Search

Abstract: Progression of myeloproliferative neoplasms (MPNs) to accelerated or blast phase is associated with poor survival outcomes. Since 2017 there have been several therapies approved for use in acute myeloid leukemia (AML); these therapies have been incorporated into the management of accelerated/blast-phase MPNs (MPN-AP/BP). We performed a multicenter analysis to investigate outcomes of patients diagnosed with MPN-AP/BP in 2017 or later. In total, 202 patients were identified; median overall survival (OS) was 0.86 years. We also analyzed patients based on first-line treatment; the 3 most common approaches were intensive chemotherapy (n = 65), DNA methyltransferase inhibitor (DNMTi)-based regimens (n = 65), and DNMTi + venetoclax-based regimens (n = 54). Median OS was not significantly different by treatment type. In addition, we evaluated response by 2017 European LeukemiaNet AML criteria and 2012 MPN-BP criteria in an effort to understand the association of response with survival outcomes. We also analyzed outcomes in 65 patients that received allogeneic hematopoietic stem cell transplant (allo-HSCT); median OS was 2.30 years from time of allo-HSCT. Our study demonstrates that survival among patients with MPN-AP/BP is limited in the absence of allo-HSCT even in the current era of therapeutics and underscores the urgent need for new agents and approaches., (© 2024 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Purpose: Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by systemic symptoms, cytopenias, organomegaly, and bone marrow fibrosis. JAK2 inhibitors afford symptom and spleen burden reduction but do not alter the disease course and frequently lead to thrombocytopenia. TGFβ, a pleiotropic cytokine elaborated by the MF clone, negatively regulates normal hematopoiesis, downregulates antitumor immunity, and promotes bone marrow fibrosis. Our group previously showed that AVID200, a potent and selective TGFβ 1/3 trap, reduced TGFβ1-induced proliferation of human mesenchymal stromal cells, phosphorylation of SMAD2, and collagen expression. Moreover, treatment of MF mononuclear cells with AVID200 led to increased numbers of progenitor cells (PC) with wild-type JAK2 rather than JAK2V617F., Patients and Methods: We conducted an investigator-initiated, multicenter, phase Ib trial of AVID200 monotherapy in 21 patients with advanced MF., Results: No dose-limiting toxicity was identified at the three dose levels tested, and grade 3/4 anemia and thrombocytopenia occurred in 28.6% and 19.0% of treated patients, respectively. After six cycles of therapy, two patients attained a clinical benefit by IWG-MRT criteria. Spleen and symptom benefits were observed across treatment cycles. Unlike other MF-directed therapies, increases in platelet counts were noted in 81% of treated patients with three patients achieving normalization. Treatment with AVID200 resulted in potent suppression of plasma TGFβ1 levels and pSMAD2 in MF cells., Conclusions: AVID200 is a well-tolerated, rational, therapeutic agent for the treatment of patients with MF and should be evaluated further in patients with thrombocytopenic MF in combination with agents that target aberrant MF intracellular signaling pathways., (©2023 The Authors; Published by the American Association for Cancer Research.)

Proinflammatory signaling is a hallmark feature of human cancer, including in myeloproliferative neoplasms (MPNs), most notably myelofibrosis (MF). Dysregulated inflammatory signaling contributes to fibrotic progression in MF; however, the individual cytokine mediators elicited by malignant MPN cells to promote collagen-producing fibrosis and disease evolution are yet to be fully elucidated. Previously, we identified a critical role for combined constitutive JAK/STAT and aberrant NF-κB proinflammatory signaling in MF development. Using single-cell transcriptional and cytokine-secretion studies of primary cells from patients with MF and the human MPLW515L (hMPLW515L) murine model of MF, we extend our previous work and delineate the role of CXCL8/CXCR2 signaling in MF pathogenesis and bone marrow fibrosis progression. Hematopoietic stem/progenitor cells from patients with MF are enriched for a CXCL8/CXCR2 gene signature and display enhanced proliferation and fitness in response to an exogenous CXCL8 ligand in vitro. Genetic deletion of Cxcr2 in the hMPLW515L-adoptive transfer model abrogates fibrosis and extends overall survival, and pharmacologic inhibition of the CXCR1/2 pathway improves hematologic parameters, attenuates bone marrow fibrosis, and synergizes with JAK inhibitor therapy. Our mechanistic insights provide a rationale for therapeutic targeting of the CXCL8/CXCR2 pathway among patients with MF., (© 2023 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with historically poor outcomes and no worldwide consensus treatment approach. Unique among most hematologic malignancies for its frequent cutaneous involvement, BPDCN can also invade other extramedullary compartments, including the central nervous system. Generally affecting older adults, many patients are unfit to receive intensive chemotherapy, and although hematopoietic stem cell transplantation is preferred for younger, fit individuals, not all are eligible. One recent therapeutic breakthrough is that all BPDCNs express CD123 (IL3Rα) and that this accessible surface marker can be pharmacologically targeted. The first-in-class agent for BPDCN, tagraxofusp, which targets CD123, was approved in December 2018 in the United States for patients with BPDCN aged ≥2 years. Despite favorable response rates in the frontline setting, many patients still relapse in the setting of monotherapy, and outcomes in patients with relapsed/refractory BPDCN remain dismal. Therefore, novel approaches targeting both CD123 and other targets are actively being investigated. To begin to formally address the state of the field, we formed a new collaborative initiative, the North American BPDCN Consortium (NABC). This group of experts, which includes a multidisciplinary panel of hematologists/oncologists, hematopoietic stem cell transplant physicians, pathologists, dermatologists, and pediatric oncologists, was tasked with defining the current standard of care in the field and identifying the most important research questions and future directions in BPDCN. The position findings of the NABC's inaugural meetings are presented herein., (© 2023 by The American Society of Hematology.)

Myelofibrosis (MF) is a myeloproliferative disorder that exhibits considerable biological and clinical heterogeneity. At the two ends of the disease spectrum are the myelodepletive or cytopenic phenotype and the myeloproliferative phenotype. The cytopenic phenotype has a high prevalence in primary MF (PMF) and is characterized by low blood counts. The myeloproliferative phenotype is typically associated with secondary MF (SMF), mild anemia, minimal need for transfusion support, and normal to mild thrombocytopenia. Differences in somatic driver mutations and allelic burden, as well as the acquisition of non-driver mutations further influences these phenotypic differences, prognosis, and response to therapies such as JAK2 inhibitors. The outcome of patients with the cytopenic phenotype are comparatively worse and frequently pose a challenge to treat given the inherent exacerbation of cytopenias. Recent data indicate that an innate immune deregulated state that hinges on the myddosome-IRAK-NFκB axis favors the cytopenic myelofibrosis phenotype and offers opportunity for novel treatment approaches. We will review the biological and clinical features of the MF disease spectrum and associated treatment considerations., (© 2022. The Author(s).)

The BCR-ABL-negative myeloproliferative neoplasms (MPNs) have a variable risk of progressing to accelerated- or blast-phase MPN (MPN-AP/MPN-BP), defined by the presence of 10% to 19% and more than or equal to 20% myeloid blasts in the peripheral blood or bone marrow, respectively. The molecular processes underlying the progression to MPN-AP/MPN-BP are becoming increasingly understood with the acquisition of additional mutations in epigenetic modifiers (eg, ASXL1, EZH2, TET2), TP53, the Ras pathway, or splicing factors (eg, SRSF2, U2AF1), having been described as important steps in this evolutionary process. At least partially driven by the enrichment of these high-risk molecular features, the prognosis of patients with MPN-BP remains inferior to other patients with acute myeloid leukemia, with a median overall survival of 3 to 6 months. Allogeneic hematopoietic cell transplantation remains the only potentially curative therapeutic modality, but only a minority of patients are eligible. In the absence of curative intent, therapeutic strategies or palliative treatment with hypomethylating agents as monotherapy or in combination with ruxolitinib or venetoclax can be considered. Several novel agents are in various stages of clinical development but are not available for routine use at this point, highlighting the need for ongoing research and the prioritization of clinical trial enrollment when feasible., (Copyright © 2022 by The American Society of Hematology.)

We found that in regenerative erythropoiesis, the erythroid progenitor landscape is reshaped, and a previously undescribed progenitor population with colony-forming unit-erythroid (CFU-E) activity (stress CFU-E [sCFU-E]) is expanded markedly to restore the erythron. sCFU-E cells are targets of erythropoietin (Epo), and sCFU-E expansion requires signaling from the Epo receptor (EpoR) cytoplasmic tyrosines. Molecularly, Epo promotes sCFU-E expansion via JAK2- and STAT5-dependent expression of IRS2, thus engaging the progrowth signaling from the IGF1 receptor (IGF1R). Inhibition of IGF1R and IRS2 signaling impairs sCFU-E cell growth, whereas exogenous IRS2 expression rescues cell growth in sCFU-E expressing truncated EpoR-lacking cytoplasmic tyrosines. This sCFU-E pathway is the major pathway involved in erythrocytosis driven by the oncogenic JAK2 mutant JAK2(V617F) in myeloproliferative neoplasm. Inability to expand sCFU-E cells by truncated EpoR protects against JAK2(V617F)-driven erythrocytosis. In samples from patients with myeloproliferative neoplasm, the number of sCFU-E-like cells increases, and inhibition of IGR1R and IRS2 signaling blocks Epo-hypersensitive erythroid cell colony formation. In summary, we identified a new stress-specific erythroid progenitor cell population that links regenerative erythropoiesis to pathogenic erythrocytosis., (© 2022 by The American Society of Hematology.)

Leukemic transformation (LT) of myeloproliferative neoplasm (MPN) has a dismal prognosis and is largely fatal. Mutational inactivation of TP53 is the most common somatic event in LT; however, the mechanisms by which TP53 mutations promote LT remain unresolved. Using an allelic series of mouse models of Jak2/Trp53 mutant MPN, we identify that only biallelic inactivation of Trp53 results in LT (to a pure erythroleukemia [PEL]). This PEL arises from the megakaryocyte-erythroid progenitor population. Importantly, the bone morphogenetic protein 2/SMAD pathway is aberrantly activated during LT and results in abnormal self-renewal of megakaryocyte-erythroid progenitors. Finally, we identify that Jak2/Trp53 mutant PEL is characterized by recurrent copy number alterations and DNA damage. Using a synthetic lethality strategy, by targeting active DNA repair pathways, we show that this PEL is highly sensitive to combination WEE1 and poly(ADP-ribose) polymerase inhibition. These observations yield new mechanistic insights into the process of p53 mutant LT and offer new, clinically translatable therapeutic approaches., (© 2022 by The American Society of Hematology.)

The majority of JAK2 V617F -negative myeloproliferative neoplasms (MPNs) have disease-initiating frameshift mutations in calreticulin ( CALR ), resulting in a common carboxyl-terminal mutant fragment (CALR MUT ), representing an attractive source of neoantigens for cancer vaccines. However, studies have shown that CALR MUT -specific T cells are rare in patients with CALR MUT MPN for unknown reasons. We examined class I major histocompatibility complex (MHC-I) allele frequencies in patients with CALR MUT MPN from two independent cohorts. We observed that MHC-I alleles that present CALR MUT neoepitopes with high affinity are underrepresented in patients with CALR MUT MPN. We speculated that this was due to an increased chance of immune-mediated tumor rejection by individuals expressing one of these MHC-I alleles such that the disease never clinically manifested. As a consequence of this MHC-I allele restriction, we reasoned that patients with CALR MUT MPN would not efficiently respond to a CALR MUT fragment cancer vaccine but would when immunized with a modified CALR MUT heteroclitic peptide vaccine approach. We found that heteroclitic CALR MUT peptides specifically designed for the MHC-I alleles of patients with CALR MUT MPN efficiently elicited a CALR MUT cross-reactive CD8 + T cell response in human peripheral blood samples but not to the matched weakly immunogenic CALR MUT native peptides. We corroborated this effect in vivo in mice and observed that C57BL/6J mice can mount a CD8 + T cell response to the CALR MUT fragment upon immunization with a CALR MUT heteroclitic, but not native, peptide. Together, our data emphasize the therapeutic potential of heteroclitic peptide-based cancer vaccines in patients with CALR MUT MPN.

Myeloproliferative neoplasms (MPNs) transform to myelofibrosis (MF) and highly lethal acute myeloid leukemia (AML), although the actionable mechanisms driving progression remain elusive. Here, we elucidate the role of the high mobility group A1 (HMGA1) chromatin regulator as a novel driver of MPN progression. HMGA1 is upregulated in MPN, with highest levels after transformation to MF or AML. To define HMGA1 function, we disrupted gene expression via CRISPR/Cas9, short hairpin RNA, or genetic deletion in MPN models. HMGA1 depletion in JAK2V617F AML cell lines disrupts proliferation, clonogenicity, and leukemic engraftment. Surprisingly, loss of just a single Hmga1 allele prevents progression to MF in JAK2V617F mice, decreasing erythrocytosis, thrombocytosis, megakaryocyte hyperplasia, and expansion of stem and progenitors, while preventing splenomegaly and fibrosis within the spleen and BM. RNA-sequencing and chromatin immunoprecipitation sequencing revealed HMGA1 transcriptional networks and chromatin occupancy at genes that govern proliferation (E2F, G2M, mitotic spindle) and cell fate, including the GATA2 master regulatory gene. Silencing GATA2 recapitulates most phenotypes observed with HMGA1 depletion, whereas GATA2 re-expression partially rescues leukemogenesis. HMGA1 transactivates GATA2 through sequences near the developmental enhancer (+9.5), increasing chromatin accessibility and recruiting active histone marks. Further, HMGA1 transcriptional networks, including proliferation pathways and GATA2, are activated in human MF and MPN leukemic transformation. Importantly, HMGA1 depletion enhances responses to the JAK2 inhibitor, ruxolitinib, preventing MF and prolonging survival in murine models of JAK2V617F AML. These findings illuminate HMGA1 as a key epigenetic switch involved in MPN transformation and a promising therapeutic target to treat or prevent disease progression., (© 2022 by The American Society of Hematology.)

Chronic myeloproliferative neoplasms (MPN) frequently evolve to a blast phase (BP) that is almost uniformly resistant to induction chemotherapy or hypomethylating agents. We explored the functional properties, genomic architecture, and cell of origin of MPN-BP initiating cells (IC) using a serial NSG mouse xenograft transplantation model. Transplantation of peripheral blood mononuclear cells (MNC) from 7 of 18 patients resulted in a high degree of leukemic cell chimerism and recreated clinical characteristics of human MPN-BP. The function of MPN-BP ICs was not dependent on the presence of JAK2V617F, a driver mutation associated with the initial underlying MPN. By contrast, multiple MPN-BP IC subclones coexisted within MPN-BP MNCs characterized by different myeloid malignancy gene mutations and cytogenetic abnormalities. MPN-BP ICs in 4 patients exhibited extensive proliferative and self-renewal capacity, as demonstrated by their ability to recapitulate human MPN-BP in serial recipients. These MPN-BP IC subclones underwent extensive continuous clonal competition within individual xenografts and across multiple generations, and their subclonal dynamics were consistent with functional evolution of MPN-BP IC. Finally, we show that MPN-BP ICs originate from not only phenotypically identified hematopoietic stem cells, but also lymphoid-myeloid progenitor cells, which were each characterized by differences in MPN-BP initiating activity and self-renewal capacity.

Leukemic transformation of myeloproliferative neoplasms (MPNs) is associated with dismal outcomes. The genetic complexity of leukemic transformation of MPNs is being deciphered and will likely result in targeted therapy approaches. Ongoing trials are investigating the efficacy of emerging treatments for this high-risk patient population. This review has outlined recent progress in the understanding and treatment of leukemia arising from MPNs., (Copyright © 2021. Published by Elsevier Ltd.)

Purpose: The JAK1/2 inhibitor ruxolitinib has demonstrated significant benefits for patients with myeloproliferative neoplasms (MPN). However, patients often lose response to ruxolitinib or suffer disease progression despite therapy with ruxolitinib. These observations have prompted efforts to devise treatment strategies to improve therapeutic efficacy in combination with ruxolitinib therapy. Activation of JAK-STAT signaling results in dysregulation of key downstream pathways, notably increased expression of cell-cycle mediators including CDC25A and the PIM kinases., Experimental Design: Given the involvement of cell-cycle mediators in MPNs, we sought to examine the efficacy of therapy combining ruxolitinib with a CDK4/6 inhibitor (LEE011) and a PIM kinase inhibitor (PIM447). We utilized JAK2-mutant cell lines, murine models, and primary MPN patient samples for these studies., Results: Exposure of JAK2-mutant cell lines to the triple combination of ruxolitinib, LEE011, and PIM447 resulted in expected on-target pharmacodynamic effects, as well as increased apoptosis and a decrease in the proportion of cells in S-phase, compared with ruxolitinib. As compared with ruxolitinib monotherapy, combination therapy led to reductions in spleen and liver size, reduction of bone marrow reticulin fibrosis, improved overall survival, and elimination of disease-initiating capacity of treated bone marrow, in murine models of MPN. Finally, the triple combination reduced colony formation capacity of primary MPN patient samples to a greater extent than ruxolitinib., Conclusions: The triple combination of ruxolitinib, LEE011, and PIM447 represents a promising therapeutic strategy with the potential to increase therapeutic responses in patients with MPN., (©2021 American Association for Cancer Research.)

Accelerated and blast phase myeloproliferative neoplasms are advanced stages of the disease with historically a poor prognosis and little improvement in outcomes thus far. The lack of responses to standard treatments likely results from the more aggressive biology reflected by the higher incidence of complex karyotype and high-risk somatic mutations, which are enriched at the time of transformation. Treatment options include induction chemotherapy (7 + 3) as that used on de novo acute myeloid leukemia or hypomethylating agent-based therapy, which has shown similar outcomes. Allogeneic stem cell transplantation remains the only potential for cure., Competing Interests: Disclosure T. Jain, consultancy for Targeted Oncology, Advisory board for CareDx and Bristol Myers Squibb; R.K. Rampal, consulting fees from: Constellation, Incyte, Celgene, Promedior, CTI, Jazz Pharmaceuticals, Blueprint, Stemline, Abbvie, Disc Medicines, and research funding from Incyte, Constellation, Stemline., (Copyright © 2020 Elsevier Inc. All rights reserved.)

This review reflects the presentations and discussion at the 14th post-American Society of Hematology (ASH) International Workshop on Chronic Myeloproliferative Malignancies, which took place on the December 10 and 11, 2019, immediately after the 61st ASH Annual Meeting in Orlando, Florida. Rather than present a resume of the proceedings, we address some of the topical translational science research and clinically relevant topics in detail. We consider how recent studies using single-cell genomics and other molecular methods reveal novel aspects of hematopoiesis which in turn raise the possibility of new therapeutic approaches for patients with myeloproliferative neoplasms (MPNs). We discuss how alternative therapies could benefit patients with chronic myeloid leukemia who develop BCR-ABL1 mutant subclones following ABL1-tyrosine kinase inhibitor therapy. In MPNs, we focus on efforts beyond JAK-STAT and the merits of integrating activin receptor ligand traps, interferon-α, and allografting in the current treatment algorithm for patients with myelofibrosis., (© 2020 The Authors. Hematological Oncology published by John Wiley & Sons Ltd.)

Myeloid malignancies, including acute myeloid leukaemia (AML), arise from the expansion of haematopoietic stem and progenitor cells that acquire somatic mutations. Bulk molecular profiling has suggested that mutations are acquired in a stepwise fashion: mutant genes with high variant allele frequencies appear early in leukaemogenesis, and mutations with lower variant allele frequencies are thought to be acquired later 1-3 . Although bulk sequencing can provide information about leukaemia biology and prognosis, it cannot distinguish which mutations occur in the same clone(s), accurately measure clonal complexity, or definitively elucidate the order of mutations. To delineate the clonal framework of myeloid malignancies, we performed single-cell mutational profiling on 146 samples from 123 patients. Here we show that AML is dominated by a small number of clones, which frequently harbour co-occurring mutations in epigenetic regulators. Conversely, mutations in signalling genes often occur more than once in distinct subclones, consistent with increasing clonal diversity. We mapped clonal trajectories for each sample and uncovered combinations of mutations that synergized to promote clonal expansion and dominance. Finally, we combined protein expression with mutational analysis to map somatic genotype and clonal architecture with immunophenotype. Our findings provide insights into the pathogenesis of myeloid transformation and how clonal complexity evolves with disease progression.

The ongoing COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 is a global public health crisis. Multiple observations indicate poorer post-infection outcomes for patients with cancer than for the general population. Herein, we highlight the challenges in caring for patients with acute leukaemias and myeloid neoplasms amid the COVID-19 pandemic. We summarise key changes related to service allocation, clinical and supportive care, clinical trial participation, and ethical considerations regarding the use of lifesaving measures for these patients. We recognise that these recommendations might be more applicable to high-income countries and might not be generalisable because of regional differences in health-care infrastructure, individual circumstances, and a complex and highly fluid health-care environment. Despite these limitations, we aim to provide a general framework for the care of patients with acute leukaemias and myeloid neoplasms during the COVID-19 pandemic on the basis of recommendations from international experts., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Secondary acute myeloid leukemias (AMLs) evolving from an antecedent myeloproliferative neoplasm (MPN) are characterized by a unique set of cytogenetic and molecular features distinct from de novo AML. Given the high frequency of poor-risk cytogenetic and molecular features, malignant clones are frequently insensitive to traditional AML chemotherapeutic agents. Allogeneic stem cell transplant, the only treatment modality shown to have any beneficial long-term outcome, is often not possible given the advanced age of patients at time of diagnosis and frequent presence of competing comorbidities. Even in this setting, relapse rates remain high. As a result, outcomes are generally poor and there remains a significant unmet need for novel therapeutic strategies. Although advances in cancer genomics have dramatically enhanced our understanding of the molecular events governing clonal evolution in MPNs, the cell-intrinsic and -extrinsic mechanisms driving leukemic transformation at this level remain poorly understood. Here, we review known risk factors for the development of leukemic transformation in MPNs, recent progress made in our understanding of the molecular features associated with leukemic transformation, current treatment strategies, and emerging therapeutic options for this high-risk myeloid malignancy., (© 2020 by The American Society of Hematology.)

Ruxolitinib is a JAK1/2 inhibitor approved for the treatment of myelofibrosis (MF) and polycythemia vera (PV). Recent data have suggested the possibility of increased infectious and secondary malignancy rates in patients treated with ruxolitinib. We conducted a dual-center, retrospective study of 202 myeloproliferative neoplasm (MPN) patients receiving ruxolitinib and a control cohort of 73 ruxolitinib-naïve MPN patients. We utilized propensity score matching to analyze the primary outcome of development of any grade infection. Infections occurred in 38.4% of ruxolitinib-naïve patients and 42.6% of ruxolitinib-treated patients and were primarily grade 1/2. After propensity score weighting, there was no difference in risk of infection between ruxolitinib-treated and -naïve patients with MF (HR 1.15 [95% CI 0.80-1.65], p  = .466) and non-MF MPNs (HR = 0.52 [95% CI 0.21-1.28, p  = .152). These results suggest that there is not an increased risk of infection with ruxolitinib therapy.

The 60th American Society of Hematology (ASH) held in San Diego in December 2018 was followed by the 13th Post-ASH chronic myeloproliferative neoplasms (MPNs) workshop on December 4 and 5, 2018. This closed annual workshop, first introduced in 2006 by Goldman and Mughal, was organized in collaboration with Alpine Oncology Foundation and allowed experts in preclinical and clinical research in the chronic MPNs to discuss the current scenario, including relevant presentations at ASH, and address pivotal open questions that impact translational research and clinical management. This review is based on the presentations and deliberations at this workshop, and rather than provide a resume of the proceedings, we have selected some of the important translational science and treatment issues that require clarity. We discuss the experimental and observational evidence to support the intimate interaction between aging, inflammation, and clonal evolution of MPNs, the clinical impact of the unfolding mutational landscape on the emerging targets and treatment of MPNs, new methods to detect clonal heterogeneity, the challenges in managing childhood and adolescent MPN, and reflect on the treatment of systemic mastocytosis (SM) following the licensing of midostaurin., (© 2019 John Wiley & Sons, Ltd.)

The myeloproliferative neoplasms (MPNs) are clonal stem cell-derived diseases. This chapter focuses on the subcategory of Philadelphia (Ph) chromosome-negative classical MPNs, polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF). These MPNs are associated with both microvascular and macrovascular thrombosis, which may occur in the venous and arterial circulation. Erythrocytosis, leukocytosis, and increased JAK2V617F allele burden are known to be risk factors. In this chapter, we review the thrombotic and hemostatic manifestations of the Philadelphia (Ph) chromosome-negative classical MPNs, including the clinical manifestations, the pathophysiology, as well as management.

The Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and the prefibrotic form of primary myelofibrosis (PMF), frequently progress to more overt forms of MF and a type of acute leukemia termed MPN-accelerated phase/blast phase (MPN-AP/BP). Recent evidence indicates that dysregulation of the tumor suppressor tumor protein p53 (TP53) commonly occurs in the MPNs. The proteins MDM2 and MDM4 alter the cellular levels of TP53. We investigated in 1,294 patients whether abnormalities involving chromosomes 1 and 12, which harbor the genes for MDM4 and MDM2 , respectively, and chromosome 17, where the gene for TP53 is located, are associated with MPN disease progression. Gain of 1q occurred not only in individuals with MPN-BP but also in patients with PV and ET, who, with further follow-up, eventually evolve to either MF and/or MPN-BP. These gains of 1q were most prevalent in patients with a history of PV and those who possessed the JAK2 V617F driver mutation. The gains of 1q were accompanied by increased transcript levels of MDM4 In contrast, 12q chromosomal abnormalities were exclusively detected in patients who presented with MF or MPN-BP, but were not accompanied by further increases in MDM2 / MDM4 transcript levels. Furthermore, all patients with a loss of 17p13, which leads to a deletion of TP53 , had either MF or MPN-AP/BP. These findings suggest that gain of 1q, as well as deletions of 17p, are associated with perturbations of the TP53 pathway, which contribute to MPN disease progression., (© 2018 by The American Society of Hematology.)

Myeloproliferative neoplasms (MPN), including polycythemia vera, essential thrombocythemia, and primary myelofibrosis, have a propensity to evolve into accelerated and blast-phase disease (MPN-AP/BP), carrying a dismal prognosis. Conventional antileukemia therapy has limited efficacy in this setting. Thus, MPN-AP/BP is an urgent unmet clinical need. Modest responses to hypomethylating agents and single-agent ruxolitinib have been reported. More recently, combination of ruxolitinib and decitabine has demonstrated synergistic in vitro activity in human and murine systems. These observations led us to conduct a phase 1 study to explore the safety of combined decitabine and dose-escalated ruxolitinib in patients with MPN-AP/BP. A total of 21 patients were accrued to this multicenter study. Ruxolitinib was administered at doses of 10, 15, 25, or 50 mg twice daily in combination with decitabine (20 mg/m 2 per day for 5 days) in 28-day cycles. The maximum tolerated dose was not reached. The most common reasons for study discontinuation were toxicity/adverse events (37%) and disease progression (21%). Fourteen patients died during study treatment period or follow-up. The median overall survival for patients on study was 7.9 months (95% confidence interval, 4.1-not reached). Among evaluable patients, the overall response rate by protocol-defined criteria (complete remission with incomplete count recovery + partial remission) was 9/17 (53%) and by intention-to-treat analysis was 9/21 (42.9%). The combination of decitabine and ruxolitinib was generally well tolerated by patients with MPN-AP/BP and demonstrates potentially promising clinical activity. A phase 2 trial evaluating the efficacy of this combination regimen is ongoing within the Myeloproliferative Disorder Research Consortium., (© 2018 by The American Society of Hematology.)

Purpose of Review: Although BCR-ABL1-negative myeloproliferative neoplasms (MPN) are chronic, clonal hematopoietic stem cell (HSC) disorders marked by proliferation of one or more myeloid lineages, a substantial proportion of patients transform to acute myeloid leukemia. Leukemic transformation (LT) from a pre-existing MPN carries a dismal prognosis. Here, we review recent genetic, biological, and clinical data regarding LT., Recent Findings: In the last decade, DNA sequencing has revolutionized our understanding of the genomic landscape of LT. Mutations in TP53, ASXL1, EZH2, IDH1/2, and SRSF2 are significantly associated with increased risk of LT of MPNs. Preclinical modeling of these mutations is underway and has yielded important biological insights, some of which have therapeutic implications. Recent progress has led to the identification of recurrent genomic alterations in patients with LT. This has allowed mechanistic and therapeutic insight into the process of LT. In turn, this may lead to more mechanism-based therapeutic strategies that may improve patient outcomes.

Mutations in the ER chaperone calreticulin (CALR) are common in myeloproliferative neoplasm (MPN) patients, activate the thrombopoietin receptor (MPL), and mediate constitutive JAK/STAT signaling. The mechanisms by which CALR mutations cause myeloid transformation are incompletely defined. We used mass spectrometry proteomics to identify CALR-mutant interacting proteins. Mutant CALR caused mislocalization of binding partners and increased recruitment of FLI1, ERP57, and CALR to the MPL promoter to enhance transcription. Consistent with a critical role for CALR-mediated JAK/STAT activation, we confirmed the efficacy of JAK2 inhibition on CALR-mutant cells in vitro and in vivo. Due to the altered interactome induced by CALR mutations, we hypothesized that CALR-mutant MPNs may be vulnerable to disruption of aberrant CALR protein complexes. A synthetic peptide designed to competitively inhibit the carboxy terminal of CALR specifically abrogated MPL/JAK/STAT signaling in cell lines and primary samples and improved the efficacy of JAK kinase inhibitors. These findings reveal what to our knowledge is a novel potential therapeutic approach for patients with CALR-mutant MPN.

Patients with myeloproliferative neoplasms (MPNs) frequently progress to bone marrow failure or acute myeloid leukemia (AML), and mutations in epigenetic regulators such as the metabolic enzyme isocitrate dehydrogenase (IDH) are associated with poor outcomes. Here, we showed that combined expression of Jak2V617F and mutant IDH1R132H or Idh2R140Q induces MPN progression, alters stem/progenitor cell function, and impairs differentiation in mice. Jak2V617F Idh2R140Q-mutant MPNs were sensitive to small-molecule inhibition of IDH. Combined inhibition of JAK2 and IDH2 normalized the stem and progenitor cell compartments in the murine model and reduced disease burden to a greater extent than was seen with JAK inhibition alone. In addition, combined JAK2 and IDH2 inhibitor treatment also reversed aberrant gene expression in MPN stem cells and reversed the metabolite perturbations induced by concurrent JAK2 and IDH2 mutations. Combined JAK2 and IDH2 inhibitor therapy also showed cooperative efficacy in cells from MPN patients with both JAK2mut and IDH2mut mutations. Taken together, these data suggest that combined JAK and IDH inhibition may offer a therapeutic advantage in this high-risk MPN subtype.

Genetic and functional studies underscore the central role of JAK/STAT signaling in myeloproliferative neoplasms (MPNs). However, the mechanisms that mediate transformation in MPNs are not fully delineated, and clinically utilized JAK inhibitors have limited ability to reduce disease burden or reverse myelofibrosis. Here we show that MPN progenitor cells are characterized by marked alterations in gene regulation through differential enhancer utilization, and identify nuclear factor κB (NF-κB) signaling as a key pathway activated in malignant and non-malignant cells in MPN. Inhibition of BET bromodomain proteins attenuated NF-κB signaling and reduced cytokine production in vivo. Most importantly, combined JAK/BET inhibition resulted in a marked reduction in the serum levels of inflammatory cytokines, reduced disease burden, and reversed bone marrow fibrosis in vivo., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Myeloproliferative neoplasms (MPNs) are a group of heterogeneous disorders of the hematopoietic system that include myelofibrosis (MF), polycythemia vera (PV), and essential thrombocythemia (ET). PV and ET are characterized by significant thrombohemorrhagic complications and a high risk of transformation to MF and acute myeloid leukemia. The diagnosis and management of PV and ET has evolved since the identification of mutations implicated in their pathogenesis. These NCCN Guideline Insights discuss the recommendations outlined in the NCCN Guidelines for the risk stratification, treatment, and special considerations for the management of PV and ET., (Copyright © 2017 by the National Comprehensive Cancer Network.)

This review is based on the deliberations at the 5th John Goldman Colloquium held in Estoril on 2nd October 2015 and the 9th post-ASH International Workshop on chronic myeloid leukemia (CML) and BCR-ABL1-negative myeloproliferative neoplasms (MPN) which took place on the 10th-11th December 2014, immediately following the 56th American Society of Hematology Annual Meeting. It has been updated since and summarizes the most recent advances in the biology and therapy of these diseases, in particular updates of genetics of MPN, novel insights from mouse MPN models, targeting CML stem cells and its niche; clinical advances include updates on JAK2 inhibitors and other therapeutic approaches to BCR-ABL1-negative MPNs, the use of alpha interferons, updates on tyrosine kinase inhibitors (TKI) randomized trials in CML, TKI cessation studies, and optimal monitoring strategies.

Although clinically tested JAK inhibitors reduce splenomegaly and systemic symptoms, molecular responses are not observed in most myeloproliferative neoplasm (MPN) patients. We previously demonstrated that MPN cells become persistent to type I JAK inhibitors that bind the active conformation of JAK2. We investigated whether CHZ868, a type II JAK inhibitor, would demonstrate activity in JAK inhibitor persistent cells, murine MPN models, and MPN patient samples. JAK2 and MPL mutant cell lines were sensitive to CHZ868, including type I JAK inhibitor persistent cells. CHZ868 showed significant activity in murine MPN models and induced reductions in mutant allele burden not observed with type I JAK inhibitors. These data demonstrate that type II JAK inhibition is a viable therapeutic approach for MPN patients., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Myeloproliferative neoplasms (MPNs) are clonal disorders of hematopoiesis characterized by a high frequency of genetic alterations, and include chronic myeloid leukemia (CML) and the BCR-ABL1-negative MPNs. Herein we summarize recent advances and controversies in our understanding of the biology and therapy of these disorders, as discussed at the 8th post-American Society of Hematology CML-MPN workshop. The principal areas addressed include the breakthrough discovery of CALR mutations in patients with JAK2/MPL wild type MPN, candidate therapies based on novel genetic findings in leukemic transformation and new therapeutic targets in MPNs, and an appraisal of bone marrow histopathology in MPNs with a focus on the potential new clinical entity of "masked" polycythemia vera. An update on clinical trials of Janus kinase (JAK) inhibitors is presented as well as current understanding regarding the definitions and mechanisms of resistance to JAK inhibitors, and updated information on the safety and efficacy of discontinuation of tyrosine kinase inhibitors in patients with CML.

Unlabelled: The identification of JAK2/MPL mutations in patients with myeloproliferative neoplasms (MPN) has led to the clinical development of JAK kinase inhibitors, including ruxolitinib. Ruxolitinib reduces splenomegaly and systemic symptoms in myelofibrosis and improves overall survival; however, the mechanism by which JAK inhibitors achieve efficacy has not been delineated. Patients with MPN present with increased levels of circulating proinflammatory cytokines, which are mitigated by JAK inhibitor therapy. We sought to elucidate mechanisms by which JAK inhibitors attenuate cytokine-mediated pathophysiology. Single-cell profiling demonstrated that hematopoietic cells from myelofibrosis models and patient samples aberrantly secrete inflammatory cytokines. Pan-hematopoietic Stat3 deletion reduced disease severity and attenuated cytokine secretion, with similar efficacy as observed with ruxolitinib therapy. In contrast, Stat3 deletion restricted to MPN cells did not reduce disease severity or cytokine production. Consistent with these observations, we found that malignant and nonmalignant cells aberrantly secrete cytokines and JAK inhibition reduces cytokine production from both populations., Significance: Our results demonstrate that JAK-STAT3-mediated cytokine production from malignant and nonmalignant cells contributes to MPN pathogenesis and that JAK inhibition in both populations is required for therapeutic efficacy. These findings provide novel insight into the mechanisms by which JAK kinase inhibition achieves therapeutic efficacy in MPNs., (©2015 American Association for Cancer Research.)

Patients with myeloproliferative neoplasms (MPNs) are at significant, cumulative risk of leukemic transformation to acute myeloid leukemia (AML), which is associated with adverse clinical outcome and resistance to standard AML therapies. We performed genomic profiling of post-MPN AML samples; these studies demonstrate somatic tumor protein 53 (TP53) mutations are common in JAK2V617F-mutant, post-MPN AML but not in chronic-phase MPN and lead to clonal dominance of JAK2V617F/TP53-mutant leukemic cells. Consistent with these data, expression of JAK2V617F combined with Tp53 loss led to fully penetrant AML in vivo. JAK2V617F-mutant, Tp53-deficient AML was characterized by an expanded megakaryocyte erythroid progenitor population that was able to propagate the disease in secondary recipients. In vitro studies revealed that post-MPN AML cells were sensitive to decitabine, the JAK1/2 inhibitor ruxolitinib, or the heat shock protein 90 inhibitor 8-(6-iodobenzo[d][1.3]dioxol-5-ylthio)-9-(3-(isopropylamino)propyl)-9H-purine-6-amine (PU-H71). Treatment with ruxolitinib or PU-H71 improved survival of mice engrafted with JAK2V617F-mutant, Tp53-deficient AML, demonstrating therapeutic efficacy for these targeted therapies and providing a rationale for testing these therapies in post-MPN AML.

The discovery of the JAK2 mutation in Philadelphia-chromosome negative myeloproliferative neoplasm (MPNs) in 2005 has heralded an era of rapid genetic discovery in the MPNs. This has lead to substantive gains in the understanding of the pathobiology of these diseases. Importantly, this has also lead to new treatment in the form of JAK inhibitors, as well as to clinical trials targeting other components thought to contribute to disease biology. However, given the number of new genomic alterations uncovered in the last several years, the relative contributions of each mutation to the development of a disease phenotype remains an area of robust investigation. Furthermore, the number of known mutations presents challenges to the practicing clinician in terms of what mutations to test for and the clinical significance of such mutations., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Genomic studies have identified somatic alterations in the majority of myeloproliferative neoplasms (MPN) patients, including JAK2 mutations in the majority of MPN patients and CALR mutations in JAK2-negative MPN patients. However, the role of JAK-STAT pathway activation in different MPNs, and in patients without JAK2 mutations, has not been definitively delineated. We used expression profiling, single nucleotide polymorphism arrays, and mutational profiling to investigate a well-characterized cohort of MPN patients. MPN patients with homozygous JAK2V617F mutations were characterized by a distinctive transcriptional profile. Notably, a transcriptional signature consistent with activated JAK2 signaling is seen in all MPN patients regardless of clinical phenotype or mutational status. In addition, the activated JAK2 signature was present in patients with somatic CALR mutations. Conversely, we identified a gene expression signature of CALR mutations; this signature was significantly enriched in JAK2-mutant MPN patients consistent with a shared mechanism of transformation by JAK2 and CALR mutations. We also identified a transcriptional signature of TET2 mutations in MPN patent samples. Our data indicate that MPN patients, regardless of diagnosis or JAK2 mutational status, are characterized by a distinct gene expression signature with upregulation of JAK-STAT target genes, demonstrating the central importance of the JAK-STAT pathway in MPN pathogenesis., (© 2014 by The American Society of Hematology.)

The discovery of JAK2/MPL mutations in patients with myeloproliferative neoplasms (MPN) led to clinical development of Janus kinase (JAK) inhibitors for treatment of MPN. These inhibitors improve constitutional symptoms and splenomegaly but do not significantly reduce mutant allele burden in patients. We recently showed that chronic exposure to JAK inhibitors results in inhibitor persistence via JAK2 transactivation and persistent JAK-signal transducer and activator of transcription signaling. We performed genetic and pharmacologic studies to determine whether improved JAK2 inhibition would show increased efficacy in MPN models and primary samples. Jak2 deletion in vivo led to profound reduction in disease burden not seen with JAK inhibitors, and deletion of Jak2 following chronic ruxolitinib therapy markedly reduced mutant allele burden. This demonstrates that JAK2 remains an essential target in MPN cells that survive in the setting of chronic JAK inhibition. Combination therapy with the heat shock protein 90 (HSP90) inhibitor PU-H71 and ruxolitinib reduced total and phospho-JAK2 and achieved more potent inhibition of downstream signaling than ruxolitinib monotherapy. Combination treatment improved blood counts, spleen weights, and reduced bone marrow fibrosis compared with ruxolitinib alone. These data suggest alternate approaches that increase JAK2 targeting, including combination JAK/HSP90 inhibitor therapy, are warranted in the clinical setting.

Purpose of Review: The myeloproliferative neoplasms (MPNs), including essential thrombocythemia, polycythemia vera and primary myelofibrosis (PMF), are a heterogeneous group of myeloid-derived chronic haematopoietic malignancies. Frequent clinical consequences of these diseases include not only an increased risk of thrombosis but also leukemic transformation, which carries a particularly poor prognosis. Here, we discuss the recent identification of risk factors for leukemic transformation, elucidate mechanisms contributing to leukemic transformation, as well as highlight the development of new treatment strategies., Recent Findings: Significant progress in the understanding of the biology of MPNs has been made in recent years, particularly with the discovery that mutations in the JAK-STAT signaling pathway cause unregulated activation. These genetic insights have been extended to leukemic transformation and have revealed a host of genetic alterations that occur at the time of transformation, and that may identify patients at risk for leukemic transformation. Such studies have demonstrated that acute myeloid leukemia (AML) evolved from a chronic phase MPN is distinct from de-novo AML both genetically and clinically given its resistance to conventional antileukemic therapy., Summary: Leukemic transformation of an MPN remains a significant clinical challenge. Recent advances in the understanding of the molecular events that contribute to the development of leukemic transformation will need to be utilized in order to produce rational therapeutic approaches for this largely fatal disease.

Leukemic transformation (LT) of a myeloproliferative neoplasm (MPN) is associated with a dismal prognosis and no medical therapies have shown a survival improvement in patients with MPN in blast phase (MPN-BP). Effective therapies for the treatment of MPN-BP are a serious unmet need. Consensus response criteria do not exist for the treatment of patients with MPN-BP and this is necessary for the uniformed reporting of treatment response in clinical trials. We have identified relevant MPN and MPN-BP features in order to define treatment response categories that reflect hematological, clinical, pathological, cytogenetic and molecular changes after therapeutic intervention. We plan to validate these proposed response criteria within multi-centered clinical trials., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Leukemic transformation (LT) of myeloproliferative neoplasms (MPNs) is associated with a poor prognosis and resistance to therapy. Although previous candidate genetic studies have identified mutations in MPN patients who develop acute leukemia, the complement of genetic abnormalities in MPN patients who undergo LT is not known nor have specific molecular abnormalities been shown to have clinical relevance in this setting. We performed high-throughput resequencing of 22 genes in 53 patients with LT after MPN to characterize the frequency of known myeloid mutations in this entity. In addition to JAK2 and TET2 mutations, which occur commonly in LT after MPN, we identified recurrent mutations in the serine/arginine-rich splicing factor 2 (SRSF2) gene (18.9%) in acute myeloid leukemia (AML) transformed from MPNs. SRSF2 mutations are more common in AML derived from MPNs compared with LT after myelodysplasia (4.8%) or de novo AML (5.6%), respectively (P=.05). Importantly, SRSF2 mutations are associated with worsened overall survival in MPN patients who undergo LT in univariate (P=.03; HR, 2.77; 95% CI, 1.10-7.00) and multivariate analysis (P<.05; HR, 2.11; 95% CI, 1.01-4.42). These data suggest that SRSF2 mutations contribute to the pathogenesis of LT and may guide novel therapeutic approaches for MPN patients who undergo LT.