New mutations and pathogenesis of myeloproliferative neoplasms

The JAK-STAT pathway: from structural biology to cytokine engineering

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway serves as a paradigm for signal transduction from the extracellular environment to the nucleus. It plays a pivotal role in physiological functions, such as hematopoiesis, immune balance, tissue homeostasis, and surveillance against tumors. Dysregulation of this pathway may lead to various disease conditions such as immune deficiencies, autoimmune diseases, hematologic disorders, and cancer. Due to its critical role in maintaining human health and involvement in disease, extensive studies have been conducted on this pathway, ranging from basic research to medical applications. Advances in the structural biology of this pathway have enabled us to gain insights into how the signaling cascade operates at the molecular level, laying the groundwork for therapeutic development targeting this pathway. Various strategies have been developed to restore its normal function, with promising therapeutic potential. Enhanced comprehension of these molecular mechanisms, combined with advances in protein engineering methodologies, has allowed us to engineer cytokines with tailored properties for targeted therapeutic applications, thereby enhancing their efficiency and safety. In this review, we outline the structural basis that governs key nodes in this pathway, offering a comprehensive overview of the signal transduction process. Furthermore, we explore recent advances in cytokine engineering for therapeutic development in this pathway.

Venetoclax therapy and emerging resistance mechanisms in acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a highly aggressive and devastating malignancy of the bone marrow and blood. For decades, intensive chemotherapy has been the frontline treatment for AML but has yielded only poor patient outcomes as exemplified by a 5-year survival rate of < 30%, even in younger adults. As knowledge of the molecular underpinnings of AML has advanced, so too has the development new strategies with potential to improve the treatment of AML patients. To date the most promising of these targeted agents is the BH3-mimetic venetoclax which in combination with standard of care therapies, has manageable non-haematological toxicity and exhibits impressive efficacy. However, approximately 30% of AML patients fail to respond to venetoclax-based regimens and almost all treatment responders eventually relapse. Here, we review the emerging mechanisms of intrinsic and acquired venetoclax resistance in AML and highlight recent efforts to identify novel strategies to overcome resistance to venetoclax.

Non-canonical Hedgehog signaling mediates profibrotic hematopoiesis-stroma crosstalk in myeloproliferative neoplasms

The role of hematopoietic Hedgehog signaling in myeloproliferative neoplasms (MPNs) remains incompletely understood despite data suggesting that Hedgehog (Hh) pathway inhibitors have therapeutic activity in patients. We aim to systematically interrogate the role of canonical vs. non-canonical Hh signaling in MPNs. We show that Gli1 protein levels in patient peripheral blood mononuclear cells (PBMCs) mark fibrotic progression and that, in murine MPN models, absence of hematopoietic Gli1, but not Gli2 or Smo, significantly reduces MPN phenotype and fibrosis, indicating that GLI1 in the MPN clone can be activated in a non-canonical fashion. Additionally, we establish that hematopoietic Gli1 has a significant effect on stromal cells, mediated through a druggable MIF-CD74 axis. These data highlight the complex interplay between alterations in the MPN clone and activation of stromal cells and indicate that Gli1 represents a promising therapeutic target in MPNs, particularly that Hh signaling is dispensable for normal hematopoiesis.

Optimizing IFN Alpha Therapy against Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are hematologic malignancies that result from acquired driver mutations in hematopoietic stem cells (HSCs), causing overproduction of blood cells and an increased risk of thrombohemorrhagic events. The most common MPN driver mutation affects the JAK2 gene (JAK2V617F ). Interferon alpha (IFNα) is a promising treatment against MPNs by inducing a hematologic response and molecular remission for some patients. Mathematical models have been proposed to describe how IFNα targets mutated HSCs, indicating that a minimal dose is necessary for long-term remission. This study aims to determine a personalized treatment strategy. First, we show the capacity of an existing model to predict cell dynamics for new patients from data that can be easily obtained in clinic. Then, we study different treatment scenarios in silico for three patients, considering potential IFNα dose-toxicity relations. We assess when the treatment should be interrupted depending on the response, the patient's age, and the inferred development of the malignant clone without IFNα We find that an optimal strategy would be to treat patients with a constant dose so that treatment could be interrupted as quickly as possible. Higher doses result in earlier discontinuation but also higher toxicity. Without knowledge of the dose-toxicity relationship, trade-off strategies can be found for each patient. A compromise strategy is to treat patients with medium doses (60-120 μg/week) for 10-15 years. Altogether, this work demonstrates how a mathematical model calibrated from real data can help build a clinical decision-support tool to optimize long-term IFNα therapy for MPN patients. SIGNIFICANCE STATEMENT: Myeloproliferative neoplasms (MPNs) are chronic blood cancers. Interferon alpha (IFNα) is a promising treatment with the potential to induce a molecular response by targeting mutated hematopoietic stem cells. MPN patients are treated over several years, and there is a lack of knowledge concerning the posology strategy and the best timing for interrupting therapy. The study opens avenues for rationalizing how to treat MPN patients with IFNα over several years, promoting a more personalized approach to treatment.

Myeloproliferative neoplasms and splanchnic vein thrombosis: Contemporary diagnostic and therapeutic strategies

Myeloproliferative neoplasms (MPNs) are the most common etiologies of primary splanchnic vein thrombosis, present in almost forty percent of patients with Budd-Chiari syndrome or portal vein thrombosis. Diagnosis of MPNs can be difficult in these patients because key characteristics, such as elevated blood cell counts and splenomegaly, are confounded by portal hypertension or bleeding complications. In recent years, diagnostic tools have improved to provide more accurate diagnosis and classification of MPNs. Although bone marrow biopsy findings remain a major diagnostic criterion, molecular markers are playing an increasing role not only in diagnosis but also in better estimating prognosis. Therefore, though screening for JAK2V617F mutation should be the starting point of the diagnostic workup performed in all patients with splanchnic vein thrombosis, a multidisciplinary approach is needed to accurately diagnose the subtype of myeloproliferative neoplasm, recommend the useful additional tests (bone marrow biopsy, search for an additional mutation using targeted next-generation sequencing), and suggest the best treatment strategy. Indeed, providing a specific expert care pathway for patients with splanchnic vein thrombosis and underlying myeloproliferative neoplasm is crucial to determine the optimal management to reduce the risk of both hematological and hepatic complications.

Biological and Exploitable Crossroads for the Immune Response in Cancer and COVID-19

The outbreak of novel coronavirus disease 2019 (COVID-19) has exacted a disproportionate toll on cancer patients. The effects of anticancer treatments and cancer patients' characteristics shared significant responsibilities for this dismal outcome; however, the underlying immunopathological mechanisms are far from being completely understood. Indeed, despite their different etiologies, SARS-CoV-2 infection and cancer unexpectedly share relevant immunobiological connections. In the pathogenesis and natural history of both conditions, there emerges the centrality of the immune response, orchestrating the timed appearance, functional and dysfunctional roles of multiple effectors in acute and chronic phases. A significant number (more than 600) of observational and interventional studies have explored the interconnections between COVID-19 and cancer, focusing on aspects as diverse as psychological implications and prognostic factors, with more than 4000 manuscripts published so far. In this review, we reported and discussed the dynamic behavior of the main cytokines and immune system signaling pathways involved in acute vs. early, and chronic vs. advanced stages of SARS-CoV-2 infection and cancer. We highlighted the biological similarities and active connections within these dynamic disease scenarios, exploring and speculating on possible therapeutic crossroads from one setting to the other.

Clinical Application of Biomarkers for Hematologic Malignancies

Over the last decade, significant advancements have been made in the molecular mechanisms, diagnostic methods, prognostication, and treatment options in hematologic malignancies. As the treatment landscape continues to expand, personalized treatment is much more important.

With the development of new technologies, more sensitive evaluation of residual disease using flow cytometry and next generation sequencing is possible nowadays. Although some conventional biomarkers preserve their significance, novel potential biomarkers accurately detect the mutational landscape of different cancers, and also, serve as prognostic and predictive biomarkers, which can be used in evaluating therapy responses and relapses. It is likely that we will be able to offer a more targeted and risk-adapted therapeutic approach to patients with hematologic malignancies guided by these potential biomarkers. This chapter summarizes the biomarkers used (or proposed to be used) in the diagnosis and/or monitoring of hematologic neoplasms.;

Cardiovascular Disease in Myeloproliferative Neoplasms: JACC: CardioOncology State-of-the-Art Review

Myeloproliferative neoplasms are associated with increased risk for thrombotic complications. These conditions most commonly involve somatic mutations in genes that lead to constitutive activation of the Janus-associated kinase signaling pathway (eg, Janus kinase 2, calreticulin, myeloproliferative leukemia protein). Acquired gain-of-function mutations in these genes, particularly Janus kinase 2, can cause a spectrum of disorders, ranging from clonal hematopoiesis of indeterminate potential, a recently recognized age-related promoter of cardiovascular disease, to frank hematologic malignancy. Beyond thrombosis, patients with myeloproliferative neoplasms can develop other cardiovascular conditions, including heart failure and pulmonary hypertension. The authors review the pathophysiologic mechanisms of cardiovascular complications of myeloproliferative neoplasms, which involve inflammation, prothrombotic and profibrotic factors (including transforming growth factor-beta and lysyl oxidase), and abnormal function of circulating clones of mutated leukocytes and platelets from affected individuals. Anti-inflammatory therapies may provide cardiovascular benefit in patients with myeloproliferative neoplasms, a hypothesis that requires rigorous evaluation in clinical trials.

Comprehensive Analysis of Acquired Genetic Variants and Their Prognostic Impact in Systemic Mastocytosis

Systemic mastocytosis (SM) is a rare clonal haematopoietic stem cell disease in which activating KIT mutations (most commonly KIT D816V) are present in virtually every (>90%) adult patient at similar frequencies among non-advanced and advanced forms of SM. The KIT D816V mutation is considered the most common pathogenic driver of SM. Acquisition of this mutation early during haematopoiesis may cause multilineage involvement of haematopoiesis by KIT D816V, which has been associated with higher tumour burden and additional mutations in other genes, leading to an increased rate of transformation to advanced SM. Thus, among other mutations, alterations in around 30 genes that are also frequently mutated in other myeloid neoplasms have been reported in SM cases. From these genes, 12 (i.e., ASXL1, CBL, DNMT3A, EZH2, JAK2, KRAS, NRAS, SF3B1, RUNX1, SF3B1, SRSF2, TET2) have been recurrently reported to be mutated in SM. Because of all the above, assessment of multilineage involvement of haematopoiesis by the KIT D816V mutation, in the setting of multi-mutated haematopoiesis as revealed by a limited panel of genes (i.e., ASXL1, CBL, DNMT3A, EZH2, NRAS, RUNX1 and SRSF2) and associated with a poorer patient outcome, has become of great help to identify SM patients at higher risk of disease progression and/or poor survival who could benefit from closer follow-up and eventually also early cytoreductive treatment.

Genetic Background of Polycythemia Vera

Polycythemia vera belongs to myeloproliferative neoplasms, essentially by affecting the erythroblastic lineage. JAK2 alterations have emerged as major driver mutations triggering PV-phenotype with the V617F mutation detected in nearly 98% of cases. That’s why JAK2 targeting therapeutic strategies have rapidly emerged to counter the aggravation of the disease. Over decades of research, to go further in the understanding of the disease and its evolution, a wide panel of genetic alterations affecting multiple genes has been highlighted. These are mainly involved in alternative splicing, epigenetic, miRNA regulation, intracellular signaling, and transcription factors expression. If JAK2 mutation, irrespective of the nature of the alteration, is known to be a crucial event for the disease to initiate, additional mutations seem to be markers of progression and poor prognosis. These discoveries have helped to characterize the complex genomic landscape of PV, resulting in potentially new adapted therapeutic strategies for patients concerning all the genetic interferences.

JAK2 and TET2 Mutation in Polycythemia Vera

The Ten-Eleven Translocation-2 (TET2) gene, located on chromosome 4q24, has been implicated in hematological malignancies. The TET2 gene shows mutations in variable myeloid malignancies with the involvement of 15% of myeloproliferative neoplasms (MPNs). The inactivation of the TET2 gene in both mice and humans has shown a high degree of deregulation of the hematopoiesis process leading to hematological malignancies. Polycythemia vera (PV), an MPN characterized by increased red blood cell mass, has been associated with the TET2 gene. Furthermore, TET2 genes have been found to facilitate Janus kinase-2 and signal transducer activator of transcription 5, as well as modulate the epigenetic composition of genomic DNA. However, little is known about the role of TET2 mutations in patients with PV. Several studies have been conducted to further assess the significant role of TET2 gene function in various disease processes and prognoses to enhance the management and care of these patients.

Differential expression of hydroxyurea transporters in normal and polycythemia vera hematopoietic stem and progenitor cell subpopulations

Polycythemia vera (PV) is a myeloproliferative neoplasm marked by hyperproliferation of the myeloid lineages and the presence of an activating JAK2 mutation. Hydroxyurea (HU) is a standard treatment for high-risk patients with PV. Because disease-driving mechanisms are thought to arise in PV stem cells, effective treatments should target primarily the stem cell compartment. We tested for the antiproliferative effect of patient treatment with HU in fluorescence-activated cell sorting-isolated hematopoietic stem/multipotent progenitor cells (HSC/MPPs) and more committed erythroid progenitors (common myeloid/megakaryocyte-erythrocyte progenitors [CMP/MEPs]) in PV using RNA-sequencing and gene set enrichment analysis. HU treatment led to significant downregulation of gene sets associated with cell proliferation in PV HSCs/MPPs, but not in PV CMP/MEPs. To explore the mechanism underlying this finding, we assessed for expression of solute carrier membrane transporters, which mediate transmembrane movement of drugs such as HU into target cells. The active HU uptake transporter OCTN1 was upregulated in HSC/MPPs compared with CMP/MEPs of untreated patients with PV, and the HU diffusion facilitator urea transporter B (UTB) was downregulated in HSC/MPPs compared with CMP/MEPs in all patient and control groups tested. These findings indicate a higher accumulation of HU within PV HSC/MPPs compared with PV CMP/MEPs and provide an explanation for the differential effects of HU in HSC/MPPs and CMP/MEPs of patients with PV. In general, the findings highlight the importance of transporter expression in linking therapeutics with human disease.

Recent advances in prognostication and treatment of polycythemia vera

Polycythemia vera (PV) is a BCR-ABL–negative myeloproliferative neoplasm marked by acquisition of an activating mutation of JAK2, which leads to not only erythrocytosis but also frequently to leukocytosis and thrombocytosis, and is associated with a high symptom burden and increased thrombotic risk. PV has the potential to progress to myelofibrosis or an aggressive form of acute myeloid leukemia. Mutational profiling of patients with PV has led to the development of risk stratification tools to determine an individual’s risk of developing progressive disease. Although the current goals of PV treatment are to alleviate symptoms and reduce thrombotic risk, there are growing efforts to identify disease-modifying agents which will also prevent progression of disease. Here, we give an overview of the developing prognostic tools and therapeutic landscape for PV, focusing on four drug classes: pegylated interferon-alpha 2, MDM2 antagonists, hepcidin mimetics, and histone deacetylase inhibitors.

Lab tests for MPN

Molecular laboratory investigations for myeloproliferative neoplasm (MPN) can ideally be divided into two distincts groups, those for the detection of the BCR-ABL rearrangement (suspect of chronic myeloid leukemia) and those for the variants determination of the driver genes of the negative Philadelphia forms (MPN Ph neg). The BCR-ABL detection is based on RT-Polymerase Chain Reaction techniques and more recently on droplet digital PCR (ddPCR). For this type of analysis, combined with chromosome banding analysis (CBA) and Fluorescent in situ hybridization (FISH), it is essential to quantify BCR-ABL mutated copies by standard curve method. The investigation on driver genes for MPN Ph neg forms includes activity for erythroid forms such as Polycythemia Vera (test JAK2V617F and JAK2 exon 12), for non-erythroid forms such as essential thrombocythemia and myelofibrosis (test JAK2V617F, CALR exon 9, MPL exon 10), for "atypical" ones such as mastocytosis (cKIT D816V test) and for hypereosinophilic syndrome (FIP1L1-PDGFRalpha test). It's crucial to assign prognosis value through calculating allelic burden of JAK2 V617F variant and determining CALR esone 9 variants (type1/1like, type2/2like and atypical ones). A fundamental innovation for investigating triple negative cases for JAK2, CALR, MPL and for providing prognostic score is the use of Next Generation Sequencing panels containing high molecular risk genes as ASXL1, EZH2, TET2, IDH1/IDH2, SRSF2. This technique allows to detect additional or subclonal mutations which are usually acquired in varying sized sub-clones of hematopoietic progenitors. These additional variants have a prognostic significance and should be indagated to exclude false negative cases.

Transformation of Acute Myeloid Leukemia with Deletion of Chromosome 7q and Additional Abnormalities in Chromosome 8 in a Patient with Essential Thrombocythemia

This is a case report of a 60-year-old male patient with essential thrombocythemia (ET) that progressed to acute myeloid leukemia (AML) in approximately 9 years. His platelet count decreased approximately 8 years after ET treatment with hydroxyurea (HU) and aspirin. The dose of HU was reduced because of suspected myelosuppression due to HU; however, myelosuppression did not improve. Bone marrow examination revealed myelofibrosis; therefore, ruxolitinib was administered. Approximately 1 year later, his leukocyte and blast counts in the peripheral blood increased; thus, ET was judged to have progressed to AML-myelodysplasia-related change. Induction chemotherapy and consolidation therapy were initiated; however, the patient unfortunately failed to achieve complete remission. We then continued to administer salvage chemotherapy; however, his general condition worsened, and he died from cerebral hemorrhage. The karyotype at the onset of ET was 46,XY, which changed to 47,XY,del(7q),+8 at the time of AML diagnosis. In addition, genetic testing revealed FLT-3 ITD mutation. His histopathological analysis showed subarachnoid and intraparenchymal hemorrhages and tumor cell infiltration into the cerebrum, brainstem, and cerebellum. In this case, deletion of the long arm of chromosome 7, additional abnormalities in chromosome 8, and FLT3-ITD mutation were confirmed as risk factors for having developed secondary AML for approximately 9 years and death from cerebral hemorrhage 1 year later.

Frequency of Zygosity in Jak-2 Positive Patients with Polycythemia Vera-Pakistan's Perspective

BACKGROUND

Estimation of JAK2V617F mutational load in Polycythemia Vera (PV) helps to determine the severity of the disease phenotype, the risk of thrombotic events, progression to post-PV myelofibrosis and survival. Amplification Refractory Mutation Screening (ARMS) PCR or Allele Specific (AS) PCR is a simple easy method with a reasonable sensitivity for screening of zygosity.The purpose of this study was to see the frequency of disease burden and phenotypic characteristics in Pakistani patients diagnosed with JAK2V617F mutation positive PV.

MATERIALS AND METHODS

A cross-sectional study using non probability consecutive sampling was conducted at Hematology Department, Liaquat National Hospital Karachi from October 2018 to July 2019.Adult newly diagnosed JAK2V617F positive PV patients of either gender were included. Patients' demographics, clinical characteristics and baseline CBC were noted. JAK2V617F zygosity was qualitatively analyzed by ARMS-PCR technique. Age and gender were stratified to see to see the result of qualitative and quantitative effect modifiers on these patients using Chi Square and fisher exact test as appropriate while mean comparison was done by independent t-test and one way ANOVAtest. P value of ≤0.05 was considered as significant.

RESULTS

Fifty one patients were included in the study with an average age of 59.60±14.29years.90.2% of patients had hypertension.All patients tested positive for heterozygous state. Significant association of gender was found with smoking (p=0.001) while age was significantly linked with hypertension (p-0.033).

CONCLUSION

JAK2V617F positive PV patients are mainly heterozygous males showing significant association with smoking and hypertension. ARMS-PCR is a robust technique to determine zygosity which can be used for screening purposes.<br />.

Genetics and Pathogenetic Role of Inflammasomes in Philadelphia Negative Chronic Myeloproliferative Neoplasms: A Narrative Review

The last decade has been very important for the quantity of preclinical information obtained regarding chronic myeloproliferative neoplasms (MPNs) and the following will be dedicated to the translational implications of the new biological acquisitions. The overcoming of the mechanistic model of clonal evolution and the entry of chronic inflammation and dysimmunity into the new model are the elements on which to base a part of future therapeutic strategies. The innate immune system plays a major role in this context. Protagonists of the initiation and regulation of many pathological aspects, from cytokine storms to fibrosis, the NLRP3 and AIM2 inflammasomes guide and condition the natural history of the disease. For this reason, MPNs share many biological and clinical aspects with non-neoplastic diseases, such as autoimmune disorders. Finally, cardiovascular risk and disturbances in iron metabolism and myelopoiesis are also closely linked to the role of inflammasomes. Although targeted therapies are already being tested, an increase in knowledge on the subject is desirable and potentially translates into better care for patients with MPNs.

Clinical impacts of the mutational spectrum in Japanese patients with primary myelofibrosis

Patients with primary myelofibrosis (PMF) have a poorer prognosis than those with other subtypes of myeloproliferative neoplasms (MPNs). To investigate the relationship between gene mutations and the prognosis of Japanese PMF patients, we analyzed mutations in 72 regions located in 14 MPN-relevant genes (CSF3R, MPL, JAK2, CALR, DNMT3A, TET2, EZH2, ASXL1, IDH1/2, SRSF2, SF3B1, U2AF1, and TP53) utilizing a target resequencing platform. In our cohort, ASXL1 mutations were more frequently detected in both overt and prefibrotic PMF patients than other mutations. The frequency of ASXL1 mutations was slightly higher among overt PMF patients than among prefibrotic PMF patients (44.6% vs 25.0%, FDR = 0.472). Decision tree classification algorithms revealed that ASXL1, EZH2, and SRSF2 mutations were associated with a poor prognosis for overt PMF. Overall survival was significantly shorter in patients harboring ASXL1, EZH2, or SRSF2 mutations than in those without these mutations (p = 0.03). These results suggest that, as reported in Western countries, MIPSS70 is applicable to Japanese PMF patients and ASXL1, EZH2, and SRSF2 mutations may be utilized as surrogate markers of a poor prognosis.

Heterogeneous bone-marrow stromal progenitors drive myelofibrosis via a druggable alarmin axis

Functional contributions of individual cellular components of the bone-marrow microenvironment to myelofibrosis (MF) in patients with myeloproliferative neoplasms (MPNs) are incompletely understood. We aimed to generate a comprehensive map of the stroma in MPNs/MFs on a single-cell level in murine models and patient samples. Our analysis revealed two distinct mesenchymal stromal cell (MSC) subsets as pro-fibrotic cells. MSCs were functionally reprogrammed in a stage-dependent manner with loss of their progenitor status and initiation of differentiation in the pre-fibrotic and acquisition of a pro-fibrotic and inflammatory phenotype in the fibrotic stage. The expression of the alarmin complex S100A8/S100A9 in MSC marked disease progression toward the fibrotic phase in murine models and in patient stroma and plasma. Tasquinimod, a small-molecule inhibiting S100A8/S100A9 signaling, significantly ameliorated the MPN phenotype and fibrosis in JAK2V617F-mutated murine models, highlighting that S100A8/S100A9 is an attractive therapeutic target in MPNs.

Murine Models of Myelofibrosis

Myelofibrosis (MF) is subtype of myeloproliferative neoplasm (MPN) characterized by a relatively poor prognosis in patients. Understanding the factors that drive MF pathogenesis is crucial to identifying novel therapeutic approaches with the potential to improve patient care. Driver mutations in three main genes (janus kinase 2 (JAK2), calreticulin (CALR), and myeloproliferative leukemia virus oncogene (MPL)) are recurrently mutated in MPN and are sufficient to engender MPN using animal models. Interestingly, animal studies have shown that the underlying molecular mutation and the acquisition of additional genetic lesions is associated with MF outcome and transition from early stage MPN such as essential thrombocythemia (ET) and polycythemia vera (PV) to secondary MF. In this issue, we review murine models that have contributed to a better characterization of MF pathobiology and identification of new therapeutic opportunities in MPN.

A proteomic study of myeloproliferative neoplasms using reverse-phase protein arrays

Myeloproliferative neoplasms polycythemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis constitute a group of haematological diseases. The comprehensive assessment of signaling pathway activation in blood cells may aid the understanding of MPN pathophysiology. Thus, levels of post-translational protein modifications and total protein expression were determined in MPN patients and control leukocytes by using reverse-phase protein arrays (RPPA). Compared to control samples, p-SRC, p-CTNNB1, c-MYC, MCL-1, p-MDM2, BAX and CCNB1 showed higher expression in PV samples than controls. P-JAK2/JAK2 and pro-apoptotic BIM showed differential expression between JAK2V617F-positive and -negative ET patients. Apoptosis, cancer and PI3K/AKT pathways proteins showed differential expression among the studied groups. For most of the proteins analyzed using Western-Blot and RPPA, RPPA showed higher sensitivity to detect subtle differences. Taken together, our data indicate deregulated protein expression in MPN patients compared to controls. Thus, RPPA may be a useful method for broad proteome analysis in MPN patients´ leukocytes.

A novel translocation t(10;17)(p13;q11.2) harboring two cryptic deletions identified by array-CGH and characterized by SUZ12 overexpression in a patient with chronic thrombocytosis

No specific translocation is associated with myeloproliferative neoplasms (MPNs). However, an interstitial deletion involving subband 17q11.2 which includes the NF1 gene, although rare, is a recurrent aberration in several myeloid disorders including MPNs. For the first time, we report an acquired novel translocation involving 10p13 and 17q11.2 in a 62-year-old Caucasian female which was referred for investigation of chronic and persistent unexplained thrombocytosis. The patient had no history of hematological sequelae and genomic testing for JAK2, CALR, and MPL mutations were negative. She was subsequently diagnosed with a triple negative essential thrombocythemia. Array-CGH analysis noted that the translocation harbored two cryptic deletions, one of which involved 17q11.2 encompassing the NF1 gene. One of the junction breakpoints involved the SUZ12 gene. Immunohistochemical assessment of the marrow trephine showed increased megakaryocytic expression of the SUZ12 protein, as well as EZH2 and Ki67; biochemical abnormalities suggestive of excess megakaryocytic hyperplasia. This novel translocation may affect the expression of SUZ12 and its downstream targets, and may represent a unique pathogenomic etiology which drives chronic thrombocytosis in essential thrombocythemia.

Different impact of calreticulin mutations on human hematopoiesis in myeloproliferative neoplasms

Mutations of calreticulin (CALRm) define a subtype of myeloproliferative neoplasms (MPN). We studied the biological and genetic features of CALR-mutated essential thrombocythemia and myelofibrosis patients. In most cases, CALRm were found in granulocytes, monocytes, B and NK cells, but also in T cells. However, the type 1 CALRm spreads more easily than the type 2 CALRm in lymphoid cells. The CALRm were also associated with an early clonal dominance at the level of hematopoietic stem and progenitor cells (HSPC) with no significant increase during granulo/monocytic differentiation in most cases. Moreover, we found that half of type 2 CALRm patients harbors some homozygous progenitors. Those patients were associated with a higher clonal dominance during granulo/monocytic differentiation than patients with only heterozygous type 2 CALRm progenitors. When associated mutations were present, CALRm were the first genetic event suggesting that they are both the initiating and phenotypic event. In blood, type 1 CALRm led to a greater increased number of all types of progenitors compared with the type 2 CALRm. However, both types of CALRm induced an increase in megakaryocytic progenitors associated with a ruxolitinib-sensitive independent growth and with a mild constitutive signaling in megakaryocytes. At the transcriptional level, type 1 CALRm seems to deregulate more pathways than the type 2 CALRm in megakaryocytes. Altogether, our results show that CALRm modify both the HSPC and megakaryocyte biology with a stronger effect for type 1 than for type 2 CALRm.

HMGA Proteins in Hematological Malignancies

The high mobility group AT-Hook (HMGA) proteins are a family of nonhistone chromatin remodeling proteins known as "architectural transcriptional factors". By binding the minor groove of AT-rich DNA sequences, they interact with the transcription apparatus, altering the chromatin modeling and regulating gene expression by either enhancing or suppressing the binding of the more usual transcriptional activators and repressors, although they do not themselves have any transcriptional activity. Their involvement in both benign and malignant neoplasias is well-known and supported by a large volume of studies. In this review, we focus on the role of the HMGA proteins in hematological malignancies, exploring the mechanisms through which they enhance neoplastic transformation and how this knowledge could be exploited to devise tailored therapeutic strategies.

No Differences in Outcomes Between JAK2 V617F-Positive Patients with Variant Allele Fraction < 2% Versus 2-10%: A 6-Year Province-wide Retrospective Analysis

INTRODUCTION

JAK2 V617F mutation is one of the major criteria in the diagnosis of myeloproliferative neoplasms (MPN) and its variant allele fraction (VAF) determines the disease phenotype and outcomes. This study aimed to define characteristics and outcomes of patients with JAK2 V617F VAF < 2% compared to patients with VAF 2%-10%.

PATIENTS AND METHODS

We included 5079 patients with JAK2 V617F tested during 2010-2015 and identified 216 patients (4.3%) with JAK2 V617F VAF < 10%. Twenty-seven patients were excluded because of missing follow-up data.

RESULTS

A total of 189 patients were included for final analysis (89 patients with VAF < 2% and 100 patients with VAF 2%-10%). Patients with JAK2 V617F 2%-10% VAF had a significantly higher rate of splenomegaly, higher platelet counts, and more MPN diagnoses than the group with VAF < 2%. Ten patients (10.0%) with VAF 2%-10% and 24 patients (27.0%) with VAF < 2% had normal blood count and no thrombosis. There were no differences between the groups in all outcomes, including thrombotic complications (18.0% in both groups), progression to hematologic or solid cancers, and death. Patients without hematologic diagnosis had similar thrombotic incidence (16.7% in VAF < 2% vs. 20.0% in VAF 2%-10%).

CONCLUSION

Patients with JAK2 V617F mutation VAF < 2% have similar survival and thrombotic incidence as patients with VAF 2%-10%. Patients with low VAF should be monitored in the same manner as patients with higher VAF with the same diagnoses to prevent morbidity and mortality. Patients without hematologic diagnosis may benefit from thrombotic risk reduction strategies such as optimization of cardiovascular risk factors.

[A new case of rare erythrocytosis due to EGLN1 mutation with review of the literature]

INTRODUCTION

The origin of polycythemia is often simple to detect. Sometimes it is necessary to look for hereditary forms, the decisive parameters being the dosage of erythropoietin and the measurement of the oxygen dissociation curve (P50). These rare diseases are related to high oxygen-affinity haemoglobins, abnormalities of the erythropoietin receptor or dysfunction of the HIF (hypoxia-inducible factor) pathway.

CASE REPORT

We report the case of a 56-year-old patient with unexplained polycythemia associated with normal serum erythropoietin and normal P50, in whom the never previously described mutation c.400C>T(p.Gln134*) on exon 1 in the EGLN1 gene (encoding PHD2) was found.

CONCLUSION

In the face of an unexplained polycythemia a good cooperation between clinicians and biologists is necessary to be able to characterize rare hereditary pathologies.

An "EZ" Epigenetic Road to Leukemia Stem Cell Metabolic Reprogramming?

In this issue of Cancer Discovery, Gu and colleagues developed a mouse model of myeloproliferative neoplasm driven by Nras G12D and Ezh2-/- , which cooperated to induce malignant transformation and metabolic reprogramming of leukemic stem cells at least in part through loss of normal epigenetic regulation of gene expression. Furthermore, their findings point to Ezh1 and branched chain amino acid metabolism as biological dependencies and potential therapeutic targets in myeloid neoplasms.See related article by Gu et al., p. 1228.

Integrating clinical, morphological, and molecular data to assess prognosis in patients with primary myelofibrosis at diagnosis: A practical approach

Currently available prognostic scoring systems in primary myelofibrosis (PMF) do not integrate clinical, histological, and molecular data, or they also required information on "other" mutations that are available in the clinical practice only in a very limited number of laboratories. In the present multicenter study, including 401 PMF patients, an integrated International Prognostic Scoring System (I-IPSS) was developed by combining IPSS, grade of bone marrow fibrosis (GBMF), and driver mutations molecular status (MS) to define PMF prognosis at diagnosis. Four prognostic categories were identified: I-IPSS-low risk (113 patients), I-IPSS-intermediate-1 risk (56 patients), I-IPSS-intermediate-2 risk (154 patients), and I-IPSS-high risk (78 patients). Median overall survival was 26.7 years in I-IPSS-intermediate-1, 10.8 in I-IPSS-intermediate-2, and 6.4 in I-IPSS-high-risk patients (log-rank test <0.0001); instead, it was not reached in the I-IPSS-low-risk cohort because of the extremely low number of registered deaths. The addition of GBMF and MS to IPSS improved the efficacy for predicting the risk of death. Indeed, the sensitivity of I-IPSS was significantly higher (P < .05) than that of IPSS, considering both total deaths and 5- and 10-year mortality. This comprehensive approach allows clinicians to evaluate mutual interactions between IPSS, GBMF, and MS and identify high-risk patients with poor prognosis who may benefit from aggressive treatments. More importantly, this integrated score can be easily applicable worldwide as it only required information that represent the good clinical practice in the management of PMF patients.

Loss of EZH2 Reprograms BCAA Metabolism to Drive Leukemic Transformation

Epigenetic gene regulation and metabolism are highly intertwined, yet little is known about whether altered epigenetics influence cellular metabolism during cancer progression. Here, we show that EZH2 and NRAS^G12D mutations cooperatively induce progression of myeloproliferative neoplasms to highly penetrant, transplantable, and lethal myeloid leukemias in mice. EZH1, an EZH2 homolog, is indispensable for EZH2-deficient leukemia-initiating cells and constitutes an epigenetic vulnerability. BCAT1, which catalyzes the reversible transamination of branched-chain amino acids (BCAA), is repressed by EZH2 in normal hematopoiesis and aberrantly activated in EZH2-deficient myeloid neoplasms in mice and humans. BCAT1 reactivation cooperates with NRAS^G12D to sustain intracellular BCAA pools, resulting in enhanced mTOR signaling in EZH2-deficient leukemia cells. Genetic and pharmacologic inhibition of BCAT1 selectively impairs EZH2-deficient leukemia-initiating cells and constitutes a metabolic vulnerability. Hence, epigenetic alterations rewire intracellular metabolism during leukemic transformation, causing epigenetic and metabolic vulnerabilities in cancer-initiating cells. SIGNIFICANCE: EZH2 inactivation and oncogenic NRAS cooperate to induce leukemic transformation of myeloproliferative neoplasms by activating BCAT1 to enhance BCAA metabolism and mTOR signaling. We uncover a mechanism by which epigenetic alterations rewire metabolism during cancer progression, causing epigenetic and metabolic liabilities in cancer-initiating cells that may be exploited as potential therapeutics.See related commentary by Li and Melnick, p. 1158.This article is highlighted in the In This Issue feature, p. 1143.

Perspectives on interferon-alpha in the treatment of polycythemia vera and related myeloproliferative neoplasms: minimal residual disease and cure?

The first clinical trials of the safety and efficacy of interferon-alpha2 (IFN-alpha2) were performed about 30 years ago. Since then, several single-arm studies have convincingly demonstrated that IFN-alpha2 is a highly potent anti-cancer agent in several cancer types but unfortunately not being explored sufficiently due to a high toxicity profile when using non-pegylated IFN-alpha2 or high dosages or due to competitive drugs, that for clinicians at first glance might look more attractive. Within the hematological malignancies, IFN-alpha2 has only recently been revived in patients with the Philadelphia-negative myeloproliferative neoplasms-essential thrombocytosis, polycythemia vera, and myelofibrosis (MPNs)-and in patients with chronic myelogenous leukemia (CML) in combination with tyrosine kinase inhibitors. In this review, we tell the IFN story in MPNs from the very beginning in the 1980s up to 2018 and describe the perspectives for IFN-alpha2 treatment of MPNs in the future. The mechanisms of actions are discussed and the impact of chronic inflammation as the driving force for clonal expansion and disease progression in MPNs is discussed in the context of combination therapies with potent anti-inflammatory agents, such as the JAK1-2 inhibitors (licensed only ruxolitinib) and statins as well. Interferon-alpha2 being the cornerstone treatment in MPNs and having the potential of inducing minimal residual disease (MRD) with normalization of the bone marrow and low-JAK2V617F allele burden, we believe that combination therapy with ruxolitinib may be even more efficacious and hopefully revert disease progression in many more patients to enter the path towards MRD. In patients with advanced and transforming disease towards leukemic transformation or having transformed to acute myeloid leukemia, "triple therapy" is proposed as a novel treatment modality to be tested in clinical trials combining IFN-alpha2, DNA-hypomethylator, and ruxolitinib. The rationale for this "triple therapy" is given, including the fact that even in AML, IFN-alpha2 as monotherapy may revert disease progression. We envisage a new and bright future with many more patients with MPNs obtaining MRD on the above therapies. From this stage-and even before-vaccination strategies may open a new horizon with cure being the goal for some patients.

Clinical Exome Sequencing unravels new disease-causing mutations in the myeloproliferative neoplasms: A pilot study in patients from the state of Qatar

Clinical Exome Sequencing (CES) has increasingly become a popular diagnostic tool in patients suffering from genetic disorders that are clinically and genetically complicated. Myeloproliferative Neoplasms (MPNs) is an example of a heterogeneous disorder. In Qatar, familial cases of MPNs are more frequently seen than described in the literature. In this study, we aimed to use CES to classify six Qatari subjects that were suspected of clinical diagnosis of MPNs, according to the WHO 2008 diagnostic criteria for hematologic malignancies, and identify variants that can potentially explain the phenotypic diversity of MPNs. We sequenced six Qatari subjects using CES, of whom, three probands were unrelated families and three members were from the same family, all probands come from consanguineous families, and had a positive family history of MPNs. CES identified 61 variants in 50 genes; of which, 13 were recurrently mutated in our patients. Ten novel variants were identified in ten known genes related to MPNs and seven variants were identified in seven novel candidate genes. The genotype of the six subjects was due to a combination of different variants in different genes. This study serves as a pilot study to investigate the complexity of the genotype of patients with MPNS in Qatar, and serves as a guide for further well-controlled genetic epidemiological studies for patients with MPNs. CES is a powerful tool to be used in the genetic clinics for differential and definitive diagnosis of patients with MPNs.

Detection of Exon 12 and 14 Mutations in Janus Kinase 2 Gene Including a Novel Mutant in V617F Negative Polycythemia Vera Patients from Pakistan

The most frequently reported genetic aberration among polycythemia vera (PV) patients is a gain of function mutation V617F in exon 14 of Janus kinase 2 (JAK2) gene. However in many investigations, V617F negative PV patients have been reported to harbor mutations in JAK 2 exon 12. We investigated 24 patients with PV (diagnosed following 2016 WHO guidelines) to detect V617F mutation through allele specific PCR. The frequency of which was found to be 19/24 (79.2 %). Later on JAK2 exon 12 and 14 was amplified by conventional PCR in V617F negative patients and subjected to sequence analysis. A total of 03 mutated sites in exon 12 were detected in only two V617F-negative patients 2/5 (40%). All three substitutions were heterozygous i.e. F537F/I found in both patients and R528R/T, which is a novel mutation. In addition, one patient 1/5 (10%) manifested amino acid substitution V617A in JAK2 exon 14. Hematological parameters of individuals harboring mutations do not vary significantly than rest of the PV patients. Previous history and 2.3 years of follow-up studies reveal 15-year survival of V617F positive patients (n=19) to be 76%, while it is 94% for wild type V617 patients (n=05). Mean TLC of the patient cohort was 17.6± 9.1 x 109/L, mean platelet count was 552± 253 x 109/L, mean hemoglobin was 16.9± 3.2 g/dl, mean corpuscular volume (MCV) was 77.2± 13.0 fl and mean corpuscular hemoglobin (MCH) was 25.6± 3.9 pg. This is the very first attempt from Pakistan to screen JAK2-exon 12 mutations in PV patients. We further aim to investigate Jak2 exon 12 mutations in larger number of PV patients to assess their clinical relevance and role in disease onset, progression and transformation.

A phase 2 study of ruxolitinib in combination with azacitidine in patients with myelofibrosis

Ruxolitinib (RUX)-based combinations may provide benefit for patients with myelofibrosis (MF). In this open-label, nonrandomized, prospective phase 2 study, patients with MF initially received RUX twice per day continuously in 28-day cycles for the first 3 cycles. Azacitidine (AZA) 25 mg/m² (days 1-5) was added starting with cycle 4 and could be subsequently increased to 75 mg/m² (days 1-5). Forty-six patients were enrolled with a median follow-up of 28 months (range, 4-50+ months). An International Working Group for Myelofibrosis Research and Treatment (IWG-MRT) response was achieved in 33 patients (72%), with a median time to response of 1.8 months (range, 0.7-19.0 months). One-fourth (7 of 33) of the IWG-MRT responses occurred after the addition of AZA. A reduction of >50% in palpable spleen length at 24 weeks and at any time on the study was achieved in 62% and 71% of the evaluable patients, respectively. Among patients who achieved a >50% reduction in spleen length at 24 weeks, 95% had maintained it at 48 weeks. Notably, improvements in bone marrow reticulin fibrosis grade occurred in 57% of the patients at 24 months. Treatment discontinuations as a result of drug-related toxicities occurred in 4 patients (9%), all as a result of cytopenias. New onset grade 3 to 4 anemia and thrombocytopenia occurred in 35% and 26% of patients, respectively. RUX and AZA were safe, with encouraging spleen response rates and improvement in bone marrow fibrosis in patients with MF. This trial was registered at www.clinicaltrials.gov as #NCT01787487.

Recommendations for the diagnosis and treatment of patients with polycythaemia vera

OBJECTIVES

To present the Central European Myeloproliferative Neoplasm Organisation (CEMPO) treatment recommendations for polycythaemia vera (PV).

METHODS

During meetings held from 2015 through 2017, CEMPO discussed PV and its treatment and recent data.

RESULTS

PV is associated with increased risks of thrombosis/thrombo-haemorrhagic complications, fibrotic progression and leukaemic transformation. Presence of Janus kinase (JAK)-2 gene mutations is a diagnostic marker and standard diagnostic criterion. World Health Organization 2016 diagnostic criteria for PV, focusing on haemoglobin levels and bone marrow morphology, are mandatory. PV therapy aims at managing long-term risks of vascular complications and progression towards transformation to acute myeloid leukaemia and myelodysplastic syndrome. Risk stratification for thrombotic complications guides therapeutic decisions. Low-risk patients are treated first line with low-dose aspirin and phlebotomy. Cytoreduction is considered for low-risk (phlebotomy intolerance, severe/progressive symptoms, cardiovascular risk factors) and high-risk patients. Hydroxyurea is suspected of leukaemogenic potential. IFN-α has demonstrated efficacy in many clinical trials; its pegylated form is best tolerated, enabling less frequent administration than standard interferon. Ropeginterferon alfa-2b has been shown to be more efficacious than hydroxyurea. JAK1/JAK2 inhibitor ruxolitinib is approved for hydroxyurea resistant/intolerant patients.

CONCLUSIONS

Greater understanding of PV is serving as a platform for new therapy development and treatment response predictors.

Safety and efficacy of combination therapy of interferon-α2 and ruxolitinib in polycythemia vera and myelofibrosis

Interferon‐α2 reduces elevated blood cell counts and splenomegaly in patients with myeloproliferative neoplasms (MPN) and may restore polyclonal hematopoiesis. Its use is limited by inflammation‐mediated toxicity, leading to treatment discontinuation in 10‐30% of patients. Ruxolitinib, a potent anti‐inflammatory agent, has demonstrated benefit in myelofibrosis (MF) and polycythemia vera (PV) patients. Combination therapy (CT) with these two agents may be more efficacious than monotherapy with either, potentially improving tolerability of interferon‐α2 as well. We report the preliminary results from a phase II study of CT with pegylated interferon‐α2 and ruxolitinib in 50 MPN patients (PV, n = 32; low‐/intermediate‐1‐risk MF, n = 18), the majority (n = 47) being resistant and/or intolerant to interferon‐α2 monotherapy. Objectives included remission (2013 revised criteria encompassing histologic, hematologic, and clinical responses), complete hematologic response (CHR), molecular response, and toxicity. Follow‐up was 12 months. Partial remission (PR) and sustained CHR were achieved in 9% and 44% of PV patients, respectively. In MF patients, complete or partial remission was achieved in 39%, and sustained CHR in 58%. The median JAK2V617F allele burden declined significantly in both groups. Hematologic toxicity was the most common adverse event and was managed by dose reduction. Thirty‐seven serious adverse events were recorded in 23 patients; the discontinuation rate was 20%. We conclude that CT with interferon‐α2 and ruxolitinib is efficacious in patients with low‐/intermediate‐1‐risk MF and, to a lesser extent, in patients with PV. These preliminary results encourage phase III studies as well as a study with CT in newly diagnosed MPN patients.

ASXL1 mutations in myeloid neoplasms: pathogenetic considerations, impact on clinical outcomes and survival

BACKGROUND

ASXL1 gene mutations include nonsense, missense, and frameshift mutations. Although their clinical significance is still debated, they may play an important role in the pathogenesis of several hematologic malignancies.

METHODS

Herein, we offer a comprehensive review on ASXL1 mutations, and link them with survival and clinical outcomes in patients with various myeloid neoplasms. Most relevant publications were identified through searching the PubMed/Medline database for articles published from inception to February 2016.

FINDINGS

In acute myeloid leukemia (AML), ASXL1 mutations tend to correlate with older age and male gender, and affect predominantly patients with secondary AML. De novo AML patients with ASXL1 mutations had significantly lower complete remission rates after standard high-dose chemotherapy and shorter survival. In chronic myelomonocytic leukemia and low- or intermediate-risk myelodysplastic syndromes, frameshift and nonsense mutations correlated with shorter survival and a higher risk of leukemic transformation. Overall survival was also shorter in primary myelofibrosis in the presence of ASXL1 mutations.

CONCLUSIONS

Further research on the role of ASXL1 mutations and therapeutic implications in neoplastic myeloid disorders is stringently needed. Given the relatively high prevalence of ASXL1 mutations, larger studies involving patients affected by these mutations will be feasible in the near future.

Survey and evaluation of mutations in the human KLF1 transcription unit

Erythroid Krüppel-like Factor (EKLF/KLF1) is an erythroid-enriched transcription factor that plays a global role in all aspects of erythropoiesis, including cell cycle control and differentiation. We queried whether its mutation might play a role in red cell malignancies by genomic sequencing of the KLF1 transcription unit in cell lines, erythroid neoplasms, dysplastic disorders, and leukemia. In addition, we queried published databases from a number of varied sources. In all cases we only found changes in commonly notated SNPs. Our results suggest that if there are mutations in KLF1 associated with erythroid malignancies, they are exceedingly rare.

Acute pro-B-Cell lymphoblastic leukemia transformed from myelodysplastic syndrome with an ASXL1 missense mutation: A case report with literature review

The development of acute lymphoblastic leukemia (ALL) from myelodysplastic syndrome (MDS) is a very rare event. The current report presents a rare case of a 33-year-old man who was diagnosed with MDS with multiple-lineage dysplasia (MDS-MLD) that transformed into pro-B-ALL. A missense mutation (S1231F) of the additional sex combs like 1, transcriptional regulator gene was identified, which may have a substantial role in the progression, however does not act as an unfavorable prognostic marker. The patient died during induction chemotherapy. The present study further conducted an analysis on 30 patients to determine progression to ALL. Patients were predominantly male (76.7%, 23/30) with a median age of 56 years (3-90 years). The median time to transformation was 5.5 months (2-50 months). The most common type of MDS with ALL transformation comprised of MDS-excess blasts (MDS-EB; 40%, 12/30), MDS with single-lineage dysplasia (MDS-SLD; 30%, 9/30) and MDS with ring sideroblasts (MDS-RS; 16.7%, 5/30). The majority of the patients transformed to B-cell (66.7%, 16/24) followed by T-cell (33.3%, 8/24) ALL. From the 25 cases where data was available, the complete remission rate was 75% (15/20) with ALL-directed chemotherapy and the median remission duration was 15 months (range 4.5 to 51 months). However, the results indicated that ALL following MDS is characterized by a high rate of early death (20%, 5/25).

The molecular basis of JAK/STAT inhibition by SOCS1

The SOCS family of proteins are negative-feedback inhibitors of signalling induced by cytokines that act via the JAK/STAT pathway. SOCS proteins can act as ubiquitin ligases by recruiting Cullin5 to ubiquitinate signalling components; however, SOCS1, the most potent member of the family, can also inhibit JAK directly. Here we determine the structural basis of both these modes of inhibition. Due to alterations within the SOCS box domain, SOCS1 has a compromised ability to recruit Cullin5; however, it is a direct, potent and selective inhibitor of JAK catalytic activity. The kinase inhibitory region of SOCS1 targets the substrate binding groove of JAK with high specificity and thereby blocks any subsequent phosphorylation. SOCS1 is a potent inhibitor of the interferon gamma (IFNγ) pathway, however, it does not bind the IFNγ receptor, making its mode-of-action distinct from SOCS3. These findings reveal the mechanism used by SOCS1 to inhibit signalling by inflammatory cytokines.

The molecular basis of JAK/STAT inhibition by SOCS1

The SOCS family of proteins are negative-feedback inhibitors of signalling induced by cytokines that act via the JAK/STAT pathway. SOCS proteins can act as ubiquitin ligases by recruiting Cullin5 to ubiquitinate signalling components; however, SOCS1, the most potent member of the family, can also inhibit JAK directly. Here we determine the structural basis of both these modes of inhibition. Due to alterations within the SOCS box domain, SOCS1 has a compromised ability to recruit Cullin5; however, it is a direct, potent and selective inhibitor of JAK catalytic activity. The kinase inhibitory region of SOCS1 targets the substrate binding groove of JAK with high specificity and thereby blocks any subsequent phosphorylation. SOCS1 is a potent inhibitor of the interferon gamma (IFNγ) pathway, however, it does not bind the IFNγ receptor, making its mode-of-action distinct from SOCS3. These findings reveal the mechanism used by SOCS1 to inhibit signalling by inflammatory cytokines.

Cytokines are key molecules in controlling haematopoiesis that signal via the JAK/STAT pathway. Here the authors present the structures of SOCS1 bound to its JAK1 target as well as in complex with elonginB and elonginC, providing a molecular explanation for the potent JAK- inhibitory activity of SOCS1.

CRISPR/Cas9-mediated ASXL1 mutations in U937 cells disrupt myeloid differentiation

Additional sex combs-like 1 (ASXL1) is a well‑known tumor suppressor gene and epigenetic modifier. ASXL1 mutations are frequent in myeloid malignances; these mutations are risk factors for the development of myelodysplasia and also appear as small clones during normal aging. ASXL1 appears to act as an epigenetic regulator of cell survival and myeloid differentiation; however, the molecular mechanisms underlying the malignant transformation of cells with ASXL1 mutations are not well defined. Using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) genome editing, heterozygous and homozygous ASXL1 mutations were introduced into human U937 leukemic cells. Comparable cell growth and cell cycle progression were observed between wild-type (WT) and ASXL1-mutated U937 cells. Drug-induced cytotoxicity, as measured by growth inhibition and apoptosis in the presence of the cell-cycle active agent 5-fluorouracil, was variable among the mutated clones but was not significantly different from WT cells. In addition, ASXL1-mutated cells exhibited defects in monocyte/macrophage differentiation. Transcriptome analysis revealed that ASXL1 mutations altered differentiation of U937 cells by disturbing genes involved in myeloid differentiation, including cytochrome B-245 β chain and C-type lectin domain family 5, member A. Dysregulation of numerous gene sets associated with cell death and survival were also observed in ASXL1-mutated cells. These data provide evidence regarding the underlying molecular mechanisms induced by mutated ASXL1 in leukemogenesis.

ASXL1 mutations in AML are associated with specific clinical and cytogenetic characteristics

Mutations of ASXL1 are early events in acute myeloid leukemia (AML) leukemogenesis and have been associated with unfavorable prognosis. In this study, we investigated the type and frequency of ASXL1 mutations in a large cohort of patients with de novo or secondary AML (s-AML) and looked for correlations with cytogenetic findings and disease features. ASXL1 mutations were associated with older age, s-AML and higher peripheral leukocytosis. We observed more frequent co-occurrence of ASXL1 mutations with trisomy 8 and chromosome 11 aberrations but a negative correlation with myelodysplastic syndromes (MDS)-related cytogenetic abnormalities, especially -5/del(5q) and -7/del(7q). ASXL1 mutations were also found in other genetically defined AML subgroups such as those with t(9;22), inv(3)/t(3;3), t(8;21) or t(15;17); however, none of our inv(16) cases carried ASXL1 mutations. We detected two previously unreported ASXL1 mutations, p.IIe593Val and p.Cys688Tyr. Our findings suggest that ASXL1 mutations tend to cluster with specific clinical and cytogenetic profiles of AML patients.

Acute lymphoblastic leukemia secondary to myeloproliferative neoplasms or after lenalidomide exposure

Philadelphia‐negative (Ph⁻) myeloproliferative neoplasms (MPN) do rarely transform to acute lymphoblastic leukemia (ALL). While causality is difficult to establish, a few cases of ALL arising after exposure to lenalidomide for registered indications (multiple myeloma, myelodysplastic syndrome with 5q deletion) have been described in the literature.

Glioblastoma and acute myeloid leukemia: malignancies with striking similarities

Acute myeloid leukemia (AML) and glioblastoma (GB) are two malignancies associated with high incidence of treatment refractoriness and generally, uniformly poor survival outcomes. While the former is a hematologic (i.e. a "liquid") malignancy and the latter a solid tumor, the two diseases share both clinical and biochemical characteristics. Both diseases exist predominantly in primary (de novo) forms, with only a small subset of each progressing from precursor disease states like the myelodysplastic syndromes or diffuse glioma. More importantly, the primary and secondary forms of each disease are characterized by common sets of mutations and gene expression abnormalities. The primary versions of AML and GB are characterized by aberrant RAS pathway, matrix metalloproteinase 9, and Bcl-2 expression, and their secondary counterparts share abnormalities in TP53, isocitrate dehydrogenase, ATRX, inhibitor of apoptosis proteins, and survivin that both influence the course of the diseases themselves and their progression from precursor disease. An understanding of these shared features is important, as it can be used to guide both the research about and treatment of each.