The clinical significance of TAT, PIC, TM, and t-PAIC in vascular events of BCR/ABL-negative myeloproliferative neoplasms.

Predicting the likelihood vascular events in patients with BCR/ABL1-negative myeloproliferative neoplasms (MPN) is essential for the treatment of the disease. However, effective assessment methods are lacking. Thrombin-antithrombin complex (TAT), plasmin-α2- plasmininhibitor complex (PIC), thrombomodulin (TM), and tissue plasminogen activator-inhibitor complex (t-PAIC) are the new direct indicators for coagulation and fibrinolysis. The aim of this study was to investigate the changes of these four new indicators in thrombotic and hemorrhagic events in BCR/ABL1-negative MPN. The study cohort of 74 patients with BCR/ABL negative myeloproliferative disorders included essential thrombocythemia, polycythemia vera, and primary myelofibrosis (PMF). A panel of 4 biomarkers, including TAT, PIC, TM, and t-PAIC were determined using Sysmex HISCL5000 automated analyzers, whereas fibrin/fibrinogen degradation products (FDP), D-dimer and Antithrombin III (ATIII) were analyzed using Sysmex CS5100 coagulation analyzer. A total of 24 (32.4%) patients experienced thrombotic events and hemorrhagic events occurred in 8 patients (10.8%). Compared to patients without hemorrhagic-thrombotic events, patients with thrombotic events had higher fibrinogen (FIB) level, FDP level and lower ATIII activity, while patients with hemorrhagic events had lower white blood cell count and hemoglobin level, higher FDP level (P < 0.05). Patients with a JAK2V617F mutation were more likely to experience thrombotic events (P < 0.05). In addtion, patients with thrombotic events had higher TAT, PIC, TM, and t-PAIC levels than patients without hemorrhagic-thrombotic events (P < 0.05), whereas patients with hemorrhagic events had a lower median value in TAT and TM (no statistical difference, P > 0.05). Patients with higher TAT, TM and t-PAIC were more likely to experience thrombotic events (P < 0.05), and only TAT was positively correlated with thrombotic events (Spearman r =0.287, P = 0.019). TAT, PIC, TM, and t-PAIC combined with ATIII and FDP have a certain value for predicting thrombosis in patients with BCR/ABL1-negative MPN. These 6 parameters are worth further exploration as predictive factors and prognostic markers for early thrombotic events.

Enhanced Molecular Response in Myeloproliferative Neoplasms with Complete JAK2V617F Inhibition.

SUMMARY: Dunbar, Bowman, and colleagues present here a novel genetic mouse model with inducible and reversible expression of the JAK2V617F mutation in the endogenous locus. Results from this study clearly demonstrate an absolute requirement for myeloproliferative neoplasm-initiating cells for this mutation in their survival and imply that more efficacious inhibitors could be curative for these patients even in the setting of additional cooperating mutations. See related article by Dunbar et al., p. 737 (8).

Immunophenotype of myeloid granulocytes in Chinese patients with BCR::ABL1-negative myeloproliferative neoplasms.

Typical BCR::ABL1-negative myeloproliferative neoplasms (MPN) are mainly referred to as polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofbrosis (PMF). Granulocytes in MPN patients are involved in their inflammation and form an important part of the pathophysiology of MPN patients. It has been shown that the immunophenotype of granulocytes in MPN patients is altered. We used flow cytometry to explore the immunophenotype of MPN patients and correlate it with clinical parameters. The results showed that PMF patients and PV patients had higher CD15+CD11b+ granulocytes than ET patients and normal controls. When grouped by gene mutation, changes in the granulocyte immunophenotype of MPN patients were independent of the JAK2V617F and CALR mutations. There was no significant heterogeneity in immunophenotype between ET patients and Pre-PMF, and between Overt-PMF and Pre-PMF patients. Granulocytes from some MPN patients showed an abnormal CD13/CD16 phenotype with a significant increase in mature granulocytes on molecular and cytomorphological grounds, and this abnormal pattern occurred significantly more frequently in PMF patients than in ET patients. CD15-CD11b- was negatively correlated with WBC and Hb and positively correlated with DIPSS score, whereas high CD10+ granulocytes were significantly and negatively associated with prognostic system IPSS and DIPSS scores in PMF patients. In conclusion, this study demonstrates the landscape of bone marrow granulocyte immunophenotypes in MPN patients. MPN patients, especially those with PMF, have a significant granulocyte developmental overmaturation phenotype. CD10+ granulocytes may be involved in the prognosis of PMF patients.

Treatment outcome and germline predictive factors of ropeginterferon alpha-2b in myeloproliferative neoplasm patients.

BACKGROUND: Studies have shown that some single nucleotide polymorphisms (SNPs) could serve as excellent markers in foretelling the treatment outcome of interferon (IFN) in myeloproliferative neoplasms (MPN). However, most work originated from western countries, and data from different ethnic populations have been lacking. METHODS: To gain insights, targeted sequencing was performed to detect myeloid-associated mutations and SNPs in eight loci across three genes (IFNL4, IFN-γ, and inosine triphosphate pyrophosphatase [ITPA]) to explore their predictive roles in our cohort of 21 ropeginterferon alpha-2b (ROPEG)-treated MPN patients, among whom real-time quantitative PCR was also performed periodically to monitor the JAK2V617F allele burden in 19 JAK2V617F-mutated cases. RESULTS: ELN response criteria were adopted to designate patients as good responders if they achieved complete hematological responses (CHR) within 1 year (CHR1) or attained major molecular responses (MMR), which occurred in 70% and 45% of the patients, respectively. IFNL4 and IFN-γ gene SNPs were infrequent in our population and were thus excluded from further analysis. Two ITPA SNPs rs6051702 A>C and rs1127354 C>A were associated with an inferior CHR1 rate and MMR rate, respectively. The former seemed to be linked to grade 2 or worse hepatotoxicity as well, although the comparison was of borderline significance only (50%, vs. 6.7% in those with common haplotype, p = 0.053). Twelve patients harbored 19 additional somatic mutations in 12 genes, but the trajectory of these mutations varied considerably and was not predictive of any response. CONCLUSIONS: Overall, this study provided valuable information on the ethnics- and genetics-based algorithm in the treatment of MPN.

Associations of the circulating levels of cytokines with the risk of myeloproliferative neoplasms: a bidirectional mendelian-randomization study.

OBJECTIVE: In the pathogenesis of myeloproliferative neoplasms (MPN), inflammation plays an important role. However, it is unclear whether there is a causal link between inflammation and MPNs. We used a bidirectional, two-sample Mendelian randomization (MR) approach to investigate the causal relationship between systemic inflammatory cytokines and myeloproliferative neoplasms. METHODS: A genome-wide association study (GWAS) of 8293 European participants identified genetic instrumental variables for circulating cytokines and growth factors. Summary statistics of MPN were obtained from a GWAS including 1086 cases and 407,155 controls of European ancestry. The inverse-variance-weighted method was mainly used to compute odds ratios (OR) and 95% confidence intervals (Cl). RESULTS: Our results showed that higher Interleukin-2 receptor, alpha subunit (IL-2rα) levels, and higher Interferon gamma-induced protein 10 (IP-10) levels were associated with an increased risk of MPN (OR = 1.36,95%CI = 1.03-1.81, P = 0.032; OR = 1.55,95%CI = 1.09-2.22, P = 0.015; respectively).In addition, Genetically predicted MPN promotes expression of the inflammatory cytokines interleukin-10 (IL-10) (BETA = 0.033, 95% CI = 0.003 ~ 0.064, P = 0.032) and monokine induced by interferon-gamma (MIG) (BETA = 0.052, 95% CI = 0.002-0.102, P = 0.043) and, on activation, normal T cells express and secrete RANTES (BETA = 0.055, 95% CI = 0.0090.1, P = 0.018). CONCLUSION: Our findings suggest that cytokines are essential to the pathophysiology of MPN. More research is required if these biomarkers can be used to prevent and treat MPN.

Exploring hematological alterations and genetics linked to SNV rs10974944 in myeloproliferative neoplasms among Amazon patients.

BCR::ABL1-negative myeloproliferative neoplasms are hematopoietic disorders characterized by panmyelosis. JAK2 V617F is a frequent variant in these diseases and often occurs in the 46/1 haplotype. The G allele of rs10974944 has been shown to be associated with this variant, specifically its acquisition, correlations with familial cases, and laboratory alterations. This study evaluated the association between the 46/1 haplotype and JAK2 V617F in patients with myeloproliferative neoplasms in a population from the Brazilian Amazon. Clinical, laboratory and molecular sequencing analyses were considered. Carriers of the G allele of rs10974944 with polycythemia vera showed an increase in mean corpuscular volume and mean corpuscular hemoglobin, while in those with essential thrombocythemia, there was an elevation in red blood cells, hematocrit, and hemoglobin. Associations were observed between rs10974944 and the JAK2 V617F, in which the G allele (OR 3.4; p < 0.0001) and GG genotype (OR 4.9; p = 0.0016) were associated with JAK2 V617F + and an increase in variant allele frequency (GG: OR 15.8; p = < 0.0001; G: OR 6.0; p = 0.0002). These results suggest an association between rs10974944 (G) and a status for JAK2 V617F, JAK2 V617F + _VAF ≥ 50%, and laboratory alterations in the erythroid lineage.

RAS mutations in myeloid malignancies: revisiting old questions with novel insights and therapeutic perspectives.

NRAS and KRAS activating point mutations are present in 10-30% of myeloid malignancies and are often associated with a proliferative phenotype. RAS mutations harbor allele-specific structural and biochemical properties depending on the hotspot mutation, contributing to variable biological consequences. Given their subclonal nature in most myeloid malignancies, their clonal architecture, and patterns of cooperativity with other driver genetic alterations may potentially have a direct, causal influence on the prognosis and treatment of myeloid malignancies. RAS mutations overall tend to be associated with poor clinical outcome in both chronic and acute myeloid malignancies. Several recent prognostic scoring systems have incorporated RAS mutational status. While RAS mutations do not always act as independent prognostic factors, they significantly influence disease progression and survival. However, their clinical significance depends on the type of mutation, disease context, and treatment administered. Recent evidence also indicates that RAS mutations drive resistance to targeted therapies, particularly FLT3, IDH1/2, or JAK2 inhibitors, as well as the venetoclax-azacitidine combination. The investigation of novel therapeutic strategies and combinations that target multiple axes within the RAS pathway, encompassing both upstream and downstream components, is an active field of research. The success of direct RAS inhibitors in patients with solid tumors has brought renewed optimism that this progress will be translated to patients with hematologic malignancies. In this review, we highlight key insights on RAS mutations across myeloid malignancies from the past decade, including their prevalence and distribution, cooperative genetic events, clonal architecture and dynamics, prognostic implications, and therapeutic targeting.

Recombinant interferon alfa in BCR/ABL-negative chronic myeloproliferative neoplasms.

The treatment landscape for BCR/ABL-negative myeloproliferative neoplasms (MPNs), driven by JAK2, CALR, and MPL mutations, has evolved significantly over the last decade. Recent regulatory approvals in polycythemia vera (PV) include the JAK inhibitor ruxolitinib, and more recently, a novel recombinant interferon alfa-2 (IFN-α) therapeutic agent. Many clinical trials have documented the safety and efficacy of IFN-α therapy in PV and essential thrombocythemia, the classical BCR/ABL-negative MPNs. Used off-label for more than 30 years as a cytoreductive agent, IFN-α therapy promotes significant clinical, hematologic, and molecular responses. In some IFN-α-treated patients, partial or complete reduction of the mutant JAK2 allele burden may lead to a durable measurable residual disease state, owing to the ability of long-term IFN-α therapy to selectively deplete mutant JAK2-harboring hematopoietic stem cells. Pegylated IFN-α forms were developed to improve the drug stability and tolerability of first-generation IFN-α therapeutics. More recently, a novel pegylated IFN-α, ropeginterferon alfa-2b, received approval for PV by the European Medicines Agency and the US Food and Drug Administration in 2019 and 2021, respectively. This article reviews the clinical research and recent advances that led to the first regulatory approval of IFN-α in a BCR/ABL-negative MPN and its future promise as a disease-modifying therapeutic agent.

Germline predisposition to myeloid neoplasms: Characteristics and management of high versus variable penetrance disorders.

Myeloid neoplasms with germline predisposition have been recognized increasingly over the past decade with numerous newly described disorders. Penetrance, age of onset, phenotypic heterogeneity, and somatic driver events differ widely among these conditions and sometimes even within family members with the same variant, making risk assessment and counseling of these individuals inherently difficult. In this review, we will shed light on high malignant penetrance (e.g., CEBPA, GATA2, SAMD9/SAMD9L, and TP53) versus variable malignant penetrance syndromes (e.g., ANKRD26, DDX41, ETV6, RUNX1, and various bone marrow failure syndromes) and their clinical features, such as variant type and location, course of disease, and prognostic markers. We further discuss the recommended management of these syndromes based on penetrance with an emphasis on somatic aberrations consistent with disease progression/transformation and suggested timing of allogeneic hematopoietic stem cell transplant. This review will thereby provide important data that can help to individualize and improve the management for these patients.

Capture-based targeted sequencing using a T-cell control in myeloid malignancies and idiopathic cytopenias.

We report on a study of next-generation sequencing in 257 patients undergoing investigations for cytopenias. We sequenced bone marrow aspirates using a target enrichment panel comprising 82 genes and used T cells from paired blood as a control. One hundred and sixty patients had idiopathic cytopenias, 81 had myeloid malignancies and 16 had lymphoid malignancies or other diagnoses. Forty-seven of the 160 patients with idiopathic cytopenias had evidence of somatic pathogenic variants consistent with clonal cytopenias. Only 39 genes of the 82 tested were mutated in the 241 patients with either idiopathic cytopenias or myeloid neoplasms. We confirm that T cells can be used as a control to distinguish between germline and somatic variants. The use of paired analysis with a T-cell control significantly reduced the time molecular scientists spent reporting compared to unpaired analysis. We identified somatic variants of uncertain significance (VUS) in a higher proportion (24%) of patients with myeloid malignancies or clonal cytopenias compared to less than 2% of patients with non-clonal cytopenias. This suggests that somatic VUS are indicators of a clonal process. Lastly, we show that blood depleted of lymphocytes can be used in place of bone marrow as a source of material for sequencing.

Cancer patients with clonal hematopoiesis die from primary malignancy or comorbidities despite higher rates of transformation to myeloid neoplasms.

BACKGROUND: The occurrence of somatic mutations in patients with no evidence of hematological disorders is called clonal hematopoiesis (CH). CH, whose subtypes include CH of indeterminate potential and clonal cytopenia of undetermined significance, has been associated with both hematologic cancers and systemic comorbidities. However, CH's effect on patients, especially those with concomitant malignancies, is not fully understood. METHODS: We performed a retrospective evaluation of all patients with CH at a tertiary cancer center. Patient characteristics, mutational data, and outcomes were collected and analyzed. RESULTS: Of 78 individuals included, 59 (76%) had a history of cancer and 60 (77%) had moderate to severe comorbidity burdens. DNMT3A, TET2, TP53, and ASXL1 were the most common mutations. For the entire cohort, the 2-year overall survival rate was 79% (95% CI: 70, 90), while the median survival was not reached. Of 20 observed deaths, most were related to primary malignancies (n = 7, 35%), comorbidities (n = 4, 20%), or myeloid neoplasms (n = 4, 20%). Twelve patients (15%) experienced transformation to a myeloid neoplasm. According to the clonal hematopoiesis risk score, the 3-year transformation rate was 0% in low-risk, 15% in intermediate-risk (p = 0.098), and 28% in high-risk (p = 0.05) patients. By multivariate analysis, transformation was associated with variant allele frequency ≥0.2 and hemoglobin <10 g/dL. CONCLUSIONS: In a population including mostly cancer patients, CH was associated with comorbidities and myeloid transformation in patients with higher mutational burdens and anemia. Nevertheless, such patients were less likely to die of their myeloid neoplasm than of primary malignancy or comorbidities.

Activating mutations in JAK2 and CALR differentially affect intracellular calcium flux in store operated calcium entry.

BACKGROUND: Calcium (Ca2+) signaling regulates various vital cellular functions, including integrin activation and cell migration. Store-operated calcium entry (SOCE) via calcium release-activated calcium (CRAC) channels represents a major pathway for Ca2+ influx from the extracellular space in multiple cell types. The impact of JAK2-V617F and CALR mutations which are disease initiating in myeloproliferative neoplasms (MPN) on SOCE, calcium flux from the endoplasmic reticulum (ER) to the cytosol, and related key signaling pathways in the presence or absence of erythropoietin (EPO) or thrombopoietin (TPO) is poorly understood. Thus, this study aimed to elucidate the effects of these mutations on the aforementioned calcium dynamics, in cellular models of MPN. METHODS: Intracellular Ca2+ levels were measured over a time frame of 0-1080 s in Fura-2 AM labeled myeloid progenitor 32D cells expressing various mutations (JAK2-WT/EpoR, JAK2-V617F/EpoR; CALR-WT/MPL, CALR-ins5/MPL, and del52/MPL). Basal Ca2+ concentrations were assessed from 0-108 s. Subsequently, cells were stimulated with EPO/TPO in Ca2+-free Ringer solution, measuring Ca2+ levels from 109-594 s (store depletion). Then, 2 mM of Ca2+ buffer resembling physiological concentrations was added to induce SOCE, and Ca2+ levels were measured from 595-1080 s. Fura-2 AM emission ratios (F340/380) were used to quantify the integrated Ca2+ signal. Statistical significance was assessed by unpaired Student's t-test or Mann-Whitney-U-test, one-way or two-way ANOVA followed by Tukey's multiple comparison test. RESULTS: Following EPO stimulation, the area under the curve (AUC) representing SOCE significantly increased in 32D-JAK2-V617F cells compared to JAK2-WT cells. In TPO-stimulated CALR cells, we observed elevated Ca2+ levels during store depletion and SOCE in CALR-WT cells compared to CALR-ins5 and del52 cells. Notably, upon stimulation, key components of the Ca2+ signaling pathways, including PLCγ-1 and IP3R, were differentially affected in these cell lines. Hyper-activated PLCγ-1 and IP3R were observed in JAK2-V617F but not in CALR mutated cells. Inhibition of calcium regulatory mechanisms suppressed cellular growth and induced apoptosis in JAK2-V617F cells. CONCLUSIONS: This report highlights the impact of JAK2 and CALR mutations on Ca2+ flux (store depletion and SOCE) in response to stimulation with EPO and TPO. The study shows that the JAK2-V617F mutation strongly alters the regulatory mechanism of EpoR/JAK2-dependent intracellular calcium balance, affecting baseline calcium levels, EPO-induced calcium entry, and PLCγ-1 signaling pathways. Our results reveal an important role of calcium flux in the homeostasis of JAK2-V617F positive cells.

[SFCE harmonization workshops: Neonatal acute myeloid leukemia]. / Orientation et prise en charge de la leucémie aiguë myéloïde néonatale : recommandations du comité leucémies de la SFCE.

Neonatal acute myeloid leukemias (AML) occurred within the first 28 days of life and constitute only a small proportion of all AL. They are distinguished from leukemias of older children by their clinical presentation, which frequently includes cutaneous localizations ("blueberry muffin rash syndrome") and a leukocytosis above 50 ×109/L. This proliferation may be transient, causing a transient leukemoid reaction in a background of constitutional trisomy 21 ("Transient Abnormal Myelopoieseis" or TAM) or Infantile Myeloproliferative Disease in the absence of constitutional trisomy 21 ("Infantile Myeloproliferative Disease" or IMD). In cases of true neonatal AML, the prognosis of patients is poor. Overall survival is around 35 % in the largest historical series. This poor prognosis is mainly due to the period of onset of this pathology making the use of chemotherapy more limited and involving many considerations, both ethical and therapeutic. The objective of this work is to review this rare pathology by addressing the clinical, biological, therapeutic and ethical particularities of patients with true neonatal AML or transient leukemoid reactions occurring in a constitutional trisomy 21 (true TAM) or somatic background (IMD).

Order-of-Mutation Effects on Cancer Progression: Models for Myeloproliferative Neoplasm.

In some patients with myeloproliferative neoplasms (MPN), two genetic mutations are often found: JAK2 V617F and one in the TET2 gene. Whether one mutation is present influences how the other subsequent mutation will affect the regulation of gene expression. In other words, when a patient carries both mutations, the order of when they first arose has been shown to influence disease progression and prognosis. We propose a nonlinear ordinary differential equation, the Moran process, and Markov chain models to explain the non-additive and non-commutative mutation effects on recent clinical observations of gene expression patterns, proportions of cells with different mutations, and ages at diagnosis of MPN. Combined, these observations are used to shape our modeling framework. Our key proposal is that bistability in gene expression provides a natural explanation for many observed order-of-mutation effects. We also propose potential experimental measurements that can be used to confirm or refute predictions of our models.

Special Issue "Advances in Molecular Pathogenesis and Targeted Therapies for Myeloid Neoplasms".

Myeloid neoplasms (MNs) constitute a diverse group of haematological malignancies that includes myelodysplastic neoplasms (MDS), myeloproliferative neoplasms (MPN), MDS/MPN overlap syndrome, and acute myeloid leukaemia (AML) [...].

[Analysis of CHIP-Related Mutation and Risk of Cardio-Cerebrovasculars Events in Patients with Myeloproliferative Neoplasms].

OBJECTIVE: To analyze the mutant spectrum of clonal hematopoiesis of indeterminate potential (CHIP) related mutations and clinical characteristics and to explore the correlation and the possible mechanism between CHIP-related mutations and cardio-cerebrovasculars events (CCEs) in patients with myeloproliferative neoplasms (MPNs). METHODS: The clinical data and next-generation sequencing results of 73 MPN patients in Beijing Anzhen Hospital from August 2019 to July 2022 were retrospectively analyzed. Statistical analyses were conducted by multivariate logistic regression for the effects of CHIP-related mutations and inflammatory cytokines on CCEs for MPNs patients. RESULTS: Fifty-five cases of MPN (75.3%) showed positive in CHIP-related genes. There was no significant difference in variant allele frequency of CHIP-related gene between essential thrombocythemia (ET) and polycythemia vera (PV). CHIP-related gene mutations were mainly single gene mutations, with mutation rate from high to low as JAK2V617F (63.0%, 46/73), ASXL1 (16.4%, 12/73), TET2 (11.0%, 8/73), DNMT3A (9.6%, 7/73), SRSF2 (6.9%, 5/73), SF3B1 (4.1%, 3/73), TP53(1.4%, 1/73) and PPM1D (1.4%, 1/73). The mutation rate of CHIP-related genes in MPN patients >60 years old was significantly higher than that in the patients ≤60 years old ï¼»91.7%(33/36) vs 59.5%(22/37)ï¼½. CCEs occurred in 27 MPNs patients (37.0%, MPNs/CCEs), and 5 had recurrent CCEs, all of which were arterial events. Age (62.8±12.8 years vs 53.9±15.8 years, P =0.015), IL-1ß level (17.7±26.0 vs 4.3±8.6, P =0.012), IL-8 level (360.7±598.6 vs 108.3±317.0, P =0.045), the proportion of the patients with thrombosis history (29.6% vs 2.2%, P =0.020), and the detection rate of CHIP-related mutations (88.9% vs 67.4%, P =0.040) in the group with CCEs were higher than those in the group without CCEs. Multivariate Logistic regression analysis showed that age（OR =0.917， 95%CI ：0.843-0.999, P =0.047）, thrombosis history (OR =34.148， 95%CI ：2.392-487.535, P =0.009), any CHIP-related mutations(OR =16.065， 95%CI ：1.217-212.024， P =0.035), and elevated level of IL-1ß (OR =0.929， 95%CI ：0.870-0.992， P =0.027) were independent risk factors for MPNs/CCEs. CHIP-related gene mutations were not associated with CCEs in MPN patients, but DNMT3A (OR =88.717， 95%CI ：2.690-292.482， P =0.012) and ASXL1 (OR =7.941， 95%CI ：1.045-60.353， P =0.045) were independent risk factors for CCEs in PV. CONCLUSION: There is a higher mutation rate of CHIP-related genes in MPN patients, especially those over 60 years old. Older age, thrombosis history, CHIP-related mutations and IL-1ß elevated levels are independent risk factors for CCEs in MPN. DNMT3A and ASXL1 mutations are independent risk factors for CCEs in PV patients. CHIP-related gene mutations and inflammatory cytokine IL-1 ß elevated levels may be the novel risk factors for CCEs in MPN.

Clinical Features and Long-Term Outcomes of a Pan-Canadian Cohort of Adolescents and Young Adults with Myeloproliferative Neoplasms: A Canadian MPN Group Study.

Myeloproliferative neoplasms (MPNs) are a group of chronic hematologic malignancies that lead to morbidity and early mortality due to thrombotic complications and progression to acute leukemia. Clinical and mutational risk factors have been demonstrated to predict outcomes in patients with MPNs and are used commonly to guide therapeutic decisions, including allogenic stem cell transplant, in myelofibrosis. Adolescents and young adults (AYA, age ≤45 years) comprise less than 10% of all MPN patients and have unique clinical and therapeutic considerations. The prevalence and clinical impact of somatic mutations implicated in myeloid disease has not been extensively examined in this population. We conducted a retrospective review of patients evaluated at eight Canadian centers for MPN patients diagnosed at ≤45 years of age. In total, 609 patients were included in the study, with median overall survival of 36.8 years. Diagnosis of prefibrotic or overt PMF is associated with the lowest OS and highest risk of AP/BP transformation. Thrombotic complications (24%), including splanchnic circulation thrombosis (9%), were frequent in the cohort. Mutations in addition to those in JAK2/MPL/CALR are uncommon in the initial disease phase in our AYA population (12%); but our data indicate they may be predictive of transformation to post-ET/PV myelofibrosis.

Calreticulin and JAK2V617F driver mutations induce distinct mitotic defects in myeloproliferative neoplasms.

Myeloproliferative neoplasms (MPNs) encompass a diverse group of hematologic disorders driven by mutations in JAK2, CALR, or MPL. The prevailing working model explaining how these driver mutations induce different disease phenotypes is based on the decisive influence of the cellular microenvironment and the acquisition of additional mutations. Here, we report increased levels of chromatin segregation errors in hematopoietic cells stably expressing CALRdel52 or JAK2V617F mutations. Our investigations employing murine 32DMPL and human erythroleukemic TF-1MPL cells demonstrate a link between CALRdel52 or JAK2V617F expression and a compromised spindle assembly checkpoint (SAC), a phenomenon contributing to error-prone mitosis. This defective SAC is associated with imbalances in the recruitment of SAC factors to mitotic kinetochores upon CALRdel52 or JAK2V617F expression. We show that JAK2 mutant CD34 + MPN patient-derived cells exhibit reduced expression of the master mitotic regulators PLK1, aurora kinase B, and PP2A catalytic subunit. Furthermore, the expression profile of mitotic regulators in CD34 + patient-derived cells allows to faithfully distinguish patients from healthy controls, as well as to differentiate primary and secondary myelofibrosis from essential thrombocythemia and polycythemia vera. Altogether, our data suggest alterations in mitotic regulation as a potential driver in the pathogenesis in MPN.