A phase II study of 5-azacitidine for patients with primary and post-essential thrombocythemia/polycythemia vera myelofibrosis

Rationale for combination therapy in myelofibrosis

Agents targeting the JAK-STAT pathway have dominated the investigational therapeutic portfolio over the last five years resulting in the first and only approved agent for the treatment of patients with myelofibrosis (MF). However, chromatin modifying agents, anti-fibrosing agents, and other signaling pathway inhibitors have also demonstrated activity and offer the potential to improve upon the clinical success of JAK2 inhibition. Due to the complex pathobiological mechanisms underlying MF, it is likely that a combination of biologically active therapies will be required to target the MF hematopoietic stem cell in order to achieve significant disease course modification. Ruxolitinib in partnership with panobinostat, decitabine, and LDE225 are being evaluated in current combination therapy trials based on pre-clinical studies that provide strong scientific rationale. The rationale of combination of danazol or lenalidomide with ruxolitinib is mainly based on mitigation of anti-JAK2-mediated myelosuppression. Combination trials of ruxolitinib and novel anti-fibrosing agents such as PRM-151 represent an attempt to address therapeutic limitations of JAK2 inhibitors such as reversal of bone marrow fibrosis. Ruxolitinib is also being incorporated in novel treatment strategies in the setting of hematopoietic stem cell transplantation for MF. As the pathogenetic mechanisms are better understood, potential drug combinations in MF will increase dramatically and demonstration of biologic activity in effective preclinical models will be required to efficiently evaluate the most active combinations with least toxicity in future trials. This manuscript will address the proposed goals of combination therapy approach and review the state of the art in combination experimental therapy for MF.

How many JAK inhibitors in myelofibrosis?

The discovery of the activating mutation JAK2 V617F ushered a new era in MPN which included new diagnostic and prognostic criteria as well as a potential therapeutic target. JAK2 inhibition became a reality with first patients receiving drugs that targeted JAK2 in 2007 and was marked by the first approval in 2011 of Ruxolitinib a JAK 1 and 2-inhibitor to treat myelofibrosis (MF). In this article entitled "How many JAK inhibitors for myelofibrosis" we discuss JAK2 as a target, review briefly the benefits to patients with MF of JAK inhibition and highlight some of the differences between the number of JAK inhibitors currently being evaluated. Reflecting upon what we have learnt from the chronic myeloid leukaemia field and for MF regarding disease complexity as well as individual patient factors including resistance we discuss why it is likely we will need several different agents with JAK inhibitory activity. The next chapter discusses combination therapies for myelofibrosis which is a logical step in both trying to cure this disease and improve patient outcome and toxicities with JAK inhibitors.

Novel myelofibrosis treatment strategies: potential partners for combination therapies

Of the myeloproliferative neoplasms (MPNs), myelofibrosis (MF) is associated with the greatest symptom burden and poorest prognosis and is characterized by constitutional symptoms, cytopenias, splenomegaly and bone marrow fibrosis. A hallmark of MF is dysregulation of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway that has led to the development of JAK inhibitors targeting this pathway. Calreticulin gene mutations have recently been identified in JAK2 mutation-negative patients with MF. Identification of JAK inhibitor resistance and broad contributions to MF disease pathogenesis from epigenetic deregulators, pathways that work in concert with JAK/STAT (that is, mammalian target of rapamycin/AKT/phosphoinositide 3-kinase, RAS/RAF/MEK, PIM kinase), fibrosis-promoting factors and the MF megakaryocyte, suggest that numerous options may be partnered with a JAK inhibitor. Therefore, we will discuss logical and potential partners for combination therapies for the treatment of patients with MF.

Hematologic improvements in a myelodysplastic syndromes with myelofibrosis (MDS-F) patient treated with azacitidine

Myelodysplastic syndromes with myelofibrosis (MDS-F) is a poor prognostic hematopoietic disorder. Azacitidine was shown to prolong survival of high-risk MDS patients. However, the effects of azacitidine on MDS-F have yet to be elucidated. Azacitidine was administered to a 74-year-old man with MDS-F at a dose of 75 mg/m(2)/daily subcutaneously for 7 days every 28 days. Hematologic improvements were observed according to the International Working Group 2006 criteria after 8 cycles of the azacitidine treatment, and complete remission was achieved after 14 cycles. The grade of myelofibrosis was also improved. The therapeutic activity of azacitidine was confirmed in our MDS-F patient.

5-Azacytidine/5-Azacitidine

The hypomethylating agent 5-Azacytidine epigenetically modulates various genes, including tumor suppressor genes. For many years, the "new agent", which was first discovered in the 1960s, remained fairly unobtrusive in the rank of salvage treatment options for myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). When the significance of epigenetics in tumorigenesis became clear, 5-Azacytidine attracted new attention. Finally, it was the first drug approved for the treatment of all categories of MDS, and its survival benefit over best conventional care was confirmed. Today, in many clinical situations, when aggressive therapies including allogeneic hematopoietic cell transplantation are not an option, 5-Azacytidine is the first treatment of choice. Preliminary data on combinations of the hypomethylating agent with other new drugs are promising, and innovative strategies involving immune modulation and regenerative tissue repair hold a broad potential for future developments.

Beyond JAK inhibitor therapy in myelofibrosis

Myelofibrosis (MF), including primary MF, postpolycythemia vera MF, and postessential thrombocythemia MF, is a clonal stem cell disorder characterized by BM fibrosis, extramedullary hematopoiesis, and a variable propensity to transform into acute leukemia. Allogeneic stem cell transplantation is the only known cure for MF, but its applicability is limited by the advanced age of most patients and by comorbid conditions. In the past decade, there has been an explosion of information on the molecular-genetic features associated with these diseases, fueled recently by the discovery of the JAK2V617F mutation. The development of JAK inhibitors has represented a significant therapeutic advance for these diseases; however, their use in MF has not yet been associated with eradication or a significant suppression of the malignant clone. In this era, much remains to be understood about MF, but it is likely that the identification of key pathogenetic drivers of the disease, coupled with the availability of novel molecularly targeted agents, will result in the discovery of new agents that significantly alter the natural history of the disease. This review focuses on recent and ongoing efforts in the development of novel agents in MF that go beyond the field of JAK inhibitors.

Practical management of patients with myelofibrosis receiving ruxolitinib

Myelofibrosis (MF) is characterized by bone marrow fibrosis, progressive anemia and extramedullary hematopoiesis, primarily manifested as splenomegaly. Patients also experience debilitating constitutional symptoms, including sequelae of splenomegaly, night sweats and fatigue. Ruxolitinib (INC424, INCB18424, Jakafi, Jakavi), a JAK1 and JAK2 inhibitor, was approved in November 2011 by the US FDA for the treatment of intermediate- or high-risk MF, and more recently in Europe and Canada for the treatment of MF-related splenomegaly or symptoms. These approvals were based on data from two randomized Phase III studies: COMFORT-I randomized against placebo, and COMFORT-II randomized against best available therapy. In these studies, ruxolitinib rapidly improved multiple disease manifestations of MF, reducing splenomegaly and improving quality of life of patients and potentially prolonging survival. However, as with other chemotherapies, ruxolitinib therapy is associated with some adverse events, such as anemia and thrombocytopenia. The aims of this article are to provide a brief overview of ruxolitinib therapy, to discuss some common adverse events associated with ruxolitinib therapy and to provide clinical management recommendations to maximize patients' benefit from ruxolitinib.

Novel therapies in the classical BCR–ABL-negative myeloproliferative neoplasms

SUMMARY Myeloproliferative neoplasms (MPN) are clonal stem cell disorders that include essential thrombocytosis, polycythemia vera and myelofibrosis. Effective therapy is challenging owing to the heterogeneity of the disease; however, recent advances in our understanding of MPN pathogenesis have led to the evaluation of novel therapies, each with its own distinct contribution and side-effect profile. This review summarizes promising approaches to the treatment of MPN, aiming to improve upon the currently used conventional therapies.

The evolving treatment paradigm in myelofibrosis

Myelofibrosis (MF) is a BCR-ABL1-negative myeloproliferative neoplasm diagnosed de novo or developed from essential thrombocythemia (ET) or polycythemia vera (PV). Average survival of a patient with MF is 5-7 years. Disease complications include fatigue, early satiety, pruritus, painful splenic infarcts, infections and leukemic transformation. Allogeneic hematopoietic stem cell transplant (HSCT) is the only potentially curative option for MF, but carries a risk of treatment-related mortality and is reserved for the few high-risk patients fit enough to endure the procedure. Other traditional therapies are palliative and supported by few randomized, controlled trials; thus, novel treatment strategies are needed. Discovery of the Janus kinase 2 (JAK2) gain-of-function mutation, JAK2V617F, in the majority (50-60%) of patients with MF led to increased understanding of the biology underlying MF and the development of JAK2 inhibitors to treat MF. Recent Food and Drug Administration (FDA) approval of the first JAK2 inhibitor, ruxolitinib, signaled a new era for treatment of MF. Additional JAK2 inhibitors, such as SAR302503, may become commercially available in the near future, and their distinct pharmacologic and efficacy profiles will help determine their use across the patient population. Data on JAK2 inhibitors, their role in an evolving treatment paradigm, and future directions for treatment of MF are discussed.

Nuclear phospholipase C β1 signaling, epigenetics and treatments in MDS

Myelodysplastic syndromes (MDS), clonal hematopoietic stem-cell disorders mainly affecting older adult patients, show ineffective hematopoiesis in one or more of the lineages of the bone marrow. Most MDS are characterized by anemia, and a number of cases progresses to acute myeloid leukemia (AML). Indeed, the molecular mechanisms underlying the MDS evolution to AML are still unclear, even though the nuclear signaling elicited by PI-PLCβ1 has been demonstrated to play an important role in the control of the balance between cell cycle progression and apoptosis in MDS cells. Here we review both the role of epigenetic therapy on PI-PLCβ1 promoter and the changes in PI-PLCβ1 expression in MDS patients treated for anemia.

Splenomegaly in myelofibrosis--new options for therapy and the therapeutic potential of Janus kinase 2 inhibitors

Splenomegaly is a common sign of primary myelofibrosis (PMF), post-polycythemia vera myelofibrosis (post-PV MF), and post-essential thrombocythemia myelofibrosis (post-ET MF) that is associated with bothersome symptoms, which have a significant negative impact on patients’ quality of life. It may also be present in patients with advanced polycythemia vera (PV) or essential thrombocythemia (ET). Until recently, none of the therapies used to treat MF were particularly effective in reducing splenomegaly. The discovery of an activating Janus kinase 2 (JAK2) activating mutation (JAK2V617F) that is present in almost all patients with PV and in about 50-60 % of patients with ET and PMF led to the initiation of several trials investigating the clinical effectiveness of various JAK2 (or JAK1/JAK2) inhibitors for the treatment of patients with ET, PV, and MF. Some of these trials have documented significant clinical benefit of JAK inhibitors, particularly in terms of regression of splenomegaly. In November 2011, the US Food and Drug Administration approved the use of the JAK1- and JAK2-selective inhibitor ruxolitinib for the treatment of patients with intermediate or high-risk myelofibrosis, including PMF, post-PV MF, and post-ET MF. This review discusses current therapeutic options for splenomegaly associated with primary or secondary MF and the treatment potential of the JAK inhibitors in this setting.

Phase 2 study of the JAK kinase inhibitor ruxolitinib in patients with refractory leukemias, including postmyeloproliferative neoplasm acute myeloid leukemia

We conducted a phase 2 study of ruxolitinib in patients with relapsed/refractory leukemias. Patients with acceptable performance status (0-2), adequate organ function, and no active infection, received ruxolitinib 25 mg orally twice a day for 4 weeks (1 cycle). Response was assessed after every 2 cycles of treatment, and patients who completed 2 cycles were allowed to continue treatment until disease progression. Dose escalation to 50 mg twice daily was permitted in patients demonstrating a benefit. Thirty-eight patients, with a median age of 69 years (range, 45-88), were treated. The median number of prior therapies was 2 (range, 1-6). Twelve patients had JAK2V617F mutation. Patients received a median of 2 cycles of therapy (range, 1-22). Three of 18 patients with postmyeloproliferative neoplasm (MPN) acute myeloid leukemia (AML) showed a significant response; 2 achieved complete remission (CR) and one achieved a CR with insufficient recovery of blood counts (CRi). The responding patients with palpable spleens also had significant reductions in spleen size. Overall, ruxolitinib was very well tolerated with only 4 patients having grade 3 or higher toxicity. Ruxolitinib has modest antileukemic activity as a single agent, particularly in patients with post-MPN AML. The study was registered at www.clinicaltrials.gov as NCT00674479.

Effects of a novel DNA methyltransferase inhibitor Zebularine on human lens epithelial cells

PURPOSE

Posterior capsular opacification (PCO) is a common long-term complication of modern cataract surgery. We have shown that Zebularine, an inhibitor of DNA methylation, suppresses transforming growth factor-β (TGFβ)-induced lens epithelial cells (LECs)-myofibroblasts transdifferentiation. The purpose of this study is to evaluate the role that Zebularine plays in the inhibition of PCO pathogenesis, including its effect on attachment, migration, and proliferation of LECs in vitro.

METHODS

A tetrazolium dye-reduction assay (MTT test) was performed to determine cell proliferation. Cell attachment was assessed by modified MTT test. Migration was determined by the transwell method after incubation of LECs with Zebularine. The effect of Zebularine on DNA-methyltransferase 1 (DNMT1), phospho-p44/42 Map Kinase, and protein kinase B (Akt) were analyzed by western blot.

RESULTS

Zebularine was an effective inhibitor of human LEC proliferation, attachment, and migration in vitro. A Zebularine concentration of 100 μM accounted for the following: inhibition of cell proliferation of 57.2%, reduction in cell attachment to 29.6%, and inhibition of cell migration of 58.9%. All effects were dose dependent. Zebularine treatment resulted in dose-dependent decreases of DNMT1, phosphorylated p44/42 MAP Kinase, and phosphorylated Akt.

CONCLUSIONS

Zebularine is capable of inhibiting the crucial cellular events in PCO pathogenesis in vitro. Zebularine acts through the inhibition of DNMT1, and it consequently down regulation of the expression of proliferative and survival genes that relate to pathogenesis of PCO. These findings suggest that Zebularine may become a therapeutic approach for the prevention of PCO.

Nuclear PI-PLC β1 and Myelodysplastic syndromes: from bench to clinics

Myelodysplastic syndromes (MDS), clonal hematopoietic stem-cell disorders mainly affecting older adult patients, show ineffective hematopoiesis in one or more of the lineages of the bone marrow. A number of MDS progresses to acute myeloid leukemia (AML) with the involvement of genetic and epigenetic mechanisms affecting PI-PLC β1. The molecular mechanisms underlying the MDS evolution to AML are still unclear, even though it is now clear that the nuclear signaling elicited by PI-PLC β1, Cyclin D3, and Akt plays an important role in the control of the balance between cell cycle progression and apoptosis in both normal and pathologic conditions. Moreover, a correlation between other PI-PLCs, such as PI-PLC β3, kinases and phosphatases has been postulated in MDS pathogenesis. Here, we review the findings hinting at the role of nuclear lipid signaling pathways in MDS, which could become promising therapeutic targets.

Targeting the epigenome for treatment of cancer

Cancer genome analyses have revealed that the enzymes involved in epigenetic gene regulation are frequently deregulated in cancer. Here we describe the enzymes that control the epigenetic state of the cell, how they are affected in cancer and how this knowledge can be exploited to treat cancer with a new arsenal of selective therapies.

Zebularine suppresses TGF-beta-induced lens epithelial cell-myofibroblast transdifferentiation by inhibiting MeCP2

PURPOSE

Posterior capsular opacification (PCO) is a common long-term complication of modern cataract surgery. Remnant lens epithelial cells (LECs) undergo a myofibroblast transdifferentiation that is thought to be the initial step of PCO pathogenesis. The purpose of this study is to determine the effects of zebularine on transforming growth factor-β (TGFβ)-induced, LEC-myofibroblast transdifferentiation.

METHODS

The expression levels of methyl CpG binding protein 2 (MeCP2) and α-smooth muscle actin (α-SMA) in human PCO membranes were evaluated by confocal microscopy. The role that MeCP2 played in TGFβ2-induced α-SMA expression was analyzed by western blotting both before and after MeCP2 knockdown with MeCP2-specific siRNA. The effect of zebularine on MeCP2 expression was analyzed over time using a variety of dosages. The effect of zebularine on TGFβ2-induced α-SMA expression was determined by western blot analysis.

RESULTS

MeCP2 and α-SMA co-localized in human PCO membranes. When MeCP2 was depleted, TGFβ2 could not induce α-SMA expression. Zebularine decreased MeCP2 expression in lens epithelial cells in a time- and dose-dependent pattern and reversed TGFβ2-induced α-SMA expression.

CONCLUSIONS

MeCP2 plays an important role in TGFβ2-induced α-SMA expression in lens epithelial cells. Zebularine could reverse the TGFβ2-induced α-SMA expression by inhibiting MeCP2 expression. Therefore, zebularine could potentially prevent PCO formation.

Epigenetic abnormalities in myeloproliferative neoplasms: a target for novel therapeutic strategies

The myeloproliferative neoplasms (MPNs) are a group of clonal hematological malignancies characterized by a hypercellular bone marrow and a tendency to develop thrombotic complications and to evolve to myelofibrosis and acute leukemia. Unlike chronic myelogenous leukemia, where a single disease-initiating genetic event has been identified, a more complicated series of genetic mutations appear to be responsible for the BCR-ABL1-negative MPNs which include polycythemia vera, essential thrombocythemia, and primary myelofibrosis. Recent studies have revealed a number of epigenetic alterations that also likely contribute to disease pathogenesis and determine clinical outcome. Increasing evidence indicates that alterations in DNA methylation, histone modification, and microRNA expression patterns can collectively influence gene expression and potentially contribute to MPN pathogenesis. Examples include mutations in genes encoding proteins that modify chromatin structure (EZH2, ASXL1, IDH1/2, JAK2V617F, and IKZF1) as well as epigenetic modification of genes critical for cell proliferation and survival (suppressors of cytokine signaling, polycythemia rubra vera-1, CXC chemokine receptor 4, and histone deacetylase (HDAC)). These epigenetic lesions serve as novel targets for experimental therapeutic interventions. Clinical trials are currently underway evaluating HDAC inhibitors and DNA methyltransferase inhibitors for the treatment of patients with MPNs.

Myeloproliferative neoplasms: new translational therapies

The myeloproliferative neoplasms represent a diverse group of hematologic malignancies that have been the subject of intense investigation over the last decade. Although clinical trials of the much anticipated small molecule inhibitors of Janus kinase 2 have shown that these experimental agents are successful in palliating many of the symptoms associated with the myeloproliferative neoplasms, they have not been reported to affect the disease initiating hematopoietic stem cell population or to alter the natural history of these disorders. Investigators remain optimistic that new information about the genetic and cellular origins gained from the efforts of numerous laboratories will ultimately translate in to the identification of new drug targets and more effective therapies. We hypothesize that ultimately, the use of combinations of drugs including chromatin modifying agents, immunomodulatory agents, anti-apoptotic agents, cellular therapies and monoclonal antibodies will be required to effectively treat patients with myeloproliferative neoplasms.

How I treat myelofibrosis

It is currently assumed that myelofibrosis (MF) originates from acquired mutations that target the hematopoietic stem cell and induce dysregulation of kinase signaling, clonal myeloproliferation, and abnormal cytokine expression. These pathogenetic processes are interdependent and also individually contributory to disease phenotype-bone marrow stromal changes, extramedullary hematopoiesis, ineffective erythropoiesis, and constitutional symptoms. Molecular pathogenesis of MF is poorly understood despite a growing list of resident somatic mutations that are either functionally linked to Janus kinase (JAK)-signal transducer and activator of transcription hyperactivation (eg JAK2, MPL, and LNK mutations) or possibly involved in epigenetic dysregulation of transcription (TET2, ASXL1, or EZH2 mutations). Current prognostication in primary MF is based on the Dynamic International Prognostic Scoring System-plus model, which uses 8 independent predictors of inferior survival to classify patients into low, intermediate 1, intermediate 2, and high-risk disease groups; corresponding median survivals are estimated at 15.4, 6.5, 2.9, and 1.3 years. Such information is used to plan a risk-adapted treatment strategy for the individual patient, which might include observation alone, conventional or investigational (eg, JAK inhibitors, pomalidomide) drug therapy, allogenic stem cell transplantation with reduced- or conventional-intensity conditioning, splenectomy, or radiotherapy. I discuss these treatment approaches in the context of who should get what and when.

New ways to use DNA methyltransferase inhibitors for the treatment of myelodysplastic syndrome

Ongoing analysis of the seminal AZA-001 study has taught many important lessons in the use of DNA methyltransferase (DNMT) inhibitors. The data emphasize the importance of patience in the use of these drugs, with several cycles required for the manifestations of hematologic responses. Improved survival in patients with high-risk myelodysplastic syndrome (MDS) treated with azacitidine extends to patients with any International Working Group-defined hematologic response; however, the benefit to patients with stable disease is less clear. A great deal remains to be learned about the optimal dosing and scheduling of the DNMT inhibitors, alone and in combination. New information on the impact of DNMT inhibitors on the immune system and on stem cells will likely lead to novel uses of these drugs in MDS and other hematologic and nonhematologic malignancies.

Deactylase inhibition in myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are clonal haemopoietic progenitor cell disorders characterized by the proliferation of one or more of the haemopoietic lineages (myeloid, erythroid and/or megakaryocytic). The MPNs include eight haematological disorders: chronic myelogenous leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF), systemic mastocytosis (SM), chronic eosinophilic leukemia, not otherwise specified (CEL, NOS), chronic neutrophilic leukemia (CNL), and unclassifiable MPN (MPN, U). Therapeutic interventions for MPNs include the use of tyrosine kinase inhibitors (TKIs) for BCR-ABL1(+) CML and JAK2 inhibitors for PV, ET and PMF. Histone deacetylase inhibitors (HDACi) are a novel class of drugs capable of altering the acetylation status of both histone and non-histone proteins, thereby affecting a repertoire of cellular functions in neoplastic cells including proliferation, differentiation, immune responses, angiogenesis and survival. Preliminary studies indicate that HDACi when used in combination with tyrosine kinase or JAK2 inhibitors may overcome resistance to the latter agents and enhance the pro-apoptotic effects on MPN cells. This review provides a review of pre-clinical and clinical studies that have explored the use of HDACi as potential therapeutics for MPNs.

New drugs for the treatment of myelofibrosis

Managing patients with myelofibrosis (MF)-either those with primary MF or those whose MF has evolved from antecedent polycythemia vera or essential thrombocythemia-presents many challenges to the hematologist. Cure is potentially achievable through allogeneic stem cell transplantation, but this therapy is either inappropriate or not feasible for most patients. MF patients suffer from a range of debilitating disease manifestations (eg, massive splenomegaly, cytopenias, constitutional symptoms, and transformation to a treatment-refractory blast phase). Currently available therapies are palliative but can be of significant value to some MF patients for anemia, splenomegaly, or sometimes both manifestations. New medical therapies for MF revolve around three main themes: immunomodulation (to assist anemia), hypomethylation strategies, and (the most robust pipeline) the use of targeted JAK2 inhibitors. These latter agents have shown the ability to improve MF-associated splenomegaly and MF-associated symptoms but do not improve (and may exacerbate) anemia or thrombocytopenia. Future targeted agents, and perhaps combinations of agents that currently show complementary benefits, are anticipated to further enhance the efficacy of medical therapy for MF.

Treatment of progression of Philadelphia-negative myeloproliferative neoplasms to myelodysplastic syndrome or acute myeloid leukemia by azacitidine: a report on 54 cases on the behalf of the Groupe Francophone des Myelodysplasies (GFM)

Transformation of Philadelphia (Ph)-negative myeloproliferative neoplasms (MPNs) to myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) is associated with poor response to chemotherapy and short survival. Fifty-four patients with Ph-negative MPN (including 21 essential thrombocythemia [ET], 21 polycythemia vera [PV], 7 primary myelofibrosis, and 5 unclassified MPN) who had progressed to AML (n = 26) or MDS (n = 28) were treated with azacitidine in a patient-named program. Overall response rate was 52% (24% complete response [CR], 11% partial response [PR], 8% marrow CR or CR with incomplete recovery of cytopenias, 9% hematologic improvement) and median response duration was 9 months. Prognostic factors were for overall response the underlying MPN (71% vs 33% responses in ET and PV, respectively; P = .016); prognostic factors for CR achievement were the underlying MPN (14% CR for PV vs 43% for ET; P = .040) and World Health Organization classification at transformation (36% vs 12% CR in MDS and AML, respectively, P = .038). Recurrence of chronic phase features of the initial MPN was observed in 39% of the responders. Median overall survival was 11 months. Azacitidine gives encouraging results in Ph-negative MPN having progressed to AML or MDS, but response duration is short, and consolidation treatments have to be evaluated.

Nuclear inositide signaling in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are defined as clonal hematopoietic stem-cell disorders characterized by ineffective hematopoiesis in one or more of the lineages of the bone marrow. Although distinct morphologic subgroups exist, the natural history of MDS is progression to acute myeloid leukemia (AML). However, the molecular the mechanisms the underlying MDS evolution to AML are not completely understood. Inositides are key cellular second messengers with well-established roles in signal transduction pathways, and nuclear metabolism elicited by phosphoinositide-specific phospholipase C (PI-PLC) beta1 and Akt plays an important role in the control of the balance between cell cycle progression and apoptosis in both normal and pathologic conditions. Recent findings evidenced the role played by nuclear lipid signaling pathways, which could become promising therapeutic targets in MDS. This review will provide a concise and updated revision of the state of art on this topic.

Recent advances in diagnosis and treatment of chronic myeloproliferative neoplasms

The Philadelphia chromosome-negative chronic myeloproliferative neoplasms (MPNs) have recently been the focus of tremendous advances in basic knowledge of disease pathophysiology following the recognition of mutations in JAK2 and MPL. These discoveries also led to refinement of the criteria employed for diagnosis. The prognostic roles of the JAK2 V617F mutation and of leukocytosis as independent risk factors for thrombosis, which represents the leading cause of death in patients with polycythemia vera and essential thrombocythemia, are supported by retrospective studies. A new risk stratification approach to the patient with primary myelofibrosis allows clinicians to distinguish categories of patients with significantly different expected survival. Finally, new drugs are currently being tested for MPNs, and molecular discoveries could ultimately lead to the development of a specific targeted therapy. Overall, significant advances in diagnosis, prognostication, and treatment have taken place in the last couple of years in the field of MPNs.

Therapy of myelofibrosis (excluding JAK2 inhibitors)

Myelofibrosis shows a progressive clinical course and usually a poor, lethal prognosis. Allogeneic transplantation is an effective, potentially curable treatment approach although only a minority of patients may currently benefit from it. New effective treatment strategies are becoming available for this disease, including not only JAK2 inhibitors, but also other innovative drugs, targeting more general oncogenic mechanisms and the epigenetic control of cell proliferation and differentiation.

Epigenetic mechanisms regulating normal and malignant haematopoiesis: new therapeutic targets for clinical medicine

It is now well established that epigenetic phenomena and aberrant gene regulation play a major role in carcinogenesis. These include aberrant gene silencing by imposing inactive histone marks on promoters, aberrant methylation of DNA at CpG islands, and the active repression of promoters by oncoproteins. In addition, many malignant cells also show aberrant gene activation due to constitutively active signalling. The next frontier in cancer research will be to examine how, at the molecular level, small mutations that alter the regulatory phenotype of a cell give rise after a number of cell divisions to the vast deregulation phenomena seen in malignant cells. This review outlines recent insights into how normal cell differentiation in the haematopoietic system is subverted in leukaemia and it introduces the molecular players involved in this process. It also summarises the results of recent clinical trials trying to reverse aberrant epigenetic regulation by employing agents influencing global epigenetic regulators.

Epigenetic therapy in myeloproliferative neoplasms: evidence and perspectives

The classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), which include polycythaemia vera, essential thrombocythaemia and primary myelofibrosis, originate from a stem cell-derived clonal myeloproliferation that manifests itself with variable haematopoietic cell lineage involvement; they are characterized by a high degree of similarities and the chance to transform each to the other and to evolve into acute leukaemia. Their molecular pathogenesis has been associated with recurrent acquired mutations in janus kinase 2 (JAK2) and myeloproliferative leukemia virus oncogene (MPL). These discoveries have simplified the diagnostic approach and provided a number of clues to understanding the phenotypic expression of MPNs; furthermore, they represented a framework for developing and/or testing in clinical trials small molecules acting as tyrosine kinase inhibitors. On the other hand, evidence of abnormal epigenetic gene regulation as a mechanism potentially contributing to the pathogenesis and the phenotypic diversity of MPNs is still scanty; however, study of epigenetics in MPNs represents an active field of research. The first clinical trials with epigenetic drugs have been completed recently, whereas others are still ongoing; results have been variable and at present do not allow any firm conclusion. Novel basic and translational information concerning epigenetic gene regulation in MPNs and the perspectives for therapy will be critically addressed in this review.

Chronic myeloproliferative diseases with and without the Ph chromosome: some unresolved issues

Ph-positive chronic myeloid leukemia (CML) and Ph-negative chronic myeloproliferative diseases (MPDs), characterized in many cases by the presence of the JAK2(V617F) mutation, have many features in common and yet also show fundamental differences. In this review, we pose five discrete and related questions relevant to both categories of hematological malignancy, namely: What are the mechanisms that underlie disease progression from a relatively benign or chronic phase? By what therapeutic methods might one target residual leukemia stem cells in CML? Is JAK2(V617F) the original molecular event in MPD? What epigenetic events must have a role in dictating disease phenotype in MPDs? And finally, Will the benefits conferred by current or future JAK2(V617F) inhibitors equal or even surpass the clinical success that has resulted from the use of tyrosine kinase inhibitors in CML? These and others questions must be addressed and in some cases should be answered in the foreseeable future.

How I treat symptomatic splenomegaly in patients with myelofibrosis

Managing patients with myelofibrosis (MF), either those with primary MF or those whose MF has evolved from antecedent polycythemia vera or essential thrombocythemia, presents many challenges to the hematologist. MF patients have a range of debilitating disease manifestations (eg, massive splenomegaly, cytopenias, constitutional symptoms, and transformation to a treatment-refractory blast phase). Cure is potentially achievable through allogeneic stem cell transplantation; however, this therapy is either inappropriate or not feasible for the majority of patients. Therefore, remaining therapies are palliative but can be of significant value to some MF patients. In particular, management of symptomatic splenomegaly remains one of the most perplexing aspects of MF clinical care. Using medications is the simplest approach for reducing splenomegaly, yet achieving symptomatic response without undue myelosuppression is challenging. Splenectomy or radiotherapy offers benefit, but careful patient selection and close monitoring are required because both have the potential for dangerous adverse effects. Experimental medical therapies, such as JAK2 inhibitors, show promise and may soon play an important role in the management of symptomatic splenomegaly in MF patients. Future care of MF patients, including splenomegaly management, will continue to require the hematologist to select therapeutic options carefully in the context of realistic, achievable goals.

Novel strategies for patients with chronic myeloproliferative disorders

PURPOSE OF REVIEW

This review focuses on new strategies for unmet clinical needs and on new targeted therapies in classical Philadelphia-negative myeloproliferative neoplasms.

RECENT FINDINGS

Meta-analyses in essential thrombocythemia documented Janus kinase 2 (JAK2) V617F as being associated with increased risk of thrombosis. New studies reinforced the evidence of leukocytosis as an independent risk factor for thrombosis in polycythemia vera and essential thrombocythemia. In a phase II trial of pegylated interferon-alpha2a in polycythemia vera patients, a decrease of JAK2 mutant expression to undetectable levels was demonstrated. New trials documented that 5-azacytidine and bortezomib have negligible effect in primary myelofibrosis, whereas thalidomide and tipifarnib produce 22 and 44% response, respectively. In primary myelofibrosis, the JAK2 inhibitor, INCB018424, resulted in a rapid and marked reduction in splenomegaly and a clinical improvement, with a modest effect on JAK2 V617F burden.

SUMMARY

Treating low-risk essential thrombocythemia and polycythemia vera patients presenting with leukocytosis or JAK2 V617F mutation in order to prevent thrombosis deserves a prospective validation. Pursuing clonal remission in polycythemia vera by interferon needs new evidence. Tipifarnib may be added to conventional therapeutic instruments for symptomatic primary myelofibrosis. The results of anti-JAK2-targeted therapies are encouraging as regards symptoms reduction but not clonal remission.

DNA demethylation protects from cleavable complex stabilization and DNA strand breakage induced by the topoisomerase type I inhibitor camptothecin

Methylation of cytosine in CpG sequences of the DNA in mammalian cells is an epigenetic feature regulated very exactly that bears importance for events like gene expression, DNA replication, transcription and genetic imprinting. Changes in the DNA methylation pattern, both hypermethylation and hypomethylation, have been observed in the carcinogenic process. These changes, in general, influence the DNA conformation in such a way that certain proteins are disturbed in their interactions with the molecule. In this paper, we investigated in cultured Chinese hamster ovary cells the influence of hypomethylation induced by the substitution of 5-aza-2'-deoxycytidine for cytidine in DNA on topoisomerase type I (topo I) function, measured as the capacity of the enzyme inhibitor camptothecin (CPT) to stabilize the topoisomerase-DNA complexes and to induce DNA strand breakage. Our results demonstrate that the degree of methylation in DNA correlates with the effectiveness of CPT to stabilize the topo I-DNA complexes and to induce DNA cleavage. A protective effect of hypomethylation, as a whole, has been observed.

From palliation to epigenetic therapy in myelofibrosis

Myelofibrosis shows a progressive clinical course and usually a poor, lethal prognosis. The molecular pathogenesis of this disease largely remains to be fully understood but the identification of the JAK2V617F mutation in more than half of patients was a major improvement in our understanding of the disease biology and may represent the first biologic marker useful for risk stratification, independently from conventional clinical predictors. After many elusive efforts, new effective treatment strategies are becoming available for this disease. Allogeneic transplantation following reduced-intensity conditioning programs, at least in some patients, may induce not only a hematologic response but also a molecular remission, thus supporting the hope of a possible, definitive eradication of the disease. Moreover, new innovative drugs, targeting either the JAK2V617F mutation or more general oncogenic mechanisms, may provide widely applicable, effective treatments to many patients for whom allogeneic transplantation is not feasible.