract hematoma-induced damage and subsequently, morbidity and mortality. More recently, clinical trials (ATACH [Antihypertensive Treatment in Acute Cerebral Hemorrhage] and INTERACT [Intensive Blood Pressure Reduction in Acute Cerebral Hemorrhage Trial]) have begun testing whether or not regulating blood pressure affects the well-being of hemorrhage patients, but the findings thus far have not conclusively demonstrated a positive result. More promising trials, such as the early stage CHANT (Cerebral Hemorrhagic And NXY-059 Treatment) and the late stage FAST (Factor VIIa for Acute Hemorrhagic Stroke Treatment), have addressed whether or not manipulating oxidative stress and components of the blood coagulation cascade can achieve an improved prognosis following spontaneous hemorrhages. However, CHANT was halted prematurely because although it showed that the spin trap agent NXY-059 was safe, it also demonstrated that the drug was ineffective in treating acute ischemic stroke. In addition, the recombinant activated factor VII FAST trial recently concluded with only modestly positive results. Despite a beneficial effect on the primary end point of reducing hemorrhage volume, controlling the coagulation cascade with recombinant factor VIIa did not decrease the mortality rate. Consequently, Novo Nordisk has abandoned further development of the drug for the treatment of intracerebral hemorrhaging. Even though progress in hemorrhage therapy that successfully reduces the escalating morbidity and mortality rate associated with brain bleeding is slow, perseverance and applied translational drug development will eventually be productive. The urgent need for such therapy becomes more evident in light of concerns related to uncontrolled high blood pressure in the general population, increased use of blood thinners by the elderly (e.g., warfarin) and thrombolytics by acute ischemic stroke patients, respectively. The future of drug development for hemorrhage may require a multifaceted approach, such as combining drugs with diverse mechanisms of action. Because of the substantial benefit of factor VIIa in reducing hemorrhage volume, it should be considered as a prime drug candidate included in combination therapy as an off-label use if the FAST trial proves that the risk of thromboembolic events is not increased with drug administration. Other promising drugs that may be considered in combination include uncompetitive NMDA receptor antagonists (such as memantine), antioxidants, metalloprotease inhibitors, statins and erythropoietin analogs, all of which have been shown to reduce hemorrhage and behavioral deficits in one or more animal models.

[Polycythemia vera and JAK-2 mutation in childhood: a case report]

Erythrocytosis is a rare disorder in childhood and is mainly secondary to causes such as long-term chronic cardiopulmonary diseases or haemoglobin dysfunction. In some cases, polycythaemia is found when renal, hepatic or cerebellar tumours are diagnosed. Polycythemia vera (PV) is uncommon in paediatrics and usually clinical and biological features are used to diagnose and classify PV. The V617F mutation of JAK-2 has been described recently and is found in almost 90% of adult patients with PV. This mutation allows now a reliable and early diagnosis. Therapeutic management is based on phlebotomy and cytoreductive therapy. In young adults and children, interferon alpha is theoretically superior as it is effective and there is no risk of inducing leukemia. We report here a case of PV in a 10-year-old girl with the V617F JAK-2 mutation.

Essential versus reactive thrombocythemia in children: retrospective analyses of 12 cases

BACKGROUND

Essential thrombocythemia (ET) rarely occurs in the pediatric population and little is known about the clinical course and the molecular characteristics.

PROCEDURE

In this retrospective multi-institutional study we examine the clinical, hematological, and molecular features of 12 children aged 5-16 years with thrombocytosis and a suspected diagnosis of ET.

RESULTS

Median follow-up was 59 months (range 10-72). Seven patients presented with clinical symptoms potentially related to thrombocytosis. The remaining five patients were diagnosed incidentally. Median platelet count at diagnosis was 1,325 x 10(9)/L (range 600-3,050). In 11 out of 12 cases bone marrow morphology was consistent with ET, the remaining patient had chronic idiopathic myelofibrosis. Cytogenetic analyses were normal in all studied cases and only one out of nine analyzed cases harbored a JAK(V617F) allele. Within 6 months after initial presentation one patient who was initially asymptomatic developed thrombosis and another patient had mild bleeding. Eight patients were treated with acetylsalicylic acid, one patient received hydroxyurea, and two patients received anagrelide. At last follow-up, all patients were alive and none had developed leukemia. Five patients experienced hematological remission. Two children had not received any therapy. During the course of their disease, nine patients developed symptoms possibly attributable to an elevated platelet count.

CONCLUSIONS

In JAK2 mutation negative cases, long-term follow-up is helpful to distinguish between primary and secondary thrombocytosis. Secondary cases are not associated with organomegaly but may present with unspecific symptoms. Indications for treatment in children remain unclear.

Analysis of JAK2(V617F) mutation in Chinese patients with myeloproliferative disorders

It is now well-recognized that the activating JAK2(V617F) mutation occurs in the majority of patients with polycythemia vera (PV) and approximately half of those with either essential thrombocythemia (ET) or myelofibrosis with myeloid metaplasia (MMM). Here we analyzed JAK2(V617F) mutation in 137 Chinese patients with myeloproliferative disorders by allele-specific polymerase chain reaction (PCR). DNA was extracted from methanol/acetic acid-fixed cells that had been routinely prepared for cytogenetic analysis. A single point mutation (Val617Phe) was identified in JAK2 in 42 (73.7%) of 57 patients with PV, 40 (58.8%) of 68 with ET, and eight (66.7%) of 12 with MMM.

Quantitative determination of JAK2 V617F by TaqMan: An absolute measure of averaged copies per cell that may be associated with the different types of myeloproliferative disorders

We report a novel TaqMan assay for JAK2 V617F that measures averaged copies per cell in absolute terms, as opposed to a ratio of mutant to wild-type alleles. Measurements were obtained by comparing the JAK2 V617F signal generated by the test samples to that generated by a set of external plasmid standards containing the sequence of interest. Specificity of the assay was demonstrated above 36 cycles of amplification, and endpoint titration experiments indicated sensitivity down to 0.05% clinical dilutions. The test measured linearly over a wide logarithmic range and exhibited good reproducibility. Combination of this assay with another TaqMan method for determining cell number allowed identification of 14 cases of myeloproliferative disease with greater than two copies per cell. Mutational frequency was 68% among polycythemia vera (n=44), 59% (n=37) among essential thrombocythemia and 46% (n=13) among idiopathic myelofibrosis. Levels of the mutation were significantly higher in polycythemia vera compared with essential thrombocythemia (P=0.0005) and correlated with the following jointly significant variables at diagnosis: PRV-1, hemoglobin, white cell count, neutrophil count, and red cell count, using multiple regression analyses (P=0.015). This method should be useful for assessing the relationship of gene dose to phenotype and possibly for monitoring therapy.

Increased risk of pregnancy complications in patients with essential thrombocythemia carrying the JAK2 (617V>F) mutation

Essential thrombocythemia (ET) may occur in women of childbearing age. To investigate the risk of pregnancy complications, we studied 103 pregnancies that occurred in 62 women with ET. The 2-tailed Fisher exact test showed that pregnancy outcome was independent from that of a previous pregnancy. The rate of live birth was 64%, and 51% of pregnancies were uneventful. Maternal complications occurred in 9%, while fetal complications occurred in 40% of pregnancies. The Mantel-Haenszel method showed that fetal loss in women with ET was 3.4-fold higher (95% confidence interval [CI]: 3-3.9; P < .001) than in the general population. Half of the women studied carried the JAK2 (617V>F) mutation, and a multivariate logistic regression model identified this mutation as an independent predictor of pregnancy complications (P = .01). Neither the platelet count nor the leukocyte count was a risk factor. JAK2 (617V>F)-positive patients had an odds ratio of 2.02 (95% CI: 1.1 - 3.8) of developing complications in comparison with JAK2 (617V>F)-negative patients. Aspirin did not prevent complication in JAK2 (617V>F)-positive patients and appeared to worsen outcome in JAK2 (617V>F)-negative patients. A relationship was found between JAK2 (617V>F) and fetal loss (P = .05). This study indicates that patients carrying the JAK2 (617V>F) mutation have higher risk of developing pregnancy complications.

Unrestrained erythroblast development in Nix-/- mice reveals a mechanism for apoptotic modulation of erythropoiesis

Normal production of RBCs requires that the antiapoptotic protein Bcl-xl be induced at end stages of differentiation in response to erythropoietin (Epo) signaling. The critical proapoptotic pathways inhibited by Bcl-xl in erythroblasts are unknown. We used gene targeting in the mouse to evaluate the BH3-only factor Nix, which is transcriptionally up-regulated during Epo-stimulated in vitro erythrocyte differentiation. Nix null mice are viable and fertile. Peripheral blood counts revealed a profound reticulocytosis and thrombocytosis despite normal serum Epo levels and blood oxygen tension. Nix null mice exhibited massive splenomegaly, with splenic and bone marrow erythroblastosis and reduced apoptosis in vivo during erythrocyte maturation. Hematopoietic progenitor populations were unaffected. Cultured Nix null erythroid cells were hypersensitive to Epo and resistant to apoptosis stimulated by cytokine deprivation and calcium ionophore. Transcriptional profiling of Nix null spleens revealed increased expression of cell cycle and erythroid genes, including Bcl-xl, and diminished expression of cell death and B cell-related genes. Thus, cell-autonomous Nix-mediated apoptosis in opposition to the Epo-induced erythroblast survival pathway appears indispensable for regulation of erythrocyte production and maintenance of hematological homeostasis. These results suggest that physiological codependence and coordinated regulation of pro- and antiapoptotic Bcl2 family members may represent a general regulatory paradigm in hematopoiesis.

Absence of FTL3 mutations in patients with JAK2V617F mutation negative essential thrombocythemia

A common point mutation in the JAK2 tyrosine kinase leads to constitutive hematopoietic growth factor receptor signaling and was recently described in many patients with myeloproliferative disorders (MPDs). However, this JAK2 mutation is present in only a subset (35-50%) of patients with essential thrombocythemia (ET). Thus, the proliferative signals responsible for MPDs in the absence of JAK2 mutations remain largely unknown. Despite intriguing pre-clinical data, where transgenic mice overexpressing FLT3-ITD developed a MPD resembling ET, none of the patient samples from ET patients who were JAK2(V617F)-negative demonstrated the presence of activating mutations in the FLT3 receptor.

The treatment of polycythaemia vera: an update in the JAK2 era

The clinical course of polycythaemia vera is marked by a high incidence of thrombotic complications, which represent the main cause of morbidity and mortality. Major predictors of vascular events are increasing age and previous thrombosis. Myelosuppressive drugs can reduce the rate of thrombosis, but there is concern that their use raises the risk of transformation into acute leukaemia. To tackle this dilemma, a risk-oriented management strategy is recommended. Low-risk patients should be treated with phlebotomy and low-dose aspirin. Cytotoxic therapy is indicated in high-risk patients, with the drug of choice being hydroxyurea because its leukaemogenicity is low. The recent discovery of JAK2 V617F mutation in the vast majority of polycythaemia vera patients opens new avenues for the treatment of this disease. Novel therapeutic options theoretically devoid of leukaemic risk, such as alpha-interferon and imatinib, affect JAK2 expression in some patients. Nevertheless, these drugs require further clinical experience and, for the time being, should be reserved for selected cases.

How I treat patients with polycythemia vera

The clinical course of polycythemia vera (PV) is marked by a high incidence of thrombotic complications; fibrotic and leukemic disease transformations are additional causes of morbidity and mortality. Major predictors of vascular events are increasing age and previous thrombosis; leukocytosis and high JAK2 V617F allele burden are currently being investigated for additional prognostic value in this regard. Myelosuppressive drugs can reduce the rate of thrombosis, but there is concern that their use raises the risk of transformation into acute leukemia. To tackle this dilemma, a risk-oriented management strategy is recommended. Low-risk patients should be treated with phlebotomy and low-dose aspirin. Cytotoxic therapy is indicated in high-risk patients, and the drug of choice is hydroxyurea because of its efficacy in preventing thrombosis and low leukemogenicity. Interferon-alpha should be reserved for selected categories of patients due to high cost and toxicity. The demonstration of JAK2 V617F mutation in the vast majority of PV patients opens the avenue for the development of promising new molecularly targeted drugs.

Epigenetic alterations complement mutation of JAK2 tyrosine kinase in patients with BCR/ABL-negative myeloproliferative disorders

An acquired autoactivating mutation with a V617F amino-acid substitution in the JAK2 tyrosine kinase is frequently found in BCR/ABL-negative myeloproliferative disorders (MPD). Hypermethylation of CpG islands within gene promoter regions is associated with transcriptional inactivation and represents an important mechanism of gene silencing in the pathogenesis of hematopoietic malignancies. In this study, we determined the DNA methylation status of 13 cancer-related genes in the context of JAK2 mutations in 39 patients with MPD. Genes analyzed for hypermethylation were SOCS-1, SHP-1, E-cadherin, MGMT, TIMP-2, TIMP-3, p15, p16, p73, DAPK1, RASSF1A, RARbeta2 and hMLH1. We found at least one hypermethylated gene in 15/39 MPD patient specimens, and in 6/39 samples aberrant methylation of the negative cytokine regulator SOCS-1 was present. The JAK2V617F mutation was found in 21/39 patients as determined by allele-specific polymerase chain reaction. Hypermethylation of SOCS-1 was observed in 3/21 patients with an autoactivating JAK2 mutation and in 3/18 patients with wild-type JAK2. Our results suggest that epigenetic inactivation of SOCS-1 may be a complementary mechanism to the JAK2V617F mutation in the pathogenesis of MPD that leads to dysregulation of JAK-STAT signal transduction and thus contributes to growth factor hypersensitivity.

Essential thrombocythemia

Essential thrombocythemia (ET) is an acquired myeloproliferative disorder (MPD) characterized by a sustained elevation of platelet number with a tendency for thrombosis and hemorrhage. The prevalence in the general population is approximately 30/100,000. The median age at diagnosis is 65 to 70 years, but the disease may occur at any age. The female to male ratio is about 2:1. The clinical picture is dominated by a predisposition to vascular occlusive events (involving the cerebrovascular, coronary and peripheral circulation) and hemorrhages. Some patients with ET are asymptomatic, others may experience vasomotor (headaches, visual disturbances, lightheadedness, atypical chest pain, distal paresthesias, erythromelalgia), thrombotic, or hemorrhagic disturbances. Arterial and venous thromboses, as well as platelet-mediated transient occlusions of the microcirculation and bleeding, represent the main risks for ET patients. Thromboses of large arteries represent a major cause of mortality associated with ET or can induce severe neurological, cardiac or peripheral artery manifestations. Acute leukemia or myelodysplasia represent only rare and frequently later-onset events. The molecular pathogenesis of ET, which leads to the overproduction of mature blood cells, is similar to that found in other clonal MPDs such as chronic myeloid leukemia, polycythemia vera and myelofibrosis with myeloid metaplasia of the spleen. Polycythemia vera, myelofibrosis with myeloid metaplasia of the spleen and ET are generally associated under the common denomination of Philadelphia (Ph)-negative MPDs. Despite the recent identification of the JAK2 V617F mutation in a subset of patients with Ph-negative MPDs, the detailed pathogenetic mechanism is still a matter of discussion. Therapeutic interventions in ET are limited to decisions concerning the introduction of anti-aggregation therapy and/or starting platelet cytoreduction. The therapeutic value of hydroxycarbamide and aspirin in high risk patients has been supported by controlled studies. Avoiding thromboreduction or opting for anagrelide to postpone the long-term side effects of hydrocarbamide in young or low risk patients represent alternative options. Life expectancy is almost normal and similar to that of a healthy population matched by age and sex.

Switch in X-inactivation in a JAK2 V617F-negative case of polycythemia vera with two acquired X-autosome translocations

We report a JAK2 V617F-negative case of polycythemia vera with two acquired balanced X-autosome translocations and no history of previous exposure to chemo/radiotherapy. The patient's first clone carried a novel translocation t(X;15)(q24;q13) as a sole abnormality. The second clone exhibited an additional translocation, t(X;20)(q13;q13.3), which is a rare recurrent abnormality in myeloid malignancies. This is the first report of a hematological disorder with both X chromosomes being translocated. Late replication studies revealed a switch in X-inactivation from the X chromosome involved in t(X;15) (first clone) to the X chromosome involved in the t(X;20)(q13;q13.3) (second clone). The inactivation of the translocated X chromosomes could provide potential for the inactivation of the adjacent autosomal regions, resulting in epigenetic gene silencing.

Thrombocytosis and thrombosis

The aim of this review is to discuss current diagnostic approaches to, and classification of, patients presenting with thrombocytosis, in light of novel information derived from the discovery of specific molecular abnormalities in chronic myeloproliferative disorders (CMPD), which represent the most common cause of primary thrombocytosis. The JAK2V617F and the MPLW515L/K mutations have been found in patients with essential thrombocythemia, polycythemia vera, and primary myelofibrosis, and less frequently in other myeloproliferative disorders complicated by thrombocytosis. However, neither mutation is disease specific nor is it universally present in patients with elevated platelet counts due to a CMPD; therefore, distinguishing between reactive and primary forms of thrombocytosis, as well as among the different clinical entities that constitute the CMPD, still requires a multifaceted diagnostic approach that includes as a key step the accurate evaluation of bone marrow histology. The role of elevated platelet counts in thrombosis, which represent the predominant complication of CMPD,significantly affecting prognosis and quality of life as well as, paradoxically, in the pathogenesis of the hemorrhagic manifestations, will be discussed. Established and novel potential risk factors for thrombosis, including the clinical relevance of the JAK2V617F mutation, and current management strategies for thrombocytosis are also briefly discussed.

Targeted Cancer Therapy: Promise and Reality

Signal transduction therapy for cancer targets specific molecular elements that are essential for survival of the tumor. Gleevec has a profound effect on early phase chronic myeloid leukemia because it inhibits the major driving factor of the tumor, BCR-ABL. Almost all other cancers depend on several factors, and blocking a single signal transduction factor is largely ineffective. Effective signal transduction therapy will entail finding the appropriate combination of signal transduction inhibitors for each cancer. We discuss the use of preclinical animal models to predict successful signal transduction therapy in the clinic, and conclude that their utility is limited.

The haematocrit and platelet target in polycythemia vera

Polycythemia vera (PV) is a chronic myeloproliferative disorder whose major morbidity and mortality are thrombohaemorragic events and progression to acute leukaemia or myelofibrosis. Whether the haematocrit and platelet count predict such complications remains unclear. The European Collaboration on Low-dose Aspirin in Polycythemia Vera prospective study included 1638 PV patients. A total of 164 deaths (10%), 145 (8.85%) major thrombosis and 226 (13.8%) total thrombosis were encountered during 4393 person-years follow-up (median 2.8 years). In time-dependent multivariable analysis, a haematocrit in the evaluable range of 40-55% was neither associated with the occurrence of thrombotic events, mortality nor with haematological progression in the studied population. The haematocrit of patients in the highest and lowest deciles at baseline was maintained within a narrow interval of haematocrit values ranging from 40% to 47% throughout follow-up. High platelet count was associated with a lower progression rate to acute leukaemia/myelofibrosis, whereas it had no significant relationship with thrombotic events or mortality. Our findings do not suggest that the range of haematocrit (<55%) and platelet counts (<600 x 10(9)/l) we encountered in our population had an impact on the outcome of PV patients treated by current therapeutic strategies.

Leukocytosis is a risk factor for thrombosis in essential thrombocythemia: interaction with treatment, standard risk factors, and Jak2 mutation status

Leukocytes contribute to the pathogenesis of thrombosis in essential thrombocythemia (ET) through recently discovered mechanisms of activation and interaction with platelets and endothelial cells. To evaluate whether an increased leukocyte count was associated with thrombosis and whether this effect can be modulated by therapy, we analyzed the clinical course of 439 patients with ET followed at the Ospedali Riuniti di Bergamo. The strength of the association was measured at diagnosis or before thrombotic events by multivariable analyses carried out using data at baseline as well as time-varying covariates. The results showed that (1) an increased leukocyte count at diagnosis was associated with thrombosis during follow-up (“baseline analysis,” relative risk [RR] 2.3, 95% confidence interval [CI] 1.4-3.9, P = .001); (2) hydroxyurea (HU) lowered leukocytosis and reduced the strength of the association between leukocytosis and thrombosis (“time-dependent analysis,” RR 1.6, 95% CI 0.9-2.0, not significant [NS]); (3) the association of leukocytosis and thrombosis was more evident in untreated low-risk patients (RR 2.7, 95% CI 1.2-6.4, P = .01) compared with HU-treated high-risk patients (RR 1.6, 95% CI 0.8-3.2, NS); and (4) the presence of JAK2 V617F was not identified as a risk factor for thrombosis during follow-up despite a significant association between the mutation and leukocytosis. We suggest validation of these findings in prospective clinical studies.

Polycythemia Vera: New Clinicopathologic Perspectives

Context.—Polycythemia vera (PV) is a clonal myeloproliferative disease characterized by an erythroid dominant trilineage proliferation of hematopoietic precursor cells. Classified as a chronic myeloproliferative disease, PV represents a histopathologic spectrum of 2 recognized stages, the polycythemic and postpolycythemic phase. The clinical manifestations of hemorrhage, thrombosis, and increased red cell mass are directly related to primary bone marrow dysfunction. Prognosis is strongly associated with thrombosis risk and disease progression; thus, treatment is directed toward minimizing coagulopathic complications and preventing leukemic transformation. Recently, a specific point mutation in the Janus kinase 2 (JAK2) gene was described in a majority of PV patients. The potential diagnostic and/or prognostic value of JAK2V617F is discussed.

Objective.—To review important developments from the recent and historical literature. Modern diagnostic criteria and emerging molecular findings are emphasized.

Data Sources.—A comprehensive review was performed of the relevant literature indexed in PubMed (National Library of Medicine) and referenced medical texts.

Conclusions.—Modified clinical, histologic, and laboratory criteria have clarified the diagnosis of PV. Also, continuing studies on the recently discovered JAK2V617F gene mutation may significantly improve our understanding of PV pathogenesis and facilitate its medical management.

Myeloproliferative disease in pregnancy and other management issues

The goal of this review is to assess the current treatment and outcomes of special clinical situations in patients with myeloproliferative disease (MPD) such as pregnancy, major thrombotic and bleeding complications and surgical interventions. However, only a limited literature to support optimal management strategies is available. Many of the proposed strategies are the results of common sense or derive from the extrapolation of data from other studies not specifically designed to solve these problems. Therefore, practical recommendations to guide clinical decisions in these settings still remain largely empirical.