Plasma levels of angiogenic factors and circulating endothelial cells in essential thrombocythemia: correlation with cytoreductive therapy and JAK2-V617F mutational status

Liquid Biopsy and Potential Liquid Biopsy-Based Biomarkers in Philadelphia-Negative Classical Myeloproliferative Neoplasms: A Systematic Review

Myeloproliferative neoplasms (MPNs) are rare, clonal disorders of the hematopoietic stem cell in which an uncontrolled proliferation of terminally differentiated myeloid cells is noted. Polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) are included in the category of Philadelphia-negative, so-called classical MPNs. The potential applications of liquid biopsy and liquid biopsy-based biomarkers have not been explored in MPNs until now. Thus, a systematic search was computed in PubMed/MEDLINE, Web of Science and The Cochrane Library and, in total, 198 potentially relevant papers were detected. Following the removal of duplicates (n = 85), 113 records were screened. After the exclusion of irrelevant manuscripts based on the screening of their titles and abstracts (n = 81), we examined the full texts of 33 manuscripts. Finally, after we applied the exclusion and inclusion criteria, 27 original articles were included in this review. Overall, the data analyzed in this review point out that liquid biopsy and liquid biopsy-based biomarkers (cell-free DNA, extracellular vesicles, microparticles, circulating endothelial cells) could be used in MPNs for diagnostic and prognostic purposes. Future research is needed to clarify whether this technique can be employed to differentiate between MPN subtypes and secondary causes of erythrocytosis, thrombocytosis and myelofibrosis, as well as to predict the development of thrombosis.

Pathogenesis of cardiovascular events in BCR-ABL1-negative myeloproliferative neoplasms

Thrombosis, both in arterial and venous territories, is the major complication of myeloproliferative neoplasms and is responsible for a high rate of morbidity and mortality. The currently accepted risk factors are an age over 60 years and a history of thrombosis. However, many complex mechanisms contribute to this increased prothrombotic risk, with involvement of all blood cell types, plasmatic factors, and endothelial cells. Besides, some cardiovascular events may originate from arterial vasospasm that could contribute to thrombotic complications. In this review, we discuss recent results obtained in mouse models in the light of data obtained from clinical studies. We emphasize on actors of thrombosis that are currently not targeted with current therapeutics but could be promising targets, i.e, neutrophil extracellular traps and vascular reactivity.

[Thrombosis and platelet dysfunction in myeloproliferative neoplasms]

Myeloproliferative neoplasms are acquired hematological malignancies, mainly affecting the adult and whose morbidity and mortality stems from haemostasis disorders. The most frequently encountered complications include thrombosis, affecting preferentially the arterial territory, but also atypical locations such as splanchnic vein thrombosis. The pathophysiology of these thromboses is complex and involves different actors: blood cells, endothelium and flow conditions. Numerous studies have been conducted to identify risk factors for thrombosis. To date, only two risk factors have been validated through prospective studies (age over 60 years old, history of thrombotic events) and allow classification of patients as "low risk" and "high risk" as the basis for current treatment recommendations. Haemorrhagic manifestations, less frequent than thrombosis, are mainly related to an alteration of primary haemostasis and are therefore manifested by mucocutaneous bleeding. In these patients, platelet dysfunctions and/or acquired Willebrand syndromes can be found. The pathophysiology of thrombosis and platelet dysfunction during myeloproliferative neoplasms remains to date partially unknown. In this review, we offer to focus on physiopathological mechanisms as well as the latest advances in their understanding.

Angiogenesis in JAK2 V617F positive myeloproliferative neoplasms and ruxolitinib decrease VEGF, HIF-1 enesis in JAK2 V617F positive cells

Angiogenesis and JAK2 V617F mutation are common in BCR-ABL1 negative myeloproliferative neoplasms (MPNs). Ruxolitinib, a JAK inhibitor, is an effective treatment for some MPNs. However, the relationship between angiogenesis and JAK2 V617F and the effects of ruxolitinib on angiogenesis are still unknown. Here, we observed the correlation of JAK2 V617F mutation burden with VEGF, HIF-1a and microvascular density (MVD) in MPNs. We investigate the effect of ruxolitinib on the expression of VEGF and HIF-1α in JAK2 V617F positive cells. We found the expression levels of p-JAK2, VEGF, HIF-1a and MVD in the newly diagnosed MPNs were significantly increased and were related to the JAK2 V617F burden. Ruxolitinib can inhibit p-JAK2, VEGF, HIF-1a expression and suppress blood vessels' formation in chick embryo choriallantoic membrane. Our findings indicated that angiogenesis is related to JAK2 V617F burden and ruxolitinib could decrease VEGF and HIF-1a expression in JAK2 V617F positive cells.

Angiogenic factors are increased in circulating granulocytes and CD34+ cells of myeloproliferative neoplasms

It has been shown that angiogenesis and inflammation play an important role in development of most hematological malignancies including the myeloproliferative neoplasm (MPN). The aim of this study was to investigate and correlate the levels of key angiogenic molecules such as hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) in peripheral blood and bone marrow cells of MPN patients, along with JAK2V617F mutation allele burden and effects of therapy. HIF-1α and VEGF gene expression were decreased, while eNOS mRNA levels were increased in granulocytes of MPN patients. Furthermore, positively correlated and increased VEGF and eNOS protein levels were in negative correlation with HIF-1α levels in granulocytes of MPN patients. According to immunoblotting, the generally augmented angiogenic factors demonstrated JAK2V617F allele burden dependence only in granulocytes of PMF. The angiogenic factors were largely reduced after hydroxyurea therapy in granulocytes of MPN patients. Levels of eNOS protein expression were stimulated by Calreticulin mutations in granulocytes of essential thrombocythemia. Immunocytochemical analyses of CD34⁺ cells showed a more pronounced enhancement of angiogenic factors than in granulocytes. Increased gene expression linked to the proinflammatory TGFβ and MAPK signaling pathways were detected in CD34⁺ cells of MPN patients. In conclusion, the angiogenesis is increased in several cell types of MPN patients supported by the transcriptional activation of inflammation-related target genes, and is not limited to bone marrow stroma cells. It also appears that some of the benefit of hydroxyurea therapy of the MPN is mediated by effects on angiogenic factors. © 2016 Wiley Periodicals, Inc.

Are MPNs vascular diseases?

A high risk of arterial and venous thrombosis is the hallmark of chronic myeloproliferative neoplasms (MPNs), particularly polycythemia vera (PV) and essential thrombocythemia (ET). Clinical aspects, pathogenesis and management of thrombosis in MPN resemble those of other paradigmatic vascular diseases. The occurrence of venous thrombosis in atypical sites, such as the splanchnic district, and the involvement of plasmatic prothrombotic factors, including an acquired resistance to activated protein C, both link MPN to inherited thrombophilia. Anticoagulants are the drugs of choice for these complications. The pathogenic role of leukocytes and inflammation, and the high mortality rate from arterial occlusions are common features of MPN and atherosclerosis. The efficacy and safety of aspirin in reducing deaths and major thrombosis in PV have been demonstrated in a randomized clinical trial. Finally, the Virchow's triad of impaired blood cells, endothelium and blood flow is shared both by MPN and thrombosis in solid cancer. Phlebotomy and myelosuppressive agents are the current therapeutic options for correcting these abnormalities and reducing thrombosis in this special vascular disease represented by MPN.

The emergence of non-secretory multiple myeloma during the non-cytotoxic treatment of essential thrombocythemia: a case report

Introduction

The emergence of multiple myeloma as a second malignancy in patients with essential thrombocythemia is extremely rare. Several cases have been published so far, pointing out the impact of a cytotoxic effect during treatment of essential thrombocythemia on the development of multiple myeloma.

Case presentation

We report the case of a 52-year-old Caucasian man who presented to our hospital because of leukocytosis, a slightly decreased hemoglobin level and thrombocytosis. After a complete hematological work-up, essential thrombocythemia was diagnosed. The patient was included in a multicenter clinical study, treated with anagrelide and his platelet counts were maintained in the normal range for more than 3 years. A sudden drop in his hemoglobin level with normal leukocyte and platelet count occurred at the same time as a back pain. Magnetic resonance imaging of his spine revealed the existence of a pathological fracture of Th4, the collapse of the upper edge of Th7 and osteolytic lesions of multiple thoracic vertebrae. Repeated hematological examinations, including bone biopsy with immunohistochemistry, disclosed diagnosis of multiple myeloma of the non-secretory type.

Conclusions

To the best of our knowledge this is the first published case in which multiple myeloma developed during the treatment of essential thrombocythemia with the non-cytotoxic drug anagrelide. Our attempts to find a common origin for the coexistence of multiple myeloma and essential thrombocythemia have not confirmed the genetic basis of their appearance. Further studies are needed to determine the biological impact of this coexistence.

Myeloproliferative neoplasms and thrombosis

Major causes of morbidity and mortality in myeloproliferative neoplasms are represented by arterial and venous complications, progression to myelofibrosis, and transformation to acute leukemia. The pathogenesis of thrombosis results from a complex interplay of clinical and disease-related factors. Abnormalities of blood cells arising from the clonal proliferation of hematopoietic stem cells involve not only quantitative changes but also qualitative modifications that characterize the switch of these cells from a resting to a procoagulant phenotype. According to age and previous thrombosis, patients are classified in a "high risk" or "low risk". Novel disease-related determinants such as leukocytosis and JAK2V617F mutational status and/or mutational burden are now under active investigation. In low-risk polycythemia vera patients, only phlebotomy and primary antithrombotic prophylaxis with aspirin is recommended, while in high-risk patients cytotoxic therapy is considered. Whether novel drugs targeting the constitutively active JAK2/STAT pathway will improve the management of thrombosis is a challenge for future studies.

Circulating endothelial cell kinetics and their potential predictive value during mobilization procedure

OBJECTIVE

Circulating endothelial cells (CECs) in patients with hematological malignancies are assessed as a noninvasive marker of angiogenesis. The aim of this study was to evaluate the numbers of CECs and their subsets during mobilization of hematopoietic stem cells.

PATIENTS AND METHODS

Thirty-eight patients were enrolled to the study (19 females and 19 males) at median age of 56.5 years. The group consisted of patients with multiple myeloma (26), lymphoma (10), and acute myeloid leukemia (2). Blood samples were collected before chemotherapy (0), 1 day after chemotherapy (Cht+1), on the day G-CSF commenced (G0), after 1 day of G-CSF (G+1), and on the day of the first apheresis. CECs were evaluated by four-color flow cytometry. Circulating progenitor cells were defined as CD45-/CD34+/CD31+/CD133+. Apoptotic CECs (ApoCECs) were defined as CD146+/AnnexinV+.

RESULTS

Median (Me) CECs number was 10.5/µl and it decreased after chemotherapy (Me = 8.3/µl, P < 0.001 when compared with baseline). Based on the number of aphereses needed to obtain 2 × 10(6)/kg CD34+ cells, patients were divided into "highly efficient" (one apheresis) and "poorly efficient" mobilizers (two or more aphereses). Median ApoCEC at Day G+1 was lower in highly efficient than in poorly efficient mobilizers (Me = 3.1/µl vs. Me = 5.1/µl, P = 0.02). ApoCEC at Day G+1 correlated with the number of aphereses (r = 0.48, P = 0.03). In multivariate analysis, ApoCEC at Day G+1 was an independent factor for successful mobilization during one apheresis.

CONCLUSIONS

CECs and their subsets change significantly during mobilization of HSCs. ApoCECs measured at the time of G-CSF commencement can predict the efficacy of HSC collection.

Thrombotic disease in the myeloproliferative neoplasms

Thrombosis is a leading cause of morbidity and mortality in patients with Philadelphia chromosome–negative myeloproliferative neoplasms (MPNs), particularly polycythemia vera and essential thrombocythemia. Mechanisms involved in the pathogenesis of the acquired thrombophilic state associated with these diseases include abnormalities of MPN clone–derived blood cells, which display prothrombotic features, and abnormalities of normal vascular cells, which become procoagulant in response to inflammatory stimuli. Ultimately, the release into the blood of elevated levels of procoagulant microparticles by platelets and vascular cells and the increase in the global thrombin generation due to an acquired activated protein C resistance result in a highly prothrombotic scenario in patients with polycythemia vera and essential thrombocythemia. The acquired point mutation in the pseudokinase domain of JAK2 (JAK2V617F) in these disorders is variably associated with thrombosis and, more consistently, with elevations in WBC counts and alterations in biomarkers of blood-clotting abnormalities. The predictive value of these biomarkers for thrombosis remains to be established to identify subsets of patients at elevated risk who may benefit from prophylaxis with antithrombotic drugs.