Classification of chronic myeloid disorders: From Dameshek towards a semi-molecular system

Molecular Pathogenesis of BCR-ABL-Negative Atypical Chronic Myeloid Leukemia

Atypical chronic myeloid leukemia is a rare disease whose pathogenesis has long been debated. It currently belongs to the group of myelodysplastic/myeloproliferative disorders. In this review, an overview on the current knowledge about diagnosis, prognosis, and genetics is presented, with a major focus on the recent molecular findings. We describe here the molecular pathogenesis of the disease, focusing on the mechanisms of action of the main mutations as well as on gene expression profiling. We also present the treatment options focusing on emerging targeted therapies.

Transcriptome research identifies four hub genes related to primary myelofibrosis: a holistic research by weighted gene co-expression network analysis

Objectives: This study aimed to identify specific diagnostic as well as predictive targets of primary myelofibrosis (PMF).

Methods: The gene expression profiles of GSE26049 were obtained from Gene Expression Omnibus (GEO) dataset, WGCNA was constructed to identify the most related module of PMF. Subsequently, Gene Ontology (GO), Kyoto Encyclopedia Genes and Genomes (KEGG), Gene Set Enrichment Analysis (GSEA) and Protein-Protein interaction (PPI) network were conducted to fully understand the detailed information of the interested green module. Machine learning, Principal component analysis (PCA), and expression pattern analysis including immunohistochemistry and immunofluorescence of genes and proteins were performed to validate the reliability of these hub genes.

Results: Green module was strongly correlated with PMF disease after WGCNA analysis. 20 genes in green module were identified as hub genes responsible for the progression of PMF. GO, KEGG revealed that these hub genes were primarily enriched in erythrocyte differentiation, transcription factor binding, hemoglobin complex, transcription factor complex and cell cycle, etc. Among them, EPB42, CALR, SLC4A1 and MPL had the most correlations with PMF. Machine learning, Principal component analysis (PCA), and expression pattern analysis proved the results in this study.

Conclusions: EPB42, CALR, SLC4A1 and MPL were significantly highly expressed in PMF samples. These four genes may be considered as candidate prognostic biomarkers and potential therapeutic targets for early stage of PMF. The effects are worth expected whether in the diagnosis at early stage or as therapeutic target.

Atypical chronic myeloid leukemia BCR-ABL 1 negative: A case report and literature review

Atypical chronic myeloid leukemia (aCML), BCR-ABL1 negative is a rare myelodysplastic syndrome/myeloproliferative neoplasm for which no current standard of care exists. The blood smear of patients with aCML showed prominent immature granulocytosis, and granulocytic dysplasia. We admitted a 58-year-old man with splenomegaly, hyperleukocytosis, anemia, and thrombocytopenia; then cytology, cytogenetic and molecular biology analysis of bone morrow were performed and the diagnosis of aCML was made according to 2016 World Health Organization diagnostic criteria. The patient was initially treated by chemotherapy; the patient achieved an aggravation of anemia. This motivated the change of treatment.

Atypical chronic myeloid leukemia: a rare entity with management challenges

The aim of our study was to review the clinicopathologic features and management of atypical chronic myeloid leukemia (aCML). Relevant manuscripts published in English were searched using PubMed. aCML is diagnosed as per WHO 2016 classification in the presence of leukocytosis ≥13 × 109/l with circulating neutrophil precursors ≥10%, monocytes less than 10%, minimal basophils, hypercellular bone marrow with granulocytic proliferation and dysplasia, bone marrow blast less than 20% and absence of BCR/ABL fusion gene. Common cytogenetic features and mutations include trisomy 8, and mutations in SETBP1 and ETNK1. Median survival is 1-2 years. Hematopoietic stem cell transplant may be the only curative option. Ruxolitinib and dasatinib are emerging therapeutic options. Thus, aCML is a rare entity with poor survival. Novel therapies are needed.

JAK2 inhibitors: what's the true therapeutic potential?

Physicians treating patients with the classic Philadelphia-negative myeloproliferative neoplasms (Ph-negative MPNs) (polycythemia vera [PV], essential thrombocythemia [ET] and primary myelofibrosis [PMF]) traditionally had few therapeutic drugs available. Spurred by the discovery of activating mutation of the JAK2 tyrosine kinase (JAK2 V617F mutation) in patients with Ph-negative MPNs several years ago, several JAK2 inhibitors were synthesized and are currently undergoing clinical trials in patients with PMF, PV and ET. Initial results from these studies have shown that these drugs can markedly reduce spleen size and alleviate constitutional symptoms, increase weight and improve exercise capacity in MF patients, thus improve quality of their life, which is significant clinical benefit. In ET and PV JAK2 inhibitor therapy may efficiently control blood cell count, as well as improve splenomegaly and control disease related symptoms. JAK2 inhibitors are a novel class of agents with promising results for treating patients with MF, PV and ET. In this article we will review the current evidence regarding the role of JAK2 mutations in the pathogenesis of Ph-negative MPNs and summarize results from the most recent clinical trials with JAK2 inhibitors in these disorders. JAK2 inhibitors are a novel class of agents with promising results for treating patients with MF, PV and ET.

Prognostic molecular markers in myelodysplastic syndromes

Cytogenetic findings in myelodysplastic syndromes play an important role in diagnosis, prognostication and clinical decision making. Therefore, they became an important aspect in scoring systems such as the International Prognostic Scoring System (IPSS) and the WHO-adapted Prognostic Scoring System (WPSS). Ongoing efforts to refine the categorization of karyotypes with regard to prognosis and therapeutic options will change scoring systems in the near future. In order to learn more about the pathophysiology of myelodysplastic syndromes, various molecular genetic aberrations are identified and their impact on prognosis discussed. New screening methods such as gene expression or single nucleotide polymorphism analysis are good candidates to find entrance in clinical practice in the future as they are useful tools in further elucidation of the underlying defects in myelodysplastic syndromes and the development of more specific classifications of the disease concerning risk assessment.

Somatic mutations and the hierarchy of hematopoiesis

Clonal disease is often regarded as almost synonymous with cancer. However, it is becoming increasingly clear that our bodies harbor numerous mutant clones that are not tumors, and mostly give rise to no disease at all. Here we discuss three somatic mutations arising within the hematopoietic system: BCR-ABL, characteristic of chronic myeloid leukemia; mutations of the PIG-A gene, characteristic of paroxysmal nocturnal hemoglobinuria; the V617F mutation in the JAK2 gene, characteristic of myeloproliferative diseases. The population frequencies of these three blood disorders fit well with a hierarchical model of hematopoiesis. The fate of any mutant clone will depend on the target cell and on the fitness advantage, if any, that the mutation confers on the cell. In general, we can expect that only a mutation in a hematopoietic stem cell will give long-term disease; the same mutation taking place in a cell located more downstream may produce just a ripple in the hematopoietic ocean.

Mixed myeloproliferative and myelodysplastic disorders

When the French-American-British (FAB) classification system was first devised in the 1970s for the myelodysplastic syndromes (MDS), chronic myelomonocytic leukemia (CMML) was included in the FAB MDS classification schema. It always appeared out of place, however, at least when compared with the other FAB MDS categories, as CMML clearly has some features of a myeloproliferative disorder. Yet CMML also did not fit well with the traditional four myeloproliferative disorders. In the 1990s there was ongoing discussion about distinguishing a proliferative type of CMML versus a dysplastic type of CMML, based primarily on the total white blood cell count. In 2001 the World Health Organization reclassified most of the hematologic malignancies, creating a new category of mixed myelodysplastic/myeloproliferative diseases. Finally, CMML has an appropriate home, along with other disorders that seem to fit quite well in this "mixed" category.

BCR-ABL-negative chronic myeloid leukemia

Constitutive activation of protein tyrosine kinases plays a central role in the pathogenesis of myeloproliferative disorders, including BCR-ABL-negative chronic myeloid leukemia. Current research is focused on elucidating the full spectrum of causative mutations in this rare, heterogeneous disease. Activated tyrosine kinases are excellent targets for signal transduction therapy, and an accurate diagnosis including morphology, karyotyping, and molecular genetics will become increasingly important to direct individualized treatment. In addition, new molecular findings need to be incorporated into disease classification systems.

Phase 2 study of CEP-701, an orally available JAK2 inhibitor, in patients with primary or post-polycythemia vera/essential thrombocythemia myelofibrosis

Few treatment options exist for patients with myelofibrosis (MF), and their survival is significantly shortened. Activating mutation of the JAK2 tyrosine kinase (JAK2(V617F)) is found in approximately 50% of MF patients. CEP-701 is a tyrosine kinase inhibitor that inhibits JAK2 in in vitro and in vivo experiments. We conducted a phase 2 clinical study of CEP-701 in 22 JAK2(V617F)-positive MF patients (80 mg orally twice daily), and 6 (27%) responded by International Working Group criteria (clinical improvement in all cases): reduction in spleen size only (n = 3), transfusion independency (n = 2), and reduction in spleen size with improvement in cytopenias (n = 1). Median time to response was 3 months, and duration of response was more than or equal to 14 months. No improvement was seen in bone marrow fibrosis or JAK2(V617F) allele burden. Phosphorylated STAT3 levels decreased from baseline in responders while on therapy. Eight patients (36%) experienced grade 3 or 4 toxicity, and 6 (27%) required dose reduction. Main side effects were myelosuppression (grade 3 or 4 anemia, 14%; and thrombocytopenia, 23%) and gastrointestinal disturbances (diarrhea, any grade, 72%; grade 3 or 4, 9%; nausea, grade 1 or 2 only, 50%; vomiting, grade 1 or 2 only, 27%). In conclusion, CEP-701 resulted in modest efficacy and mild but frequent gastrointestinal toxicity in MF patients. The study was registered at http://clinicaltrials.gov as NCT00494585.

A role for JAK2 mutations in myeloproliferative diseases

Myeloproliferative disorders (MPDs) are characterized by a clonal expansion of myeloid cells. Over the past two years, the identification of the JAK2V617F mutation in most cases of polycythemia vera (PV) as well as approximately 50% of patients with essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF) has greatly advanced our understanding of MPDs. The JAK2V617F mutation alters the JAK2 tyrosine kinase to confer constitutive activation and affect downstream signaling pathways. Data from mouse models demonstrate that the mutation is sufficient for development of PV, but additional work is needed to better understand how this allele functions in ET and IMF. Regardless of the various pathologies, the JAK2V617F discovery highlights the importance of JAK-STAT signaling in myeloid differentiation and focuses effort on developing a clinically relevant JAK2 inhibitor.

Advances in molecular diagnostics of myeloproliferative disorders

Incremental advances in the molecular pathogenesis of myeloproliferative disorders (MPDs) have had a substantial impact on clinical practice in terms of both diagnosis and treatment. An array of novel molecular methods are being developed and integrated into the current battery of tests for diagnosis and monitoring of treatment response. Primarily, subjective clinico-histologic approaches to diagnosis are being replaced by more objective semimolecular diagnostic algorithms. Furthermore, identification of disease-specific molecular markers has facilitated the development of small-molecule drugs for targeted therapy. This review provides an overview of MPDs with emphasis on molecular diagnostic tests and their incorporation into contemporary diagnostic and therapeutic algorithms.

Chronic myeloproliferative disorders: the role of tyrosine kinases in pathogenesis, diagnosis and therapy

The term chronic myeloproliferative disorders was originally used by Damashek to describe the link amongst a group of acquired blood diseases. Recent molecular genetic analysis has provided a scientific basis for this observation. Underlying myeloproliferative disorders are acquired abnormalities of tyrosine kinase genes. These may be chromosomal translocations resulting in the creation of a fusion kinase gene, examples of which include ABL, FGFR, and PDGFR as seen in disorders CML, 8p11 myeloproliferative syndrome, atypical CML and chronic eosinophilic leukaemia. The second group of tyrosine kinase abnormalities are point mutations in JAK2, a cytosolic TK. This abnormality is seen in 30-97% of cases of MPD with the phenotype PV, ET or CIMF.

Prospective identification of high-risk polycythemia vera patients based on JAK2(V617F) allele burden

The aim of this study was to determine whether the burden of JAK2(V617F) allele correlated with major clinical outcomes in patients with polycythemia vera (PV). To this end, we determined JAK2 mutant allele levels in granulocytes of 173 PV patients at diagnosis. The mean (+/-s.d.) mutant allele burden was 52% (+/-29); 32 patients (18%) had greater than 75% mutant allele. The burden of JAK2(V617F) allele correlated with measurements of stimulated erythropoiesis (higher hematocrit, lower mean cell volume, serum ferritin and erythropoietin levels) and myelopoiesis (higher white cell count, neutrophil count and serum lactate dehydrogenase) and with markers of neutrophil activation (elevated leukocyte alkaline phosphatase and PRV-1 expression). As compared to those with less than 25% mutant allele, patients harboring greater than 75% JAK2(V617F) allele were at higher relative risk (RR) of presenting larger spleen (RR 4.7; P<0.001) or suffering from pruritus (RR 3.1; P<0.001). In these patients, the risk of requiring chemotherapy (RR 1.8; P=0.001) or developing major cardiovascular events (RR 7.1; P=0.003) during follow up were significantly increased. We conclude that a burden of JAK2(V617F) allele greater than 75% at diagnosis points to PV patients with high-risk disease.

KIT D816V-associated systemic mastocytosis with eosinophilia and FIP1L1/PDGFRA-associated chronic eosinophilic leukemia are distinct entities

BACKGROUND

The broad and overlapping clinical manifestations of D816V KIT-associated systemic mastocytosis with eosinophilia and FIP1L1/PDGFRA-associated chronic eosinophilic leukemia (CEL), coupled with the increase in activated eosinophils and mast cells seen in both disorders, have led to confusion in the nomenclature. It is of paramount importance, however, to distinguish between these 2 groups of patients because of differences in clinical sequelae, prognoses, and selection of treatment.

OBJECTIVE

We thus sought to identify clinical and laboratory features that could be used to distinguish these 2 diagnoses.

METHODS

We compared 12 patients with D816V-positive systemic mastocytosis with eosinophilia with 17 patients with FIP1L1/PDGFRA-positive CEL. Distinguishing features were used to create a risk factor scoring system.

RESULTS

This system correctly classified 16 of 17 FIP1L1/PDGFRA-positive patients with CEL and all 12 patients with systemic mastocytosis with eosinophilia. Thirty-four FIP1L1/PDGFRA-positive patients described in the literature were also classified using this system, and although a complete set of data was not available for any of the historical patients, 21 were correctly classified.

CONCLUSION

These results reinforce the hypothesis that the FIP1L1/PDGFRA gene fusion and D816V-KIT mutation cause distinct clinical syndromes.

CLINICAL IMPLICATIONS

This novel diagnostic approach should prove helpful in clinical practice in the evaluation of patients with increased mast cells and peripheral eosinophilia.

Monocytosis is an adverse prognostic factor for survival in younger patients with primary myelofibrosis

We recently developed a modified Dupriez prognostic scoring system (PSS) that effectively discriminated between high-, intermediate-, and low-risk young patients (age < or =60 years) with primary myelofibrosis (PMF) based on the respective presence of none, one, or two or more of the following parameters: hemoglobin <10 g/dL, leukocyte count <4 or >30 x 10(9)L(-1), and platelet count <100 x 10(9)L(-1). The current study (n=129; median age, 52 years; 69 males) reveals, on multivariable analysis, that an absolute monocyte count of > or =1 x 10(9)L(-1) carries an independent predictive value (p=0.02), for an inferior survival, in addition to that provided by hemoglobin level (p=0.002), platelet count (0.02), and leukocyte count (p=0.16). The inclusion of the monocyte count as a fourth risk factor enabled the construction of a new and improved Mayo PSS; median survival was 173, 61, and 26 months in the absence of all four (low-risk), three (intermediate-risk), or two or less (high-risk) adverse features, respectively (p<0.0001). The independent prognostic value of monocytosis was validated in a separate database of 97 patients with PMF from another institution.

Cytogenetic and molecular aspects of Philadelphia negative chronic myeloproliferative disorders: clinical implications

Chronic myeloproliferative disorders (CMPD) are clonal disorders of the hematopoietic stem cell. The myeloid lineage shows increased proliferation with effective maturation, while peripheral leukocytosis, thrombocytosis or elevated red blood cell mass are found. In Philadelphia negative CMPD recurrent cytogenetic abnormalities occur, but no specific abnormality has been defined to date. The spectrum of cytogenetic aberrations is heterogeneous ranging from numerical gains and losses to structural changes including unbalanced translocations. The most common chromosomal abnormalities are 20q-, 13q-, 12p-, +8, +9, partial duplication of 1q, balanced translocations involving 8p11 and gains in 9p. Cytogenetic analysis of CMPD by conventional or molecular techniques has an important role in establishing the diagnosis of a malignant disease, adding also more information for disease outcome. Molecular studies may detect the possible role of candidate genes implicated in the neoplastic process, addressing new molecular target therapies. FIP1L1/PDGFRalpha rearrangements, as well as alterations of PDGFRbeta or FGFR1 gene have been found to be associated with specific types of CMPD. Recently, a novel somatic mutation, JAK2V617F, has been reported in most of the polycthemia vera (PV) patients, as well as in a lower percentage in essential thrombocythemia (ET) or idiopathic myelofibrosis (IMF) patients. This finding represents the most important advance in understanding of the molecular mechanisms underlined the pathogenesis of CMPD, contributing to the classification and management of patients.

Diagnosis and treatment of hypereosinophilic syndromes

PURPOSE OF REVIEW

The aim of this article is to provide an update of causes of hypereosinophilia, including advances in knowledge of eosinophilic leukemia, and to outline an approach to investigation. We also aim to discuss in more detail the diagnosis and management of various hypereosinophilic syndromes including the clonal eosinophilias and those driven by abnormal cytokine-secreting T cells.

RECENT FINDINGS

Our understanding of the causative genetic abnormalities in eosinophilic leukemia is increasing, as is the repertoire of techniques available to detect them. New treatments on the horizon include further tyrosine kinase inhibitors for use in eosinophilic leukemia, which should provide an alternative to imatinib for those patients who develop resistance. These may also prove useful for other hypereosinophilic syndromes without PDGFRA or PDGFRB rearrangements. Other new therapies including anti-IL5 monoclonal antibodies are proving beneficial for some patients, especially those with abnormal T-cell populations.

SUMMARY

As our understanding of the various hypereosinophilic syndromes increases, and we are able to characterize many of the causative genetic lesions in the clonal eosinophilias, we are increasingly able to select appropriate therapy for an individual patient. New therapies based on this knowledge should serve to further improve the prognosis for many patients with hypereosinophilia.