Red Blood Cell Contribution to Thrombosis in Polycythemia Vera and Essential Thrombocythemia.

Polycythemia vera (PV) and essential thrombocythemia (ET) are myeloproliferative neoplasms (MPN) characterized by clonal erythrocytosis and thrombocytosis, respectively. The main goal of therapy in PV and ET is to prevent thrombohemorrhagic complications. Despite a debated notion that red blood cells (RBCs) play a passive and minor role in thrombosis, there has been increasing evidence over the past decades that RBCs may play a biological and clinical role in PV and ET pathophysiology. This review summarizes the main mechanisms that suggest the involvement of PV and ET RBCs in thrombosis, including quantitative and qualitative RBC abnormalities reported in these pathologies. Among these abnormalities, we discuss increased RBC counts and hematocrit, that modulate blood rheology by increasing viscosity, as well as qualitative changes, such as deformability, aggregation, expression of adhesion proteins and phosphatidylserine and release of extracellular microvesicles. While the direct relationship between a high red cell count and thrombosis is well-known, the intrinsic defects of RBCs from PV and ET patients are new contributors that need to be investigated in depth in order to elucidate their role and pave the way for new therapeutical strategies.

JAK2 R683S Mutation Resulting in Dual Diagnoses of Chronic Eosinophilic Leukemia and Myelodysplastic/Myeloproliferative Overlap Syndrome.

A 66-year-old male presented with hypereosinophilia, thrombocytosis, extensive thrombosis refractory to direct oral anticoagulant therapy, and evidence of end-organ damage, including rash, splenic infarcts, and pulmonary infiltrates. Bone marrow biopsy revealed myeloid malignancy consistent with both chronic eosinophilic leukemia and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) with SF3B1 mutation and thrombocytosis. Next-generation sequencing of the patient's eosinophils and neutrophil compartments revealed pathologic variants in EZH2 and SF3B1 in addition to a noncanonical JAK2 R683S mutation that has not been previously described in myeloproliferative disorders or other chronic myeloid neoplasms. These mutations were not present in the patient's lymphoid cell fraction, suggesting that the hematopoietic malignancy arose in a myeloid-committed progenitor cell. Based on this case and previous work from our group, we propose that noncanonical JAK2 mutations may permit signal transduction that biases toward eosinophilic differentiation in chronic myeloid neoplasms. Although the patient's blood counts initially responded to ruxolitinib and hydroxyurea, the response was not durable. Early referral for allogenic bone marrow transplant appears necessary to prevent long-term complications and disease progression in myeloid neoplasms with clonal hypereosinophilia driven by noncanonical JAK2 mutations.

Myelofibrosis-type megakaryocyte dysplasia (MTMD) as a distinct category of BCR::ABL-negative myeloproliferative neoplasms. Challenges and perspectives.

In this Perspective, we discuss criteria for defining a new disease entity or variant of a recognized disease or disorder. We do so in the context of the current topography of the BCR::ABL-negative myeloproliferative neoplasms (MPNs) where two new variants are reported: clonal megakaryocyte dysplasia with normal blood values (CMD-NBV) and clonal megakaryocyte dysplasia with isolated thrombocytosis (CMD-IT). The cardinal feature of these variants is bone marrow megakaryocyte hyperplasia and atypia corresponding the WHO histological criteria for primary myelofibrosis (myelofibrosis-type megakaryocyte dysplasia-MTMD). Persons with these new variants have a different disease course and features from others in the MPN domain. In a broader context we suggest myelofibrosis-type megakaryocyte dysplasia defines a spectrum of related MPN variants including CMD-NBV, CMD-IT, pre-fibrotic myelofibrosis and overt myelofibrosis, which differ from polycythemia vera and essential thrombocythemia. Our proposal needs external validation and we stress the need for a consensus definition of the megakaryocyte dysplasia which is the hallmark of these disorders.

Platelet Count as a Prognostic Factor in Stage IV Non-Small Cell Lung Cancer.

Increase platelet count can accompany various cancers including lung cancer. This finding has recently been suggested to indicate poor prognosis. In patients with malignancies, thrombocytosis has previously been related disease stage, histological type and survival. In this study, the prevalence of thrombocytosis and the prognostic information provided by platelet count were analyzed in patients with stage IV Non-Small Cell Lung Cancer (NSCLC) with an aim to assess elevated platelet count as a prognostic factor in patients with stage IV NSCLC and to investigate whether there is relationship between thrombocytosis, other clinico-pathologic factors and median survival. This prospective observational study was conducted in National Institute of Cancer Research and Hospital (NICRH), Dhaka, Bangladesh from September 2019 to August 2020. A total of 108 patients were enrolled purposively. Detail history taking, thorough physical examination was done along with relevant investigations. Data were collected by semi structured questionnaire and analysis was done with the help of Statistical Package for Social Science (SPSS), version 21.0. The mean age of the patients was found 56.4±12.2 years with range from 35 to 75 years. Majority (79.6%) patients were male, 52.8% patients came from low income and 36.1% were farmer. Majority (40.7%) were symptomatic; in bed >50.0% of day. Almost two third (59.3%) had <5.0% weight loss. Almost three fourth (69.4%) had squamous cell carcinoma. At the time of first assessment 75(69.4%) patients had normal and 33(30.6%) had elevated platelet count level. Age, sex and histological type were statistically not significant between normal and elevated platelet count level groups. But performance status, weight loss were statistically significant (p<0.05) between two groups. According to univariate analysis, age, performance status at presentation, weight loss more than 10.0% for 3 months and platelet count prior the start of treatment were all significant predictors for the overall survival. In multivariate analysis age, performance status at presentation and initial thrombocytosis were independent prognostic determinants for overall survival. Median survival time was significantly higher for the normal platelet count group and elevated platelet count group (7.5 months versus 5.5 months) respectively (95% CI, 5.5-7.5), p<0.001. The frequency of thrombocytosis in patients with stage-IV NSCLC at first presentation was 30.6% and median survival time in these patients was significantly shorter compared in patients without thrombocytosis. These results concluded that an elevated platelet count could be a useful prognostic factor for survival in patients with stage-IV NSCLC.

Pro106Leu MPL mutation is associated with thrombocytosis and a low risk of thrombosis, splenomegaly and marrow fibrosis.

The P106L mutation in the human myeloproliferative leukemia virus oncogene (MPL) was shown to be associated with hereditary thrombocythemia in Arabs. The clinical and bone marrow (BM) features of P106L mutation are unknown. Genetic databases at two tertiary hospitals in Saudi Arabia were searched to identify patients with the MPL P106L mutation. Clinical data were collected retrospectively and the BM aspirates and biopsies were independently reviewed by two hematopathologists. In total, 115 patients were included. Median age was 33 years of which 31 patients were pediatric and 65 were female. The mutation was homozygous in 87 patients. Thrombocytosis was documented in 107 patients, with a median platelet count of 667 × 109/L. The homozygous genotype was associated with a higher platelet count. Thirty-three patients had an evaluable BM and clustering of megakaryocytes was observed in 30/33 patients. At the time of last follow-up, 114 patients were alive. The median follow-up was 7.8 years from the time of thrombocytosis. No patients developed disease progression to myelofibrosis. The P106L mutation was associated with marked thrombocytosis at a younger age and with a low risk of thrombosis, splenomegaly, and marrow fibrosis. The BM demonstrated normal or hypocellular marrow with megakaryocyte clusters.

Platelet count and breast cancer stage.

INTRODUCTION: The relationship between increased platelet count and cancer classification stage has long been established. The prevalence of thrombocytosis varies from 10% to 57% in cancer patients. The pathogenesis of thrombocytosis in malignancy is uncertain. However, there is evidence that tumor cells secrete humoral factors that can cause thrombocytosis. Preoperative thrombocytosis is a poor prognostic variable in malignancies. This study investigated the correlation between platelet count and breast cancer stage. METHODS: This cross-sectional study was conducted from February 2020 to January 2021. Patient data were collected from medical records. The study population comprised breast cancer patients at Dr. Wahidin Sudirohusodo Makassar. The staging examinations were based on the tumor, node, metastasis (TNM) classification according to the American Joint Committee on Cancer (AJCC) 8th Edition. RESULTS: The study group comprised 171 breast cancer patients of varying ages. Metastasis was present in five (2.92%) patients and absent in 166 (97.8%) patients. Analyses found no statistically significant differences between the three staging groups based on the platelet count (p = 0.952). CONCLUSION: There was no statistically significant relationship between increased platelet count and staging according to the TNM classification in breast cancer patients.

Treatment breaks in first line treatment of advanced colorectal cancer: An individual patient data meta-analysis.

BACKGROUND: Intermittent systemic anti-cancer therapy in patients with advanced colorectal cancer (aCRC) may improve quality of life without compromising overall survival (OS). We aimed to use individual patient data meta-analysis (IPDMA) from multiple randomised controlled trials evaluating intermittent strategies to inform clinical practice. We also aimed to validate whether thrombocytosis as a predictive biomarker identified patients with significantly reduced OS receiving a complete treatment break. PATIENTS AND METHODS: An IPDMA of intermittent strategy impact on survival was undertaken, including all relevant trials in which data were available. Intermittent strategies were classified into two groups: a planned stopping of all therapy ("treatment break strategy"; 6 trials; 2,907 patients) or to the same treatment omitting oxaliplatin ("maintenance strategy"; 3 trials; 1,271 patients). The primary analysis sample was of patients successfully completing induction therapy. Additionally, a pre-planned analysis of the predictive value of thrombocytosis on survival under a continuous versus an intermittent strategy was undertaken. RESULTS: All trials had comparable inclusion criteria. The overall IPDMA of intermittent therapy versus continuous therapy demonstrated no detriment in OS (HR = 1.03 [95% CI 0.93-1.14]), whether from complete break (HR 1.04 [95% CI 0.87-1.26]) or maintenance strategies (HR 0.99 [95% CI 0.87-1.13]). Thrombocytosis was confirmed as a marker of poor prognosis in aCRC, but did not predict for OS detriment from treatment break strategies (interaction HR = 0.97 [95% CI 0.66-1.40] compared to continuous therapy). CONCLUSION: The highest levels of evidence from this IPDMA indicate no detriment in survival for patients receiving an intermittent therapy strategy, either for maintenance or complete break strategies. Although, thrombocytosis is confirmed as a marker of poor prognosis, it is not predictive of poor outcome for patients treated with intermittent therapy. An intermittent chemotherapy strategy can therefore be applied irrespective of baseline platelet count and does not result in inferior OS compared to continuous chemotherapy.

Distinct effects of V617F and exon12-mutated JAK2 expressions on erythropoiesis in a human induced pluripotent stem cell (iPSC)-based model.

Activating mutations affecting the JAK-STAT signal transduction is the genetic driver of myeloproliferative neoplasms (MPNs) which comprise polycythemia vera (PV), essential thrombocythemia (ET) and myelofibrosis. The JAK2p.V617F mutation can produce both erythrocytosis in PV and thrombocytosis in ET, while JAK2 exon 12 mutations cause only erythrocytosis. We hypothesized that these two mutations activated different intracellular signals. In this study, the induced pluripotent stem cells (iPSCs) were used to model JAK2-mutated MPNs. Normal iPSCs underwent lentiviral transduction to overexpress JAK2p.V617F or JAK2p.N542_E543del (JAK2exon12) under a doxycycline-inducible system. The modified iPSCs were differentiated into erythroid cells. Compared with JAK2V617F-iPSCs, JAK2exon12-iPSCs yielded more total CD71+GlycophorinA+ erythroid cells, displayed more mature morphology and expressed more adult hemoglobin after doxycycline induction. Capillary Western immunoassay revealed significantly higher phospho-STAT1 but lower phospho-STAT3 and lower Phospho-AKT in JAK2exon12-iPSCs compared with those of JAK2V617F-iPSCs in response to erythropoietin. Furthermore, interferon alpha and arsenic trioxide were tested on these modified iPSCs to explore their potentials for MPN therapy. Both agents preferentially inhibited proliferation and promoted apoptosis of the iPSCs expressing mutant JAK2 compared with those without doxycycline induction. In conclusion, the modified iPSC model can be used to investigate the mechanisms and search for new therapy of MPNs.

Evaluation of angiogenic signaling molecules associated with reactive thrombocytosis in an iron-deficient rat model.

BACKGROUND: Iron deficiency anemia (IDA)-induced reactive thrombocytosis can occur in children and adults. The underlying mechanism for this phenomenon is indeterminate. Traditional cytokines such as thrombopoietin (TPO), interleukin-6 (IL-6), and IL-11 involved in megakaryopoiesis have not been shown to be the cause. Recent studies suggest that growth factors and signaling molecules involved with angiogenesis influence the proliferation and differentiation of megakaryocytes. METHODS: We investigated the possible association between angiogenic cytokines with reactive thrombocytosis due to IDA in an iron-deficient (ID) rat model. Complete blood count, iron panels, and TPO levels were measured at baseline and 5 weeks later in both control (C) and ID rats. Angiogenic cytokines were evaluated in the bone marrow in all rats. RESULTS: We successfully induced IDA in our rats by phlebotomy and reduced iron diet. We did not find an increase of TPO in ID rats. A review of the bone marrow showed an increase in the number of megakaryocytes, vascular structures, as well as increased intensity of stain for vascular endothelial growth factor (VEGF), and CXC chemokine receptor 4 (CXCR4) in rats with IDA compared to controls. CONCLUSIONS: Our results of histological bone marrow data suggest an important role for angiogenesis in the development of IDA-induced thrombocytosis. IMPACT: Thrombocytosis is common with IDA in both children and adults, but the mechanism is unclear. We confirmed that TPO is not the major driver of iron deficiency-associated thrombocytosis. We confirmed the increase in the number of megakaryocytes in the bone marrow despite stable TPO levels. We provided evidence supporting an important role of angiogenesis in megakaryocytopoiesis/thrombopoiesis with increased vascular structures and angiogenic cytokines in the bone marrow of iron-deficient rats. The demonstration that angiogenesis may play an important role in secondary thrombocytosis could lead to a new approach in treating symptomatic reactive thrombocytosis by targeting angiogenesis.

Thrombocytosis in an infant with a TRPV4 mutation: a case report.

Mutations in the calcium channel gene Transient Receptor Potential cation channel subfamily V member 4 (TRPV4) cause autosomal dominant skeletal dysplasia, with phenotypes ranging from mild to perinatal lethality. A recent report detailed enhanced proplatelet formation and increased murine platelet count in the context of TRPV4 activation. No prior reports have described platelet count abnormalities in human TRPV4 disease. Here, we report a case of prolonged thrombocytosis in the context of TRPV4-associated metatropic dysplasia that was lethal in the infantile period.