The diagnosis of BCR/ABL-negative chronic myeloproliferative diseases (CMPD): a comprehensive approach based on morphology, cytogenetics, and molecular markers

Genetic alterations in myeloproliferative and myelodysplastic/myeloproliferative neoplasms - a practical guide to WHO-HAEM5

Within the World Health Organization (WHO) classification of haematopoietic neoplasms, particularly its fifth version from 2022 (WHO-HAEM5), myeloid neoplasms are not only grouped into myeloproliferative (MPN) and myelodysplastic neoplasms (MDS). There is also a group of haematological disorders that share features of both categories termed myelodysplastic /myeloproliferative neoplasms (MDS/MPN). In this article, we aim to provide a comprehensive and practical guide to WHO-HAEM5 highlighting the genetic alterations that underlie MPN and MDS/MPN. This guide provides an overview of the overlapping commonalities among these entities, as well as their unique characteristics.

Chronic myeloid leukemia: a type of MPN

This review article classifies chronic myeloid leukemia (CML) based on cytogenetic analyses and different mutations detected in CML patients. The use of advanced technologies, such as karyotyping, fluorescent in situ hybridization, and comparative genomic hybridization, has allowed us to study CML in detail and observe the different biochemical changes that occur in different CML types. This review also highlights the different types of receptor and signaling pathway mutations that occur in CML.

Conformation sensitive gel electrophoresis for the detection of calreticulin mutations in BCR-ABL1-negative myeloproliferative neoplasms

INTRODUCTION

Calreticulin (CALR) mutations in myeloproliferative neoplasms (MPN) have been reported to be key markers in the molecular diagnosis, particularly in patients lacking JAK2 V617F mutation. In most current reports, CALR mutations were analysed by either allele-specific PCR (AS-PCR), or the more expensive quantitative real-time PCR, pyrosequencing and next-generation sequencing. Hence, we report the use of an alternative method, the conformation sensitive gel electrophoresis (CSGE) for the detection of CALR mutations in BCR-ABL1-negative MPN patients.

METHODS

Forty BCR-ABL1-negative MPN patients' DNA: 19 polycythemia vera (PV), 7 essential thrombocytosis (ET) and 14 primary myelofibrosis (PMF), were screened for CALR mutations by CSGE. PCR primers were designed to amplify sequences spanning between exons 8 and 9 to target the mutation hotspots in CALR. Amplicons displaying abnormal CSGE profiles by electrophoresis were directly sequenced, and results were analysed by BioEdit Sequence Alignment Editor v7.2.6. CSGE results were compared with AS-PCR and confirmed by Sanger sequencing.

RESULTS

CSGE identified 4 types of mutations; 2 PMF patients with either CALR type 1 (c.1099_1150del52) or type 2 (c.1155_1156insTTGTC), 1 ET patient with nucleotide deletion (c.1121delA) and insertion (c.1190insA) and 1 PV patient with p.K368del (c.1102_1104delAAG) and insertion (c.1135insA) inframe mutations. Three patients have an altered KDEL motif at the C-terminal of CALR protein. In comparison, AS-PCR only able to detect two PMF patients with mutations, either type 1 and type 2.

CONCLUSION

CSGE is inexpensive, sensitive and reliable alternative method for the detection of CALR mutations in BCR-ABL1-negative MPN patients.

Clinicopathological spectrum of BCR-ABL-Negative myeloproliferative neoplasms with correlation with janus-associated kinase 2 mutation

Background: Non chronic myelogenous leukemia (non-CML)/BCR-ABL-negative myeloproliferative neoplasms (MPNs) include essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF) (apart from chronic neutrophilic leukemia and chronic eosinophilic leukemia, which are rare). They are uncommon clonal disorders of adults, with an incidence ranging from 0.5 to 3/100,000 persons, BCR-ABL negative, and characterized by the activation of Janus-associated kinase 2 (JAK2). Very few studies have been reported from India. Aims and Objectives: The aims and objectives of this study were to analyze the clinicopathological spectrum and to determine the frequency of JAK2 mutation in patients of non-CML/BCR-ABL negative MPNs. Materials and Methods: Clinical and morphological features and frequency of JAK2 mutation in patients with PV, ET, and PMF were studied at a tertiary care hospital. The material was retrieved from the hematopathology records and reviewed. Results: JAK2V617F mutation was found in 10 of 14 cases (71%) of MPNs, 100% in PV, 50% in ET, and 71% of idiopathic myelofibrosis. The presence of JAK2V617F mutation was associated with a higher hemoglobin level (P < 0.05), a higher TLC (P < 0.05), and higher age (P < 0.05). Results showed that there are morphologic differences, and megakaryocytic morphology represents a useful clue for the differential diagnosis of these three BCR-ABL-negative MPN subtypes. Conclusion: The JAK2 V617F mutation was detected in 71% of patients with MPN disorders. Peripheral blood mutation screening for JAK2 V617F should be incorporated into the initial evaluation of patients suspected to have MPNs. Differences in megakaryocytic morphology provide the histomorphological hallmark of BCR-ABL-negative MPN subtypes.

Associations of Physical and Psychologic Symptom Burden in Patients With Philadelphia Chromosome-Negative Myeloproliferative Neoplasms

BACKGROUND

The physical symptom burden of patients with myeloproliferative neoplasms (MPNs) may last for extended periods during their disease trajectories and lead to psychologic distress, anxiety, or depression or all of these.

OBJECTIVE

This study evaluated the relationship between physical symptom burden captured by the Physical Problem List (PPL) on the Distress Thermometer and Problem List and psychologic outcomes (distress, anxiety, and depression) in the MPN setting.

METHODS

Patients (N = 117) with MPNs completed questionnaires containing the Distress Thermometer and Problem List and the Hospital Anxiety and Depression Scale in a dedicated MPN clinic within an academic medical center. They reported symptoms from any of 22 physical problems on the PPL. Items endorsed by more than 10% of participants were assessed for their associations with distress (Distress Thermometer and Problem List), anxiety (Hospital Anxiety and Depression Scale-Anxiety), and depression (Hospital Anxiety and Depression Scale-Depression). The total number of endorsed PPL items per participant was also evaluated.

RESULTS

Nine of 22 PPL items (fatigue, sleep, pain, dry skin/pruritus, memory/concentration, feeling swollen, breathing, and sexual) were reported by >10% of participants. In univariate analyses, all PPL items but one were associated with distress and depression, and all but 2 were associated with anxiety. In multivariate analyses, the total number of PPL items was associated with depression only (p < 0.001) when controlling for covariates.

CONCLUSION

Physical symptom burden in MPN patients was clearly associated with psychologic symptoms. Depression was uniquely associated with overall physical symptom burden. As such, the endorsement of multiple PPL items on the Distress Thermometer and Problem List should prompt an evaluation for psychologic symptoms to improve MPN patients' overall morbidity and quality of life.

Directly targeting transcriptional dysregulation in cancer

Drugs that target intracellular signalling pathways have markedly improved progression-free survival of patients with cancers who were previously regarded as untreatable. However, the rapid emergence of therapeutic resistance, as a result of bypass signalling or downstream mutation within kinase-mediated signalling cascades, has curtailed the benefit gained from these therapies. Such resistance mechanisms are facilitated by the linearity and redundancy of kinase signalling pathways. We argue that, in each cancer, the dysregulation of key transcriptional regulators not only defines the cancer phenotype but is essential for its development and maintenance. Furthermore, we propose that, as therapeutic targets, these transcriptional regulators are less prone to bypass by alternative mutational events or clonal heterogeneity, and therefore we must rekindle our efforts to directly target transcriptional regulation across a broad range of cancers.

Myeloproliferative neoplasms and the JAK/STAT signaling pathway: an overview

Myeloproliferative neoplasms are caused by a clonal proliferation of a hematopoietic progenitor. First described in 1951 as ‘Myeloproliferative Diseases’ and reevaluated by the World Health Organization classification system in 2011, myeloproliferative neoplasms include polycythemia vera, essential thrombocythemia and primary myelofibrosis in a subgroup called breakpoint cluster region-Abelson fusion oncogene-negative neoplasms. According to World Health Organization regarding diagnosis criteria for myeloproliferative neoplasms, the presence of the JAK2 V617F mutation is considered the most important criterion in the diagnosis of breakpoint cluster region-Abelson fusion oncogene-negative neoplasms and is thus used as a clonal marker. The V617F mutation in the Janus kinase 2 (JAK2) gene produces an altered protein that constitutively activates the Janus kinase/signal transducers and activators of transcription pathway and other pathways downstream as a result of signal transducers and activators of transcription which are subsequently phosphorylated. This affects the expression of genes involved in the regulation of apoptosis and regulatory proteins and modifies the proliferation rate of hematopoietic stem cells.

Does the level of WT1 expression predict the outcome in Philadelphia-negative myeloproliferative neoplasms?

AIMS

Despite the clinical importance of the leukemic transformation of chronic myeloproliferative neoplasms (MPNs), very little is known about markers that predict leukemic transformation. We studied WT1 expression in 37 MPN patients diagnosed as bcr-abl negative and JAK2 (V617F) positive with a molecular genetic test, and 23 healthy controls.

RESULTS

WT1 expression is higher in MPN patients compared with normal controls (p=0.002). According to the WT1 expression levels, patients were divided into two groups: high (≥0.205) and low (0-0.205) WT1 expression. Two out of six patients with a high WT1 expression level transformed to myelodysplastic syndrome at a 42- and 46-month follow-up, respectively.

CONCLUSIONS

Our results suggest that the overexpression of WT1 may play an important role in the leukemic transformation of MPNs.

E- and p-selectins are essential for repopulation of chronic myelogenous and chronic eosinophilic leukemias in a scid mouse xenograft model

In chronic myelogenous (CML) and chronic eosinophilic leukemia (CEL), neoplastic cells spread via the circulation into various extramedullary organs. As E- and P-selectin constitute the starting point for the leucocyte adhesion/invasion cascade, and CEL and CML cells share many properties with normal granulocytes, we investigated the role of these selectins in CEL and CML cell expansion and organ invasion in a xenotransplantation model using scid mice. Using two human leukemic cell lines (EOL-1 and K562), we were able to show that E- and P-selectins mediate leukemia cell tethering and adherence in a laminar flow assay. While E-selectin binding depended on sialylated carbohydrate moieties, P-selectin binding was completely (K562) or partially (EOL-1) independent of these carbohydrates indicating the involvement of non-canonical selectin ligands. In a xenograft model in scid mice, both cell lines invaded the bone marrow and other organs, formed chloromas, and ultimately produced an overt leukemia. In contrast, in E- and P-selectin knockout scid mice, the cells failed to show engraftment in 8 out of 10 animals and even if they did engraft, they produced only little organ invasion and chloroma formation. Together, these data suggest that E- and P-selectins play an important role in leukemic dissemination in CML and CEL.

Myelofibrosis in Philadelphia chromosome-negative myeloproliferative neoplasms is associated with aberrant karyotypes

In Philadelphia chromosome-negative myeloproliferative neoplasms (Ph¯ MPN), non-specific chromosomal defects are detectable and essential thrombocythemia (ET) has the lowest rate of aberrations, whereas primary myelofibrosis (PMF) and post-polycythemia vera (PV) myelofibrosis have the highest rates of aberrations. The frequency of cytogenetic defects in pre-fibrotic stage PMF has not been characterized thus far and the underlying molecular defects of chromosomal instability are unknown. In this study, histopathological findings were correlated with cytogenetic data (n = 249). The expression of DNA repair factors ERCC1 and LIG4 were determined in Ph¯ MPN with and without cytogenetic aberrations. Pre-fibrotic PMF and ET have similarly low frequencies of karyotype anomalies. The expression of ERCC1, but not LIG4, is increased in fibrotic stage PMF but is not associated with accumulation of cytogenetic defects. In conclusion, aberrant karyotypes in Ph¯ MPN reflect the chromosomal instability in these diseases and, in comparison with pre-fibrotic stages, Ph¯ MPN with fibrosis has the highest frequency of cytogenetic aberrations.

Allelic expression imbalance of JAK2 V617F mutation in BCR-ABL negative myeloproliferative neoplasms

The discovery of a single point mutation in the JAK2 gene in patients with BCR/ABL-negative myeloproliferative neoplasms (MPNs) has not only brought new insights and pathogenesis, but also has made the diagnosis of MPNs much easier. Although, to date, several mechanisms for the contribution of single JAK2V617F point mutation to phenotypic diversity of MPNs have been suggested in multiple studies, but it is not clear how a unique mutation can cause the phenotypic diversity of MPNs. In this study, our results show that allelic expression imbalance of JAK2 V617F mutant frequently occurs and contributes to phenotypic diversity of BCR-ABL-negative MPNs. The proportion of JAK2 V617F mutant allele was significantly augmented in RNA levels as compared with genomic DNA differently by distinct MPNs subtypes. In detail, preferential expression of JAK2 mutant allele showed threefold increase from the cDNA compared with the genomic DNA from patients with essential thrombocythemia and twofold increase in polycythemia vera. In conclusion, allelic expression imbalance of JAK2 V617F mutant proposes another plausible mechanism for the contribution of single JAK2 point mutation to phenotypic diversity of MPNs.

Molecular approach to diagnose BCR/ABL negative chronic myeloproliferative neoplasms

Chronic myeloproliferative neoplasms arise from clonal proliferation of hematopoietic stem cells. According to the World Health Organization myeloproliferative neoplasms are classified as: chronic myelogenous leukemia, polycythemia vera, essential thrombocythemia, primary myelofibrosis, chronic neutrophilic leukemia, chronic eosinophilic leukemia, hypereosinophilic syndrome, mast cell disease, and unclassifiable myeloproliferative neoplasms. In the revised 2008 WHO diagnostic criteria for myeloproliferative neoplasms, mutation screening for JAK2V617F is considered a major criterion for polycythemia vera diagnosis and also for essential thrombocythemia and primary myelofibrosis, the presence of this mutation represents a clonal marker. There are currently two hypotheses explaining the role of the JAK2V617F mutation in chronic myeloproliferative neoplasms. According to these theories, the mutation plays either a primary or secondary role in disease development. The discovery of the JAK2V617F mutation has been essential in understanding the genetic basis of chronic myeloproliferative neoplasms, providing some idea on how a single mutation can result in three different chronic myeloproliferative neoplasm phenotypes. But there are still some issues to be clarified. Thus, studies are still needed to determine specific molecular markers for each subtype of chronic myeloproliferative neoplasm.

Emerging therapeutic options for myelofibrosis: a Canadian perspective

Myelofibrosis (MF) is a clonal stem cell disorder characterized by cytopenias, splenomegaly, marrow fibrosis, and systemic symptoms due to elevated inflammatory cytokines. MF is associated with decreased survival. The quality of life of patients with MF is similar to other advanced malignancies. Allogeneic hematopoietic cell transplantation is a curative treatment, but is applicable to a minority of patients with MF. None of the conventional therapies are known to alter the natural history of the disease. Significant progress has been made in the last few years in the understanding of disease biology of MF. Discovery of the JAK2V617F mutation paved the way for drug discovery in MF, and the first JAK1/2 inhibitor, ruxolitinib, has been approved by FDA and Health Canada. Several other JAK1/2 inhibitors are at various stages of clinical development. As a consequence, the therapeutic landscape of MF is changing from a disease where no effective therapies existed to one with several novel treatment options on the horizon. In this report, we assess the changing therapeutic options for MF, and critically analyze the position of novel treatments in the current armamentarium.

Pathogenesis and classification of eosinophil disorders: a review of recent developments in the field

Eosinophils and their products play an essential role in the pathogenesis of various reactive and neoplastic disorders. Depending on the underlying disease, molecular defect and involved cytokines, hypereosinophilia may develop and may lead to organ damage. In other patients, persistent eosinophilia is accompanied by typical clinical findings, but the causative role and impact of eosinophilia remain uncertain. For patients with eosinophil-mediated organ pathology, early therapeutic intervention with agents reducing eosinophil counts can be effective in limiting or preventing irreversible organ damage. Therefore, it is important to approach eosinophil disorders and related syndromes early by using established criteria, to perform all appropriate staging investigations, and to search for molecular targets of therapy. In this article, we review current concepts in the pathogenesis and evolution of eosinophilia and eosinophil-related organ damage in neoplastic and non-neoplastic conditions. In addition, we discuss classifications of eosinophil disorders and related syndromes as well as diagnostic algorithms and standard treatment for various eosinophil-related disorders.

Contemporary consensus proposal on criteria and classification of eosinophilic disorders and related syndromes

Eosinophilia is an important indicator of various neoplastic and nonneoplastic conditions. Depending on the underlying disease and mechanisms, eosinophil infiltration can lead to organ dysfunction, clinical symptoms, or both. During the past 2 decades, several different classifications of eosinophilic disorders and related syndromes have been proposed in various fields of medicine. Although criteria and definitions are, in part, overlapping, no global consensus has been presented to date. The Year 2011 Working Conference on Eosinophil Disorders and Syndromes was organized to update and refine the criteria and definitions for eosinophilic disorders and to merge prior classifications in a contemporary multidisciplinary schema. A panel of experts from the fields of immunology, allergy, hematology, and pathology contributed to this project. The expert group agreed on unifying terminologies and criteria and a classification that delineates various forms of hypereosinophilia, including primary and secondary variants based on specific hematologic and immunologic conditions, and various forms of the hypereosinophilic syndrome. For patients in whom no underlying disease or hypereosinophilic syndrome is found, the term hypereosinophilia of undetermined significance is introduced. The proposed novel criteria, definitions, and terminologies should assist in daily practice, as well as in the preparation and conduct of clinical trials.

JAK2 V617F mutation prevalence in myeloproliferative neoplasms in Pernambuco, Brazil

BACKGROUND

The JAK2 V617F mutation is associated with three myeloproliferative neoplasms (MPNs): polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). It generates an unregulated clonal hematopoietic progenitor and leads to abnormal increased proliferation of one or more myeloid lineages. Subjects bearing this mutation may present more frequently with complications such as thrombosis and bleeding, and no specific treatment has yet been developed for BCR-ABL-negative JAK2 V617F-negative MPNs.

AIMS

To determine the prevalence of JAK2 V617F in MPNs in Pernambuco, Brazil, and to compare it with previous studies.

MATERIAL AND METHODS

144 blood samples were collected at the Hospital of Hematology of the HEMOPE Foundation and were genotyped by polymerase chain reaction-restriction fragment length polymorphism with BsaXI enzymatic digestion.

RESULTS AND DISCUSSION

88% (46/52) of the patients with PV, 47% (39/81) with ET, and 77% (8/11) with PMF were positive for JAK2 V617F, while more than 35% of the individuals were JAK2 V617F-negative, confirming a high prevalence of this abnormality in MPNs, more frequently with a low mutated allele burden, similar to what has been reported in other Western countries, despite differences among methods used to detect this mutation. Screening for JAK2 V617F may allow specific management of these diseases with JAK2 inhibitors in the future and highlights the need for further studies on the pathogenesis of BCR-ABL-negative JAK2 V617F-negative MPNs.

World health organization classification, evaluation, and genetics of the myeloproliferative neoplasm variants

There is no single category in the fourth edition (2008) of the World Health Organization (WHO) classification of myeloid neoplasms that encompasses all of the diseases referred to by some authors as the myeloproliferative neoplasm (MPN) "variants." Instead, they are considered as distinct entities and are distributed among various subgroups of myeloid neoplasms in the classification scheme. These relatively uncommon neoplasms do not meet the criteria for any so-called "classical" MPN (chronic myelogenous leukemia, polycythemia vera, primary myelofibrosis, or essential thrombocythemia) and, although some exhibit myelodysplasia, none meets the criteria for any myelodysplastic syndrome (MDS). They are a diverse group of neoplasms ranging from fairly well-characterized disorders such as chronic myelomonocytic leukemia to rare and thus poorly characterized disorders such as chronic neutrophilic leukemia. Recently, however, there has been a surge of information regarding the genetic infrastructure of neoplastic cells in the MPN variants, allowing some to be molecularly defined. Nevertheless, in most cases, correlation of clinical, genetic, and morphologic findings is required for diagnosis and classification. The fourth edition of the WHO classification provides a framework to incorporate those neoplasms in which a genetic abnormality is a major defining criterion of the disease, such as those associated with eosinophilia and abnormalities of PDGFRA, PDGFRB, and FGFR1, as well as for those in which no specific genetic defect has yet been discovered and which remain clinically and pathologically defined. An understanding of the clinical, morphologic, and genetic features of the MPN variants will facilitate their diagnosis.

A real-time polymerase chain reaction assay for rapid, sensitive, and specific quantification of the JAK2V617F mutation using a locked nucleic acid-modified oligonucleotide

The JAK2V617F mutation has emerged as an essential molecular determinant of myeloproliferative neoplasms (MPNs). The aim of this study was to evaluate the analytical and clinical performances of a real-time PCR (qPCR) assay using a combination of hydrolysis probes and a wild-type blocking oligonucleotide, all containing locked nucleic acid (LNA) bases. Moreover, we validated a procedure for precise quantification of the JAK2V617F allele burden. We used DNA samples from patients suspected to suffer from MPN and dilutions of HEL cells, carrying the mutation, to compare the LNA-qPCR assay to two previously published methods. All assays detected the same 36 JAK2V617F positive patients of 116 suspected MPN diagnostic samples. No amplification of normal donor DNA was observed in the LNA-qPCR, and the assay was able to detect and reproducibly quantify as few as 0.4% of the JAK2V617F allele in wild-type alleles. Quantification of the JAK2V617F allele burden showed similar proportion levels among the different MPN entities as described by other groups. In conclusion, the LNA-qPCR is a rapid, robust, sensitive, and highly specific assay for quantitative JAK2V617F determination that can be easily implemented in clinical molecular diagnostic laboratories. Moreover, precise quantification allows determination of JAK2V617F burden at diagnosis as well as the evaluation of response to JAK2 inhibitors.

Therapeutic potential of Janus-activated kinase-2 inhibitors for the management of myelofibrosis

Myelofibrosis (either primary or postpolycythemia vera/essential thrombocythemia) is a chronic and debilitating myeloproliferative neoplasm for which there is no well-accepted standard of care. Clinical manifestations of this disease (e.g., cytopenias, splenomegaly, bone marrow fibrosis) and constitutional symptoms (e.g., hypercatabolic state, fatigue, night sweats, fever) create significant treatment challenges. For example, progressive splenomegaly increases the risk for more serious clinical sequelae (e.g., portal hypertension, splenic infarction). Myelofibrosis arises from hematopoietic stem cells or early progenitor cells. However, the molecular mechanisms underlying its pathogenesis and clinical presentation are poorly understood, delaying the development of effective and targeted treatments. Recent studies have implicated mutations that directly or indirectly lead to the deregulated activation of Janus-activated kinase 2 (JAK2). Appreciation for the activation of JAK2 and the importance of increased levels of circulating proinflammatory cytokines in the pathogenesis and clinical manifestations of myelofibrosis has led to novel therapeutic agents targeting JAKs. This review will briefly discuss the origins of the JAK2 hypothesis, the clinical relevance of JAK2 mutations in myelofibrosis, and recent clinical progress in targeting JAKs as a therapeutic intervention for patients with this chronic and debilitating disease.

Pathogenesis, classification, and therapy of eosinophilia and eosinophil disorders

Eosinophilia is a recurrent feature and diagnostic clue in several hematologic malignancies. In stem cell- and myelopoietic neoplasms, eosinophils are derived from the malignant clone, whereas in lymphoid neoplasms and reactive states, eosinophilia is usually triggered by eosinopoietic cytokines. Myeloid neoplasms typically presenting with eosinophilia include chronic myeloid leukemia, chronic eosinophilic leukemia (CEL), other myeloproliferative neoplasms, some acute leukemias, advanced mast cell disorders, and rare forms of myelodysplastic syndromes. Diagnostic evaluations in unexplained eosinophilia have to take these diagnoses into account. In such patients, a thorough hematologic work-up including bone marrow histology and immunohistochemistry, cytogenetics, molecular markers, and a complete staging of potentially affected organ systems has to be initiated. Endomyocardial fibrosis, the most dangerous cardiovascular complication of the hypereosinophilic state, is frequently detected in PDGFR-mutated neoplasms, specifically in FIP1L1/PDGFRA+ CEL, but is usually not seen in other myeloid neoplasms or reactive eosinophilia, even if eosinophilia is recorded for many years. Treatment of hypereosinophilic patients depends on the variant of disease, presence of end organ damage, molecular targets, and the overall situation in each case. In a group of patients, oncogenic tyrosine kinases (TK) such as FIP1L1/PDGFRA, can be employed as therapeutic targets by using imatinib or other TK-blocking agents.

Preclinical and clinical experience with dasatinib in Philadelphia chromosome-negative leukemias and myeloid disorders

Recent advances in the molecular characterization of Philadelphia chromosome-negative (Ph-) leukemias and related myeloid disorders have provided a clear rationale for investigating novel targeted therapies. Dasatinib is a tyrosine kinase inhibitor with activity against BCR-ABL, platelet-derived growth factor receptors (PDGFRs), c- KIT, fibroblast growth factor receptors (FGFRs), SRC family kinases (SFKs), and EPHA receptors, all of which have been implicated in the pathogenesis of Ph- leukemias and myeloid disorders. This review presents emerging data on the preclinical and clinical activity of dasatinib in these diseases, which suggest that larger clinical studies are warranted.