Deregulation of apoptosis-related genes is associated with PRV1 overexpression and JAK2 V617F allele burden in Essential Thrombocythemia and Myelofibrosis

Tyrosine phosphorylation of CARM1 promotes its enzymatic activity and alters its target specificity

An important epigenetic component of tyrosine kinase signaling is the phosphorylation of histones, and epigenetic readers, writers, and erasers. Phosphorylation of protein arginine methyltransferases (PRMTs), have been shown to enhance and impair their enzymatic activity. In this study, we show that the hyperactivation of Janus kinase 2 (JAK2) by the V617F mutation phosphorylates tyrosine residues (Y149 and Y334) in coactivator-associated arginine methyltransferase 1 (CARM1), an important target in hematologic malignancies, increasing its methyltransferase activity and altering its target specificity. While non-phosphorylatable CARM1 methylates some established substrates (e.g. BAF155 and PABP1), only phospho-CARM1 methylates the RUNX1 transcription factor, on R223 and R319. Furthermore, cells expressing non-phosphorylatable CARM1 have impaired cell-cycle progression and increased apoptosis, compared to cells expressing phosphorylatable, wild-type CARM1, with reduced expression of genes associated with G2/M cell cycle progression and anti-apoptosis. The presence of the JAK2-V617F mutant kinase renders acute myeloid leukemia (AML) cells less sensitive to CARM1 inhibition, and we show that the dual targeting of JAK2 and CARM1 is more effective than monotherapy in AML cells expressing phospho-CARM1. Thus, the phosphorylation of CARM1 by hyperactivated JAK2 regulates its methyltransferase activity, helps select its substrates, and is required for the maximal proliferation of malignant myeloid cells.

Ratio of stemness to interferon signalling as a biomarker and therapeutic target of myeloproliferative neoplasm progression to acute myeloid leukaemia

Progression to aggressive secondary acute myeloid leukaemia (sAML) poses a significant challenge in the management of myeloproliferative neoplasms (MPNs). Since the physiopathology of MPN is closely linked to the activation of interferon (IFN) signalling and that AML initiation and aggressiveness is driven by leukaemia stem cells (LSCs), we investigated these pathways in MPN to sAML progression. We found that high IFN signalling correlated with low LSC signalling in MPN and AML samples, while MPN progression and AML transformation were characterized by decreased IFN signalling and increased LSC signature. A high LSC to IFN expression ratio in MPN patients was associated with adverse clinical prognosis and higher colony forming potential. Moreover, treatment with hypomethylating agents (HMAs) activates the IFN signalling pathway in MPN cells by inducing a viral mimicry response. This response is characterized by double-stranded RNA (dsRNA) formation and MDA5/RIG-I activation. The HMA-induced IFN response leads to a reduction in LSC signature, resulting in decreased stemness. These findings reveal the frequent evasion of viral mimicry during MPN-to-sAML progression, establish the LSC-to-IFN expression ratio as a progression biomarker, and suggests that HMAs treatment can lead to haematological response in murine models by re-activating dsRNA-associated IFN signalling.

Targeting apoptosis dysregulation in myeloid malignancies - The promise of a therapeutic revolution

In recent years, the therapeutic landscape of myeloid malignancies has been completely revolutionized by the introduction of several new drugs, targeting molecular alterations or pathways crucial for leukemia cells survival. Particularly, many agents targeting apoptosis have been investigated in both pre-clinical and clinical studies. For instance, venetoclax, a pro-apoptotic agent active on BCL-2 signaling, has been successfully used in the treatment of acute myeloid leukemia (AML). The impressive results achieved in this context have made the apoptotic pathway an attractive target also in other myeloid neoplasms, translating the experience of AML. Therefore, several drugs are now under investigation either as single or in combination strategies, due to their synergistic efficacy and capacity to overcome resistance. In this paper, we will review the mechanisms of apoptosis and the specific drugs currently used and under investigation for the treatment of myeloid neoplasia, identifying critical research necessities for the upcoming years.

Treating accelerated and blast phase myeloproliferative neoplasms: progress and challenges

Myeloproliferative neoplasms (MPNs) are a group of clonal hematologic malignancies that include polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF). MPNs are characterized by activating mutations in the JAK/STAT pathway and an increased risk of transformation to an aggressive form of acute leukemia, termed MPN-blast phase (MPN-BP). MPN-BP is characterized by the presence of ⩾20% blasts in the blood or bone marrow and is almost always preceded by an accelerated phase (MPN-AP) defined as ⩾10-19% blasts in the blood or bone marrow. These advanced forms of disease are associated with poor prognosis with a median overall survival (mOS) of 3-5 months in MPN-BP and 13 months in MPN-AP. MPN-AP/BP has a unique molecular landscape characterized by increased intratumoral complexity. Standard therapies used in de novo acute myeloid leukemia (AML) have not demonstrated improvement in OS. Allogeneic hematopoietic stem cell transplant (HSCT) remains the only curative therapy but is associated with significant morbidity and mortality and infrequently utilized in clinical practice. Therefore, an urgent unmet need persists for effective therapies in this advanced phase patient population. Here, we review the current management and future directions of therapy in MPN-AP/BP.

Putative Role of Neutrophil Extracellular Trap Formation in Chronic Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are hematologic malignancies characterized by gene mutations that promote myeloproliferation and resistance to apoptosis via constitutively active signaling pathways, with Janus kinase 2-signal transducers and the activators of transcription (JAK-STAT) axis as a core part. Chronic inflammation has been described as a pivot for the development and advancement of MPNs from early stage cancer to pronounced bone marrow fibrosis, but there are still unresolved questions regarding this issue. The MPN neutrophils are characterized by upregulation of JAK target genes, they are in a state of activation and with deregulated apoptotic machinery. Deregulated neutrophil apoptotic cell death supports inflammation and steers them towards secondary necrosis or neutrophil extracellular trap (NET) formation, a trigger of inflammation both ways. NETs in proinflammatory bone marrow microenvironment induce hematopoietic precursor proliferation, which has an impact on hematopoietic disorders. In MPNs, neutrophils are primed for NET formation, and even though it seems obvious for NETs to intervene in the disease progression by supporting inflammation, no reliable data are available. We discuss in this review the potential pathophysiological relevance of NET formation in MPNs, with the intention of contributing to a better understanding of how neutrophils and neutrophil clonality can orchestrate the evolution of a pathological microenvironment in MPNs.

Combination of ruxolitinib with ABT-737 exhibits synergistic effects in cells carrying concurrent JAK2V617F and ASXL1 mutations

The V617F mutation in Janus kinase 2 is considered one of the driver mutations leading to Philadelphia-negative myeloproliferative neoplasms (MPNs). Concurrent JAK2V617F and ASXL1 mutations accelerate the progression of myelofibrosis in patients with MPNs. Few therapies are currently available for patients with these two mutations. In our study, the combination of ruxolitinib with ABT-737 was evaluated in cells carrying JAK2V617F and ASXL1 double mutations. RNA sequencing indicated overactivated oxidative phosphorylation in JAK2V617F;Asxl1+/- cKit+ cells. The cell line model with JAK2V617F and ASXL1 double mutations (HEL-AKO cells) also exhibited dysregulated mitochondrial function with an increase in the reactive oxygen species levels and a decrease in the ATP levels. The colony growth inhibition rates of cells with JAK2V617F and ASXL1 double mutations were significantly lower than those of cells with only the JAK2V617F mutation. Combined treatment with ruxolitinib and ABT-737 promoted apoptosis and inhibited the proliferation of HEL-AKO cells. Cotreatment with the two drugs also inhibited the growth of bone marrow mononuclear cells isolated from patients with concurrent JAK2V617F and ASXL1 mutations. In conclusion, we provide preclinical evidence showing that the combination of ruxolitinib and ABT-737 is a promising therapeutic strategy for MPN patients with concurrent JAK2V617F and ASXL1 mutations.

Novel Therapies in Myelofibrosis: Beyond JAK Inhibitors

PURPOSE OF REVIEW

To discuss the current treatment paradigm, review novel targets, and summarize completed and ongoing clinical trials that may lead to a paradigm shifts in the management of myelofibrosis (MF).

RECENT FINDINGS

In addition to the recent approval and ongoing late-stage development of multiple novel JAK inhibitors, recent clinical studies demonstrate therapeutic potential of targeting multiple alternate proteins and pathways including BET, MDM2, telomerase, BCL2, LSD1, PI3K, SMAC, and PTX2 in patients with MF. MF is a myeloproliferative neoplasm characterized by clonal proliferation of myeloid cells and bone marrow fibrosis often causing cytopenias, extramedullary hematopoiesis resulting in hepatosplenomegaly, and increased pro-inflammatory cytokine production driving systemic symptoms. A significant proportion of morbidity and mortality is related to the propensity to transform to acute leukemia. Allogeneic hematopoietic stem cell transplantation is the only curative therapy; however, due to the high associated mortality, this treatment is not an option for the majority of patients with MF. Currently, there are three targeted Food and Drug Administration (FDA)-approved therapies for MF which include ruxolitinib, fedratinib, and pacritinib, all part of the JAK inhibitor class. Many patients are unable to tolerate, do not respond, or develop resistance to existing therapies, leaving a large unmet medical need. In this review, we discuss the current treatment paradigm and novel therapies in development for the treatment of MF. We review the scientific rationale of each targeted pathway. We summarize updated clinical data and ongoing trials that may lead to FDA approval of these agents.

Defining disease modification in myelofibrosis in the era of targeted therapy

The development of targeted therapies for the treatment of myelofibrosis highlights a unique issue in a field that has historically relied on symptom relief, rather than survival benefit or modification of disease course, as key response criteria. There is, therefore, a need to understand what constitutes disease modification of myelofibrosis to advance appropriate drug development and therapeutic pathways. Here, the authors discuss recent clinical trial data of agents in development and dissect the potential for novel end points to act as disease modifying parameters. Using the rationale garnered from latest clinical and scientific evidence, the authors propose a definition of disease modification in myelofibrosis. With improved overall survival a critical outcome, alongside the normalization of hematopoiesis and improvement in bone marrow fibrosis, there will be an increasing need for surrogate measures of survival for use in the early stages of trials. As such, the design of future clinical trials will require re-evaluation and updating to incorporate informative parameters and end points with standardized definitions and methodologies.

Addition of Navitoclax to Ongoing Ruxolitinib Therapy for Patients With Myelofibrosis With Progression or Suboptimal Response: Phase II Safety and Efficacy

PURPOSE

Targeting the BCL-XL pathway has demonstrated the ability to overcome Janus kinase inhibitor resistance in preclinical models. This phase II trial investigated the efficacy and safety of adding BCL-XL/BCL-2 inhibitor navitoclax to ruxolitinib therapy in patients with myelofibrosis with progression or suboptimal response to ruxolitinib monotherapy (ClinicalTrials.gov identifier: NCT03222609).

METHODS

Thirty-four adult patients with intermediate-/high-risk myelofibrosis who had progression or suboptimal response on stable ruxolitinib dose (≥ 10 mg twice daily) were administered navitoclax at 50 mg once daily starting dose, followed by escalation to a maximum of 300 mg once daily in once in weekly increments (if platelets were ≥ 75 × 109/L). The primary end point was ≥ 35% spleen volume reduction (SVR35) from baseline at week 24. Secondary end points included ≥ 50% reduction in total symptom score (TSS50) from baseline at week 24, hemoglobin improvement, change in bone marrow fibrosis (BMF) grade, and safety.

RESULTS

High molecular risk mutations were identified in 58% of patients, and 52% harbored ≥ 3 mutations. SVR35 was achieved by 26.5% of patients at week 24, and by 41%, at any time on study, with an estimated median duration of SVR35 of 13.8 months. TSS50 was achieved by 30% (6 of 20) of patients at week 24, and BMF improved by 1-2 grades in 33% (11 of 33) of evaluable patients. Anemia response was achieved by 64% (7 of 11), including one patient with baseline transfusion dependence. Median overall survival was not reached with a median follow-up of 21.6 months. The most common adverse event was reversible thrombocytopenia without clinically significant bleeding (88%).

CONCLUSION

The addition of navitoclax to ruxolitinib in patients with persistent or progressive myelofibrosis resulted in durable SVR35, improved TSS, hemoglobin response, and BMF. Further investigation is underway to qualify the potential for disease modification.

Selenocystine-Derived Label-Free Fluorescent Schiff Base Nanocomplex for siRNA Delivery Synergistically Kills Cancer Cells

Chemo and siRNA synergic treatments for tumors is a promising new therapeutic trend. Selenocystine, a selenium analog of cysteine, has been considered a potential antitumor agent due to its redox perturbing role. In this study, we developed a nanocarrier for siRNA based on a selenocystine analog engineered polyetherimide and achieved traceable siRNA delivery and the synergic killing of tumor cells. Notably, we applied the label-free Schiff base fluorescence mechanism, which enabled us to trace the siRNA delivery and to monitor the selenocystine analogs' local performance. A novel selenocystine-derived fluorescent Schiff base linker was used to crosslink the polyetherimide, thereby generating a traceable siRNA delivery vehicle with green fluorescence. Moreover, we found that this compound induced tumor cells to undergo senescence. Together with the delivery of a siRNA targeting the anti-apoptotic BCL-xl/w genes in senescent cells, it achieved a synergistic inhibition function by inducing both senescence and apoptosis of tumor cells. Therefore, this study provides insights into the development of label-free probes, prodrugs, and materials towards the synergic strategies for cancer therapy.

Neutrophil Death in Myeloproliferative Neoplasms: Shedding More Light on Neutrophils as a Pathogenic Link to Chronic Inflammation

Neutrophils are an essential component of the innate immune response, but their prolonged activation can lead to chronic inflammation. Consequently, neutrophil homeostasis is tightly regulated through balance between granulopoiesis and clearance of dying cells. The bone marrow is both a site of neutrophil production and the place they return to and die. Myeloproliferative neoplasms (MPN) are clonal hematopoietic disorders characterized by the mutations in three types of molecular markers, with emphasis on Janus kinase 2 gene mutation (JAK2V617F). The MPN bone marrow stem cell niche is a site of chronic inflammation, with commonly increased cells of myeloid lineage, including neutrophils. The MPN neutrophils are characterized by the upregulation of JAK target genes. Additionally, MPN neutrophils display malignant nature, they are in a state of activation, and with deregulated apoptotic machinery. In other words, neutrophils deserve to be placed in the midst of major events in MPN. Our crucial interest in this review is better understanding of how neutrophils die in MPN mirrored by defects in apoptosis and to what possible extent they can contribute to MPN pathophysiology. We tend to expect that reduced neutrophil apoptosis will establish a pathogenic link to chronic inflammation in MPN.

Novel therapeutics and targets in myelofibrosis

Myelofibrosis is a myeloproliferative neoplasm characterized by clonal proliferation of myeloid cells, bone marrow fibrosis and cytopenias, extramedullary hematopoiesis and hepatosplenomegaly, increased pro-inflammatory cytokine production, and systemic symptoms. Patients with MF also have a propensity toward leukemic transformation. Allogeneic hematopoietic stem cell transplantation (aHCT) is the only curative therapy for patients with MF; however, transplant-related morbidity and mortality precludes this option for the majority of patients. In the last decade, two targeted therapies have been approved for the treatment of MF, both JAK2 inhibitors, ruxolitinib and fedratinib. Despite the clinical efficacy of these two compounds in terms of splenomegaly and symptom burden reduction, there remain many areas of unmet need in the treatment of myelofibrosis. In this review, we discuss the limitations of currently approved treatment options and novel therapeutic targets with drug candidates in late-stage (phase II or III) clinical development for the treatment of MF. We delve into the mechanism of action and scientific rational of each candidate agent as well as the available clinical data, and ongoing trials that could lead to the approval of some of these novel therapies.

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs): A continuum of different disease entities

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell-derived disorders characterized by uncontrolled proliferation of differentiated myeloid cells and close pathobiologic and clinical features. According to the 2016 World Health Organization (WHO) classification, MPNs include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The 2016 revision aimed in particular at strengthening the distinction between masked PV and JAK2-mutated ET, and between prefibrotic/early (pre-PMF) and overt PMF. Clinical manifestations in MPNs include constitutional symptoms, microvascular disorders, thrombosis and bleeding, splenomegaly secondary to extramedullary hematopoiesis, cytopenia-related symptoms, and progression to overt MF and acute leukemia. A dysregulation of the JAK/STAT pathway is the unifying mechanistic hallmark of MPNs, and is guided by somatic mutations in driver genes including JAK2, CALR and MPL. Additional mutations in myeloid neoplasm-associated genes have been also identified, with established prognostic relevance, particularly in PMF. Prognostication of MPN patients relies on disease-specific clinical models. The increasing knowledge of MPN biology led to the development of integrated clinical and molecular prognostic scores that allow a more refined stratification. Recently, the therapeutic landscape of MPNs has been revolutionized by the introduction of potent, selective JAK inhibitors (ruxolitinib, fedratinib), that proved effective in controlling disease-related symptoms and splenomegaly, yet leaving unmet critical needs, owing the lack of disease-modifying activity. In this review, we will deal with molecular, clinical, and therapeutic aspects of the three classical MPNs aiming at highlighting either shared characteristics, that overall define a continuum within a single disease family, and uniqueness, at the same time.

Next Generation Therapeutics for the Treatment of Myelofibrosis

Myelofibrosis is a myeloproliferative neoplasm characterized by splenomegaly, constitutional symptoms, bone marrow fibrosis, and a propensity towards transformation to acute leukemia. JAK inhibitors are the only approved therapy for myelofibrosis and have been successful in reducing spleen and symptom burden. However, they do not significantly impact disease progression and many patients are ineligible due to coexisting cytopenias. Patients who are refractory to JAK inhibition also have a dismal survival. Therefore, non-JAK inhibitor-based therapies are being explored in pre-clinical and clinical settings. In this review, we discuss novel treatments in development for myelofibrosis with targets outside of the JAK-STAT pathway. We focus on the mechanism, preclinical rationale, and available clinical efficacy and safety information of relevant agents including those that target apoptosis (navitoclax, KRT-232, LCL-161, imetelstat), epigenetic modulation (CPI-0610, bomedemstat), the bone marrow microenvironment (PRM-151, AVID-200, alisertib), signal transduction pathways (parsaclisib), and miscellaneous agents (tagraxofusp. luspatercept). We also provide commentary on the future of therapeutic development in myelofibrosis.

Somatically acquired mutations in primary myelofibrosis: A case report and meta-analysis

Familial myeloproliferative disease (MPD) cases account for 7.6% of the global MPD cases. The present study reported 2 cases of primary myelofibrosis (PMF). The patients were two sisters; the older sister succumbed to the disease at the age of 37, whereas the younger sister maintained a stable disease status and gave birth to a son through in vitro fertilization. Genetic analysis of bone marrow DNA samples showed that both sisters carried a Janus kinase 2 (JAK2) V617F mutation, and the older sister also had a trisomy 8 chromosomal abnormality (47, XX, +8). A systematic literature search was also performed using PubMed, CNKI and Wanfang databases, to determine the association between JAK2 and PMF. Following comprehensive screening of the published literature, 19 studies were found to be eligible for the current meta-analysis. The results showed that JAK2 V617F was a risk factor of PMF, and no sex dimorphism was observed in JAK2 V617F mutation prevalence amongst all PMF cases. In addition, there was a lack of association between the JAK2 V617F mutation and PMF-related mortality.

Current clinical strategies and emergent treatment landscapes in leukemic transformation of Philadelphia-negative myeloproliferative neoplasms

Introduction: Transformation to acute myeloid leukemia (AML) of Philadelphia chromosome-negative (Ph-) chronic myeloproliferative neoplasms (MPN) represents a challenging medical concern and an unmet clinical need, since it charts a very poor outcome and a low rate of response to standard treatments with the exception of allogeneic hematopoietic stem cell transplantation (HSCT). Recent novel insights into the molecular disease pathways and the genomic features characterizing the transformation of Ph-MPN have led to new therapeutic individualized approaches with the potential to modify the clinical management of these difficult-to-treat patients. Areas covered: Literature review (MeSH headings/PubMed) of risk factors of MPNs progression and treatment options for transformed disease with traditional standard approaches, and novel and investigational agents was performed. One or combinations of related subject headings like transformed MPN, epigenetics, molecular alterations, HSCT, ruxolitinib, azacytidine, decitabine, gliterinib, novel agents, personalized therapy was screened. Informative papers were selected by the appropriate actual evidence and suggesting strategies for improving outcomes in the future. Expert opinion: Current and emerging treatments for transformed Ph-MPN, are presented. Novel targeted or experimental agents to be used both before HSCT, to induce blast-free state, or to modify the disease prognosis and improve survival and quality of life are critically reviewed.

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.

Bcl-xL represents a therapeutic target in Philadelphia negative myeloproliferative neoplasms

Myeloproliferative neoplasms are divided into essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF). Although ruxolitinib was proven to be effective in reducing symptoms, patients rarely achieve complete molecular remission. Therefore, it is relevant to identify new therapeutic targets to improve the clinical outcome of patients. Bcl‐xL protein, the long isoform encoded by alternative splicing of the Bcl‐x gene, acts as an anti‐apoptotic regulator. Our study investigated the role of Bcl‐xL as a marker of severity of MPN and the possibility to target Bcl‐xL in patients. 129 MPN patients and 21 healthy patients were enrolled in the study. We analysed Bcl‐xL expression in leucocytes and in enriched CD34+ and CD235a+ cells. Furthermore, ABT‐737, a Bcl‐xL inhibitor, was tested in HEL cells and in leucocytes from MPN patients. Bcl‐xL was found progressively over‐expressed in cells from ET, PV and PMF patients, independently by JAK2 mutational status. Moreover, our data indicated that the combination of ABT‐737 and ruxolitinib resulted in a significantly higher apoptotic rate than the individual drug. Our study suggests that Bcl‐xL plays an important role in MPN independently from JAK2 V617F mutation. Furthermore, data demonstrate that targeting simultaneously JAK2 and Bcl‐xL might represent an interesting new approach.

Investigational non-JAK inhibitors for chronic phase myelofibrosis

INTRODUCTION

Patients with myelofibrosis (MF) have no effective treatment option after the failure of approved JAK inhibitor (JAKi) therapy. Non-JAK inhibitors (non-JAKi) that target non-canonical molecular pathways are undergoing clinical evaluations to optimize efficacy and/or to reduce hematological toxicity of JAKi.

AREA COVERED

This article reviews the efficacy data from completed and ongoing early phase clinical trials of non-JAKi agents for chronic phase MF. The article also illuminates some of the challenges of myelofibrosis drug development.

EXPERT OPINION

Most non-JAKi agents tested so far have shown modest benefit in improving the efficacy of ruxolitinib. Several novel agents such as BET inhibitor- CPI-0610, activin receptor ligand trap- luspatercept, recombinant pentraxin-PRM-151, telomerase inhibitor- imetelstat and bcl-2 inhibitor- navitoclax, have shown promising activity; however, they require vigorous evaluation in randomized controlled trials to understand the clinical benefit. Drugs that target new molecular pathways (MDM2, p-selectin, TIM-3, TGF-β, aurora kinase) and immune-based strategies (CALR vaccine, anti-PD-1, allogeneic cord blood regulatory T cells) are in early phase trials. Further translational studies to target leukemic stem cells, improvement in trial designs by incorporating control arm and survival endpoints, and patient-focused collaborations among all stakeholders could pave a way for future success in MF drug development.

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.

Effects of polymorphic DNA genes involved in BER and caspase pathways on the clinical outcome of myeloproliferative neoplasms under treatment with hydroxyurea

Several single nucleotide polymorphisms (SNPs) influencing DNA repair capacity and apoptotic status may confer genetic predisposition to Philadelphia‑chromosome negative myeloproliferative neoplasms (PN‑MPNs), and influence therapeutic response and the clinical course. In the present study, whether SNPs in genes involved in apoptosis and the base excision repair (BER) pathway was evaluated. In addition, some known risk factors in PN‑MPNs that may influence survival and therapeutic response to hydroxyurea (HU) were analyzed, taking into account three items: Disease progression, predisposition to new non‑myeloid neoplasms and thrombotic events. The present study involved a total of 133 Caucasian Portuguese PN‑MPNs patients treated with HU, whereby 17 cases showed progression to myelofibrosis/leukemia, 11 developed new non‑myeloid neoplasms and 22 presented with thrombotic events. Progression to secondary myelofibrosis/leukemia is influenced by exposure to cytoreductive agents, and caspase and BER polymorphisms {globally, CASP8 3'untranslated region [odds ratio (OR)=0.24; 95% confidence interval (CI), 0.08‑0.69], XRCC1 Arg194Trp [OR=3.58; 95% CI, 0.98‑13.01]; for essential thrombocythemia patients CASP9 Arg173His [OR=11.27; 95% CI, 1.13‑112.28], APEX1 Asp148Glu [OR=0.28; 95% CI, 0.74‑1.03], and XRCC1 Arg194Trp [OR=6.60; 95% CI, 1.60‑27.06]}. Moreover, globally caspase and BER polymorphisms influenced the development of new nonmyeloid malignancies [CASP8 Asp270His (OR=5.90; 95% CI, 1.42‑24.62) and XRCC1 Arg399Gln (OR=0.27; 95% CI, 0.07‑1.03)]. On the other hand, only the BER pathway had a role in the presence of thrombotic events [XRCC1 Gln399Arg (OR=0.35; 95% CI, 0.14‑0.88)]. JAK2 mutation had no influence on these complications. Larger studies are required to confirm these results, and to provide conclusive evidence of association between these and other variants with PN‑MPNs therapeutic response and clinical evolution. However, this study may allow the development of drugs more directly targeted to the pathophysiology of the disease, with high efficacy, fewer adverse effects, contributing to compliance of patients with treatments. The clinical indication for classical drugs, including HU, may be guided by variant genes, which may provide additional beneficial effects.

The Role of Caspase Genes Polymorphisms in Genetic Susceptibility to Philadelphia-Negative Myeloproliferative Neoplasms in a Portuguese Population

Our main aim was to evaluate the role of caspases' genes SNPs in Philadelphia-chromosome negative chronic myeloproliferative neoplasms (PN-MPNs) susceptibility. A case-control study in 133 Caucasian Portuguese PN-MPNs patients and 281 matched controls was carried out, studying SNPs in apoptosis related caspases: rs1045485 and rs1035142 (CASP8), rs1052576, rs2308950, rs1132312 and rs1052571 (CASP9), rs2227309 and rs2227310 (CASP7) and rs13006529 (CASP10). After stratification by pathology diagnosis for essential thrombocythemia (ET), female gender or JAK2 positive, there is a significant increased risk for those carrying at least one variant allele for CASP9 (C653T) polymorphism (OR 2.300 CI 95% [1.180-4.484], P = 0.014). However, when considered individually, none of the studied caspases polymorphisms was associated with PN-MPNs risk. Our results do not reveal a significant involvement of caspase genes polymorphisms on the individual susceptibility towards PN-MPNs as a whole. However, for essential thrombocythemia (ET), female gender or JAK2 positive, there is a significant increased risk to those carrying at least one variant allele for CASP9. Although larger studies are required to confirm these results and to provide conclusive evidence of association between these and other caspases variants and PN-MPNs susceptibility, these new data may contribute to a best knowledge of the pathophysiology of these disorders and, in the future, to a more rational and efficient choice of therapeutic strategies to be adopted in PN-MPNs treatment.

Management of myelofibrosis: JAK inhibition and beyond

INTRODUCTION

Myelofibrosis (MF) is characterized by bone marrow fibrosis with subsequent extramedullary hematopoiesis and abnormal cytokine expression leading to splenomegaly, constitutional symptoms and cytopenias. The discovery of the JAK2 V617F mutation in the majority of MF patients has been followed by significant progress in drug development for MF. Areas covered: In this article, we review advances in the understanding of the underlying disease biology, prognostic assessment and therapeutic modalities for MF. We provide clinical trial evidence behind using the JAK2 inhibitor ruxolitinib, erythropoiesis stimulating agents, androgens, immunomodulatory drugs, interferon, cytoreductive drugs and hypomethylating agents in MF. Finally, we review novel therapeutic options for MF including the new JAK1/2 inhibitors, ruxolitinib based combination approaches as well as novel therapeutic agents. Expert commentary: Despite significant reduction of splenomegaly and improvement of symptom burden and a signal for survival improvement, ruxolitinib does not lead to major reductions in JAK2 V617F allele burden and bone marrow fibrosis. No ruxolitinib-based combination approach has so far demonstrated superiority over ruxolitinib monotherapy. The novel JAK2 inhibitors pacritinib and momelotinib, other JAK inhibitors, telomerase inhibitors, anti-fibrosis agents and hsp90 inhibitors are in different stages of development.

Non-invasive imaging of retinal blood flow in myeloproliferative neoplasms

PURPOSE

To study the circulation in the retinal vessels in patients with blood dyscrasia due to myeloproliferative neoplasms using non-invasive retinal imaging.

METHODS

Prospective consecutive case series of seven treatment-naïve patients with chronic myeloid leukaemia (n = 2), polycythemia vera (n = 4), essential thrombocytosis (n = 1) examined before and after cytoreductive treatment. We investigated retinal circulation with motion-contrast imaging, retinal oximetry and spectral-domain optical coherence tomography.

RESULTS

Retinal venous blood velocity increased by 8.14% (CI₉₅ 3.67% to 12.6%, p = 0.004) and retinal arterial oxygen saturation increased by 7.23% (CI₉₅ 2.9% to 11.6%, p = 0.010) at follow-up (mean 12 weeks, range 5-14 weeks) where complete haematological remission had been achieved by cytoreductive treatment. Abnormal optical coherence tomography reflectivity patterns were present at baseline in patients with chronic myeloid leukaemia and were replaced by normal patterns at follow-up. Retinopathy, in the form of cotton-wool spots and retinal haemorrhages, was found at presentation in the two patients with chronic myeloid leukaemia and in one patient with polycythemia vera. The retinopathy had resolved at follow-up in all patients.

CONCLUSION

With non-invasive retinal imaging, we were able to demonstrate increased retinal venous blood velocity, increased retinal arterial blood oxygenation and normalization of intravascular reflectivity patterns after successful treatment of myeloproliferative neoplasms. Larger prospective studies are needed to assess the prognostic value of these non-invasive imaging methods in predicting circulatory complications in myeloproliferative neoplasms.

Different expression patterns of LGALS1 and LGALS3 in polycythemia vera, essential thrombocythemia and primary myelofibrosis

Despite all the knowledge, the cellular and molecular mechanisms involved in myeloproliferative neoplasm (MPN) pathophysiology remain unclear. Authors have shown galectin-1 (Gal-1) and 3 playing roles in tumour angiogenesis and fibrosis, which were correlated with poor prognosis in patients with MPN. In the present study LGALS1 and LGALS3 were differently expressed between polycythemia vera, essential thrombocythemia (ET) and primary myelofibrosis (PMF) diseases. Increased LGALS3 expression was associated with a negative JAK2 V617F status mutation in leucocytes from PMF but not in patients with ET without this mutation. However, a positive Janus kinase 2 (JAK2) V617F cell line established from patients with ET (SET-2 cells) when treated with JAK inhibitor presented high levels of LGALS3. Additionally, high LGALS1 expression was found in CD34(+) cells but not in leucocytes from patients with PMF, in absence of JAK2 V617F mutation, and also in SET-2 cells treated with JAK inhibitor. Thus, our findings indicate that differential expression of LGALS1 and/or LGALS3 in patients with MPN is linked with JAK2 V617F status mutation in these diseases and state of cell differentiation.

Acute promyelocytic leukemia co-existing with JAK2 V617F positive myeloproliferative neoplasm: a case report

The V617F mutation of Janus-associated kinase 2 (JAK2) is commonly seen in myeloproliferative neoplasms (MPN). Transformation of JAK2 positive MPNs to acute leukemia has been reported. We here report a case of acute promyelocytic leukemia which was later confirmed to have a co-existing JAK2 V617F positive MPN. In addition, the patient was found to have FLT3-TKD mutation, which, together with PML/RARa, could play a role in the MPN transformation to APL.

l-Amino acid oxidase isolated from Calloselasma rhodostoma snake venom induces cytotoxicity and apoptosis in JAK2V617F-positive cell lines

BACKGROUND

Myeloproliferative neoplasms are Philadelphia chromosome-negative diseases characterized by hyperproliferation of mature myeloid cells, associated or not with the Janus kinase 2 tyrosine kinase mutation, JAK2V617F. As there is no curative therapy, researchers have been investigating new drugs to treat myeloproliferative neoplasms, including l-amino acid oxidase from Calloselasma rhodostoma snake venom (CR-LAAO), which is a toxin capable of eliciting apoptosis in several tumor cell lines.

OBJECTIVE

To evaluate the effects of l-amino acid oxidase from C. rhodostoma snake venom in the apoptotic machinery of JAK2-mutated cell lines.

METHODS

The HEL 92.1.7 and SET-2 cell lines were cultured with l-amino acid oxidase and catalase for 12h at 37°C in 5% carbon dioxide. The cell viability was assessed by the multi-table tournament method, the level of apoptosis was measured by flow cytometry, and the expression of cysteine-dependent aspartate-specific proteases and cleaved Poly(ADP-ribose) polymerase were analyzed by Western blotting.

RESULTS

l-Amino acid oxidase from C. rhodostoma snake venom was cytotoxic to HEL 92.1.7 and SET-2 cells (50% inhibitory concentration=0.15μg/mL and 1.5μg/mL, respectively) and induced apoptosis in a concentration-dependent manner. Cell treatment with catalase mitigated the l-amino acid oxidase toxicity, indicating that hydrogen peroxide is a key component of its cytotoxic effect.The activated caspases 3 and 8 expression and cleaved PARP in HEL 92.1.7 and SET-2 cells confirmed the apoptosis activation by CR-LAAO.

CONCLUSIONS

l-Amino acid oxidase from C. rhodostoma snake venom is a potential antineoplastic agent against HEL 92.1.7 and SET-2 JAK2V617F-positive cells as it activates the extrinsic apoptosis pathway.

The expression of Death Inducer-Obliterator (DIDO) variants in Myeloproliferative Neoplasms

Chronic Myeloid Leukemia (CML), Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF) are Myeloproliferative Neoplasms (MPN) characterized by clonal myeloproliferation without cell maturation impairment. CML pathogenesis is associated with the Ph chromosome leading to BCR-ABL tyrosine-kinase constitutive expression. The Ph negative MPN (PV, ET and PMF) are characterized by the mutation JAK2(V617F) of the JAK2 protein in the auto-inhibitory JH2 domain, which is found in most PV patients and in approximately half of ET and PMF patients. Considerable effort is being made to understand the role of JAK2(V617F) at the MPN initiation and to clarify the pathogenesis and apoptosis resistance in CML, PV, ET and PMF patients. In the present investigation, we evaluated the Death Inducer-Obliterator (DIDO) (variants DIDO 1, 2 and 3) levels in CML, PV, ET and PMF patients. Our data reported the DIDO 1, 2 and 3 differential expressions in Myeloproliferative Neoplasms.

A link between the driver mutations and dysregulated apoptosis in BCR-ABL1 negative myeloproliferative neoplasms

The current understanding of BCR-ABL1 negative myeloproliferative neoplasms pathogenesis is centred on the phenotypic driver mutations in JAK2, MPL, or CALR genes, and the constitutive activation of JAK-STAT pathway. Nonetheless, there is still a need to better characterize the cellular processes that are triggered by these genetic alterations, such as apoptosis that might play a role in the pathological expansion of the myeloid lineages and, especially, in the morphological anomalies of the bone marrow megakaryocytes. In this article we will explore the connection between the driver mutations in MPN and the abnormal apoptosis that might be translated in new therapeutic strategies.

Megakaryocytic hyperplasia in myeloproliferative neoplasms is driven by disordered proliferative, apoptotic and epigenetic mechanisms

AIMS

Myeloproliferative neoplasms (MPN) are a heterogeneous group of clonal proliferative bone marrow diseases characterised by extensive megakaryocytic hyperplasia and morphological atypia. Despite knowledge of genomic defects, the pathobiological processes driving these megakaryocytic abnormalities in MPN remain poorly explained. We have explored the proliferative, apoptotic and epigenetic profiles of megakaryocytes in human MPN.

METHODS

Immunohistochemical staining was performed on bone marrow trephine biopsies of 81 MPN (with and without JAK2(V617F) and CALR mutations) and 15 normal controls to assess the megakaryocytic expression of biomarkers associated with proliferation (Ki67), apoptosis (Bcl-XL, BNIP-3) and epigenetic regulation (EZH2, SUZ12).

RESULTS

Myeloproliferative megakaryocytes showed significantly greater expression of proliferative Ki67 and anti-apoptotic Bcl-XL, reduced pro-apoptotic BNIP-3 and increased SUZ12 compared with controls. In essential thrombocythaemia, large-giant megakaryocytes with hyperlobated nuclei showed a trend towards a proliferative signature. In contrast, myelofibrotic megakaryocytes with condensed nuclear chromatin, and cases with CALR mutations, had significant reductions in pro-apoptotic BNIP-3.

CONCLUSIONS

Uncontrolled megakaryocytic expansion in MPN results from a combination of increased proliferation, attenuated apoptosis and defective epigenetic regulation with CALR mutations favouring apoptotic failure. The higher platelet counts reported to be seen in MPN with CALR mutations may be due to greater dysregulation of megakaryocyte apoptosis.

Methaneseleninic acid and γ-Tocopherol combination inhibits prostate tumor growth in Vivo in a xenograft mouse model

Studies have shown that vitamin E and selenium possess antiproliferative effects against prostate cancer (PCa). However, results from the Selenium and Vitamin E Cancer Prevention Trial (SELECT) suggest that vitamin E (α-tocopheryl acetate; 400 mg) and/or selenium (L-selenomethionine; 200 μg) were ineffective against PCa in humans. It is arguable that the selected dose/formulation of vitamin E/selenium were not optimal in SELECT. Thus, additional studies are needed to define the appropriate formulations/dose regimens of these agents. Here, we investigated the effect of methaneseleninic acid (MSA; 41 μg/kg) and/or γ-tocopherol (γT; 20.8 mg/kg or 41.7 mg/kg) in Nu/J mice implanted with 22Rν1 tumors. MSA (41 μg/kg) and γT (20.8 mg/kg) combination was most consistent in imparting anti-proliferative response; resulting in a significant decrease in i) tumor volume/weight, ii) serum PSA, and iii) Ki-67 immunostaining. Further, we observed i) an upregulation of pro-apoptosis Bax and a down-regulation of the pro-survival Bcl2, and ii) an increase in pro-apoptosis Bad. Furthermore, the combination resulted in a modulation of apolipoprotein E, selenoprotein P and Nrf2 in a fashion that favors antiproliferative responses. Overall, our study suggested that a combination of MSA and γT, at lower dose regimen, could be useful in PCa management.

Apoptosis deregulation in myeloproliferative neoplasms

Philadelphia-chromosome negative chronic myeloproliferative neoplasms are clonal hematologic diseases characterized by hematopoietic progenitor independence from or hypersensitivity to cytokines. The cellular and molecular mechanisms involved in the pathophysiology of myeloproliferative neoplasms have not yet been fully clarified. Pathophysiologic findings relevant for myeloproliferative neoplasms are associated with genetic alterations, such as, somatic mutation in the gene that codifies JAK-2 (JAK V617F). Deregulation of the process of programmed cellular death, called apoptosis, seems to participate in the pathogenesis of these disorders. It is known that expression deregulation of pro- and anti-apoptotic genes promotes cell resistance to apoptosis, culminating with the accumulation of myeloid cells and establishing neoplasms. This review will focus on the alterations in apoptosis regulation in myeloproliferative neoplasms, and the importance of a better understanding of this mechanism for the development of new therapies for these diseases.

JAK2 mutants (e.g., JAK2V617F) and their importance as drug targets in myeloproliferative neoplasms

The Janus kinase 2 (JAK2) mutant V617F and other JAK mutants are found in patients with myeloproliferative neoplasms and leukemias. Due to their involvement in neoplasia and inflammatory disorders, Janus kinases are promising targets for kinase inhibitor therapy. Several small-molecule compounds are evaluated in clinical trials for myelofibrosis, and ruxolitinib (INCB018424, Jakafi®) was the first Janus kinase inhibitor to receive clinical approval. In this review we provide an overview of JAK2V617F signaling and its inhibition by small-molecule kinase inhibitors. In addition, myeloproliferative neoplasms are discussed regarding the role of JAK2V617F and other mutant proteins of possible relevance. We further give an overview about treatment options with special emphasis on possible combination therapies.

Dysregulation of JAK-STAT pathway in hematological malignancies and JAK inhibitors for clinical application

JAK-STAT (Janus associated kinase-signal transducer and activator of transcription) pathway plays a critical role in transduction of extracellular signals from cytokines and growth factors involved in hematopoiesis, immune regulation, fertility, lactation, growth and embryogenesis. JAK family contains four cytoplasmic tyrosine kinases, JAK1-3 and Tyk2. Seven STAT proteins have been identified in human cells, STAT1-6, including STAT5a and STAT5b. Negative regulators of JAK-STAT pathways include tyrosine phosphatases (SHP1 and 2, CD45), protein inhibitors of activated STATs (PIAS), suppressors of cytokine signaling (SOCS) proteins, and cytokine-inducible SH2-containing protein (CIS). Dysregulation of JAK-STAT pathway have been found to be key events in a variety of hematological malignancies. JAK inhibitors are among the first successful agents reaching clinical application. Ruxolitinib (Jakafi), a non-selective inhibitor of JAK1 & 2, has been approved by FDA for patients with intermediate to high risk primary or secondary myelofibrosis. This review will also summarize early data on selective JAK inhibitors, including SAR302503 (TG101348), lestaurtinib (CEP701), CYT387, SB1518 (pacritinib), LY2784544, XL019, BMS-911543, NS-018, and AZD1480.