Assessing the thrombotic risk of patients with essential thrombocythemia in the genomic era

Cancer-associated thrombosis in hematologic malignancies

Patients with hematologic malignancies are often complicated not only by severe bleeding due to thrombocytopenia and disseminated intravascular coagulation but also by thromboembolic events, just like in patients with solid cancers, and these events can negatively impact patient outcomes. Nevertheless, the prevention and treatment of cancer-associated thrombosis (CAT) in hematologic malignancies has not been adequately investigated due to the limited size, heterogeneity, and unique pathophysiology of the patient population. This article summarizes the current understanding, risk factors, prediction models, and optimal prevention and treatment strategies of CAT in hematologic malignancies on a disease-by-disease basis, including acute leukemia, lymphoma, myeloma, and myeloproliferative neoplasms. Specific considerations of novel molecular targeted therapeutics introduced in recent years, such as immunomodulatory drugs and tyrosine kinase inhibitors, are also discussed based on the latest clinical trials.

Understanding triple negative myeloproliferative neoplasms: pathogenesis, clinical features, and management

ABSTRACTMyeloproliferative neoplasms (MPNs) that lack the classical "driver mutations," termed triple negative MPNs, remain a poorly understood entity. Despite considerable progress toward understanding MPN pathobiology, the mechanisms leading to the development of these MPNs remains inadequately elucidated. While triple negative primary myelofibrosis (TN-PMF) portends a poor prognosis, triple negative essential thrombocythemia (TN-ET) is more favorable as compared with JAK2 mutated ET. In this review, we summarize the clinical features and prognosis of TN-PMF and -ET as well as diagnostic challenges including identification of non-canonical driver mutations. We also discuss additional molecular drivers to better understand possible pathogenic mechanisms underlying triple negative MPNs. Finally, we highlight current therapeutic approaches as well as novel targets, particularly in the difficult to treat TN-PMF population.

Abdominal venous thromboses: detection of the JAK2 p.V617F mutation by next-generation ultradeep sequencing-A prevalence study of patients in Mecklenburg-West Pomerania (2017-2021)

Background

Abdominal venous thromboses are rare thrombotic events with heterogeneous etiologies. They are related to myeloproliferative neoplasms (MPNs) in some patients and can occur as first signs of the disease. MPNs are characterized by mutations in the genes of Janus kinase 2 (JAK2), myeloproliferative leukemia virus oncogene (MPL), and calreticulin (CALR).

Methods

Within the prospective trial "Prevalence of JAK2 mutations in patients with abdominal venous thromboses" (JAK2 MV study; German Clinical Trials Register: DRKS00026943), the peripheral blood of patients with abdominal venous thromboses in Mecklenburg-West Pomerania, a federal state located in north-east Germany, was analyzed by next-generation ultradeep sequencing for MPN-associated mutations. Clinical characteristics and blood cell counts were also of interest. The primary endpoint was the detection of the mutation JAK2 p.V617F. Secondary endpoints were the detection of other acquired variants of JAK2, as well as MPL and CALR.

Results

A total of 68 patients with abdominal venous thromboses were included from February 2017 to January 2021, with splanchnic veins affected in 65 patients. The mutation JAK2 p.V617F was present in 13 patients (19%), with four patients showing low variant allele frequencies (VAF 0.1% to 1.9%). The time interval from the thrombotic event to analysis was longer for patients with the mutation. The mutation MPL p.W515R was detected in three cases, all of them with low VAF. One patient among them had a concurrent mutation of JAK2 p.V617F. The mutations CALR type I or type II were not found.

Discussion

By analyzing peripheral blood for the mutation JAK2 p.V617F, an important cause of these rare thrombotic events can be identified. The development of a diagnostic workup with next-generation ultradeep sequencing for the analysis of the JAK2 p.V617F mutation and further mutations has the potential to better understand the etiology of abdominal venous thromboses in individual patients in regional clinical care, as abdominal venous thromboses are diagnosed by various medical disciplines.

Retinal neovascularization in the setting of CALR-mutation positive essential thrombocythemia

Patients with Calreticulin (CALR) mutation positive essential thrombocythemia are often thought of as having a "low-risk" of thrombotic complications. This report examines a case of a patient with CALR-mutation positive essential thrombocythemia presenting with peripheral retinal ischemia and subsequent retinal neovascularization. This patient had a 2-year documented history of CALR-mutation positive essential thrombocythemia with a maximum platelet count of over 800,000 cells/µL. Fluorescein angiogram showed significant leakage in the areas of the vascular lesions with peripheral vascular nonperfusion consistent with neovascularization. The patient was treated with photocoagulation to the areas of avascular retina. At 6-month follow-up, some regression of neovascularization was noted with no signs of progression in the retinopathy. Furthermore, essential thrombocythemia patients can present with neovascularization secondary to retinal ischemia due to microvascular thrombotic events. Identification of these changes is important for guiding medical and procedural interventions in order to preserve vision.

Molecular Genetics of Thrombotic Myeloproliferative Neoplasms: Implications in Precision Oncology

Classical BCR-ABL-negative myeloproliferative neoplasms (MPN) include polycythaemia vera, essential thrombocythaemia, and primary myelofibrosis. Unlike monogenic disorders, a more complicated series of genetic mutations are believed to be responsible for MPN with various degrees of thromboembolic and bleeding complications. Thrombosis is one of the early manifestations in patients with MPN. To date, the driver genes responsible for MPN include JAK2, CALR, MPL, TET2, ASXL1, and MTHFR. Affords have been done to elucidate these mutations and the incidence of thromboembolic events. Several lines of evidence indicate that mutations in JAK2, MPL, TET2 and ASXL1 gene and polymorphisms in several clotting factors (GPIa, GPIIa, and GPIIIa) are associated with the occurrence and prevalence of thrombosis in MPN patients. Some polymorphisms within XRCC1, FBG, F2, F5, F7, F12, MMP9, HPA5, MTHFR, SDF-1, FAS, FASL, TERT, ACE, and TLR4 genes may also play a role in MPN manifestation. This review aims to provide an insightful overview on the genetic perspective of thrombotic complications in patients with MPN.

Hematological relevance of JAK2 V617F and calreticulin mutations in Tunisian patients with essential thrombocythemia

Background

The genetic investigation of essential thrombocythemia(ET) has highlighted the presence of driver mutations in ET. Janus kinase JAK2V617F and calreticulin(CALR) mutations are the most frequent driver mutations and have significantly improved the molecular diagnosis of ET. The impact of genetic heterogeneity on clinical features has not been fully elucidated.

This is the first study which aimed to determine the frequency of JAK2V617F and CALR exon9 mutations in Tunisian ET patients and to establish the correlation between hematological characteristics and mutational status.

Methods

This study included Tunisian patients suspected with ET and was conducted between September 2017 and March 2021. Genomic DNA of patients was isolated from peripheral blood samples. JAK2V617F was detected by AS‐PCR and CALR mutations were detected by PCR/direct sequencing. Clinical and hematological characteristics were also analyzed.

Results

Two hundred and fifty ET patients were enrolled in this study. JAK2V617F mutation was found in 166/250 (66.4%) of patients, whereas CALR mutations were detected in 27/84 (32.1%) patients without JAK2V617F. Compared with JAK2V617F‐positive patients, those with CALR mutations showed lower hemoglobin level and lower leucocytes count (p = 0.007 and p = 0.004,respectively). CALR type 2 was the most frequent mutation of CALR detected in 55.55% of CALR mutated. Six of seven patients with thrombotic events harbored JAK2V617F mutation.

Conclusion

The prevalence of driver mutations JAK2V617F or CALR mutations was 77.2% in Tunisian ET patients. Moreover, patients with JAK2 V617F mutation had a higher risk of thrombosis. The mutational status is necessary to improve the diagnosis and contribute to the therapeutic decisions.

Acute Limb Ischemia in the Young: A Rare Case of Essential Thrombocytosis

Acute limb ischemia (ALI) is rarely observed in young populations. The hypercoagulable state is a notable cause of ALI other than artery disease progression and cardiac embolization. A hypercoagulable state occurs in essential thrombocytosis because of the overproduction of hematopoietic cells secondary to the mutation of the JAK2, CALR, or MPL genes. We report a rare case of a 37-year-old woman presenting with Rutherford IIA ALI in the left lower extremity. Laboratory data revealed she had a platelet count reaching up to 1.38 mil/μL, with other blood profiles being normal. A JAK2 mutation examination was later performed and proved positive. After careful management with catheter-directed thrombolysis, surgical thrombectomy, and cytoreductive therapy using hydroxyurea, the symptoms subsided and eventually restored the patient to physical activity in less than one month.

The risk of thrombosis in essential thrombocythemia is associated with the type of CALR mutation: A multicentre collaborative study

OBJECTIVES

In patients with essential thrombocythemia (ET), after the JAK2V617F driver mutation, mutations in CALR are common (classified as type 1, 52-bp deletion or type 2, 5-bp insertion). CALR mutations have generally been associated with a lower risk of thrombosis. This study aimed to confirm the impact of CALR mutation type on thrombotic risk.

METHODS

We retrospectively investigated 983 ET patients diagnosed in Spanish and Polish hospitals.

RESULTS

With 7.5 years of median follow-up from diagnosis, 155 patients (15.8%) had one or more thrombotic event. The 5-year thrombosis-free survival (TFS) rate was 83.8%, 91.6% and 93.9% for the JAK2V617F, CALR-type 1 and CALR-type 2 groups, respectively (P = .002). Comparing CALR-type 1 and CALR-type 2 groups, TFS for venous thrombosis was lower in CALR-type 1 (P = .046), with no difference in TFS for arterial thrombosis observed. The cumulative incidence of thrombosis was significantly different comparing JAK2V617F vs CALR-type 2 groups but not JAK2V617F vs CALR-type 1 groups. Moreover, CALR-type 2 mutation was a statistically significant protective factor for thrombosis with respect to JAK2V617F in multivariate logistic regression (OR: 0.45, P = .04) adjusted by age.

CONCLUSIONS

Our results suggest that CALR mutation type has prognostic value for the stratification of thrombotic risk in ET patients.

Correlation Between PAI-1 Gene 4G/5G Polymorphism and the Risk of Thrombosis in Ph Chromosome-Negative Myeloproliferative Neoplasms

Thrombosis has been recognized as one of the most significant risk factors of high mortality and disability in patients with Philadelphia (Ph) chromosome negative myeloproliferative neoplasms (MPNs). However, the risk factors of thrombotic events in these patients have not been completely understood. In this study, the clinical data of 58 patients with Ph-MPNs were obtained and analyzed, including 34 cases of essential thrombocytopenia (ET), 23 thrombotic events happened in 21 (36%) patients, among which 60% (14 of 23) with cerebral infarction, 17% (4 of 23) with coronary heart disease and 23% (5 of 23) with venous thrombosis. There were no significant differences in age, sex, and blood cell count between polycythemia vera (PV) and ET patients who have experienced thrombotic events and those who have not. In ET patients, the incidence of thrombotic events in plasminogen activator inhibitor-1 (PAI-1) genotype 4G4G was significantly higher than that in genotype 4G5G and genotype 5G5G (P < .05). The incidence of thrombotic events in PV and ET patients with infection was higher than those without infection (P < .05). Using logistic regression analysis, we found that PAI-1 genotype 4G4G and infection were associated with thrombotic events (odds ratio 6.744, 95% CI: 1.195-38.056 and 15.641 95% CI: 3.327-73.522). The 4G/4G polymorphism of PAI-1 gene and infection are independent risk factors of thrombotic events in patients with Ph-MPNs. PAI-1 gene 4G4G and infection in ET and PV patients with Janus kinase 2 (JAK2) V617F mutation were shown to be high risk of thrombotic events. Therefore, clinical doctors should put more attention on PAI-1 genotype 4G4G and infection in JAK2 V617F mutated patients with Ph-MPNs to prevent the thrombosis.

Thrombophilic Risk of Factor V Leiden, Prothrombin G20210A, MTHFR, and Calreticulin Mutations in Essential Thrombocythemia Egyptian Patients

Objectives

Essential thrombocythemia (ET) is one of the myeloproliferative neoplasms characterized by a sustained elevation of platelet numbers with a tendency for thrombosis and hemorrhage. The aim of this work is to establish the relation between calreticulin, factor V Leiden, prothrombin G20210A, and MTHFR mutations in ET patients and the thrombotic risk of these patients.

Methods

This study was carried out on 120 ET patients and 40 apparently healthy individuals as a control group.

Results

There were increases in WBCs, PLT counts, PT, fibrinogen concentration factor V Leiden, and MTHFR mutation in ET patients as compared to the control group (P < 0.05). Also, there were increases in WBCs, PLT counts, and hematocrit value in thrombosed ET patients as compared to the nonthrombosed ones (P < 0.05). On the contrary, there was no significantly statistical difference in ET patients with JAK2 V617F positive mutation versus the JAK2 negative group (P > 0.05) and in patients with cardiovascular risk factors versus patients with noncardiovascular risk factors (P > 0.05). ET patients with factor V Leiden, prothrombin gene, and CALR mutations were more prone to thrombosis (odds ratio 5.6, 5.7 and 4.7, respectively). On the contrary, JAk2V 617F and MTHFR mutations have no effect on the thrombotic state of those patients.

Conclusion

There is a significant increase risk of thrombosis in ET patients with CALR mutation, thrombophilic mutations, as well as factor V Leiden and prothrombin gene mutation with a risk of developing leukemic transformation.

Thrombotic, inflammatory, and HIF-regulated genes and thrombosis risk in polycythemia vera and essential thrombocythemia

Thrombosis is a major cause of morbidity and mortality in polycythemia vera (PV) and essential thrombocythemia (ET). The pathophysiology of thrombosis in these disorders remains unclear, and we hypothesized that upregulation of thrombotic, inflammatory, and hypoxia-inducible factor (HIF)-regulated genes may play a role in it. We performed unbiased RNA sequencing in granulocytes and platelets of PV patients and found differential expression of several thrombotic, inflammatory, and HIF-regulated genes. The expression of many of these genes positively correlated with JAK2 expression and JAK2V617F allelic burden. We then validated these findings by quantitative polymerase chain reaction analyses of selected gene transcripts in a larger number of PV and ET granulocytes and platelets (58 patients) and in 28 controls, and we compared these findings in patients with and without thrombosis. The study included 29 females and 29 males; of these, 28 had a history of thrombosis. We found that transcripts of several selected genes were upregulated in patients with PV or ET compared with controls. In granulocytes, the expression levels of F3, SELP, VEGFA, and SLC2A1 were significantly higher in patients with a history of thrombosis compared with those who did not have thrombosis. Patients with a history of thrombosis have significantly higher expression of IL1RAP (P < .05) in platelets compared with those without thrombosis. Our study confirms the presence of a thrombo-inflammatory state and augmented HIF activity in PV and ET and its role in thrombosis. These data may provide the background for targeted therapies in PV and ET.

Thrombosis among 1537 patients with JAK2V617F -mutated myeloproliferative neoplasms: Risk factors and development of a predictive model

To explore the risk factors of thrombosis in patients with JAK2^V617F‐mutated myeloproliferative neoplasms (MPNs), a cohort of 1537 Chinese patients with JAK2^V617F‐mutated MPN was retrospectively analyzed. The Kaplan‐Meier method and multivariate Cox analysis were used to study the risk factors of thrombosis in patients with JAK2^V617F‐mutated MPN. Among the 1537 MPN patients, 931, 468, and 138 had polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), respectively. The median follow‐up time was 7 years (range 1‐47), and 12.8% of patients (197/1537) died during this period. A total of 16.8% (259/1399) of PV and ET patients had secondary myelofibrosis, and 2.5% (38/1537) of patients developed acute myeloid leukemia (AML). Thrombotic events occurred in 43.9% (675/1537) of patients, among which 91.4% (617/675) were arterial thrombosis and 16.6% (112/675) were venous thrombosis. The number of thrombotic events in PV, ET, and PMF patients was 439 (47.2%), 197 (42.1%) and 39 (28.2%), respectively. The multivariate analysis indicated that age ≥60 years old, HCT ≥48%, at least one cardiovascular risk factor, a history of thrombosis, and JAK2^V617F allele burden (V617F%) ≥50% are risk factors for thrombosis in JAK2^V617F‐mutated MPN. According to the results of the multivariate analysis, a risk model of thrombosis was established and comprised low‐risk (0 points), intermediate‐risk (1 points) and high‐risk (≥2 points) groups, among which the incidence of thrombosis was 9.1%, 33.7% and 72.9%. For elderly patients with JAK2^V617F‐mutated MPN and a history of thrombosis, reducing the V617F%, controlling HCT and preventing cardiovascular risk factors are necessary measures to prevent thrombosis.

Calreticulin mutation specific CAL2 immunohistochemistry accurately identifies rare calreticulin mutations in myeloproliferative neoplasms

Mutations of the multifunctional protein calreticulin (CALR) are recognised as one of the main driver alterations involved in the pathogenesis of Philadelphia negative myeloproliferative neoplasms (Ph^- MPN) and also represent a major diagnostic criterion in the most recent World Health Organization classification of myeloid neoplasms. Nowadays, quantitative assessment of the driver mutations is gaining importance, as recent studies demonstrated the clinical relevance of the mutation load reflecting the size of the mutant clone. Here, we performed for the first time a manual and automated quantitative assessment of the CALR mutation load at protein level using CAL2, a recently developed CALR mutation specific monoclonal antibody, on a cohort of 117 patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF) and compared the CALR protein mutation loads with the CALR mutation load values established by a molecular assay. Eighteen different CALR mutations were detected in the cohort of the 91 CALR mutant cases. Mutation loads of the CALR mutations were between 13% and 94% with mean value in PMF cases significantly higher than ET cases (49.94 vs 41.09; t-test, p=0.004). Cases without CALR mutation (n=26) showed no or only minimal labelling with the CAL2 antibody, while all 18 different types of CALR mutations were associated with CAL2 labelling. The CALR mutation load showed a significant correlation (p=0.03) with the occurrence of major thrombotic events, with higher mutation load in patients presenting with these complications. We report a 100% concordance between the mutation status determined by immunohistochemistry and the CALR molecular assay, and we extend the applicability of this approach to 16 rare CALR mutations previously not analysed at protein level.

A spotlight on the management of complications associated with myeloproliferative neoplasms: a clinician's perspective

INTRODUCTION

Myeloproliferative neoplasms (MPNs) are associated with a variety of symptoms and signs which cause major morbidity for the patients. The disorders are associated with increased incidence of thromboembolic and hemorrhagic events which can lead to complications and shortened life expectancy. Areas covered: Using systematic literature review and expert clinical and research experience the authors discuss strategies for the management of symptoms and signs including pruritus, fatigue, splenomegaly, and cytopenia. Cytoreduction including treatments to inhibit the JAK/STAT pathway are considered. Pathogenesis and prevention and treatment of thrombotic and hemorrhagic events and their management is addressed and the suggested management of the special situations such as surgery and pregnancy are discussed. Expert commentary: Management of disease has traditionally focused on symptom treatment and complication prevention but the discovery of driver mutations has led to treatments aiming to eliminate the clone, which should be the ultimate goal of therapy. A future challenge is to develop safe and effective MPN therapy and to personalize therapy.