Validation of two clinically useful assays for evaluation of JAK2 V617F mutation in chronic myeloproliferative disorders

CRISPR/Cas12a-Based Ultrasensitive and Rapid Detection of JAK2 V617F Somatic Mutation in Myeloproliferative Neoplasms

The JAK2 V617F mutation is a major diagnostic, therapeutic, and monitoring molecular target of Philadelphia-negative myeloproliferative neoplasms (MPNs). To date, numerous methods of detecting the JAK2 V617F mutation have been reported, but there is no gold-standard diagnostic method for clinical applications. Here, we developed and validated an efficient Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR associated protein 12a (Cas12a)-based assay to detect the JAK2 V617F mutation. Our results showed that the sensitivity of the JAK2 V617F/Cas12a fluorescence detection system was as high as 0.01%, and the JAK2 V617F/Cas12a lateral flow strip assay could unambiguously detect as low as 0.5% of the JAK2 V617F mutation, which was much higher than the sensitivity required for clinical application. The minimum detectable concentration of genomic DNA achieved was 0.01 ng/μL (~5 aM, ~3 copies/μL). In addition, the whole process only took about 1.5 h, and the cost of an individual test was much lower than that of the current assays. Thus, our methods can be applied to detect the JAK2 V617F mutation, and they are highly sensitive, rapid, cost-effective, and convenient.

Optimization of a Low-Cost, Sensitive PNA Clamping PCR Method for JAK2 V617F Variant Detection

BACKGROUND

The JAK2 V617F variant is diagnostic for myeloproliferative neoplasms, a group of clonal disorders of hematopoietic stem and progenitor cells. Although several approaches have been developed to detect the variant, a gold standard diagnostic method has not yet been defined. We describe a simple, fast, and cost-effective PCR-based approach that enhances test specificity and sensitivity by blocking the amplification of the large excess of wild-type DNA.

METHODS

The method involves using an oligo peptide nucleic acid (PNA) perfectly matching its corresponding DNA sequence. The PCR protocol was optimized by collecting a detailed thermodynamic data set on PNA-DNA wild-type duplexes by circular dichroism melting experiments. The specificity and sensitivity of PNA clamping PCR were assessed by genotyping 50 patients with myeloproliferative neoplasm who carried the JAK2 V617F variant and 50 healthy donors.

RESULTS

The optimized protocol enabled selective amplification of the variant alleles, achieving maximum sensitivity (100%) and specificity (100%). Analytical sensitivity was 0.05% of variant alleles as assessed by serial dilutions of DNA from the HEL cell line (which carries the JAK2 V617F variant) mixed to wild-type DNA from healthy donors. The JAK2 V617F variant test performed according to this method has better diagnostic performance than its 2 main PCR-based competitors, at much lower cost.

CONCLUSIONS

High sensitivity and specificity and cost-effectiveness make PNA clamping PCR a useful testing platform for the detection of minor allele variants in small-scale diagnostic laboratories. It promises to improve patient care while enabling significant healthcare savings.

Assessment of the interlaboratory variability and robustness of JAK2V617F mutation assays: A study involving a consortium of 19 Italian laboratories

To date, a plenty of techniques for the detection of JAK2^V617F is used over different laboratories, with substantial differences in specificity and sensitivity. Therefore, to provide reliable and comparable results, the standardization of molecular techniques is mandatory.

A network of 19 centers was established to 1) evaluate the inter- and intra-laboratory variability in JAK2^V617F quantification, 2) identify the most robust assay for the standardization of the molecular test and 3) allow consistent interpretation of individual patient analysis results. The study was conceived in 3 different rounds, in which all centers had to blindly test DNA samples with different JAK2^V617F allele burden (AB) using both quantitative and qualitative assays.

The positivity of samples with an AB < 1% was not detected by qualitative assays. Conversely, laboratories performing the quantitative approach were able to determine the expected JAK2^V617F AB. Quantitative results were reliable across all mutation loads with moderate variability at low AB (0.1 and 1%; CV = 0.46 and 0.77, respectively). Remarkably, all laboratories clearly distinguished between the 0.1 and 1% mutated samples.

In conclusion, a qualitative approach is not sensitive enough to detect the JAK2^V617F mutation, especially at low AB. On the contrary, the ipsogen JAK2 MutaQuant CE-IVD kit resulted in a high, efficient and sensitive quantification detection of all mutation loads. This study sets the basis for the standardization of molecular techniques for JAK2^V617F determination, which will require the employment of approved operating procedures and the use of certificated standards, such as the recent WHO 1st International Reference Panel for Genomic JAK2^V617F.

The relevance of a low JAK2V617F allele burden in clinical practice: a monocentric study

Since low JAK2^V617F allele burden (AB) has been detected also in healthy subjects, its clinical interpretation may be challenging in patients with chronic myeloproliferative neoplasms (MPNs). We tested 1087 subjects for JAK2^V617F mutation on suspicion of hematological malignancy. Only 497 (45.7%) patients were positive. Here we present clinical and laboratory parameters of a cohort of 35/497 patients with an AB ≤ 3%.

Overall, 22/35 (62.9%) received a WHO-defined diagnosis of MPN and in 14/35 cases (40%) diagnosis was supported by bone marrow (BM) histology (‘’Histology-based’’ diagnosis). In patients that were unable or refused to perform BM evaluation, diagnosis relied on prospective clinical observation (12 cases, 34.3%) and molecular monitoring (6 cases, 17.1%) (‘’Clinical-based’’ or ‘’Molecular-based’’ diagnosis, respectively). In 11/35 (31.4%) patients, a low JAK2^V617F AB was not conclusive of MPN. The probability to have a final hematological diagnosis (ET/PV/MF) was higher in patients with thrombocytosis than in patients with polyglobulia (73.7% vs 57.1%, respectively). The detection of AB ≥ 0.8% always corresponded to an overt MPN phenotype. The repetition of JAK2^V617F evaluation over time timely detected the spontaneous expansion (11 cases) or reduction (4 cases) of JAK2^V617F-positive clones and significantly oriented the diagnostic process.

Our study confirms that histology is relevant to discriminate small foci of clonal hematopoiesis with uncertain clinical significance from a full blown disease. Remarkably, our data suggest that a cut-off of AB ≥ 0.8% is very indicative for the presence of a MPN. Monitoring of the AB over time emerged as a convenient and non-invasive method to assess clonal hematopoiesis expansion.

Summary and Review of the Abstracts on Philadelphia-Negative Myeloproliferative Neoplasms Presented at Haematocon 2017

There are lot of grey zones in Philadelphia negative chronic myeloproliferative neoplasms (CMPNs) and that's the reason they are in hit list of researchers. Having a spectrum of disorders their diagnosis is very important and especially to differentiate from each other since they overlap with each other in many ways. Diagnosis doesn't start from lab but with clinical phenotype. Clinical phenotype not only able to provide us the diagnosis but also helps in management of the disease per se. When diagnosis comes, the old timer but an evergreen morphology plays an important role which along with the newer generation tool "molecular" helps in differentiating these disorders. Lot of studies have already come up from the world. Indian data has also started coming up. When we say about the Indian data nothing holds more important role than Indian Society of Haematology and Blood Transfusion, ISHBT. This small review will cover all papers with BCR-ABL negative CMPNs which were presented at the annual national conference of the ISHBT (Haematocon 2017) which was conducted at Guwahati. These abstract papers from various reputed institutes and centres will provide a short academic journey towards ongoing research activities at these places and will able to guide us regarding Philadelphia negative CMPNs and also stimulate our brain for some left or conflicted areas.

Myeloproliferative Neoplasm or Reactive Process? A Rare Case of Acute Myeloid Leukemia and Transient Posttreatment Megakaryocytic Hyperplasia with JAK-2 Mutation

Myeloproliferative neoplasms (MPNs) are hematopoietic malignancies characterized by unchecked proliferation of differentiated myeloid cells. The most common BCR-ABL1-negative MPNs are polycythemia vera, essential thrombocythemia, and primary myelofibrosis. The discovery of JAK2 V617F mutation has improved our understanding of the molecular basis of MPN. The high frequency of JAK2 mutation in MPN makes JAK2 mutation testing an essential diagnostic tool and potential therapeutic target for MPN. Here, we present a rare case of a 34-year-old patient who was initially diagnosed with acute myeloid leukemia (AML) with mutated NPM1. After chemotherapy treatment followed by granulocyte colony stimulating factor administration, the patient achieved complete remission of AML. However, the bone marrow showed hypercellularity with granulocytic hyperplasia, markedly increased atypical megakaryocytes (50.2/HPF) with focal clustering, and reticulin fibrosis (3/4). JAK2 V617F mutation was also detected. Considering the possibility of AML transformed from a previous undiagnosed MPN, patient underwent peripheral blood allogenic stem cell transplant. This case illustrates the diagnostic challenges of firmly establishing a diagnosis between similar, but distinct, disease entities and an accurate clinicopathological differentiation is crucial.

BCR-JAK2 fusion in a myeloproliferative neoplasm with associated eosinophilia

Janus kinase 2 (JAK2) is located on chromosome 9 at band p24 and JAK2V617F is the most common mutation in Philadelphia chromosome-negative myeloproliferative neoplasms (Ph-MPN). However, rearrangement of JAK2 is a rare event. We report a case of myeloproliferative neoplasm, unclassifiable (MPN-U) with BCR-JAK2 fusion confirmed by molecular studies. Conventional chromosome analysis (CC) revealed t(9;22)(p24;q11.2) and fluorescence in situ hybridization (FISH) showed a JAK2 gene rearrangement in 88% of interphase nuclei. The BCR-JAK2 fusion was confirmed by multiplex reverse transcriptase polymerase chain reaction (RT-PCR) and demonstrated two in-frame 5'BCR/3'JAK2 transcripts with BCR exon 1 juxtaposed to JAK2 exon 15 and exon 17, respectively. Our results, together with literature review, reveal BCR-JAK2 fusions as oncogenic genetic alterations that are associated with myeloid or lymphoid neoplasms and are frequently characterized by eosinophilia. Further, patients with BCR-JAK2 are candidates for JAK2 inhibitor therapy. Given the distinct clinical and pathological characteristics, we believe that hematological neoplasms harboring BCR-JAK2 should be included as an additional distinct entity to the current WHO category of "myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR", and testing for a JAK2 fusion should be pursued in neoplasms with a karyotypic 9p24 abnormality.

Comparative study of different methodologies to detect the JAK2 V617F mutation in chronic BCR-ABL1 negative myeloproliferative neoplasms

Objectives

A mutation in the JAK2 gene, V617F, has been identified in several BCR-ABL1 negative myeloproliferative neoplasms (MPN): polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Defining the presence or absence of this mutation is an essential part of clinical diagnostic algorithms and patient management. Here, we aimed to evaluate the performance of three PCR-based assays: Amplification Refractory Mutation System (ARMS), High-Resolution Melting analysis (HRM), and Sanger direct sequencing, and compare their results with those obtained by a PCR restriction fragment polymorphism assay (PCR-RFLP).

Design and methods

We used blood samples from 136 patients (PV=20; PMF=20; ET=28, and other MPN suspected cases=68).

Results

Comparable results were observed among the four assays in patients with PV, PMF, and MPN suspected cases. In patients with a diagnosis of ET, the JAK2 V617F mutation was detected in 67.8% of them by the PCR-ARMS and PCR-HRM assay and in 64% of them by the conventional Sanger sequence approach. The PCR-ARMS and PCR-HRM assays were 100% concordant. With these tests, only one of the 20 patients with ET and one of the three patients with clinically suspected MPN gave different results compared with those obtained by the PCR-RFLP.

Conclusions

Our results have demonstrated that the PCR-ARMS and PCR-HRM assays could detect the JAK2 V617F mutation effectively in MPN patients, but PCR-HRM assays are rapid and the most cost-effective procedures.

Ruxolitinib in combination with lenalidomide as therapy for patients with myelofibrosis

Ruxolitinib and lenalidomide may target distinct clinical and pathological manifestations of myelofibrosis and prevent therapy-related worsening of blood cell counts. To determine the efficacy and safety of the combination in patients with myelofibrosis, patients were given 15 mg ruxolitinib orally twice daily in continuous 28-day cycles, plus 5 mg lenalidomide orally once daily on days 1-21. Thirty-one patients were treated, with a median followup of 28 months (range, 12 - 35+). Due to failure to meet the predetermined efficacy rules for treatment success the study was terminated early. Simultaneous administration of ruxolitinib and lenalidomide was difficult: 20 of the 23 dose interruptions occurred within the first 3 months of therapy. Lenalidomide was interrupted in all 20 cases. Fourteen patients (45%) were completely off lenalidomide within 3 months of initiation. Responses were noted in 17 patients (55%). The median time to response was 1.8 months (range, 0.4 - 31). All responses were International Working Group for Myelofibrosis Research and Treatment-defined clinical improvement in palpable spleen size. One spleen responder also met the criteria for clinical improvement in hemoglobin. The response rate was higher (73%) among patients who did not require early dose interruption than among those who required early interruption (45%). Improvements in bone marrow fibrosis and serial reductions in lactate dehydrogenase >50% were noted in 17% and 50% of evaluable responders, respectively. Alternate approaches such as sequential dosing need to be evaluated when considering novel combination strategies for myelofibrosis. This trial was registered with clinicaltrials.gov identifier: NCT01375140.

Development and validation of a tetra-primer amplification refractory mutation system-polymerase chain reaction combined with melting analysis-assay for clinical JAK2 V617F mutation detection

BACKGROUND AND OBJECTIVE

JAK2 V617F mutation is a molecular marker for myeloproliferative neoplasms (MPNs). As there are no China Food and Drug Administration-approved assays for the detection of JAK2 V617F mutation in China, validation of the analytic performance of this assay is important for the clinical laboratory before its clinical implementation. We have established a method for detecting JAK2 V617F using tetra-primer amplification refractory mutation system-polymerase chain reaction (tetra-primer ARMS-PCR) combined with melting-curve analysis.

METHODS

A total of 202 blood samples and 20 bone marrow aspirates were obtained from MPNs patients at Huashan Hospital, Fudan University. The accuracy, precision, reproducibility, analytical sensitivity, lower limit of detection, analytical specificity, interfering substances, ruggedness, robustness, reportable range and reporting of this assay were validated.

RESULTS

There was a close agreement between the reference method (sequencing) and melting-curve analysis (κ = 0.89). The precision was 100 % and the results of the assay were unaffected by lipoprotein (<27 mmol/L) or bilirubin (<450 µmol/L). The analytical sensitivity of the JAK2 mutation was 1.25 %.

CONCLUSIONS

Tetra-primer amplification refractory mutation system-polymerase chain reaction (tetra-primer ARMS-PCR) combined with melting-curve analysis can be used in the clinical laboratory for detection of the JAK2 V617F mutation.

Increased likelihood of post-polycythemia vera myelofibrosis in Ph-negative MPN patients with chromosome 12 abnormalities

Chromosome 12 (Chr12) abnormalities have been described for individual patients with Philadelphia chromosome-negative myeloproliferative neoplasms (Ph-neg MPN), however the frequency, characteristics, and outcomes of such patients as a whole have not been investigated. We reviewed a database of 1787 consecutive Ph-neg MPN patients seen at our institution and determined that 2% of Ph-neg MPN patients harbored an alteration involving Chr12 by cytogenetic evaluation. Retrospective chart review revealed that patients with Chr12 abnormalities had a higher likelihood of having myelofibrosis (MF) compared to patients without a Chr12 abnormality, and were more likely to have post-polycythemia vera MF. The most common alterations in Chr12 in MF patients involved 12q13, 12q15, 12q24, and trisomy 12, and >40% of Chr12 Ph-neg MPN patients had cytogenetic evolution. Chr12 abnormalities did not significantly correlate with JAK2 status, progression to acute myeloid leukemia, or survival, however patients with 12q24 abnormalities trended toward poorer outcomes.

Significance of cytogenetic abnormalities in patients with polycythemia vera

We analyzed 133 patients with polycythemia vera (PV) who were followed at our institution (median 7.5 years) and had adequate cytogenetics information. The 5-, 10- and 15-year survival rates were 93%, 79% and 64%, respectively, with a median projected overall survival of 24 years. Nineteen patients (14%) had abnormal cytogenetics at any time during the disease course (no survival difference). Sixteen patients (12%) underwent disease transformation during follow-up, after a median of 8.5 years, to myelofibrosis (n = 11), acute myeloid leukemia (n = 4) or myelodysplastic syndrome (n = 1); eight had cytogenetic abnormalities. Among 133 patients, 39 were newly diagnosed: 33 with normal and six with abnormal cytogenetics (no survival difference); nine underwent disease transformation (six with normal and three with abnormal cytogenetics at diagnosis). In keeping with other smaller series, the presence of chromosomal abnormalities may have had a role in disease transformation in patients with PV; survival was not affected likely due to short follow-up.

Validation of standards for quantitative assessment of JAK2 c.1849G>T (p.V617F) allele burden analysis in clinical samples

The substitution of valine with phenylalanine at amino acid 617 of the Janus kinase 2 (JAK2) gene (JAK2 p.V617F) occurs in a high proportion of patients with myeloproliferative neoplasms (MPNs). The ability to accurately measure JAK2 p.V617F allele burden is of great interest given the diagnostic relevance of the mutation and the ongoing clinical evaluation of JAK inhibitors. A main hurdle in developing quantitative assays for allele burden measurement is the unavailability of accurate standards for both assay validation and use in a standard curve for quantification. We describe our approach to the validation of standards for quantitative assessment of JAK2 p.V617F allele burden in clinical MPN samples. These standards were used in two JAK2 p.V617F assays, which were used to support clinical studies of ruxolitinib (Jakafi(®)) in myelofibrosis, a real-time polymerase chain reaction assay for initial screening of all samples, and a novel single-nucleotide polymorphism typing (SNaPshot)-based assay for samples with less than 5% mutant allele burden. Comparisons of allele burden data from clinical samples generated with these assays show a high degree of concordance with each other and with a pyrosequencing-based assay used for clinical reporting from an independent laboratory, thus providing independent validation to the accuracy of these standards.

Chromosome 5q deletion is extremely rare in patients with myelofibrosis

Chromosome 5q deletion can be found in rare cases of myelofibrosis (MF) but the incidence, clinical significance and response to therapies are not well studied. We retrospectively reviewed charts of 939 patients with MF and identified 8 patients [0.8%] who carried 5q deletion. Of the 8, seven had complex cytogenetic abnormalities and one had additional clone with different cytogenetic abnormality. All 8 had significant three-lineage pancytopenia. Three patients took lenalidomide and one (patient with 5q-clone) achieved long-lasting hematologic response. Two patients responded to JAK2 inhibitor therapy. MF patients with 5q deletion often have complex karyotype and poor outcome.

JAK2 V617F, MPL W515L and JAK2 Exon 12 Mutations in Chinese Patients with Primary Myelofibrosis

OBJECTIVE

JAK2 V617F, MPL W515L and JAK2 exon 12 mutations are novel acquired mutations that induce constitutive cytokine-independent activation of the JAK-STAT pathway in myeloproliferative disorders (MPD). The discovery of these mutations provides novel mechanism for activation of signal transduction in hematopoietic malignancies. This research was to investigate their prevalence in Chinese patients with primary myelofibrosis (PMF).

METHODS

We introduced allele-specific PCR (AS-PCR) combined with sequence analysis to simultaneously screen JAK2 V617F, MPL W515L and JAK2 exon 12 mutations in 30 patients with PMF.

RESULTS

Fifteen PMF patients (50.0%) carried JAK2 V617F mutation, and only two JAK2 V617F-negative patients (6.7%) harbored MPL W515L mutation. None had JAK2 exon 12 mutations. Furthermore, these three mutations were not detected in 50 healthy controls.

CONCLUSION

MPL W515L and JAK2 V617F mutations existed in PMF patients but JAK2 exon 12 mutations not. JAK2 V617F and MPL W515L and mutations might contribute to the primary molecular pathogenesis in patients with PMF.

Methods for detecting mutations in the human JAK2 gene

Mutations in the JAK2 gene are prevalent in the human myeloid malignancies, being present in virtually all cases of polycythemia vera, and a significant proportion of patients with other myeloproliferative disorders. Various methods for the detection of acquired mutations in this gene are available depending on the need for sensitivity, quantification, or the ability to detect many different mutations. We summarize the various methods published and discuss their relative merits for each application. Two commonly used methods, quantitative real-time PCR (QPCR) for the detection of the JAK2 V617F mutation and high resolution melt-curve analysis (HRM) for the detection of multiple mutations within JAK2 exon 12, demonstrate the utility of each method and their limitations. The choice of methodology is dependent on the application; therefore there is no gold standard for detecting mutations in this gene.

Therapy with the histone deacetylase inhibitor pracinostat for patients with myelofibrosis

Approximately half of the patients with myelofibrosis (MF) carry mutant JAK2(V617F) proteins. JAK2(V617F) has been recently shown to translocate to the nucleus and modify specific histones, thus regulating transcription. We report on a phase II study testing the activity and tolerability of the histone deacetylase inhibitor pracinostat given at 60 mg every other day for three weeks per month in 22 patients with intermediate or high risk MF. Eight (36%) patients experienced clinical benefit, with 6 (27%) experiencing reductions in splenomegaly (median 3 cm, range 1-4 cm). According to International Working Group criteria, 2 (9%) patients had clinical improvement (anemia response in both cases). The most frequent side effect associated to pracinostat therapy was fatigue, which occurred in 20 (91%) patients (grade 2 in 3 patients). Grade 3-4 neutropenia, anemia, and thrombocytopenia occurred in 13%, 0%, and 21%, respectively. Twenty-one patients permanently discontinued pracinostat, mainly due to lack of efficacy. In conclusion, pracinostat at the dose tested is reasonably tolerated and has modest activity in patients with MF.

Detection of Acquired Janus Kinase 2 V617F Mutation in Myeloproliferative Disorders by Fluorescence Melting Curve Analysis

BACKGROUND

The genetic lesion underlying the pathogenesis of chronic myeloproliferative disorders (MPDs) has been identified in the Janus kinase 2 (JAK2) gene. A point mutation in codon 617 causes a valine to phenylalanine substitution (V617F) in the JH2 autoinhibitory region of the protein, resulting in constitutive activation of the tyrosine kinase. The high prevalence of this conserved mutation in MPD makes it an excellent candidate as a diagnostic molecular marker.

METHODS AND RESULTS

We report here the development and validation of a single oligonucleotide probe-based PCR approach using fluorescence melting curve analysis for point mutation detection in DNA derived from unfractionated peripheral blood samples. Using this assay and serial dilutions of an erythroleukemia cell line harboring the homozygous JAK2 V617F mutation, we successfully detected the mutation within a background of wild type sequences at a sensitivity of 2.5%. Our novel fluorescence probe-based assay was compared with allele-specific PCR-gel assay and sequencing techniques. Using the single probe assay, we examined 70 cases with a presumptive diagnosis of MPD, of which 38 (54%) yielded positive results for the presence of the JAK2 V617F mutation, and 92 follicular lymphoma cases, which were negative for the JAK2 V617F mutation. Additionally, the probe-based assay detected a previously unreported T>C base substitution at nucleotide 2342 (JAK2, codon 616), which was not detected by an allele-specific PCR assay.

CONCLUSION

The single fluorescent probe-based assay described here is a rapid, homogeneous, and robust method for the detection of the JAK2 V617F mutation with favorable performance characteristics that make it advantageous for clinical diagnosis.

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.

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.

Visual screening for JAK2V617F mutation by a disposable dipstick

During the last 5 years, it was discovered that the JAK2V617F somatic mutation is present in virtually all patients with polycythemia vera and a large proportion of patients with essential thrombocythemia, primary myelofibrosis, and refractory anemia with ring sideroblasts and thrombocytosis. As a result, JAK2V617F was incorporated as a new clonal marker in the 2008 revision of the WHO diagnostic criteria. Current methods for JAK2 genotyping include direct sequencing, pyrosequencing, allele-specific PCR with electrophoresis, restriction fragment length polymorphism, real-time PCR, DNA-melting curve analysis, and denaturing HPLC. Some of these methods are labor intensive and time consuming, while the others require specialized costly equipment and reagents. We report a method for direct detection of the JAK2V617F allele by the naked eye using a dipstick test in a dry-reagent format. The method comprises a triprimer PCR combined with visual detection of the products within minutes by the dipstick test. Specialized instrumentation is not involved. The requirements for highly qualified technical personnel are minimized. Because the detection reagents exist in dry form on the dipstick, there is no need for multiple pipetting and incubation steps.

Molecular pathology of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs; formerly chronic myeloproliferative disorders) are a class of myeloid hematologic malignancies that represent a stem cell-derived expansion of 1 or more hematopoietic cell lineages. The current 2008 World Health Organization system recognizes 8 types of MPN: chronic myelogenous leukemia, chronic neutrophilic leukemia, polycythemia vera, primary myelofibrosis, essential thrombocythemia, chronic eosinophilic leukemia, mastocytosis, and myeloproliferative neoplasm, unclassifiable. This review summarizes the salient characteristics of the MPNs, with emphasis on recent developments in the molecular pathophysiology and therapeutic monitoring of these disorders.

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.

Comparison of JAK2V617F mutation assessment employing different molecular diagnostic techniques

BACKGROUND

The JAK2(V617F) mutation is present in the majority of patients with polycythaemia vera and in approximately half of patients with essential thrombocythaemia and primary myelofibrosis. In this study we compare the results of JAK2(V617F) mutation detection using three different molecular techniques in the same group of patients affected by essential thrombocythaemia.

PATIENTS AND METHODS

The JAK2 mutation was investigated with a qualitative method in 115 consecutive outpatients with a diagnosis of essential thrombocythaemia made according to WHO 2001 criteria. In 48/115 (41.7%) the allele burden was also evaluated with two different qualitative methods, of which one was a method developed in-house and the other was a commercially available method.

RESULTS

The JAK2(V617F) mutation was detected by the qualitative method in 81/115 (69.6%) of the patients. Among the 48/115 patients in whom all three methods were applied, the qualitative method detected the mutation in 38 (79%). According to the quantitative method developed in-house, the mutation was present in 35/48 (73%) of the patients: of these, 2/35 (5.7%) patients were homozygous for the JAK2(V617F) mutation. The commercial quantitative method showed the mutation in 37/48 (77%) patients: of these, 9/37 (18%) patients were homozygous. Three of the 13 patients in whom no mutation was detected by the in-house method were positive for the JAK2(V617F) according to the commercial method. In one patient the search for the JAK2(V617F) mutation was positive with the in-house method but negative with the commercial kit.

CONCLUSION

Detection of the JAK2(V617F) mutation may depend on the molecular technique used. Considering that detection of this mutation will not only have a diagnostic value, but also a role in treatment given the development of JAK2(V617F) pathway inhibiting drugs, indications on a reference molecular diagnostic technique for JAK2(V617F) assessment and quantification of its allele burden from a panel of experts are warranted.

Lenalidomide plus prednisone results in durable clinical, histopathologic, and molecular responses in patients with myelofibrosis

PURPOSE

To investigate the safety and efficacy of the combination of lenalidomide and prednisone in patients with myelofibrosis (MF).

PATIENTS AND METHODS

Forty patients with MF were treated. Therapy consisted of lenalidomide 10 mg/d (5 mg/d if baseline platelet count < 100 x 10(9)/L) on days 1 through 21 of a 28-day cycle for six cycles, in combination with prednisone 30 mg/d orally during cycle 1, 15 mg/d during cycle 2, and 15 mg/d every other day during cycle 3. Lenalidomide therapy was continued indefinitely in patients exhibiting clinical benefit.

RESULTS

The median follow-up was 22 months (range, 6 to 27). Responses were recorded in 12 patients (30%) and are ongoing in 10 (25%). The median time to response was 12 weeks (range, 2 to 32). According to the International Working Group for Myelofibrosis Research and Treatment consensus criteria, three patients (7.5%) had partial response and nine patients (22.5%) had clinical improvement durable for a median of 18 months (range, 3.5 to 24+). Overall response rates were 30% for anemia and 42% for splenomegaly. Moreover, 10 of 11 assessable responders who started therapy with reticulin fibrosis grade 4 experienced reductions to at least a score of 2. All eight JAK2(V617F)-positive responders experienced a reduction of the baseline mutant allele burden, which was greater than 50% in four, including one of whom the mutation became undetectable. Grade 3 to 4 hematologic adverse events included neutropenia (58%), anemia (42%), and thrombocytopenia (13%).

CONCLUSION

The combination of lenalidomide and prednisone induces durable clinical, molecular, and pathologic responses in MF.

Cytogenetic abnormalities in essential thrombocythemia at presentation and transformation

Cytogenetic abnormalities in patients with essential thrombocythemia (ET) are infrequent. Their role in survival of patients and disease transformation is not extensively studied. We describe cytogenetic abnormalities in 172 patients with ET at a single institution. At presentation nine (5.2%) patients had cytogenetic abnormality and three (1.7%) additional patients acquired them during follow-up. Survival of patients with cytogenetic changes at presentation did not differ when compared to the patients with normal karyotype. The more common were abnormalities of chromosome 9 (n = 4), 20 (n = 2), 5 (n = 2), and complex abnormalities (n = 2). Forty-one patients (23.8%) had additional cytogenetic tests performed for monitoring purposes during follow-up. Five patients (2.9%) with normal karyotype transformed to myelofibrosis (MF) without developing new cytogenetic changes at transformation. Two patients (1.2%) with normal karyotypes at presentation transformed to myelodysplastic syndrome and acute myeloid leukemia, respectively. Both acquired complex cytogenetic changes at the time of transformation. There is no rationale for repeating cytogenetic tests in ET patients on follow up, unless blood cell count changes suggest possible transformation.

JAK2(V617F) allele burden discriminates essential thrombocythemia from a subset of prefibrotic-stage primary myelofibrosis

OBJECTIVE

Among Philadelphia chromosome-negative myeloproliferative neoplasms (Ph(-) MPN), essential thrombocythemia (ET) and the prefibrotic phase of primary myelofibrosis (PMF) represent two subtypes with considerable overlap.

MATERIALS AND METHODS

In this study, histopathological classification of 490 MPN cases was correlated with the allelic burden of JAK2(V617F) and MPL(W515L).

RESULTS

Ph(-) MPN entities largely overlap with regard to JAK2(V617F) and MPL(W515L) allele burden, but ET displayed mutant allele burden <50%. PMF with different stages of myelofibrosis all yielded similar JAK2(V617F) allele burden. At initial presentation one-quarter of prefibrotic PMF cases exhibited an allele burden exceeding 50% (38% median JAK2(V617F) alleles, n=102). In ET, its main differential diagnosis, not a single case was found with >40% JAK2(V617F) alleles (median, 24% JAK2(V617F) alleles; n=90; p<0.001). Increase in JAK2(V617F) alleles during follow-up could not be linked to fibrosis or blastic progression but was related to polycythemic transformation in ET. MPL(W515L) was found in 3% of ET and 8% of PMF, with a significantly higher percentage of mutated alleles in fibrotic than prefibrotic PMF (median, 78% MPL(W515L) alleles; p<0.05).

CONCLUSION

Histopathological categories ET and prefibrotic PMF correlate with significant differences in mutant allelic burden of JAK2(V617F), but not of MPL(W515L) which, by contrast to JAK2(V617F), shows a higher percentage of mutated alleles in fibrotic than in prefibrotic cases. Thus, for Ph(-) MPN in which ET and prefibrotic PMF represent the most probable diagnoses, a JAK2(V617F) allele burden >50% favors a diagnosis of prefibrotic PMF.

Detection of the JAK2 V617F missense mutation by high resolution melting analysis and its validation

BACKGROUND

Janus kinase 2 (JAK2) is a tyrosine kinase involved in the cytokine signaling of several growth factors such as erythropoietin and thrombopoietin in normal and neoplastic cells. The G to T exchange at nucleotide 1849 in exon 14 of the JAK2 gene leads to a substitution of valine with phenylalanine at the amino acid position 617 (V617F) of the JAK2 protein. Currently, the occurrence of the JAK2 V617F mutation is well recognized in chronic myeloproliferative disorders (MPDs).

METHODS

We identified JAK2 V617F missense mutation in patients with MPD by high resolution melting (HRM) analysis. HRM analysis is a new gene scan tool that quickly performs the PCR and identifies sequences alterations without requiring post-PCR treatment. This study included 7 PV patients (41.1%), 6 ET patients (35.3%), and 4 myelofibrosis patients (23.5%). Additionally, our methodology was compared with amplification refractory mutation system (ARMS) assay.

RESULTS

Up to 5% of the JAK2 V617F mutation was successfully detected in patients with MPD using HRM analysis. Eleven out of 17 patients (64.7%) were positive for the presence of JAK2 V617F mutation. The prevalence of mutation in the different subtypes of MPDs was 85.7% in PV (6 of 7 patients), 66.7% in ET (4 of 6) and 5.9% in myelofibrosis (1 of 4). The results proved 100% comparable to those obtained by ARMS assay.

CONCLUSIONS

The HRM analysis is a rapid and effective technique for the detection of JAK2 V617F missense mutation.

TheJAK2V617F Mutation is Absent in Patients with Erythrocytosis Due to High Oxygen Affinity Hemoglobin Variants

High oxygen affinity hemoglobin (Hb) variants are an important and well characterized cause of secondary erythrocytosis. We tested 22 patients with high oxygen affinity beta chain variants for the presence of the JAK2 V617F mutation that has been reported in chronic myeloproliferative disorders, particularly polycythemia vera. All specimens showed the absence of this mutation. This observation contributes to the overall clinical specificity of the JAK2 V617F mutation.

Comparison of mutated ABL1 and JAK2 as oncogenes and drug targets in myeloproliferative disorders

Constitutively activated mutants of the non-receptor tyrosine kinases (TK) ABL1 (Abelson murine leukemia viral (v-abl) homolog (1) protein) and JAK2 (JAnus Kinase 2 or Just Another Kinase 2) play a central role in the pathogenesis of clinically and morphologically distinct chronic myeloproliferative disorders but are also found in some cases of de novo acute leukemia and lymphoma. Ligand-independent activation occurs as a consequence of point mutations or insertions/deletions within functionally relevant regulatory domains (JAK2) or the creation of TK fusion proteins by balanced reciprocal translocations, insertions or episomal amplification (ABL1 and JAK2). Specific abnormalities are correlated with clinical phenotype, although some are broad and encompass several World Health Organization-defined entities. TKs are excellent drug targets as exemplified by the activity of imatinib in BCR-ABL1-positive disease, particularly chronic myeloid leukemia. Resistance to imatinib is seen in a minority of cases and is often associated with the appearance of secondary point mutations within the TK domain of BCR-ABL1. These mutations are highly variable in their sensitivity to increased doses of imatinib or alternative TK inhibitors such as nilotinib or dasatinib. Selective and non-selective inhibitors of JAK2 are currently being developed, and encouraging data from pre-clinical experiments and initial phase-I studies regarding efficacy and potential toxicity of these compounds have already been reported.

The saga of JAK2 mutations and translocations in hematologic disorders: pathogenesis, diagnostic and therapeutic prospects, and revised World Health Organization diagnostic criteria for myeloproliferative neoplasms

JAK2 is a tyrosine kinase involved in cytokine signaling. The JAK2V617F point mutation, first described in 2005, results in constitutive activation of JAK2 and is now widely used as a diagnostic marker for Philadelphia chromosome negative myeloproliferative neoplasms. In recent years, more novel JAK2 mutations and fusion genes have been discovered in myeloproliferative neoplasms and other hematologic malignancies. This review aims to summarize the discovery and use of the JAK2V617F point mutation, other novel JAK2 mutations, and JAK2 translocations in diagnosing myeloproliferative neoplasms, acute myeloid leukemia, and acute lymphoid leukemia. JAK2 mutation testing is addressed, including the sensitivity and specificity of the different JAK2 mutation testing methods, clinical indications for use, and the use of quantitative JAK2 mutation testing for routine pathologic diagnosis, prognosis, and monitoring response to therapy. The relationship of JAK2 mutation to endogenous erythroid colony formation, thrombopoietin receptor mutation, polycythemia rubra vera-1 overexpression, and thrombopoietin receptor underexpression in myeloproliferative neoplasms are explored. Also discussed are the JAK2 inhibitors for clinical trials. Finally, the advantages of the newly proposed World Health Organization classification for myeloproliferative neoplasms are reviewed.

Validity test study of JAK2 V617F and allele burden quantification in the diagnosis of myeloproliferative diseases

Several sensitive methods for the detection of JAK2 V617F mutation have been published recently, most of them based on Real Time polymerase chain reaction (PCR). However, only some of them have performed studies of diagnostic validity. This study compares three methods based on Real Time PCR to detect JAK2 V617F mutation: two based on hybridization probes (HP) and peptide nucleic acid probe (PNA) and a third employing allele specific oligonucleotide primers for JAK2 V617F quantification. One hundred forty-nine healthy subjects, 61 essential thrombocythemia (ET), 32 polycythemia vera (PV), 38 secondary thrombocytoses, and 35 secondary erythrocytoses were included. Validity test study for JAK2 617 HP PCR in PV Sensitivity (Se) was 88% and in Specificity (Sp), 100%. In ET, Se was 57% and Sp, 100%. For JAK2 617 PNA PCR in PV, Se was 94% and Sp, 97.8%. In ET, Se was 70% and Sp, 95.7%. In JAK2 V671F allelo-specific-oligonucleotide (ASO) quantitative PCR (qPCR), cutoff point of 1% was established by receiving operating characteristic (ROC) curves. In PV, Se was 93.8% and Sp, 98.5%. In ET, Se was 80% and Sp, 95.9%. Two percent of the healthy subjects were positive by JAK2 617 PNA PCR and 2% by JAK2 617 ASO qPCR. JAK2 V617F mutation was detected in healthy subjects by cloning and sequencing. JAK2 617 HP is an adequate test in differential diagnosis for both erythrocytosis and thrombocytosis. When JAK2 V617F allele burden is low, JAK2 617 ASO qPCR should be performed. Simultaneous determination of JAK2 V617F and PRV-1 overexpression does not improve the diagnostic value of JAK2 V617F tests in MPD.

The presence of JAK2V617F in primary myelofibrosis or its allele burden in polycythemia vera predicts chemosensitivity to hydroxyurea

JAK2V617F-positive patients with essential thrombocythemia, as opposed to their mutation-negative counterparts, require lower doses of hydroxyurea (HU) for control of their platelet count. In the current study, we looked for predictors of HU response in 69 patients with primary myelofibrosis (PMF) and 56 with polycythemia vera (PV). JAK2V617F analysis was performed on bone marrow-derived DNA obtained at or near the time of diagnosis. HU response in PMF was associated with a shorter disease duration (P = 0.008), absence of previous therapy (P = 0.01), older age at diagnosis (P = 0.009), and presence of JAK2V617F (P = 0.02). On multivariable analysis, only the latter retained its significance (48% vs. 8% response in mutation positive vs. negative cases). In PV, JAK2V617F allele burden correlated directly with HU response (P = 0.05) and inversely with daily HU dose in responding patients (P = 0.02). The current study suggests that JAK2V617F presence identifies PMF patients who are likely to respond to HU therapy, and information on its allele burden helps in assigning the optimal starting dose in individual patients with PV.

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

Myelofibrosis (MF; primary or post-essential thrombocythemia/polycythemia vera) is incurable clonal myeloproliferative disorder, with no effective treatment. Epigenetic changes play an important role in cancer pathogenesis through transcriptional silencing of critical tumor suppressor genes. We conducted a phase-II study to evaluate the activity of DNA methyltransferase inhibitor, 5-azacitidine, in patients with MF. Thirty-four patients (76% previously treated) received 5-azacitidine at 75 mg/m(2) subcutaneously daily for 7 days, every 4 weeks. Twelve (35%) patients had abnormal cytogenetics and 19 (70%) of 27 evaluable patients had JAK2(V617F) mutation. Responses occurred in 8 (24%) patients after a median of 5 months (range, 3-10). Partial response occurred in 1 (3%) patient (duration 22+ months) and clinical improvement in 7 (21%) patients (median duration 4 months; range, 2-8.5). Myelosuppression was the major adverse effect, with grade 3-4 neutropenia in 10 (29%) patients. Global DNA methylation assessed by the long interspersed nucleotide element (LINE) bisulfite/pyrosequencing assay decreased from 53% pretherapy to 44% on day 14 (P=0.0014) and returned to 50% at the end of the first 28-day cycle (P=0.016). 5-azacitidine is relatively well tolerated and results in induction of global hypomethylation in patients with MF, but results in limited clinical activity.

Targeting survival cascades induced by activation of Ras/Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT pathways for effective leukemia therapy

The Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT pathways are frequently activated in leukemia and other hematopoietic disorders by upstream mutations in cytokine receptors, aberrant chromosomal translocations as well as other genetic mechanisms. The Jak2 kinase is frequently mutated in many myeloproliferative disorders. Effective targeting of these pathways may result in suppression of cell growth and death of leukemic cells. Furthermore it may be possible to combine various chemotherapeutic and antibody-based therapies with low molecular weight, cell membrane-permeable inhibitors which target the Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT pathways to ultimately suppress the survival pathways, induce apoptosis and inhibit leukemic growth. In this review, we summarize how suppression of these pathways may inhibit key survival networks important in leukemogenesis and leukemia therapy as well as the treatment of other hematopoietic disorders. Targeting of these and additional cascades may also improve the therapy of chronic myelogenous leukemia, which are resistant to BCR-ABL inhibitors. Furthermore, we discuss how targeting of the leukemia microenvironment and the leukemia stem cell are emerging fields and challenges in targeted therapies.