Establishing optimal quantitative-polymerase chain reaction assays for routine diagnosis and tracking of minimal residual disease in JAK2-V617F-associated myeloproliferative neoplasms: a joint European LeukemiaNet/MPN&MPNr-EuroNet (COST action BM0902) study

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.

Pegylated interferon alfa-2a in patients with essential thrombocythaemia or polycythaemia vera: a post-hoc, median 83 month follow-up of an open-label, phase 2 trial

BACKGROUND

Pegylated interferon alfa-2a is an immunomodulatory agent used to treat polycythemia vera. The durability of responses and long-term safety of this drug in patients with polycythaemia vera and essential thrombocythaemia have not been reported. Here, we present long-term efficacy and safety data from a single-centre, open-label, phase 2 trial, after a median of 83 months follow up.

METHODS

Patients older than 18 years who were diagnosed with essential thrombocythaemia or polycythaemia vera according to 2001 WHO criteria were eligible to enrol in our study. The initial starting dose of pegylated interferon alfa-2a was 450 μg subcutaneously once per week, but was decreased in a stepwise manner due to toxic effects to a final starting dose of 90 mg per week: three patients were started at a dose of 450 mg per week, three at 360 mg per week, 19 at 270 mg per week, 26 at 180 mg per week, and 32 at 90 mg per week. Treatment was continued for as long as the patients derived clinical benefit with reductions in dose and frequency of administration allowed at the discretion of the treating physician. Haematological responses were assessed every 3-6 months on the basis of blood counts as defined by the European LeukemiaNet critieria. The primary endpoint of the initial study was the proportion of patients with a haematological response. Complete haematological response was defined as normalisation of blood counts (for patients with essential thrombocythaemia, platelets ≤440 × 109 per L; for patients with polycythaemia vera, haemoglobin <15·0 g/L without phlebotomy) with complete resolution of palpable splenomegaly or symptoms in the absence of a thrombotic event. Data were analysed with descriptive statistics and in the intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT00452023 and is ongoing but not enrolling new patients.

FINDINGS

Between May 21, 2005, and Dec 1, 2015, patients were followed up for a median of 83 months (IQR 69-94 months). Pegylated interferon alfa-2a induced haematological (66 [80%] of 83 patients) and molecular responses (35 [63%] of 55 patients) in 40 patients with essential thrombocythaemia and 43 patients with polycythaemia vera, with median durations of 66 months (IQR 35-83) and 53 months (24-70), respectively. 26 (39%) of 66 haematological responders and 25 (71%) of 35 molecular responders (with the JAK2 Val617Phe mutation) have maintained some response during follow-up: 49% maintained their best molecular response (nine of ten patients who had a complete response, five of 20 who had a partial response, and three of five who had a minor response). The incidence of major venous-thrombotic events during the study was 1·22 per 100 person-years. Overall, 18 (22%) of 83 patients discontinued therapy due to treatment-related toxicity. Although toxicity rates decreased over time, five patients had treatment-limiting grade 3 or 4 toxicities after 60 months on therapy. 32 patients are still enrolled on the study.

INTERPRETATION

Pegylated interferon alfa-2a can induce durable haematological and molecular responses in patients with essential thrombocythaemia and polycythaemia vera. This drug alone and in combination with other drugs could be explored further in clinical trials.

FUNDING

US National Cancer Institute.

Driver mutations (JAK2V617F, MPLW515L/K or CALR), pentraxin-3 and C-reactive protein in essential thrombocythemia and polycythemia vera

Background

The driver mutations JAK2V617F, MPLW515L/K and CALR influence disease phenotype of myeloproliferative neoplasms (MPNs) and might sustain a condition of chronic inflammation. Pentraxin 3 (PTX3) and high-sensitivity C-reactive protein (hs-CRP) are inflammatory biomarkers potentially useful for refining prognostic classification of MPNs.

Methods

We evaluated 305 with essential thrombocythemia (ET) and 172 polycythemia vera (PV) patients diagnosed according to the 2016 WHO criteria and with full molecular characterization for driver mutations.

Results

PTX3 levels were significantly increased in carriers of homozygous JAK2V617F mutation compared to all the other genotypes and triple negative ET patients, while hs-CRP levels were independent of the mutational profile. The risk of haematological evolution and death from any cause was about 2- and 1.5-fold increased in individuals with high PTX-3 levels, while the thrombosis rate tended to be lower. High hs-CRP levels were associated with risk of haematological evolution, death and also major thrombosis. After sequential adjustment for potential confounders (age, gender, diagnosis and treatments) and the presence of JAK2V617F homozygous status, high hs-CRP levels remained significant for all outcomes, while JAK2V617F homozygous status as well as treatments were the factors independently accounting for adverse outcomes among patients with high PTX3 levels.

Conclusions

These results provide evidence that JAK2V617F mutation influences MPN-associated inflammation with a strong correlation between allele burden and PTX3 levels. Plasma levels of hs-CRP and PTX3 might be of prognostic value for patients with ET and PV, but their validation in future prospective studies is needed.

Risk factors for infections in myelofibrosis: role of disease status and treatment. A multicenter study of 507 patients

Although infectious complications represent a relevant cause of morbidity and mortality in patients with myelofibrosis (MF), little is known about their incidence, outcome and risk factors. We retrospectively evaluated a cohort of 507 MF patients, diagnosed between 1980 and 2014 in five Italian hematology centers, to define the epidemiology of infections and describe the impact of ruxolitinib (RUX) treatment. Overall, 112 patients (22%) experienced 160 infectious events (grade 3-4, 45%) for an incidence rate of 3.9% per patient-year. Infections were mainly bacterial (78%) and involving the respiratory tract (52% of cases). Also, viral (11%) and fungal infections (2%) were recorded. Overall, infections were fatal in 9% of the cases. Among baseline features, high/intermediate-2 IPSS category (HR 1.8, 95%CI:1.2-2.7; P = 0.02) and spleen length ≥10 cm below left costal margin (HR 1.6, 95%CI:1.1-2.5; P = 0.04) were associated with higher infectious risk in multivariate analysis. Overall, the rate of infections was higher in the cohort of 128 RUX-treated patients (44% vs. 20%, P < 0.001). In conclusion, IPSS-category and splenomegaly, emerged as the main risk factors for infections in MF. RUX-treated patients experienced significantly more infection episodes; however, future prospective studies are needed to isolate the confounding contribution of other risk factors such as disease stage. Am. J. Hematol. 92:37-41, 2017. © 2016 Wiley Periodicals, Inc.

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.

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.

Differential Dynamics of CALR Mutant Allele Burden in Myeloproliferative Neoplasms during Interferon Alfa Treatment

Discovery of somatic mutations in the calreticulin gene (CALR) has identified a subgroup of Philadelphia-negative chronic myeloproliferative neoplasms (MPN) with separate haematological characteristics and prognosis. CALR mutations serve as novel markers both of diagnostic value and as targets for monitoring molecular responses during therapy. Interferon-α (IFN) selectively targets the malignant clone in a subset of MPN patients and can induce both haematological and molecular remissions in CALR mutated essential thrombocythemia (ET) patients. We investigated the response to IFN in a cohort of 21 CALR mutated MPN patients including ET, prefibrotic primary myelofibrosis (pre-PMF), and primary myelofibrosis (PMF) with a median follow-up of 31 months. For evaluation of a molecular response, we developed highly sensitive quantitative PCR (qPCR) assays for monitoring the mutant allele burden of the two most prevalent CALR mutations (type 1 and type 2). Thirteen patients (62%) experienced a decrease in the mutant allele burden with a median decline of 29% from baseline. However, only four patients, including patients with ET, pre-PMF, and PMF diagnosis, achieved molecular responder (MR) status with >50% reduction in mutant allele burden according to European LeukemiaNet (ELN) guidelines. MR patients displayed significant differences in the dynamics of the CALR mutant load with regard to time to response and dynamics in mutant allele burden after discontinuation of IFN treatment. Furthermore, we highlight the prognostic value of the CALR mutant allele burden by showing a close association with leucocyte- and platelet counts, hemoglobin concentration, in addition to plasma lactate dehydrogenase (LDH) irrespective of molecular response and treatment status.

Genetically distinct leukemic stem cells in human CD34- acute myeloid leukemia are arrested at a hemopoietic precursor-like stage

Quek and colleagues identify human leukemic stem cells (LSCs) present in CD34⁻ AML. In-depth characterization of the functional and clonal aspects of CD34⁻ LSCs indicates that most are similar to myeloid precursors.

Our understanding of the perturbation of normal cellular differentiation hierarchies to create tumor-propagating stem cell populations is incomplete. In human acute myeloid leukemia (AML), current models suggest transformation creates leukemic stem cell (LSC) populations arrested at a progenitor-like stage expressing cell surface CD34. We show that in ∼25% of AML, with a distinct genetic mutation pattern where >98% of cells are CD34⁻, there are multiple, nonhierarchically arranged CD34⁺ and CD34⁻ LSC populations. Within CD34⁻ and CD34⁺ LSC–containing populations, LSC frequencies are similar; there are shared clonal structures and near-identical transcriptional signatures. CD34⁻ LSCs have disordered global transcription profiles, but these profiles are enriched for transcriptional signatures of normal CD34⁻ mature granulocyte–macrophage precursors, downstream of progenitors. But unlike mature precursors, LSCs express multiple normal stem cell transcriptional regulators previously implicated in LSC function. This suggests a new refined model of the relationship between LSCs and normal hemopoiesis in which the nature of genetic/epigenetic changes determines the disordered transcriptional program, resulting in LSC differentiation arrest at stages that are most like either progenitor or precursor stages of hemopoiesis.

Canonical Wnt/β-Catenin Signaling Pathway Is Dysregulated in Patients With Primary and Secondary Myelofibrosis

INTRODUCTION

β-Catenin is a central effector molecule of the canonical wingless-related integration site (Wnt) signaling pathway. It is important for maintenance of stem cell homeostasis and its aberrant activation has been implicated in a wide array of malignant hematological disorders. There are few reports suggesting its dysregulation in Philadelphia chromosome-negative (Ph-) myeloproliferative neoplasms (MPNs).

PATIENTS AND METHODS

We analyzed β-catenin mRNA expression in bone marrow (BM) aspirates of 29 patients with primary (PMF) and 4 patients with secondary, post Ph- MPN, myelofibrosis (SMF) using quantitative real-time polymerase chain reaction (qRT PCR). The control group consisted of 16 BM aspirates from patients with limited-stage aggressive non-Hodgkin lymphoma without BM involvement. We compared relative gene expression with clinical and hematological parameters.

RESULTS

Relative expression of β-catenin differed significantly among groups (P = .0002), it was significantly higher in patients with PMF and SMF than in the control group, but did not differ between patients with PMF and SMF. A negative correlation was found regarding hemoglobin level in PMF (P = .017). No association according to Janus kinase 2 (JAK2) V617F mutational status or JAK2 V617F allele burden was detected.

CONCLUSION

Our results show for the first time that β-catenin mRNA expression is increased in patients with PMF and SMF and its upregulation might potentiate anemia. A number of inflammatory cytokines associated with PMF are capable of mediating their effects through increased β-catenin expression. Accordingly, β-catenin can induce expression of a number of genes implicated in processes of cell cycle control, fibrosis, and angiogenesis, which are central to the PMF pathogenesis. Therefore, β-catenin might represent an interesting new therapeutic target in these diseases.

[Leukemia research in Germany: the Competence Network Acute and Chronic Leukemias]

The Competence Network "Acute and Chronic Leukemias" was founded in 1997 by the consolidation of the leading leukemia study groups in Germany. Key results are the development of new trials and cooperative studies, the setup of patient registries and biobanking facilities, as well as the improvement of study infrastructure. In 2003, the concept of the competence network contributed to the foundation of the European LeukemiaNet (ELN). Synergy with the ELN resulted in cooperation on a European and international level, standardization of diagnostics and treatment, and recommendations for each leukemia and interdisciplinary specialty. The ultimate goal of the network is the cure of leukemia through cooperative research.

Interferon-α induces marked alterations in circulating regulatory T cells, NK cell subsets, and dendritic cells in patients with JAK2V617F-positive essential thrombocythemia and polycythemia vera

Long-term therapy with IFN-α2 is associated with sustained major molecular remissions in JAK2-positive ET and PV. The efficacy of IFN-α2 may be partly mediated by modulation of immune cells, which was investigated in twenty patients with ET (n = 6) and PV (n = 14). The frequency of CD4(+) CD25(+) Foxp3(+) T cells was significantly increased during IFN-α2 treatment in all patients (P < 0.0001). A significant expansion of the CD56(bright) NK cells (P = 0.0002) and a concomitant decrease in the frequency of CD56(dim) NK cells (P < 0.0001) were also detected. Myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) were studied in nine patients, and decreased frequencies of both cell types were observed during the course of treatment. On both mDCs and pDCs, HLA-ABC expression was upregulated (P = 0.003), but decreasing expression levels of HLA-DR was detected on mDCs. The expression of CD40 (P = 0.002), CD83 (P = 0.03), and CD86 (P = 0.01) increased, but was confined to pDCs. Furthermore, PD-L1 expression was reduced on mDC (P = 0.003) and increased on pDCs (P = 0.02). No significant correlations were found between the changes in immune cells and hematological or molecular responses achieved in our cohort of patients. So forth, it remains to be revealed whether the profound changes in circulating immune cells contribute to the beneficial effects of long-term IFN-α2 treatment in some patients.

Interferon-alpha for the therapy of myeloproliferative neoplasms: targeting the malignant clone

Interferon alpha (IFN-α) has been used for over 30 years to treat myeloproliferative neoplasms (MPNs). IFN-α was shown to induce clinical, hematological, molecular and histopathological responses in small clinical studies. Such combined efficacy has never been achieved with any other drug to date in such a significant proportion of patients. However, toxicity remains a limitation to its broader use despite the development of pegylated forms with better tolerance. Several on going phase 3 studies of peg- IFN-α versus hydroxyurea will help to define its exact place in MPN management. IFN-α efficacy is likely the consequence of a broad range of biological properties, including enhancement of immune response, direct effects on malignant cells and ability to cycle dormant malignant stem cells. However, comprehensive elucidation of its mechanism of action is still lacking. Sustained clinical, molecular and morphological responses after IFN-α discontinuation raised the hope that this drug could eradicate MPN. There is now consistent evidence showing that IFN-α is able to eliminate malignant clones harboring JAK2V617F or Calreticulin mutations. However, the molecular complexity of these diseases could hamper IFN-α efficacy, as the presence of additional non-driver mutations, like in the TET2 gene, could be associated with resistance to IFN-α. Therefore, combined therapy with another targeted agent could be required to eradicate MPN, and the best IFN-α companion for achieving this challenge remains to be determined.

Evading Capture by Residual Disease Monitoring: Extramedullary Manifestation of JAK2 V617F-Positive Primary Myelofibrosis After Allogeneic Stem Cell Transplantation

Monitoring of the JAK2 V617F allele burden in myeloproliferative neoplasms after allogeneic stem cell transplantation is useful to determine levels of residual disease and has the potential to detect early relapse and guide subsequent clinical intervention. A case is described of a JAK2 V617F-positive primary myelofibrosis patient who underwent allogeneic stem cell transplantation. Prospective residual disease monitoring of the peripheral blood failed to detect an extramedullary manifestation of the disease, a periorbital myeloid sarcoma, arising nearly three years after transplant. This case serves to highlight a pitfall in residual disease monitoring for myeloproliferative neoplasm-associated mutations in the post-allogeneic stem cell transplantation setting.

A phase 2 randomized dose-ranging study of the JAK2-selective inhibitor fedratinib (SAR302503) in patients with myelofibrosis

In this phase 2 open-label randomized study, 31 patients with intermediate-2 or high-risk myelofibrosis received fedratinib 300, 400 or 500 mg once daily in consecutive 4-week cycles. Mean spleen volume reductions at 12 weeks (primary end point) were 30.3% (300 mg), 33.1% (400 mg) and 43.3% (500 mg). Spleen response rates (patients achieving ⩾35% spleen reduction) at 12/24 weeks were 30%/30% (300 mg), 50%/60% (400 mg) and 64%/55% (500 mg), respectively. By 4 weeks, improvements in myelofibrosis (MF)-associated symptoms were observed. At 48 weeks, 68% of patients remained on fedratinib and 16% had discontinued because of adverse events (AEs). Common grade 3/4 AEs were anemia (58%), fatigue (13%), diarrhea (13%), vomiting (10%) and nausea (6%). Serious AEs included one case of reversible hepatic failure and one case of Wernicke's encephalopathy (after analysis cutoff). Fedratinib treatment led to reduced STAT3 phosphorylation but no meaningful change in JAK2V617F allele burden. Significant modulation (P<0.05, adjusted for multiple comparisons) of 28 cytokines was observed, many of which correlated with spleen reduction. These data confirm the clinical activity of fedratinib in MF. After the analysis cutoff date, additional reports of Wernicke's encephalopathy in other fedratinib trials led to discontinuation of the sponsored clinical development program.

Real-Time PCR and Droplet Digital PCR: two techniques for detection of the JAK2(V617F) mutation in Philadelphia-negative chronic myeloproliferative neoplasms

INTRODUCTION

Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) are clonal disorders that present JAK2(V617F) mutation in 50-95% of cases. The main objective of this study was the comparison of two PCR methods, real-time (qPCR) and droplet digital PCR (DD-PCR) for detection of the JAK2(V617F) mutation, to assess analytic sensitivity, specificity, and feasibility of the two methods.

METHODS

Ninety-nine patients with MPN of 225 presenting the JAK2(V617F) mutation by qPCR have been evaluated by DD-PCR also.

RESULTS

We demonstrated an absolute concordance in terms of specificity between the two methods, DD-PCR showing a higher sensitivity (half a log higher than qPCR). As expected, a progressive increase of mutant allele burden was observed from essential thrombocythemia (ET) to polycythemia vera (PV) and primary myelofibrosis (PMF) to secondary myelofibrosis (SMF).

CONCLUSION

In conclusion, our study showed that DD-PCR could represent a new and promising technological evolution for detection of JAK2 mutation in MPNs.

Minimal residual disease after long-term interferon-alpha2 treatment: a report on hematological, molecular and histomorphological response patterns in 10 patients with essential thrombocythemia and polycythemia vera

Essential thrombocythemia (ET) and polycythemia vera (PV) are Philadelphia chromosome-negative chronic myeloproliferative neoplasms (MPNs) characterized by the JAK2 V617F mutation, which can be found in more than 98% of PV patients and in ∼ 50% of ET patients. Assessment of the JAK2 V617F allele burden by a highly sensitive quantitative PCR (qPCR) assay appears to be a useful tool for monitoring minimal residual disease (MRD) and evaluating treatment efficacy. This report expands and substantiates existing data, showing that IFN-alpha2 is a highly potent immunomodulating agent capable of inducing MRD with low-burden JAK2 V617F, major molecular response (MMR), complete hematological remission (CHR) and complete histomorphological normalization of the bone marrow in a sub-set of patients with ET and PV after long-term treatment (≥ 3.5 years). Furthermore, long-lasting hematological, molecular and histomorphological remissions are sustained after discontinuation of IFN-alpha2 for up to ∼ 5-6 years.

Impact of JAK2(V617F) mutation status on treatment response to anagrelide in essential thrombocythemia: an observational, hypothesis-generating study

A JAK2(V617F) mutation is found in approximately 55% of patients with essential thrombocythemia (ET), and represents a key World Health Organization diagnostic criterion. This hypothesis-generating study (NCT01352585) explored the impact of JAK2(V617F) mutation status on treatment response to anagrelide in patients with ET who were intolerant/refractory to their current cytoreductive therapy. The primary objective was to compare the proportion of JAK2-positive versus JAK2-negative patients who achieved at least a partial platelet response (≤600×10⁹/L) after anagrelide therapy. Of the 47 patients enrolled, 46 were included in the full analysis set (JAK2-positive, n=22; JAK2-negative, n=24). At 12 months, 35 patients (n=14 and n=21, respectively) had a suitable platelet sample; of these, 74.3% (n=26) achieved at least a partial response. The response rate was higher in JAK2-positive (85.7%, n=12) versus JAK2-negative patients (66.7%, n=14) (odds ratio [OR] 3.00; 95% confidence interval [CI] 0.44, 33.97). By using the last observation carried forward approach in the sensitivity analysis, which considered the imbalance in patients with suitable samples between groups, the overall response rate was 71.7% (n=33/46), with 77.3% (n=17/22) of JAK2-positive and 66.7% (n=16/24) of JAK2-negative patients achieving at least a partial response (OR 1.70; 95% CI 0.39, 8.02). There was no significant change in median allele burden over 12 months in the 12 patients who achieved a response. In conclusion, the overall platelet response rate was high in both JAK2-positive and JAK2-negative patients; however, a larger study would be required to confirm the differences observed according to JAK2(V617F) mutation status.

Molecular diagnostics of myeloproliferative neoplasms

Since the discovery of the JAK2 V617F mutation in the majority of the myeloproliferative neoplasms (MPN) of polycythemia vera, essential thrombocythemia and primary myelofibrosis ten years ago, further MPN-specific mutational events, notably in JAK2 exon 12, MPL exon 10 and CALR exon 9 have been identified. These discoveries have been rapidly incorporated into evolving molecular diagnostic algorithms. Whilst many of these mutations appear to have prognostic implications, establishing MPN diagnosis is of immediate clinical importance with selection, implementation and the continual evaluation of the appropriate laboratory methodology to achieve this diagnosis similarly vital. The advantages and limitations of these approaches in identifying and quantitating the common MPN-associated mutations are considered herein with particular regard to their clinical utility. The evolution of molecular diagnostic applications and platforms has occurred in parallel with the discovery of MPN-associated mutations, and it therefore appears likely that emerging technologies such as next-generation sequencing and digital PCR will in the future play an increasing role in the molecular diagnosis of MPN.

Mutations and long-term outcome of 217 young patients with essential thrombocythemia or early primary myelofibrosis

We investigated the influence of molecular status on disease characteristics and clinical outcome in young patients (⩽ 40 years) with World Health Organization (WHO)-defined essential thrombocythemia (ET) or early/prefibrotic primary myelofibrosis (early-PMF). Overall, 217 patients with ET (number 197) and early-PMF (number 20) were included in the analysis. Median follow-up time was 10.2 years. The cumulative incidence of thrombosis, hemorrhages and disease evolution into myelofibrosis/acute leukemia were 16.6%, 8.6% and 3% at 15 years, respectively. No differences were detectable between ET and early-PMF patients, although the latter cohort showed a trend for worse combined-event free survival (EFS). Mutation frequency were 61% for JAK2V617F, 25% for CALR and 1% for MPLW515K, and were comparable across WHO diagnosis; however, JAK2V617F allele burden was higher in the early-PMF group. Compared with JAK2V617F-positive patients, CALR-mutated patients displayed higher platelet count and lower hemoglobin level. CALR mutations significantly correlated with lower thrombotic risk (9.1% versus 21.7%, P = 0.04), longer survival (100% versus 96%, P = 0.05) and better combined-EFS (86% versus 71%, P = 0.02). However, non-type 1/type 2 CALR mutations ('minor' mutations) and abnormal karyotype were found to correlate with increased risk of disease evolution. At last contact, six patients had died; in five cases, the causes of death were related to the hematological disease and occurred at a median age of 64 years (range: 53-68 years). Twenty-eight patients (13%) were unmutated for JAK2, CALR and MPL: no event was registered in these 'triple-negative' patients.

Melting curve analysis after T allele enrichment (MelcaTle) as a highly sensitive and reliable method for detecting the JAK2V617F mutation

Detection of the JAK2V617F mutation is essential for diagnosing patients with classical myeloproliferative neoplasms (MPNs). However, detection of the low-frequency JAK2V617F mutation is a challenging task due to the necessity of discriminating between true-positive and false-positive results. Here, we have developed a highly sensitive and accurate assay for the detection of JAK2V617F and named it melting curve analysis after T allele enrichment (MelcaTle). MelcaTle comprises three steps: 1) two cycles of JAK2V617F allele enrichment by PCR amplification followed by BsaXI digestion, 2) selective amplification of the JAK2V617F allele in the presence of a bridged nucleic acid (BNA) probe, and 3) a melting curve assay using a BODIPY-FL-labeled oligonucleotide. Using this assay, we successfully detected nearly a single copy of the JAK2V617F allele, without false-positive signals, using 10 ng of genomic DNA standard. Furthermore, MelcaTle showed no positive signals in 90 assays screening healthy individuals for JAK2V617F. When applying MelcaTle to 27 patients who were initially classified as JAK2V617F-positive on the basis of allele-specific PCR analysis and were thus suspected as having MPNs, we found that two of the patients were actually JAK2V617F-negative. A more careful clinical data analysis revealed that these two patients had developed transient erythrocytosis of unknown etiology but not polycythemia vera, a subtype of MPNs. These findings indicate that the newly developed MelcaTle assay should markedly improve the diagnosis of JAK2V617F-positive MPNs.

Minimal residual disease testing in hematologic malignancies and solid cancer

Minimal residual disease (MRD) assays are of a great value to assess treatment efficacy and may provide prognostic information. This is particularly relevant in the era of targeted therapy where the introduction of MRD monitoring has fundamentally transformed the way in which cancer patients are managed. While MRD guidelines are well-established for chronic myeloid leukemia, acute promyelocytic leukemia and acute lymphoblastic leukemia, areas for continuing development are available. High level of standardization and regular external quality control rounds and recommendations for data interpretation remain essential to improve MRD monitoring. In this review, we describe the different applications of MRD assays in most frequent hematologic malignancies and solid cancer and provide an overview of the strengths and potential weaknesses of each method.

[Complex molecular genetic algorithm in the diagnosis of myeloproliferative neoplasms]

INTRODUCTION

Mutations in Janus kinase 2, calreticulin and thrombopoietin receptor genes have been identified in the genetic background of Philadelphia chromosome negative, "classic" myeloproliferative neoplasms.

AIM

The aim of the authors was to identify driver mutations in a large myeloproliferative cohort of 949 patients.

METHOD

A complex array of molecular techniques (qualitative and quantitative allele-specific polymerase chain reactions, fragment analyzes, high resolution melting and Sanger sequencing) was applied.

RESULTS

All 354 patients with polycythemia vera carried Janus kinase 2 mutations (V617F 98.6%, exon 12: 1.4%). In essential thrombocythemia (n = 468), the frequency of V617F was 61.3% (n = 287), that of calreticulin 25.2% (n = 118), and that of thrombopoietin receptor mutations 2.1% (n = 10), while 11.3% (n = 53) were triple-negative. Similar distribution was observed in primary myelofibrosis (n = 127): 58.3% (n = 74) V617F, 23.6% (n = 30) calreticulin, 6.3% (n = 8) thrombopoietin receptor mutation positive and 11.8% (n = 15) triple-negative.

CONCLUSIONS

The recent discovery of calreticulin gene mutations led to definite molecular diagnostics in around 90% of clonal myeloproliferative cases.

Defining minimal residual disease in acute myeloid leukemia: which platforms are ready for “prime time”?

The past 40 years have witnessed major advances in defining the cytogenetic aberrations, mutational landscape, epigenetic profiles, and expression changes underlying hematological malignancies. Although it has become apparent that acute myeloid leukemia (AML) is highly heterogeneous at the molecular level, the standard framework for risk stratification guiding transplant practice in this disease remains largely based on pretreatment assessment of cytogenetics and a limited panel of molecular genetic markers, coupled with morphological assessment of bone marrow (BM) blast percentage after induction. However, application of more objective methodology such as multiparameter flow cytometry (MFC) has highlighted the limitations of morphology for reliable determination of remission status. Moreover, there is a growing body of evidence that detection of subclinical levels of leukemia (ie, minimal residual disease, MRD) using MFC or molecular-based approaches provides powerful independent prognostic information. Consequently, there is increasing interest in the use of MRD detection to provide early end points in clinical trials and to inform patient management. However, implementation of MRD assessment into clinical practice remains a major challenge, hampered by differences in the assays and preferred analytical methods employed between routine laboratories. Although this should be addressed through adoption of standardized assays with external quality control, it is clear that the molecular heterogeneity of AML coupled with increasing understanding of its clonal architecture dictates that a “one size fits all” approach to MRD detection in this disease is not feasible. However, with the range of platforms now available, there is considerable scope to realistically track treatment response in every patient.

Defining minimal residual disease in acute myeloid leukemia: which platforms are ready for "prime time"?

The past 40 years have witnessed major advances in defining the cytogenetic aberrations, mutational landscape, epigenetic profiles, and expression changes underlying hematological malignancies. Although it has become apparent that acute myeloid leukemia (AML) is highly heterogeneous at the molecular level, the standard framework for risk stratification guiding transplant practice in this disease remains largely based on pretreatment assessment of cytogenetics and a limited panel of molecular genetic markers, coupled with morphological assessment of bone marrow (BM) blast percentage after induction. However, application of more objective methodology such as multiparameter flow cytometry (MFC) has highlighted the limitations of morphology for reliable determination of remission status. Moreover, there is a growing body of evidence that detection of subclinical levels of leukemia (ie, minimal residual disease, MRD) using MFC or molecular-based approaches provides powerful independent prognostic information. Consequently, there is increasing interest in the use of MRD detection to provide early end points in clinical trials and to inform patient management. However, implementation of MRD assessment into clinical practice remains a major challenge, hampered by differences in the assays and preferred analytical methods employed between routine laboratories. Although this should be addressed through adoption of standardized assays with external quality control, it is clear that the molecular heterogeneity of AML coupled with increasing understanding of its clonal architecture dictates that a "one size fits all" approach to MRD detection in this disease is not feasible. However, with the range of platforms now available, there is considerable scope to realistically track treatment response in every patient.

Management of MPN beyond JAK2

Thrombocytosis has a large number of potential underlying causes, but the dominant group of hematological conditions for consideration in this setting are the myeloproliferative neoplasms (MPNs). In this chapter, we consider several key linked questions relating to the management of thrombocytosis in MPNs and discuss several issues. First, we discuss the differential diagnosis of thrombocytosis, which myeloid disorders to consider, and practical approaches to the discrimination of each individual MPN from other causes. Second, there have been several major advances in our understanding of the molecular biology of these conditions and we discuss how these findings are likely to be practically applied in the future. Third, we consider whether there is evidence that thrombocytosis contributes to the complications known to be associated with MPN: thrombosis, hemorrhage and transformation to leukemia and myelofibrosis. Last, we review current ideas for risk stratification and management of essential thrombocythemia and polycythemia vera as the 2 entities within the MPN family that are most frequently associated with thrombocytosis.

Frequency and molecular characteristics of calreticulin gene (CALR) mutations in patients with JAK2 -negative myeloproliferative neoplasms

In 2013, Nangalia et al. and Klampfl et al. found a recurrent and abundant mutation in the calreticulin gene (CALR), mutually exclusive with JAK2 and MPL alterations. At present, the data concerning the new mutation, i.e. its prevalence, allele burden and clinical significance, are scarce. We report the incidence and molecular characteristics of CALR mutations in a group of 184 Polish patients with myeloproliferative neoplasms (MPNs). Clinical data analysis revealed significant differences between JAK2 V617F-mutated and CALR-mutated groups. In essential thrombocythemia patients, hemoglobin levels and leukocyte counts were significantly higher in JAK2-positive than in CALR-positive patients (p = 0.023 and p = 0.017, respectively), but the CALR-positive patients had significantly higher platelet counts (p = 0.022). Patients harboring CALR mutations were also younger at the time of diagnosis (p = 0.039). In primary myelofibrosis patients, the degree of anemia was less severe in those who were CALR exon 9 mutation-positive than in those who were JAK2 V617F-positive (p = 0.048).

How I treat polycythemia vera

Polycythemia vera (PV) is a chronic myeloproliferative neoplasm associated with JAK2 mutations (V617F or exon 12) in almost all cases. The World Health Organization has defined the criteria for diagnosis, but it is still unclear which parameter (hemoglobin or hematocrit) is the most reliable for demonstrating increased red cell volume and for monitoring response to therapy; also, the role of bone marrow biopsy is being revisited. PV is associated with reduced survival because of cardiovascular complications and progression to post-PV myelofibrosis or leukemia. Criteria for risk-adapted treatment rely on the likelihood of thrombosis. Controlled trials have demonstrated that incidence of cardiovascular events is reduced by sustained control of hematocrit with phlebotomies (low-risk patients) and/or cytotoxic agents (high-risk patients) and antiplatelet therapy with aspirin. Hydroxyurea and interferon may be used as first-line treatments, whereas busulfan is reserved for patients that are refractory or resistant to first-line agents. However, there is no evidence that therapy improves survival, and the significance of reduction of JAK2 mutated allele burden produced by interferon is unknown. PV is also associated with a plethora of symptoms that are poorly controlled by conventional therapy. This article summarizes my approach to the management of PV in daily clinical practice.

Defining minimal residual disease in acute myeloid leukemia: which platforms are ready for "prime time"?

The past 40 years have witnessed major advances in defining the cytogenetic aberrations, mutational landscape, epigenetic profiles, and expression changes underlying hematological malignancies. Although it has become apparent that acute myeloid leukemia (AML) is highly heterogeneous at the molecular level, the standard framework for risk stratification guiding transplant practice in this disease remains largely based on pretreatment assessment of cytogenetics and a limited panel of molecular genetic markers, coupled with morphological assessment of bone marrow (BM) blast percentage after induction. However, application of more objective methodology such as multiparameter flow cytometry (MFC) has highlighted the limitations of morphology for reliable determination of remission status. Moreover, there is a growing body of evidence that detection of subclinical levels of leukemia (ie, minimal residual disease, MRD) using MFC or molecular-based approaches provides powerful independent prognostic information. Consequently, there is increasing interest in the use of MRD detection to provide early end points in clinical trials and to inform patient management. However, implementation of MRD assessment into clinical practice remains a major challenge, hampered by differences in the assays and preferred analytical methods employed between routine laboratories. Although this should be addressed through adoption of standardized assays with external quality control, it is clear that the molecular heterogeneity of AML coupled with increasing understanding of its clonal architecture dictates that a "one size fits all" approach to MRD detection in this disease is not feasible. However, with the range of platforms now available, there is considerable scope to realistically track treatment response in every patient.

Safety evaluation of ruxolitinib for treating myelofibrosis

INTRODUCTION

In 2005, the JAK2 V617F mutation was identified and found to be highly prevalent in the 'Philadephia Chromosome-negative' Myeloproliferative neoplasms (MPN). This led to new diagnostic criteria for MPN in addition to the development of the first targeted therapy for myelofibrosis (MF), ruxolitinib .

AREAS COVERED

Ruxolitinib was approved within 5 years of 'first-in-man' trials; it has been assessed in two large Phase III trials, and to date, several thousand patients have been prescribed this drug. This article reviews the latest data from the Phase III trials concerning efficacy and safety in addition to post-authorisation data for this agent. Ruxolitinib is an extremely well-tolerated drug; it is associated with bruising, headaches, dizziness, anaemia and thrombocytopaenia. In addition, an augmented risk of infections has been documented.

EXPERT OPINION

Ruxolitinib has radically altered the therapeutic landscape for MF with demonstrated advantages over standard therapy, irrespective of JAK2 mutational status and a signal suggesting survival benefit. Other JAK inhibitors are also in late stages of development, although the furthest advanced has just been withdrawn due to cases of encephalopathy (not documented with ruxolitinib). This reminds the clinical community of the need for post-marketing surveillance of safety for these agents. Challenges ahead are identification of appropriate surrogates for survival benefit and perhaps how to best use ruxolitinib either alone or in combination with other therapies.

Calreticulin mutation-specific immunostaining in myeloproliferative neoplasms: pathogenetic insight and diagnostic value

Mutations in the gene calreticulin (CALR) occur in the majority of JAK2- and MPL-unmutated patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF); identifying CALR mutations contributes to the diagnostic pathway of ET and PMF. CALR mutations are heterogeneous spanning over the exon 9, but all result in a novel common protein C terminus. We developed a polyclonal antibody against a 17-amino-acid peptide derived from mutated calreticulin that was used for immunostaining of bone marrow biopsies. We show that this antibody specifically recognized patients harboring different types of CALR mutation with no staining in healthy controls and JAK2- or MPL-mutated ET and PMF. The labeling was mostly localized in megakaryocytes, whereas myeloid and erythroid cells showed faint staining, suggesting a preferential expression of calreticulin in megakaryocytes. Megakaryocytic-restricted expression of calreticulin was also demonstrated using an antibody against wild-type calreticulin and by measuring the levels of calreticulin RNA by gene expression analysis. Immunostaining using an antibody specific for mutated calreticulin may become a rapid, simple and cost-effective method for identifying CALR-mutated patients complementing molecular analysis; furthermore, the labeling pattern supports the preferential expansion of megakaryocytic cell lineage as a result of CALR mutation in an immature hematopoietic stem cell.

Improved diagnosis of the transition to JAK2 (V⁶¹⁷F) homozygosity: the key feature for predicting the evolution of myeloproliferative neoplasms

Most cases of BCR-ABL1-negative myeloproliferative neoplasms (MPNs), essential thrombocythemia, polycythemia vera and primary myelofibrosis are associated with JAK2^V617F mutations. The outcomes of these cases are critically influenced by the transition from JAK2^V617F heterozygosity to homozygosity. Therefore, a technique providing an unbiased assessment of the critical allele burden, 50% JAK2^V617F, is highly desirable. In this study, we present an approach to assess the JAK2^V617F burden from genomic DNA (gDNA) and complementary DNA (cDNA) using one-plus-one template references for allele-specific quantitative-real-time-PCR (qPCR). Plasmidic gDNA and cDNA constructs encompassing one PCR template for JAK2^V617F spaced from one template for JAK2^{Wild Type} were constructed by multiple fusion PCR amplifications. Repeated assessments of the 50% JAK2^V617F burden within the dynamic range of serial dilutions of gDNA and cDNA constructs resulted in 52.53±4.2% and 51.46±4.21%, respectively. The mutation-positive cutoff was estimated to be 3.65% (mean +2 standard deviation) using 20 samples from a healthy population. This qPCR approach was compared with the qualitative ARMS-PCR technique and with two standard methods based on qPCR, and highly significant correlations were obtained in all cases. qPCR assays were performed on paired gDNA/cDNA samples from 20 MPN patients, and the JAK2^V617F expression showed a significant correlation with the allele burden. Our data demonstrate that the qPCR method using one-plus-one template references provides an improved assessment of the clinically relevant transition of JAK2^V617F from heterozygosity to homozygosity.

A highly specific q-RT-PCR assay to address the relevance of the JAK2WT and JAK2V617F expression levels and control genes in Ph-negative myeloproliferative neoplasms

In Ph- myeloproliferative neoplasms, the quantification of the JAK2V617F transcripts may provide some advantages over the DNA allele burden determination. We developed a q-RT-PCR to assess the JAK2WT and JAK2V617F mRNA expression in 105 cases (23 donors, 13 secondary polycythemia, 22 polycythemia vera (PV), 38 essential thrombocythemia (ET), and 9 primary myelofibrosis (PMF)). Compared with the standard allele-specific oligonucleotide (ASO)-PCR technique, our assay showed a 100 % concordance rate detecting the JAK2V617F mutation in 22/22 PV (100 %), 29/38 (76.3 %) ET, and 5/9 (55.5 %) PMF cases, respectively. The sensitivity of the assay was 0.01 %. Comparing DNA and RNA samples, we found that the JAK2V617F mutational ratios were significantly higher at the RNA level both in PV (p = 0.005) and ET (p = 0.001) samples. In PV patients, JAK2WT expression levels positively correlated with the platelets (PLTs) (p = 0.003) whereas a trend to negative correlation was observed with the Hb levels (p = 0.051). JAK2V617F-positive cases showed the lowest JAK2WT and ABL1 mRNA expression levels. In all the samples, the expression pattern of beta-glucoronidase (GUSB) was more homogeneous than that of ABL1 or β2 microglobulin (B2M). Using GUSB as normalizator gene, a significant increase of the JAK2V617F mRNA levels was seen in two ET patients at time of progression to PV. In conclusion, the proposed q-RT-PCR is a sensitive and accurate method to quantify the JAK2 mutational status that can also show clinical correlations suggesting the impact of the residual amount of the JAK2WT allele on the Ph- MPN disease phenotype. Our observations also preclude the use of ABL1 as a housekeeping gene for these neoplasms.

JAK2 p.V617F detection and allele burden measurement in peripheral blood and bone marrow aspirates in patients with myeloproliferative neoplasms

Detection of the JAK2 p.V617F mutation and measurement of its allele burden can be performed using both peripheral blood (PB) and bone marrow (BM) samples from patients with myeloproliferative neoplasms (MPNs). However, the diagnostic accuracy of detecting the JAK2 p.V617F mutation and quantifying its allele burden in PB and BM samples has not been systematically compared. We retrospectively analyzed 388 patients with MPN who had been tested for JAK2 p.V617F allele burden using both PB and BM samples within 3 months of each other. The sensitivity and specificity of detecting JAK2 p.V617F in PB when compared with BM were both 100%. Furthermore, the JAK2 p.V617F allele burden measured in PB and BM were equivalent by linear regression analysis (R(2) = 0.991; P < .0001). We therefore conclude that PB is a reliable source for testing for the JAK2 p.V617F mutation and quantifying its allele burden in patients with MPN.