Biological rationale and clinical use of interferon in the classical BCR-ABL-negative myeloproliferative neoplasms

Upregulated SPAG6 correlates with increased STAT1 and is associated with reduced sensitivity of interferon-α response in BCR::ABL1 negative myeloproliferative neoplasms

Sperm-associated antigen 6 (SPAG6) has been identified as an oncogene or tumor suppressor in various types of human cancer. However, the role of SPAG6 in BCR::ABL1 negative myeloproliferative neoplasms (MPNs) remains unclear. Herein, we found that SPAG6 was upregulated at the mRNA level in primary MPN cells and MPN-derived leukemia cell lines. The SPAG6 protein was primarily located in the cytoplasm around the nucleus and positively correlated with β-tubulin expression. In vitro, forced expression of SPAG6 increased cell clone formation and promoted G1 to S cell cycle progression. Downregulation of SPAG6 promoted apoptosis, reduced G1 to S phase transition, and impaired cell proliferation and cytokine release accompanied by downregulated signal transducer and activator of transcription 1 (STAT1) expression. Furthermore, the inhibitory effect of interferon-α (INF-α) on the primary MPN cells with high SPAG6 expression was decreased. Downregulation of SPAG6 enhanced STAT1 induction, thus enhancing the proapoptotic and cell cycle arrest effects of INF-α both in vitro and in vivo. Finally, a decrease in SPAG6 protein expression was noted when the STAT1 signaling was blocked. Chromatin immunoprecipitation assays indicated that STAT1 protein could bind to the SPAG6 promoter, while the dual-luciferase reporter assay indicated that STAT1 could promote the expression of SPAG6. Our results substantiate the relationship between upregulated SPAG6, increased STAT1, and reduced sensitivity to INF-α response in MPN.

Long-acting interferon: pioneering disease modification of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clonal disorders of hematopoietic stem cells. The malignant clones produce cytokines that drive self-perpetuating inflammatory responses and tend to transform into more aggressive clones, leading to disease progression. The progression of MPNs follows a biological sequence from the early phases of malignancy, polycythemia vera, and essential thrombocythemia, to advanced myelofibrosis and leukemic transformation. To date, the treatment of MPNs has focused on preventing thrombosis by decreasing blood cell counts and relieving disease-related symptoms. However, interferon (IFN) has been used to treat MPNs because of its ability to attack cancer cells directly and modulate the immune system. IFN also has the potential to modulate diseases by inhibiting JAK2 mutations, and recent studies have demonstrated clinical and molecular improvements. Long-acting IFN is administered less frequently and has fewer adverse effects than conventional IFN. The current state of research on long-acting IFN in patients with MPNs is discussed, along with future directions.

Immunomodulatory Role of Interferons in Viral and Bacterial Infections

Interferons are a group of immunomodulatory substances produced by the human immune system in response to the presence of pathogens, especially during viral and bacterial infections. Their remarkably diverse mechanisms of action help the immune system fight infections by activating hundreds of genes involved in signal transduction pathways. In this review, we focus on discussing the interplay between the IFN system and seven medically important and challenging viruses (herpes simplex virus (HSV), influenza, hepatitis C virus (HCV), lymphocytic choriomeningitis virus (LCMV), human immunodeficiency virus (HIV), Epstein-Barr virus (EBV), and SARS-CoV coronavirus) to highlight the diversity of viral strategies. In addition, the available data also suggest that IFNs play an important role in the course of bacterial infections. Research is currently underway to identify and elucidate the exact role of specific genes and effector pathways in generating the antimicrobial response mediated by IFNs. Despite the numerous studies on the role of interferons in antimicrobial responses, many interdisciplinary studies are still needed to understand and optimize their use in personalized therapeutics.

Recombinant Interferon-β in the Treatment of Polycythemia Vera and Related Neoplasms: Rationales and Perspectives

About 30 years ago, the first clinical trials of the safety and efficacy of recombinant interferon-α2 (rIFN-α2) were performed. Since then, several single-arm studies have shown rIFN-α2 to be a highly potent anticancer agent against several cancer types. Unfortunately, however, a high toxicity profile in early studies with rIFN-α2 -among other reasons likely due to the high dosages being used-disqualified rIFN-α2, which was accordingly replaced with competitive drugs that might at first glance look more attractive to clinicians. Later, pegylated IFN-α2a (Pegasys) and pegylated IFN-α2b (PegIntron) were introduced, which have since been reported to be better tolerated due to reduced toxicity. Today, treatment with rIFN-α2 is virtually outdated in non-hematological cancers, where other immunotherapies-e.g., immune-checkpoint inhibitors-are routinely used in several cancer types and are being intensively investigated in others, either as monotherapy or in combination with immunomodulatory agents, although only rarely in combination with rIFN-α2. Within the hematological malignancies, rIFN-α2 has been used off-label for decades in patients with Philadelphia-negative chronic myeloproliferative neoplasms (MPNs)-i.e., essential thrombocythemia, polycythemia vera, and myelofibrosis-and in recent years rIFN-α2 has been revived with the marketing of ropeginterferon-α2b (Besremi) for the treatment of polycythemia vera patients. Additionally, rIFN-α2 has been revived for the treatment of chronic myelogenous leukemia in combination with tyrosine kinase inhibitors. Another rIFN formulation-recombinant interferon-β (rIFN-β)-has been used for decades in the treatment of multiple sclerosis but has never been studied as a potential agent to be used in patients with MPNs, although several studies and reviews have repeatedly described rIFN-β as an effective anticancer agent as well. In this paper, we describe the rationales and perspectives for launching studies on the safety and efficacy of rIFN-β in patients with MPNs.

Transformation of Polycythemia Vera to Pure Erythroid Leukemia

Pure erythroid leukemia (PEL) is an aggressive and exceedingly rare form of acute leukemia characterized as a neoplastic proliferation of immature cells committed to the erythroid lineage. It has a poor overall median survival of two to three months. To our knowledge, there are currently only a handful of reports of PEL arising from polycythemia vera. Most reported cases have been associated with radiation therapy or chemotherapeutic alkylating agents. Here we report a rare occurrence of polycythemia vera treated with phlebotomy and hydroxyurea that underwent leukemic transformation to pure erythroid leukemia.

Interferons: role in cancer therapy

Interferons (IFNs) are a group of signaling cytokines, secreted by host cells to induce protection against various disorders. IFNs can directly impact on tumor cells or indirectly induce the immune system to protect host cells. The expression levels of IFNs and its functions of are excellently modulated in a way to protect host cells from probable toxicities caused by extreme responses. The efficacy of anticancer therapies is correlated to IFNs signaling. Although IFN signaling is involved in induction of antitumor responses, chronic stimulation of the IFN signaling pathway can induce resistance to various antineoplasm therapies. Hence, IFNs are expressed by both cancer and immune cells, and modulate their biological function. Understanding this mechanism of action might be a key target of combination therapies.

Data-driven analysis of JAK2V617F kinetics during interferon-alpha2 treatment of patients with polycythemia vera and related neoplasms

Treatment with PEGylated interferon-alpha2 (IFN) of patients with essential thrombocythemia and polycythemia vera induces major molecular remissions with a reduction in the JAK2V617F allele burden to undetectable levels in a subset of patients. A favorable response to IFN has been argued to depend upon the tumor burden, implying that institution of treatment with IFN should be as early as possible after the diagnosis. However, evidence for this statement is not available. We present a thorough analysis of unique serial JAK2V617F measurements in 66 IFN-treated patients and in 6 untreated patients. Without IFN treatment, the JAK2V617F allele burden increased exponentially with a period of doubling of 1.4 year. During monotherapy with IFN, the JAK2V617F allele burden decreased mono- or bi-exponentially for 33 responders of which 28 patients satisfied both descriptions. Bi-exponential description improved the fits in 19 cases being associated with late JAK2V617F responses. The decay of the JAK2V617F allele burden during IFN treatment was estimated to have half-lives of 1.6 year for the monoexponential response and 1.0 year in the long term for the bi-exponential response. In conclusion, through data-driven analysis of the JAK2V617F allele burden, we provide novel information regarding the JAK2V617F kinetics during IFN-treatment, arguing for early intervention.

Potent antileukemic activity of curaxin CBL0137 against MLL-rearranged leukemia

Around 10% of acute leukemias harbor a rearrangement of the MLL/KMT2A gene, and the presence of this translocation results in a highly aggressive, therapy-resistant leukemia subtype with survival rates below 50%. There is a high unmet need to identify safer and more potent therapies for MLL-rearranged (MLL-r) leukemia that can be combined with established chemotherapeutics to decrease treatment-related toxicities. The curaxin, CBL0137, has demonstrated nongenotoxic anticancer and chemopotentiating effects in a number of preclinical cancer models and is currently in adult Phase I clinical trials for solid tumors and hematological malignancies. The aim of our study was to investigate whether CBL0137 has potential as a therapeutic and chemopotentiating compound in MLL-r leukemia through a comprehensive analysis of its efficacy in preclinical models of the disease. CBL0137 decreased the viability of a panel of MLL-r leukemia cell lines (n = 12) and xenograft cells derived from patients with MLL-r acute lymphoblastic leukemia (ALL, n = 3) in vitro with submicromolar IC50s. The small molecule drug was well-tolerated in vivo and significantly reduced leukemia burden in a subcutaneous MV4;11 MLL-r acute myeloid leukemia model and in patient-derived xenograft models of MLL-r ALL (n = 5). The in vivo efficacy of standard of care drugs used in remission induction for pediatric ALL was also potentiated by CBL0137. CBL0137 exerted its anticancer effect by trapping Facilitator of Chromatin Transcription (FACT) into chromatin, activating the p53 pathway and inducing an Interferon response. Our findings support further preclinical evaluation of CBL0137 as a new approach for the treatment of MLL-r leukemia.

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.

Underlying Causes and Therapeutic Targeting of the Inflammatory Tumor Microenvironment

Historically, the link between chronic inflammation and cancer has long been speculated. Only more recently, pre-clinical and epidemiologic data as well as clinical evidence all point to the role of the tumor microenvironment as inextricably connected to the neoplastic process. The tumor microenvironment (TME), a complex mix of vasculature, inflammatory cells, and stromal cells is the essential "soil" helping to modulate tumor potential. Increasingly, evidence suggests that chronic inflammation modifies the tumor microenvironment, via a host of mechanisms, including the production of cytokines, pro-inflammatory mediators, angiogenesis, and tissue remodeling. Inflammation can be triggered by a variety of different pressures, such as carcinogen exposure, immune dysfunction, dietary habits, and obesity, as well as genetic alterations leading to oncogene activation or loss of tumor suppressors. In this review, we examine the concept of the tumor microenvironment as related to both extrinsic and intrinsic stimuli that promote chronic inflammation and in turn tumorigenesis. Understanding the common pathways inherent in an inflammatory response and the tumor microenvironment may shed light on new therapies for both primary and metastatic disease. The concept of personalized medicine has pushed the field of oncology to drill down on the genetic changes of a cancer, in the hopes of identifying individually targeted agents. Given the complexities of the tumor microenvironment, it is clear that effective oncologic therapies will necessitate targeting not only the cancer cells, but their dynamic relationship to the tumor microenvironment as well.

Genetic variation in IL28B (IFNL3) and response to interferon-alpha treatment in myeloproliferative neoplasms

OBJECTIVE

In myeloproliferative neoplasms (MPN), interferon-alpha (IFN-α) is an effective treatment with disease-modifying properties but currently with no clear predictors of treatment outcome. Recent genomewide association studies in chronic hepatitis C have found a strong influence of genetic polymorphism near the IL28B (IFNL3) gene in response to IFN-α treatment. In this study, we sought to evaluate the prognostic impact of IL28B rs12979860, rs8099917, and rs12980275 on IFN-α treatment response in myeloproliferative neoplasms.

METHOD

We retrospectively evaluated 100 patients with MPN treated with IFN-α. The hematologic treatment response on IFN-α was compared between patients and correlated with host genetic variations in IL28B. The genotypes of IL28B were determined by allelic discrimination assays.

RESULTS

The CC genotype of rs12979860 was found significantly associated with hematologic response in polycythemia vera (PV) with a complete response (CR) in 79% (CC) compared to 48% (non-CC), (P = .036). No association between the genotypes and treatment response on hydroxyurea was found.

CONCLUSION

These results imply an effect of IL28B genotype on the outcome of IFN-α treatment in MPN.

Recent Progress in Chronic Neutrophilic Leukemia and Atypical Chronic Myeloid Leukemia

PURPOSE OF REVIEW

We reviewed recent diagnostic and therapeutic progress in chronic neutrophilic leukemia (CNL) and atypical chronic myeloid leukemia (aCML). We summarized recent genetic data that may guide future efforts towards implementing risk-adapted therapy based on mutational profile and improving disease control and survival of affected patients.

RECENT FINDINGS

Recent genetic data in CNL and aCML prompted modifications to the World Health Organization (WHO) diagnostic criteria, which have improved our understanding of how CNL and aCML are different diseases despite sharing common findings of peripheral granulocytosis and marrow myeloid hyperplasia. The overlap of recurrently mutated genes between aCML and CMML support considering CSF3R-T618I mutated cases as a distinct entity, either as CNL or CNL with dysplasia. Ongoing preclinical and clinical studies will help to further inform the therapeutic approach to these diseases. Our understanding of CNL and aCML has greatly advanced over the last few years. This will improve clarity for the diagnosis of these diseases, provide a strategy for risk stratification, and guide risk-adapted therapy.

Experience with ruxolitinib in the treatment of polycythaemia vera

Polycythaemia vera (PV) is a myeloproliferative neoplasm classically characterized by an erythrocytosis and is associated with a high risk of thromboembolic events, constitutional symptoms burden and risk of transformation to myelofibrosis and acute myeloid leukaemia. Therapy is directed at the haematocrit (HCT) to reduce the risk of thrombotic events and usually comprises low-dose aspirin and phlebotomy to maintain HCT at >45%. Frequently in addition, cytoreductive therapy is indicated in high-risk patients for normalizing haematological parameters to mitigate the occurrence of thromboembolic events. Unfortunately, there is no clear evidence that current therapies reduce the risk of transformation to myelofibrosis and for some a risk of a therapy related complication is unknown for example leukaemia due to hydroxycarbamide (HC). First-line therapy for treating PV remains HC or interferon, the latter most often in younger patients, especially those of childbearing age. However, therapy related intolerance or resistance is a common feature and results in limited treatment options for such patients. The discovery of the JAK2 V617F mutation and consequently targeted therapy with Janus kinase inhibitors, in particular ruxolitinib, has extended the spectrum of agents that can be used as second or third line in PV. The findings of the phase II trial RESPONSE and the preliminary data from RESPONSE 2 trial have identified a role for ruxolitinib in PV patients who are resistant or intolerant to HC. In this article, using clinical cases we demonstrate our experience with ruxolitinib highlighting the clinical benefits and limitations we encountered in clinical practice.

The impact of interferon-alpha2 on HLA genes in patients with polycythemia vera and related neoplasms

Gene expression profiling in Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) have unraveled significant deregulation of several immune and inflammation genes of potential importance for clonal evolution. Other mechanisms might be downregulation of major histocompatibility class I and II genes used by tumor cells to escape antitumor T-cell-mediated immune responses. Several genes encoding human leukocyte antigen (HLA) class I and II molecules have been shown to be significantly downregulated. Upregulation of HLA genes is considered one of the mechanisms of action of interferon (IFN)-alpha2, but regulation of these genes during IFN-alpha2 treatment in MPNs has never been studied. Our findings show a significant upregulation of several HLA genes of importance for tumor immune surveillance by IFN-alpha2 treatment in MPNs. This mechanism might enhance the cytotoxic potential of immune cells against MPNs and explain the induction of minimal residual disease by IFN-alpha2 treatment in these patients.

New Therapeutic Approaches in Polycythemia Vera

Polycythemia vera (PV) is 1 of the 3 Philadelphia-negative myeloproliferative neoplasms. Clinically, PV is an indolent disease, but its course can be complicated by arterial and venous vascular incidents, evolution to myelofibrosis, or leukemic transformation. Treatment of PV is therefore aimed at preventing such acute complications. The cornerstone of therapy of low-risk patients remains strict control of cardiovascular risk factors, the use of phlebotomy, and low-dose aspirin. Higher-risk patients should also receive cytoreductive treatments. Hydroxyurea and interferon α represent standard first-line options for newly diagnosed high-risk PV patients. Recommendations for patients whose disease fails to respond to these therapies are less clearly defined. The discovery of a mutation in the Janus kinase (JAK) 2 gene (V617F) in almost all cases of PV has prompted the development of molecularly targeted agents for the treatment of these patients. In this review, we discuss key clinical aspects, the current therapeutic armamentarium, and data on the use of novel agents in patients with PV.

Proteostasis alterations in myeloproliferative neoplasms: Oncogenic relevance and therapeutic opportunities

Myeloproliferative neoplasms (MPNs) represent a frequently occurring group of heterogeneous hematologic malignancies. In the last decade, the identification of JAK2-activating mutations in a significant proportion of MPN patients gave rise to the first molecularly driven therapy for BCR-ABL-negative patients. Nevertheless, current efforts are still focused on the identification of novel therapeutic targets to achieve permanent remission. In this perspective, we focus on the recent findings in this field and highlight new evidence linking proteostasis deregulation with myeloid transformation. We recently reported that the proteostasis regulator AIRAPL acts as a tumor suppressor in MPNs through the modulation of insulin-like growth factor receptor levels at the endoplasmic reticulum. This finding paves the way for new therapeutic approaches to these neoplasms and indicates the importance of protein homeostasis maintenance for normal hematopoiesis.

Antitumour actions of interferons: implications for cancer therapy

The interferons (IFNs) are a family of cytokines that protect against disease by direct effects on target cells and by activating immune responses. The production and actions of IFNs are finely tuned to achieve maximal protection and avoid the potential toxicity associated with excessive responses. IFNs are back in the spotlight owing to mounting evidence that is reshaping how we can exploit this pathway therapeutically. As IFNs can be produced by, and act on, both tumour cells and immune cells, understanding this reciprocal interaction will enable the development of improved single-agent or combination therapies that exploit IFN pathways and new 'omics'-based biomarkers to indicate responsive patients.

Recombinant interferon-α in myelofibrosis reduces bone marrow fibrosis, improves its morphology and is associated with clinical response

Recombinant interferon-α represents a well-established therapeutic option for the treatment of polycythemia vera and essential thrombocythemia. Recent studies also suggest a role for recombinant interferon-α in the treatment of 'early stage' primary myelofibrosis, but few studies have reported the bone marrow changes after clinically successful interferon therapy. The aim of the present study is to detail the histological responses to recombinant interferon-α in primary myelofibrosis and post-polycythemia vera/post-essential thrombocythemia myelofibrosis and to correlate these with clinical findings. We retrospectively studied 12 patients with primary myelofibrosis or post-polycythemia vera/post-essential thrombocythemia myelofibrosis, who had been treated with recombinant interferon-α. Six patients had received other prior cytoreductive therapies. Bone marrow biopsy was assessed for the following histological parameters: (i) cellularity; (ii) myeloid-to-erythroid ratio; (iii) megakaryocyte tight clusters; (iv) megakaryocyte and naked nuclei density; (v) megakaryocytic atypia; (vi) fibrosis; and (vii) the percentage of blasts. Clinical and laboratory data were included: (i) constitutional symptoms; (ii) splenomegaly, if present; and (iii) complete cell blood count. The clinical response to therapy was evaluated using the International Working Group for Myelofibrosis Research and Treatment/European LeukemiaNet response criteria. The Dynamic International Prognostic Scoring System (DIPSS) score was calculated before and after recombinant interferon-α administration. Successful interferon therapy for myelofibrosis was associated with a significant reduction of marrow fibrosis, cellularity, megakaryocyte density and naked nuclei density. The presence of JAK2(V617F) mutation correlated with improved DIPSS score. JAK2(V617F)-negative cases showed worsening of such score or evolution to acute myeloid leukemia. Cytogenetic analysis documented a normal karyotype in all cases. In conclusion, successful clinical response to interferon-α correlates well with an improvement of bone marrow morphology. The prognostic effect of such therapy may be influenced by the JAK2 mutational status. Additional studies are needed to confirm these preliminary data.

Ropeginterferon alfa-2b, a novel IFNα-2b, induces high response rates with low toxicity in patients with polycythemia vera

In this prospective, open-label, multicenter phase 1/2 dose escalation study, we used a next-generation, mono-pegylated interferon (IFN) α-2b isoform, ropeginterferon alfa-2b. The unique feature of ropeginterferon alfa-2b is a longer elimination half-life, which allows administration every 2 weeks. We present data from 51 polycythemia vera patients. The main goal was to define the maximum tolerated dose and to assess safety and efficacy. A dose range of 50 to 540 µg was tested without the appearance of dose-limiting toxicities. All drug-related adverse events were known toxicities associated with IFN-α. The cumulative overall response rate was 90%, comprising complete response in 47% and partial response in 43% of patients; the best individual molecular response level was a complete response in 21% of patients and partial response in 47%. Notably, we did not observe any correlation between the dose level and the response rate or response duration, suggesting that already low levels of ropeginterferon alfa-2b are sufficient to induce significant hematologic and molecular responses. These data suggest promising efficacy and safety of ropeginterferon alfa-2b and support the development of the drug in a randomized phase 3 clinical trial. The study was disclosed at www.clinicaltrials.gov as #NCT01193699 before including the first patient.

Central role of ULK1 in type I interferon signaling

We provide evidence that the Unc-51-like kinase 1 (ULK1) is activated during engagement of the type I interferon (IFN) receptor (IFNR). Our studies demonstrate that the function of ULK1 is required for gene transcription mediated via IFN-stimulated response elements (ISRE) and IFNγ activation site (GAS) elements and controls expression of key IFN-stimulated genes (ISGs). We identify ULK1 as an upstream regulator of p38α mitogen-activated protein kinase (MAPK) and establish that the regulatory effects of ULK1 on ISG expression are mediated possibly by engagement of the p38 MAPK pathway. Importantly, we demonstrate that ULK1 is essential for antiproliferative responses and type I IFN-induced antineoplastic effects against malignant erythroid precursors from patients with myeloproliferative neoplasms. Together, these data reveal a role for ULK1 as a key mediator of type I IFNR-generated signals that control gene transcription and induction of antineoplastic responses.

The interferon-alpha revival in CML

Interferon-alpha (IFNα) was once the standard of frontline treatment for chronic myeloid leukemia (CML). Its pleiotropic mechanism of action in CML includes immune activation and specific targeting of CML stem cells. Early studies of IFNα in CML demonstrated that patients in chronic phase could attain extremely stable remissions, which correlated with long-term survival. Some patients even sustained their remission after discontinuing therapy, but the mechanism underlying this phenomenon is not well understood. Today, BCR-ABL tyrosine kinase inhibitors (TKIs), such as imatinib, induce remarkable responses in CML patients and have become the mainstay of CML therapy. Although TKIs target the pathogenic BCR-ABL protein in CML, they cannot fully eradicate CML stem cells. Some of the clinical trials testing IFNα plus imatinib combination therapy suggest that addition of IFNα increases the speed and rate of responses with imatinib therapy. However, the undesirable side effects of IFNα can make this therapy difficult to deliver, and the optimal therapeutic window for using IFNα in combination therapy is unknown. Further studies are needed to clarify the best niche for IFNα use in CML.

Investigations of interferon-lambda for the treatment of cancer

Interferon-lambda (IFN-λ), a recently discovered cytokine, overlaps broadly with type I IFN signaling, producing antiviral, antiproliferative, and proapoptotic responses. In comparison to type I IFNs, IFN-λ has a limited spectrum of responsive tissues due to variation in expression of the IFN-λ receptor IFNLR1. Type I IFNs have been investigated for their antitumor effects and used in the clinical setting for a number of different cancers. Given the overlap in signaling and function between IFN-λ and type I IFNs, IFN-λ has also drawn interest for the treatment of cancer. To date, a number of studies using both murine and human models of cancer have investigated the antitumor effects of IFN-λ. These studies have found that IFN-λ is capable of directly targeting cancer cells to reduce their tumorigenicity, induce cell cycle arrest, and cause apoptosis. In addition, IFN-λ has been shown to have indirect effects against cancer cells through immune system responses and immune modulatory effects. This review aims to detail the findings of studies investigating IFN-λ for the treatment of cancer as well as suggest areas of potential interest for future studies.

Therapeutic options for patients with polycythemia vera and essential thrombocythemia refractory/resistant to hydroxyurea

Hydroxyurea (HU) has traditionally been the first-line treatment for patients with polycythemia vera (PV) or essential thrombocythemia (ET) at high risk for vascular complications. However, approximately 20-25% of patients develop resistance or intolerance to HU and must be treated with second-line therapies. Resistance is associated with disease transformation and reduced survival. However, given the dearth of large-scale controlled clinical trials in this patient population, there is no clear consensus on how to best treat patients who develop resistance or intolerance to HU. Herein, we review current literature on treatment options for patients with HU-refractory/resistant PV or ET and provide recommendations for treating these patients.

Essential role for the Mnk pathway in the inhibitory effects of type I interferons on myeloproliferative neoplasm (MPN) precursors

The mechanisms of generation of the antineoplastic effects of interferons (IFNs) in malignant hematopoietic cells remain to be precisely defined. We examined the activation of type I IFN-dependent signaling pathways in malignant cells transformed by Jak2V617F, a critical pathogenic mutation in myeloproliferative neoplasms (MPNs). Our studies demonstrate that during engagement of the type I IFN receptor (IFNAR), there is activation of Jak-Stat pathways and also engagement of Mnk kinases. Activation of Mnk kinases is regulated by the Mek/Erk pathway and is required for the generation of IFN-induced growth inhibitory responses, but Mnk kinase activation does not modulate IFN-regulated Jak-Stat signals. We demonstrate that for type I IFNs to exert suppressive effects in malignant hematopoietic progenitors from patients with polycythemia vera, induction of Mnk kinase activity is required, as evidenced by studies involving pharmacological inhibition of Mnk or siRNA-mediated Mnk knockdown. Altogether, these findings provide evidence for key and essential roles of the Mnk kinase pathway in the generation of the antineoplastic effects of type I IFNs in Jak2V617F-dependent MPNs.