Laboratory Practice Guidelines for Detecting and Reporting JAK2 and MPL Mutations in Myeloproliferative Neoplasms

Mutational Landscape of Patients Referred for Elevated Hemoglobin Level

Background: Since the identification of JAK2 V617F and exon 12 mutations as driver mutations in polycythemia vera (PV) in 2005, molecular testing of these mutations for patients with erythrocytosis has become a routine clinical practice. However, the incidence of myeloid mutations other than the common JAK2 V617F mutation in unselected patients referred for elevated hemoglobin is not well studied. This study aimed to characterize the mutational landscape in a real-world population of patients referred for erythrocytosis using a targeted next-generation sequencing (NGS)-based assay. Method: A total of 529 patients (hemoglobin levels >160 g/L in females or >165 g/L in males) were assessed between January 2018 and May 2021 for genetic variants using the Oncomine Myeloid Research Assay (ThermoFisher Scientific, Waltham, MA, USA) targeting 40 key genes with diagnostic and prognostic implications in hematological conditions (17 full genes and 23 genes with clinically relevant "hotspot" regions) and a panel of 29 fusion driver genes (>600 fusion partners). Results: JAK2 mutations were detected in 10.9% (58/529) of patients, with 57 patients positive for JAK2 V617F, while one patient had a JAK2 exon 12 mutation. Additional mutations were detected in 34.5% (20/58) of JAK2-positive patients: TET2 (11; 19%), DNMT3A (2;3.4%), ASXL1 (2; 3.4%), SRSF2 (2; 3.4%), BCOR (1; 1.7%), TP53 (1; 1.7%), and ZRSR2 (1; 1.7%). Diagnosis of PV was suspected in 2 JAK2-negative patients based on the 2016 World Health Organization (WHO) diagnostic criteria. Notably, one patient carried mutations in the SRSF2 and TET2 genes, and the other patient carried mutations in the SRSF2, IDH2, and ASXL1 genes. Three JAK2-negative patients with elevated hemoglobin who tested positive for BCR/ABL1 fusion were diagnosed with chronic myeloid leukemia (CML) and excluded from further analysis. The remaining 466 JAK2-negative patients were diagnosed with secondary erythrocytosis and mutations were found in 6% (28/466) of these cases. Conclusion: Mutations other than JAK2 mutations were frequently identified in patients referred for erythrocytosis, with mutations in the TET2, DNMT3A, and ASXL1 genes being detected in 34.5% of JAK2-positive PV patients. The presence of additional mutations, such as ASXL1 mutations, in this population has implications for prognosis. Both the incidence and mutation type identified in patients with secondary erythrocytosis likely reflects incidental, age-associated clonal hematopoiesis of indeterminate potential (CHIP).

Clinical and Pathological Features of Renal Presentations in Polycythemia Vera

BACKGROUND

Polycythemia vera (PV) is a common type of Philadelphia chromosome-negative chronic myeloproliferative disorder. PV-associated kidney disease is rarely reported and remains poorly understood. It has been observed that chronic kidney disease could be a risk factor for poor prognosis in PV.

METHODS

We retrospectively analyzed the clinicopathological features of renal presentations in eight patients with confirmed PV-associated kidney disease.

RESULTS

The eight patients were 6 males and 2 females, with a mean age of 46.4±16.8 years. Six patients had a history of PV, with a duration range 0.5-16 years. The other two patients were newly diagnosed with PV simultaneously with glomerular disease. Seven patients conducted a JAK2 V617F mutation test, with a positive result in five. Proteinuria and renal dysfunction were the patients' main complaints, with only one having nephrotic syndrome and three having microscopic hematuria. The level of proteinuria ranged from 0.52-10.96 g/day. Three patients had advanced chronic kidney disease (CKD), two in stage 3b and one in stage 4, but only one patient had anemia. Three patients had monoclonal immunoglobulinemia, one patient with immunoglobulin (Ig) G kappa plus light chain lambda, one patient with IgG kappa, and one patient with IgG lambda. Five patients underwent a renal biopsy. The pathological diagnosis was IgA nephropathy in three, non-IgA mesangial proliferative glomerulopathy in one, and glomerular hypertrophy with ischemic renal injury in one patient. Glomerular ischemia, ischemic shrinkage, focal segmental sclerosis, and glomerulomegaly were common pathological features. Glomerular crescents and endocapillary proliferation were also observed. All patients were administered hydroxyurea, and seven were administered renin-angiotensin system inhibitors. During follow-up, one patient with uncontrolled PV developed secondary myelofibrosis and died, three patients were lost to follow-up, and four patients remained alive with CKD.

CONCLUSIONS

Patients with untreated or uncontrolled PV could have massive proteinuria and advanced CKD, pathologically showing ischemic, sclerosing glomerular lesions with hypercellurity, glomerular crescents and endocapillary proliferation. IgA nephropathy was most commonly diagnosed. These findings deserve attention because early screening and effective control of PV may benefit the long-term kidney prognosis.

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.

The first report of a JAK2 V617F-positive myeloproliferative neoplasm with initial manifestation as a rare pampiniform venous plexus thrombosis and review of the literature

Pampiniform venous plexus (PVP) thrombosis is exceedingly rare, with fewer than 25 cases described. Thus, the etiology and pathophysiology remain largely unknown. A 38-year-old male with no known risk factors incidentally noted a 10-day history of right testicular discomfort prompting evaluation. Findings included extensive right PVP thrombus, critically elevated hematocrit, and a JAK2 V617F gene variant. Despite no treatment guidelines, conservative management was initiated with therapeutic apixaban, and therapeutic phlebotomy and hydroxyurea for newly diagnosed primary polycythemia vera (PV), sparing exploratory genitourinary surgery. This represents the first reported case of PVP thrombosis as the initial manifestation of a JAK2 V617F positive PV and the first documented report of PVP thrombosis associated with an acquired hypercoagulable state. Of the 8 previous cases with hypercoagulable testing performed, 2 involved inherited hypercoagulable states, suggesting hereditary and acquired prothrombotic disorders should be considered as predisposing factors. Testing for the JAK2 V617F variant in patients with mesenteric, cerebral, and splanchnic venous thromboses is currently recommended, but testing patients with venous thromboses in other anatomical locations remains controversial. We reviewed all previously described cases to expound upon this diagnosis, potential association with hypercoagulable disorders, treatment options, and observed clinical outcomes. This case adds to the minimal literature and supports genetic testing all patients with spontaneous PVP thrombosis for the JAK2 V617F variant and other hypercoagulable conditions. Additionally, conservative management with therapeutic anticoagulation and treatment of the underlying precipitating disease state may be acceptable in select patients, following exclusion of surgical emergencies.

Recent Advances in the Use of Molecular Analyses to Inform the Diagnosis and Prognosis of Patients with Polycythaemia Vera

Genetic studies in the past decade have improved our understanding of the molecular basis of the BCR-ABL1-negative myeloproliferative neoplasm (MPN) polycythaemia vera (PV). Such breakthroughs include the discovery of the JAK2V617F driver mutation in approximately 95% of patients with PV, as well as some very rare cases of familial hereditary MPN caused by inherited germline mutations. Patients with PV often progress to fibrosis or acute myeloid leukaemia, both associated with very poor clinical outcome. Moreover, thrombosis and major bleeding are the principal causes of morbidity and mortality. As a result of increasingly available and economical next-generation sequencing technologies, mutational studies have revealed the prognostic relevance of a few somatic mutations in terms of thrombotic risk and risk of transformation, helping to improve the risk stratification of patients with PV. Finally, knowledge of the molecular basis of PV has helped identify targets for directed therapy. The constitutive activation of the tyrosine kinase JAK2 is targeted by ruxolitinib, a JAK1/JAK2 tyrosine kinase inhibitor for PV patients who are resistant or intolerant to cytoreductive treatment with hydroxyurea. Other molecular mechanisms have also been revealed, and numerous agents are in various stages of development. Here, we will provide an update of the recent published literature on how molecular testing can improve the diagnosis and prognosis of patients with PV and present recent advances that may have prognostic value in the near future.

Lab tests for MPN

Molecular laboratory investigations for myeloproliferative neoplasm (MPN) can ideally be divided into two distincts groups, those for the detection of the BCR-ABL rearrangement (suspect of chronic myeloid leukemia) and those for the variants determination of the driver genes of the negative Philadelphia forms (MPN Ph neg). The BCR-ABL detection is based on RT-Polymerase Chain Reaction techniques and more recently on droplet digital PCR (ddPCR). For this type of analysis, combined with chromosome banding analysis (CBA) and Fluorescent in situ hybridization (FISH), it is essential to quantify BCR-ABL mutated copies by standard curve method. The investigation on driver genes for MPN Ph neg forms includes activity for erythroid forms such as Polycythemia Vera (test JAK2V617F and JAK2 exon 12), for non-erythroid forms such as essential thrombocythemia and myelofibrosis (test JAK2V617F, CALR exon 9, MPL exon 10), for "atypical" ones such as mastocytosis (cKIT D816V test) and for hypereosinophilic syndrome (FIP1L1-PDGFRalpha test). It's crucial to assign prognosis value through calculating allelic burden of JAK2 V617F variant and determining CALR esone 9 variants (type1/1like, type2/2like and atypical ones). A fundamental innovation for investigating triple negative cases for JAK2, CALR, MPL and for providing prognostic score is the use of Next Generation Sequencing panels containing high molecular risk genes as ASXL1, EZH2, TET2, IDH1/IDH2, SRSF2. This technique allows to detect additional or subclonal mutations which are usually acquired in varying sized sub-clones of hematopoietic progenitors. These additional variants have a prognostic significance and should be indagated to exclude false negative cases.

Myeloid somatic mutation panel testing in myeloproliferative neoplasms

Myeloproliferative neoplasms are characterised by somatic mutations in pathways that regulate cell proliferation, epigenetic modifications, RNA splicing or DNA repair. Assessment of the mutational profile assists diagnosis and classification, but also aids assessment of prognosis, and may guide the use of emerging targeted therapies. The most practical way to provide information on numerous genetic variants is by using massively parallel sequencing, commonly in the form of disease specific next generation sequencing (NGS) panels. This review summarises the diagnostic and prognostic value of somatic mutation testing in Philadelphia-negative myeloproliferative neoplasms: polycythaemia vera, essential thrombocythaemia, primary myelofibrosis, chronic neutrophilic leukaemia, systemic mastocytosis, and chronic eosinophilic leukaemia. NGS panel testing is increasing in routine practice and promises to improve the accuracy and efficiency of pathological diagnosis and prognosis.

Prefibrotic Myelofibrosis Presenting with Multiple Cerebral Embolic Infarcts and the Rare MPL W515S Mutation

Acquired, activating mutations of MPL W515 are recognised driver mutations of the myeloproliferative neoplasms (MPN), namely, essential thrombocythemia and primary myelofibrosis. The most common mutation at this codon is W515L with several other mutations also described at a lower frequency. Of these less common mutations, MPL W515S has only been reported sporadically with limited information on clinicopathological associations. We describe the case of an elderly man with persistent thrombocytosis presenting with an ischemic cerebral event. Bone marrow biopsy showed evidence of prefibrotic myelofibrosis with targeted sequencing demonstrating the presence of the rare MPL W515S mutation. Thrombolytic and cytoreductive therapies resulted in a favorable outcome and follow-up. This case provides additional, necessary, and phenotypic data for the rare MPN-associated MPL W515S mutation.

JAK2 exon 12 mutations in cases with JAK2V617F-negative polycythemia vera and primary myelofibrosis

Molecular detection of JAK2 mutation (V617F or exon 12) is included as a major diagnostic criterion for polycythemia vera (PV) by the WHO 2016 guidelines. JAK2 exon 12 mutations are seen in about 2-5% of JAK2V617F-negative cases of PV. Mutations in JAK2 cause constitutive activation of JAK-STAT pathway which results in variable phenotypes. PV patients with exon 12 mutations in JAK2 present characteristically with erythrocytosis. There are limited reports describing the spectrum of JAK2 exon12 mutations in myeloproliferative neoplasms (MPNs). Here, we describe the characteristics of a series of MPN patients with mutations in exon 12 of JAK2 of which two were novel variants associated with polycythemia. Interestingly, we noted two patients presenting as myelofibrosis having JAK2 exon 12 mutations.

Serum Has Higher Proportion of Janus Kinase 2 V617F Mutation Compared to Paired EDTA-Whole Blood Sample: A Model for Somatic Mutation Quantification Using qPCR and the 2-∆∆Cq Method

Detection of the Janus Kinase-2 (JAK2) V617F mutation is a diagnostic criterion for myeloproliferative neoplasms, and high levels of mutant alleles are associated with worse outcomes. This mutation is usually tested on blood DNA by allele-specific qPCR (AS-qPCR) and measured using absolute quantification. However, some automated DNA extractions co-extracts of PCR inhibitors from blood and qPCR absolute quantification need increased efforts in order to maintain standard curves. JAK2 V617F can also be detected in serum using droplet digital PCR (ddPCR), a specimen with less inhibitors and favorable to automated extractions, but ddPCR instruments are not wide available as qPCR thermocyclers. Here, we evaluate whether JAK2 V617F could be accurately quantified by AS-qPCR using the 2-∆∆Cq method on blood DNA and validate the assay using gold-standard molecular diagnostic protocols. Next, we apply the validated method to assess if the mutation could be reliably detected/quantified in serum. JAK2 V617F could be quantified by AS-qPCR using the 2-∆∆Cq method-the assay was highly accurate (bias of 1.91%) compared to a commercial kit, highly precise (total CV% of 0.40%, 1.92%, 11.12% for samples with 93%, 54%, and 2.5% of mutant allele), highly sensitive (limit of detection of 0.15%), and demonstrated a linear detection response from 1.1% to 99.9%. Serum presented a higher mutant allele burden compared to the paired whole blood (mean of 4%), which allows for an increased JAK2 mutant detection rate and favors increased JAK2 V617F high-throughput analysis.

The Journal of Molecular Diagnostics: 20 Years Defining Professional Practice

This editorial highlights 20 years of JMD defining professional practice.

Feasibility of Qualitative Testing of BCR-ABL and JAK2 V617F in Suspected Myeloproliperative Neoplasm (MPN) Using RT-PCR Reversed Dot Blot Hybridization (RT-PCR RDB)

BACKGROUND

Defining the presence of BCR-ABL transcript in suspected myeloproliferative neoplasm is essential in establishing chronic myeloid leukemia. In the absence of BCR-ABL, the conventional diagnostic algorithm recommends JAK2 V617F mutation testing to support diagnosis of other MPN diseases such as polycythemia vera, essential thrombocythemia, and primary myelofibrosis. In certain cases of thrombocythemia, simultaneous upfront testing of both BCR-ABL and JAK2 may be desirable. We wanted to test the feasibility of multiplex detection of BCR-ABL transcript variants and JAK2 V617F mutation simultaneously using the reverse transcriptase polymerase chain reaction (RT-PCR)-based reverse dot-blot hybridization (RDB) method.

MATERIAL AND METHODS

Separate biotinylated RT-PCR primers were designed to amplify specific BCR-ABL transcripts and JAK2 V617F mutant alleles. Specific hybridization of RT-PCR products with arrays of membrane-bound probes followed by colorimetric development would allow simultaneous visualization of BCR-ABL and/or JAK2 mutant transcripts in a given specimen. To validate the RDB method, we used cDNA specimens previously referred to our laboratory for routine clinical testing of BCR-ABL and/or JAK2.

RESULTS

The limit of detection or analytical sensitivity of the RDB method using cDNA specimens was 0.5% and 6.25% in detecting BCR-ABL and JAK2 mutant transcripts, respectively. The diagnostic specificity and sensitivity to detect BCR-ABL and JAK2 were 100% and 92.3% (N = 38); and 100% and 100% (N = 27), respectively. RDB also detected BCR-ABL transcripts in 22% of JAK2 V617F mutation-positive samples (N = 14).

CONCLUSIONS

RT-PCR RDB is a promising qualitative multiplex method to detect BCR-ABL and JAK2 mutant transcripts simultaneously.

European recommendations and quality assurance for cytogenomic analysis of haematological neoplasms

Cytogenomic investigations of haematological neoplasms, including chromosome banding analysis, fluorescence in situ hybridisation (FISH) and microarray analyses have become increasingly important in the clinical management of patients with haematological neoplasms. The widespread implementation of these techniques in genetic diagnostics has highlighted the need for guidance on the essential criteria to follow when providing cytogenomic testing, regardless of choice of methodology. These recommendations provide an updated, practical and easily available document that will assist laboratories in the choice of testing and methodology enabling them to operate within acceptable standards and maintain a quality service.

JAK2-tree: a simple CBC-based decision rule to guide appropriate JAK2 V617F mutation testing

Aims

The JAK2 V617F mutation is highly recurrent in many of the myeloproliferative neoplasms, a molecular variant that can be easily detected using sensitive and minimally invasive techniques. Given the ease of JAK2 V617F testing, this test may be improperly requested for the purposes of patient ‘screening’ and to optimise laboratory resource utilisation, it behooves clinicians and laboratorians to perform JAK2 V617F testing only when most appropriate.

Methods

To assist with the screening of patients being considered for JAK2 V617F testing, we developed a clinical decision rule, “JAK2-tree”, which can be easily applied to basic CBC parameters (haemoglobin, platelet and white blood cell counts).

Results

We tested JAK2-tree on two independent datasets, one an unselected population-based sample (the Copenhagen General Population Study) and the other an historical clinical laboratory referral set, with sensitivities for JAK2 V617F detection of 91% and 94%, respectively. As applied to the historical laboratory referral dataset, moreover, the JAK2-tree algorithm would have reduced JAK2 V617F testing volume over the period of evaluation by 15%.

Conclusions

Our work supports a simple decision-tree-based screening approach to optimize the selection of patients most appropriate for JAK2 V617F testing.

Quantitation of JAK2 V617F Allele Burden by Using the QuantStudio™ 3D Digital PCR System

The JAK2 V617F mutation is highly prevalent in patients with myeloproliferative neoplasms (MPN). Furthermore, it has been shown that its allelic burden correlates with hematologic characteristics, drug response, and clinical endpoints in MPN patients. Digital PCR is an emerging technology for sensitive mutation detection and quantitation, based on dilution and high-grade partitioning of a sample. Here, we describe the use of the nanofluidic chip-based QuantStudio™ 3D Digital PCR System for quantitation of the JAK2 V617F mutation.

Detection of the Janus kinase 2 V617F mutation using a locked nucleic-acid, real-time polymerase chain reaction assay

The purpose of this study was to develop a real time polymerase chain reaction (PCR) assay for the detection of the JAK2 V617F mutation that could be used in diagnostic laboratories. Sanger sequencing and a newly developed locked nucleic-acid, real-time PCR assay were used to detect the JAK2 V617F mutation. There was 100% agreement between the sequencing and PCR analysis. Both assays were able to detect the mutation in all 24 of the 60 test specimens harbouring the mutation.

Development of a Targeted Next-Generation Sequencing Assay to Detect Diagnostically Relevant Mutations of JAK2, CALR, and MPL in Myeloproliferative Neoplasms

BACKGROUND

The classical Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), consisting of polycythemia vera, essential thrombocythemia, and primary myelofibrosis, are a heterogeneous group of neoplasms that harbor driver mutations in the JAK2, CALR, and MPL genes. The detection of mutations in these genes has been incorporated into the recent World Health Organization (WHO) diagnostic criteria for MPN. Given a pressing clinical need to screen for mutations in these genes in a routine diagnostic setting, a targeted next-generation sequencing (NGS) assay for the detection of MPN-associated mutations located in JAK2 exon 14, JAK2 exon 12, CALR exon 9, and MPL exon 10 was developed to provide a single platform alternative to reflexive, stepwise diagnostic algorithms.

METHODS

Polymerase chain reaction (PCR) primers were designed to target mutation hotspots in JAK2 exon 14, JAK2 exon 12, MPL exon 10, and CALR exon 9. Multiplexed PCR conditions were optimized by using qualitative PCR followed by NGS. Diagnostic genomic DNA from 35 MPN patients, known to harbor driver mutations in one of the target genes, was used to validate the assay.

RESULTS

One hundred percent concordance was observed between the previously-identified mutations and those detected by NGS, with no false positives, nor any known mutations missed (specificity = 100%, CI = 0.96, sensitivity = 100%, CI = 0.89). Improved resolution of mutation sequences was also revealed by NGS analysis.

CONCLUSION

Detection of diagnostically relevant driver mutations of MPN is enhanced by employing a targeted multiplex NGS approach. This assay presents a robust solution to classical MPN mutation screening, providing an alternative to time-consuming sequential analyses.

The Case for Laboratory Developed Procedures: Quality and Positive Impact on Patient Care

An explosion of knowledge and technology is revolutionizing medicine and patient care. Novel testing must be brought to the clinic with safety and accuracy, but also in a timely and cost-effective manner, so that patients can benefit and laboratories can offer testing consistent with current guidelines. Under the oversight provided by the Clinical Laboratory Improvement Amendments, laboratories have been able to develop and optimize laboratory procedures for use in-house. Quality improvement programs, interlaboratory comparisons, and the ability of laboratories to adjust assays as needed to improve results, utilize new sample types, or incorporate new mutations, information, or technologies are positive aspects of Clinical Laboratory Improvement Amendments oversight of laboratory-developed procedures. Laboratories have a long history of successful service to patients operating under Clinical Laboratory Improvement Amendments. A series of detailed clinical examples illustrating the quality and positive impact of laboratory-developed procedures on patient care is provided. These examples also demonstrate how Clinical Laboratory Improvement Amendments oversight ensures accurate, reliable, and reproducible testing in clinical laboratories.

Recommendations for molecular testing in classical Ph1-neg myeloproliferative disorders-A consensus project of the Italian Society of Hematology

The discovery that Philadelphia-negative classical myeloproliferative neoplasms (MPNs) present with several molecular abnormalities, including the mostly represented JAK2V617F mutation, opened new horizons in the diagnosis, prognosis, and monitoring of these disorders. However, the great strides in the knowledge on molecular genetics need parallel progresses on the best approach to methods for detecting and reporting disease-associated mutations, and to shape the most effective and rationale testing pathway in the diagnosis, prognosis and monitoring of MPNs. The MPN taskforce of the Italian Society of Hematology (SIE) assessed the scientific literature and composed a framework of the best, possibly evidence-based, recommendations for optimal molecular methods as well as insights about the applicability and interpretation of those tests in the clinical practice, and clinical decision for testing MPNs patients. The issues dealt with: source of samples and nucleic acid template, the most appropriate molecular abnormalities and related detection methods required for diagnosis, prognosis, and monitoring of MPNs, how to report a diagnostic molecular test, calibration and quality control. For each of these issues, practice recommendations were provided.

Molecular testing for JAK2, MPL, and CALR in myeloproliferative neoplasms

Polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) are myeloproliferative neoplasms characterized by recurrent somatic mutations in JAK2, CALR, and MPL. This short review addresses (1) the spectrum of mutations seen in PV, ET, and PMF, (2) the emerging genotype-phenotype correlations, (3) the current role of molecular testing in disease classification and management, and (4) several important considerations for selecting an appropriate molecular test. In our view, sequential testing algorithms and simultaneous assessment of multiple mutations by next-generation sequencing are both valid approaches to testing. Am. J. Hematol. 91:1277-1280, 2016. © 2016 Wiley Periodicals, Inc.

Chasing down the triple-negative myeloproliferative neoplasms: Implications for molecular diagnostics

The majority of patients with classical myeloproliferative neoplasms (MPN) of polycythemia vera, essential thrombocythemia, and primary myelofibrosis harbor distinct disease-driving mutations within the JAK2, CALR, or MPL genes. The term triple-negative has been recently applied to those MPN without evidence of these consistent mutations, prompting whole or targeted exome sequencing approaches to determine the driver mutational status of this subgroup. These strategies have identified numerous novel mutations that occur in alternative exons of both JAK2 and MPL, the majority of which result in functional activation. Current molecular diagnostic approaches may possess insufficient coverage to detect these alternative mutations, prompting further consideration of targeted exon sequencing into routine diagnostic practice. How to incorporate these illuminating findings into the expanding molecular diagnostic algorithm for MPN requires continual attention.

Monitoring Minimal Residual Disease in the Myeloproliferative Neoplasms: Current Applications and Emerging Approaches

The presence of acquired mutations within the JAK2, CALR, and MPL genes in the majority of patients with myeloproliferative neoplasms (MPN) affords the opportunity to utilise these mutations as markers of minimal residual disease (MRD). Reduction of the mutated allele burden has been reported in response to a number of therapeutic modalities including interferon, JAK inhibitors, and allogeneic stem cell transplantation; novel therapies in development will also require assessment of efficacy. Real-time quantitative PCR has been widely adopted for recurrent point mutations with assays demonstrating the specificity, sensitivity, and reproducibility required for clinical utility. More recently, approaches such as digital PCR have demonstrated comparable, if not improved, assay characteristics and are likely to play an increasing role in MRD monitoring. While next-generation sequencing is increasingly valuable as a tool for diagnosis of MPN, its role in the assessment of MRD requires further evaluation.

Coexistence of JAK2 and CALR mutations and their clinical implications in patients with essential thrombocythemia

Janus kinase 2 (JAK2) and calreticulin (CALR) constitute the two most frequent mutations in essential thrombocythemia (ET), and both are reported to be mutually exclusive. Hence, we examined a cohort of 123 myeloproliferative neoplasm (MPN) patients without BCR-ABL1 rearrangement and additional ET patients (n=96) for coexistence of JAK2 and CALR mutations. The frequency of CALR mutations was 20.3% in 123 MPN patients; 31.1% in ET (n=74), 25% in primary myelofibrosis (n=4) and 2.2% in polycythemia vera (n=45). JAK2 and CALR mutations coexisted in 7 (4.2%) of 167 ET patients. Clinical characteristics, progression-free survival (PFS), and elapsed time to achieve partial remission across 4 groups (JAK2+/CALR+, JAK2+/CALR-, JAK2-/CALR+, JAK2-/CALR-) were reviewed. The JAK2+/CALR- group had higher leukocyte counts and hemoglobin levels and more frequent thrombotic events than JAK2-/CALR- group. JAK2 mutations have a greater effect on the disease phenotype and the clinical features of MPN patients rather than do CALR mutation. JAK2+ groups showed a tendency of poor PFS than JAK2- groups regardless of CALR mutation. CALR+ was a predictor of late response to the treatment. Our study also showed that thrombosis was more frequent in ET patients with type 2 CALR mutations than in those with type 1 CALR mutations.

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.

Molecular heterogeneity of familial myeloproliferative neoplasms revealed by analysis of the commonly acquired JAK2, CALR and MPL mutations

The myeloproliferative neoplasms (MPN) are clonal, hematological malignancies that include polycythemia vera, essential thrombocythemia and primary myelofibrosis. While most cases of MPN are sporadic in nature, a familial pattern of inheritance is well recognised. The phenotype and status of the commonly acquired JAK2 V617F, CALR exon 9 and MPL W515L/K mutations in affected individuals from a consecutive series of ten familial MPN (FMPN) kindred are described. Affected individuals display the classical MPN phenotypes together with one kindred identified suggestive of hereditary thrombocytosis. In affected patients the JAK2 V617F mutation is the most commonly acquired followed by CALR exon nine mutations with no MPL W515L/K mutations detected. The JAK2 V617F and CALR exon 9 mutations appear to occur at approximately the same frequency in FMPN as in the sporadic forms of these diseases. The familial nature of MPN may often be overlooked and accordingly more common than previously considered. Characterisation of these FMPN kindred may allow for the investigation of molecular events that contribute to this inheritance.

JAK2 mutations to the fore in hereditary thrombocythemia

Acquired mutations of the gene that encodes the intracellular signalling molecule JAK2 are the most frequently observed disease-driving events of the common myeloproliferative neoplasms. A number of germline JAK2 mutations have recently been described in several kindred with the rare disease of hereditary thrombocythemia, also known as familial thrombocythemia or familial thrombocytosis. These inherited mutations are all located within the pseudo-kinase and kinase domains of JAK2 and have been shown to directly contribute to the thrombocythemic phenotype. Molecular characterisation of the resulting, aberrant signalling signatures may provide insights into genotype-phenotype relationships of both hereditary thrombocythemia and the common myeloproliferative neoplasms.