The mutation profile of JAK2 and CALR in Chinese Han patients with Philadelphia chromosome-negative myeloproliferative neoplasms

Management of classical Philadelphia chromosome-negative myeloproliferative neoplasms in Asia: consensus of the Asian Myeloid Working Group

Myeloproliferative neoplasms (MPN) are a heterogeneous group of clonal hematopoietic stem cell disorders characterized clinically by the proliferation of one or more hematopoietic lineage(s). The classical Philadelphia-chromosome (Ph)-negative MPNs include polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). The Asian Myeloid Working Group (AMWG) comprises representatives from fifteen Asian centers experienced in the management of MPN. This consensus from the AMWG aims to review the current evidence in the risk stratification and treatment of Ph-negative MPN, to identify management gaps for future improvement, and to offer pragmatic approaches for treatment commensurate with different levels of resources, drug availabilities and reimbursement policies in its constituent regions. The management of MPN should be patient-specific and based on accurate diagnostic and prognostic tools. In patients with PV, ET and early/prefibrotic PMF, symptoms and risk stratification will guide the need for early cytoreduction. In younger patients requiring cytoreduction and in those experiencing resistance or intolerance to hydroxyurea, recombinant interferon-α preparations (pegylated interferon-α 2A or ropeginterferon-α 2b) should be considered. In myelofibrosis, continuous risk assessment and symptom burden assessment are essential in guiding treatment selection. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) in MF should always be based on accurate risk stratification for disease-risk and post-HSCT outcome. Management of classical Ph-negative MPN entails accurate diagnosis, cytogenetic and molecular evaluation, risk stratification, and treatment strategies that are outcome-oriented (curative, disease modification, improvement of quality-of-life).

Expression properties, structural features and functional analysis of CALR E381A in MPN patients

OBJECTIVE

To investigate the expression properties, structural features and function of CALR E381A in myeloproliferative neoplasms (MPN) patients.

METHODS

In this retrospective study, 435 MPN patients admitted to the Department of Hematology, Ningbo First Hospital from July 2015 to July 2021 were selected as the study subjects. Mutations in CALR exon 9 from genomic DNA samples were identified by PCR, followed by Sanger sequencing. The physicochemical properties of the wild-type calreticulin and the p.E381A variant, and the structural information of the p.E381A variant were analyzed by using the bioinformatics databases. Growth assay of UT-7/mpl cells with CALR E381A was used for the functional analysis of CALR E381A.

RESULTS

The predominant types of CALR variants were identified as follows: p.L367fs*46 (38.1%), p.K385fs*47 (25.8%) and p.E381A (19.6%). Notably, the frequency of the p.E381A variant (c.1142A >C) in polycythemia vera or essential thrombocythemia was significantly higher than the frequency of that as a single nucleotide polymorphism (SNP) in the East Asian population. Furthermore, CALR E381A coexisted with other genetic variants, of which JAK2 V617F was more common. Bioinformatics analysis confirmed that CALR E381A did not change the physicochemical properties of the calreticulin protein, but did change the electrical charge, energy state and steric hindrance of amino acid residues at site 381. UT-7/mpl cells harboring CALR E381A overexpression did not exhibit altered cell growth, which is distinctly different from the stereotypical frameshift mutation.

CONCLUSION

CALR E381A is not a driver mutation for the development of MPN but may be a risk SNP implying an inherited predisposition for MPN disease in East Asian populations.

TET2 Mutation May Be More Valuable in Predicting Thrombosis in ET Patients Compared to PV Patients: A Preliminary Report

Thrombosis is a common complication of myeloproliferative neoplasm (MPN), and it is a major cause of disability and death. With the development of next-generation gene-sequencing technology, the relationship between non-driver mutations and thrombotic risk factors has also attracted considerable attention. To analyze the risk factors of thrombosis in patients with essential thrombocythemia (ET) and polycythemia vera (PV), we retrospectively analyzed the clinical data of 125 MPN patients (75 ET and 50 PV) and performed a multivariate analysis of the risk factors of thrombosis using a Cox proportional risk model. Among the 125 patients, 35 (28.0%) had thrombotic events, and the incidence of thrombotic events was 21.3% and 38.0% in ET and PV patients, respectively. In ET patients, the multivariate analysis showed that a TET2 mutation and history of remote thrombosis were independent risk factors for thrombosis in ET patients, with an HR of 4.1 (95% CI: 1.40-12.01; p = 0.01) for TET2 mutation and 6.89 (95% CI: 1.45-32.68; p = 0.015) for a history of remote thrombosis. In PV patients, the multivariate analysis presented the neutrophil-to-lymphocyte ratio (NLR) (HR: 4.77, 95% CI: 1.33-17.16; p = 0.017) and a history of remote thrombosis (HR: 1.67, 95% CI: 1.03-1.32; p = 0.014) as independent risk factors for thrombosis, with no significant change in the risk of thrombosis in patients with TET2 mutations. A further analysis of the clinical characteristics and coagulation occurring in ET patients with a TET2 mutation revealed that the values of age and D-dimer were significantly higher and antithrombin III was significantly lower in TET2-mutated ET patients compared to TET2-unmutated patients. In summary, TET2 mutation may be more valuable in predicting thrombosis in ET patients than in PV patients. ET patients with a TET2 mutation are older and present differences in coagulation compared to TET2-unmutated patients.

CALR-ETdb, the database of calreticulin variants diversity in essential thrombocythemia

Essential thrombocythemia (ET) is a blood cancer defined by a strong increase of platelet numbers. A quarter of patients suffering from ET show mutations in the last exon of calreticulin (CALR) gene. Two variants named type 1 and type 2 represent 85% of these patients. However, a large number of other variants have been determined. In this study, we have compiled variants taken from COSMIC database and literature leading to 155 different variants. This large number of variants allowed redefining 5 new classes extending the classification of type 1-like and type 2-like to a finer description. These analyses showed that last class, named E, corresponding to more than 10% of CALR variants seemed not attached to ET. Structural properties analyzed showed that CALR variants associated to ET have common features. All the compiled and refined information had been included into a freely dedicated database CALR-ETdb (https://www.dsimb.inserm.fr/CALR-ET).

Detection of single-base mutation of DNA oligonucleotides with different lengths by terahertz attenuated total reflection microfluidic cell

Many human genetic diseases are caused by single-base mutation in the gene sequence. Since DNA molecules with single-base mutation are extremely difficult to differentiate, existing detection methods are invariably complex and time-consuming. We propose a new label-free and fast terahertz (THz) spectroscopic technique based on a home-made terahertz attenuated total reflection (ATR) microfluidic cell and a terahertz time-domain spectroscopy (THz-TDS) system to detect single-base-mutated DNA molecules. The detected object DNA molecules are normal hemoglobin gene, sickle cell anemia gene (15 nt), JAK2 gene wild type and JAK2 V617F gene mutation (39 nt) from sickle cell anemia and thrombocytopenia, respectively. Results show that the oligonucleotide fragments with single-base mutation can be identified by THz spectroscopy combined with the ATR microfluidic cell, and the recognition effect of short oligonucleotide fragments with single-base mutation is better than that of long oligonucleotide fragments. The terahertz biosensor is shown to have high sensitivity and can be used to detect DNA molecules directly in the solution environment.

An exploratory study comparing students' science identity perceptions derived from a hands-on research and nonresearch-based summer learning experience

Although multiple efforts have been initiated to increase students' science proficiency scores, most of the schools in the United States do not reach the expected student academic performance. This study addresses the impact of a one-week summer scientific learning experience on students that worked with experimental procedures and students that did not. We describe and evaluate these two different interventions to explore what components influence high school students' perception of their scientific competence, performance, and recognition, using science identity as an analytical lens. Science identity score was increased at the end of both interventions. Interestingly, science identity change index was higher for the group that did not work with experimental procedures. Although this group did not perform any hands-on experiments, they report, through reflexive diaries and interviews that working with CRISPR-Cas9 models, being in a research laboratory, and seeing the instrumentation made them feel like scientists. Regarding science competence, both groups report exponential learning gains, although the group that performed the experiments reports more difficulties. Both groups report that mentorship was key in their competence and performance development. These findings suggest that our one-week scientific learning programs influence participants' perception of scientific competence and performance and create an opportunity to develop further studies on short scientific learning experiences using models and active learning activities.

Systematization of analytical studies of polycythemia vera, essential thrombocythemia and primary myelofibrosis, and a meta-analysis of the frequency of JAK2, CALR and MPL mutations: 2000-2018

BACKGROUND

Research into Philadelphia-negative chronic myeloproliferative neoplasms is heterogeneous. In addition, no systematization of studies of polycythemia vera (PV), essential thrombocythemia (ET) or primary myelofibrosis (PMF) have been carried out. The objective of this review is to characterize studies on BCR-ABL1-negative chronic myeloproliferative neoplasms and to compare the frequency of JAK2, MPL and CALR mutations in PV, ET and PMF.

METHOD

A systematic review of the scientific literature was conducted, as was meta-analysis with an ex-ante selection of protocol, according to phases of the PRISMA guide in three interdisciplinary databases. To guarantee reproducibility in the pursuit and retrieval of information, the reproducibility and methodological quality of the studies were evaluated by two researchers.

RESULTS

Fifty-two studies were included, the majority having been carried out in the United States, China, Brazil and Europe. The frequency of the JAK2V617F mutation ranged from 46.7 to 100% in patients with PV, from 31.3 to 72.1% in patients with ET, and from 25.0 to 85.7% in those with PMF. The frequency of the MPL mutation was 0% in PV, from 0.9 to 12.5% in ET, and from 0 to 17.1% in PMF. The CALR mutation occurred at a frequency of 0.0% in PV, whereas in ET, it ranged from 12.6 to 50%, and in PMF, it ranged from 10 to 100%. The risk of this mutation presenting in PV is 3.0 times that found for ET and 4.0 times that found for PMF.

CONCLUSION

Given the specificity and reported high frequencies of the JAK2V617F, MPL and CALR mutations in this group of neoplasms, the diagnosis of these diseases should not be made on clinical and hematological characteristics alone but should include genetic screening of patients.

Correlation analysis between JAK2, MPL, and CALR mutations in patients with myeloproliferative neoplasms of Chinese Uygur and Han nationality and their clinical characteristics

Background

Genetic factors play a role in the etiology of BCR-ABL-negative myeloproliferative neoplasms (MPNs). This study explored the relationship between mutations in the Janus kinase 2 gene (JAK2), MPL, and the calreticulin gene (CALR) in Uygur and Han Chinese patients with BCR-ABL fusion gene-negative MPN and corresponding clinical features.

Methods

A total of 492 BCR-ABL-negative MPN patients treated in our hospital from May 2013 to August 2016 were enrolled. Genomic DNA was extracted from peripheral blood and used for PCR amplification and DNA sequencing. Mutations including JAK2 V617F, MPL W515L/K, and those in JAK2 exon 12 and CALR were analyzed and compared with patient clinical characteristics.

Results

Of the 492 MPN patients, 169 were Uygur and 323 were Han. In these two patient groups, JAK2 mutations were detected in 39.64% and 52.63%, respectively, CALR mutations were detected in 10.06% and 20.43%, respectively, and MPL mutations were detected in 0.93% of Han patients. The age, white blood cell count, platelet levels, and hemoglobin levels in JAK2 in Han patients were higher than those in Uygur patients.

Conclusion

Han MPN patients harboring JAK2 mutations had higher level of age, WBC, PLT, and Hb than Uyghur patients with the same mutations.

A triplex probe-based TaqMan qPCR assay for Calreticulin type I and II mutation detection

BACKGROUND

Calreticulin (CALR) exon 9 frameshift mutations have recently been identified in 30-40% of patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF) without JAK2 or MPL mutations. We aimed to develop a qPCR assay to screen type I and II mutations of CALR.

METHODS

Three different fluorescent-labeled hydrolysis probes and one pair of primers in a closed-tube system were developed to detect CALR type I and II mutations and distinguish them from wild-type. The sensitivity and specificity were validated using TA-cloning plasmids containing CALR wild-type and type I and II mutants, respectively. Fifty-nine ET and PMF specimens were screened by TaqMan qPCR and sequenced by Sanger sequencing. For intra-assay validation, 20 replicates of the assay were performed with each sample. For inter-assay validation, four replications of each sample were carried out and repeated continuously for 5 days.

RESULTS

We found that triplex probe-based TaqMan qPCR was reliable in detecting CALR type I and II mutants within DNA that was diluted to 1% of total DNA with the wild-type DNA as background. In 59 patient specimens, six of the observed mutations of CALR were type I and five were type II. Genotyping results obtained from TaqMan qPCR were 100% concordant with Sanger sequencing. The intra- and inter-assay CVs of TaqMan qPCR were less than 3%, respectively.

CONCLUSIONS

Triplex probe-based TaqMan qPCR is an accurate and sensitive method for screening ET or PMF patients with type I and II mutations in CALR.

Somatic Mutations in Philadelphia Chromosome-Negative Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPN) include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). MPN are characterized by clonal proliferation of myeloid progenitors leading to erythrocytosis, thrombocytosis, or leukocytosis, and risk of hemorrhagic and thrombotic events, as well as myelofibrosis and blast transformation. The discovery of somatic mutations in MPN, namely JAK2 V617F, JAK2 exon 12, MPL, and CALR mutations, has permitted a more specific approach to diagnosis and treatment. The prevalence of JAK2 V617F mutations is higher than 95% in PV, 50%-75% in ET and 40%-75% in PMF. JAK2 exon 12 mutations are specific of PV. A 20%-30% of patients with ET and PMF present a CALR mutation. The screening of mutations strengthens the diagnosis of MPN since 97% of MPN have at least 1 somatic mutation. Interestingly, different mutations grant different phenotype and prognosis. Of particular importance, CALR mutations grant a favorable prognosis in ET and PMF, while ASXL1 mutations confer a poorer outcome. In fact, the use of CALR/ASXL1 status for the prognostication of patients has increased clinical value and is now suggested for guidance of therapy in PMF. The increasing importance of mutations in the management of MPN warrants a more frequent revision of current diagnostic criteria and prognostic models and a better understanding of the mechanisms leading to MPN subset differentiation.

Increased B cell activation is present in JAK2V617F-mutated, CALR-mutated and triple-negative essential thrombocythemia

Essential thrombocythemia (ET) is a BCL-ABL1-negative myeloproliferative neoplasm. We have reported that increased activated B cells can facilitate platelet production mediated by cytokines regardless JAK2 mutational status in ET. Recently, calreticulin (CALR) mutations were discovered in ~30% JAK2/MPL-unmutated ET and primary myelofibrosis. Here we sought to screen for CALR mutations and to evaluate B cell immune profiles in a cohort of adult Taiwanese ET patients. B cell populations, granulocytes/monocytes membrane-bound B cell-activating factor (mBAFF) levels, B cells toll-like receptor 4 (TLR4) expression and intracellular levels of interleukin (IL)-1β/IL-6 and the expression of CD69, CD80, and CD86 were quantified by flow cytometry. Serum BAFF concentration was measured by ELISA. 48 healthy adults were used for comparison. 19 (35.2%) of 54 ET patients harbored 8 types of CALR exon 9 mutations including 4 (7.4%) patients with concomitant JAK2V617F mutations. Compared to JAK2V617F mutation, CALR mutations correlated with younger age at diagnosis (p=0.04), higher platelet count (p=0.004), lower hemoglobin level (p=0.013) and lower leukocyte count (p=0.013). Multivariate analysis adjusted for age, sex, follow-up period and hematological parameters confirmed that increased activated B cells were universally present in JAK2-mutated, CALR-mutated and triple-negative ET patients when compared to healthy adults. JAK2- and CALR-mutated ET have significantly higher fraction of B cells with TLR4 expression when compared to triple-negative ET (p=0.019 and 0.02, respectively). CALR-mutated ET had significantly higher number of CD69-positive activated B cells when compared to triple-negative ET (p=0.035). In conclusion, increased B cell activation is present in ET patients across different mutational subgroups.

Elevated expression of the EZH2 gene in CALR-mutated patients with primary myelofibrosis

Primary myelofibrosis (PMF) is one of the BCR/ABL-negative myeloproliferative neoplasms (MPNs), characterized by the diffuse fibrous hyperproliferation, bone marrow osteosclerosis, extramedullary hematopoiesis, and marked splenomegaly. The patients with PMF have an insidious onset, a long duration of clinical course, and the deteriorated quality of life. It has been reported that the CALR gene 9 exon mutations were detected in 25-30% PMF patients, particularly as high as 80% in the JAK2/MPL-negative ones. As the second most common mutation in BCR/ABL-negative MPNs, CALR mutation has been included in the latest World Health Organization (WHO) classification criteria as one of the main diagnostic criteria for both essential thrombocythemia (ET) and PMF. Moreover, the CALR mutations indicated a favorable prognosis, which the mechanism is still under investigation. It was demonstrated that a characterized high expression of EZH2 and SUZ12 in CALR-mutated patients. Taking EZH2 as the research entry point, we initially discussed the mechanism that the CALR-positive patients with PMF exhibited a better prognosis in the current study.

The clinical and prognostic relevance of driver mutations in 203 Taiwanese patients with primary myelofibrosis

AIMS

We investigated the clinical and prognostic relevance of the mutational status of driver genes with allele burden and endogenous erythroid colony (EEC) growth in 203 Taiwanese patients with primary myelofibrosis (PMF).

METHODS

Pyrosequencing was used to detect JAK2^V617F mutational status and measure allele burden, while MPL (exon 10) mutations were analysed by PCR assay and then by direct sequencing. CALR exon 9 mutations were first screened for length changes by GeneScan followed by sequencing. The allele burden of the mutated CALR gene was measured by pyrosequencing. The EEC assay was conducted using a serum-free culture system.

RESULTS

The frequencies of the three driver mutations and triple-negative status were similarly distributed between pre-PMF and overt PMF patients, except that pre-PMF patients had a higher incidence of CALR type 2/type-2 like mutations and a lower JAK2^V617F allele burden. EEC growth and CALR mutations conferred favourable overall survival (OS). A lower JAK2^V617F allele burden and grade 3 bone marrow fibrosis were associated with shorter OS and decreased leukaemia-free survival (LFS). Type 2/type 2-like CAL mutations were associated with better LFS compared with type1/type 1-like mutations. Patients with triple-negative mutation status had significantly worse OS and LFS. The allele burden of CALR mutations remained unchanged, while some JAK2^V617F mutations showed clonal expansion in patients during secondary acute myeloid leukaemia transformation.

CONCLUSIONS

Our study showed that EEC growth, a higher JAK2^V617F allele burden and CALR mutations, especially type 2, were independent predictors for better outcomes in PMF. The allele burden of CALR mutations remained stable, but the allele burden of JAK2^V617Fmutations was variable during leukaemia transformation.

Atypical haematological presentation in a case of polycythaemia vera with a new variant mutation detected in exon 12: c.1605G>T (p.Met535Ile)

One of the major genetic insights into the pathogenesis of polycythaemia vera included the identification of the somatic point gain-of-function mutations in Janus kinase 2 gene-first JAK2V617F on exon 14, present in 95%-97% of the cases, and later on exon 12. In the literature, we can find some reported studies where different exon 12 mutations are identified. Unlike patients with JAK2V617F mutation in exon 14, the mutation at exon 12 is not usually associated with an increase in the three haematopoietic series (erythrocytosis, leucocytosis and thrombocytosis). It appears to be associated with a distinct syndrome, mostly characterised by isolated and more marked erythrocytosis, independently of the mutational variant. We report here the case of a patient who is JAK2exon 12 positive, presenting a novel mutation-c.1605G>T (p.Met535Ile)-associated with c.1612C>T (p.His538Tyr) mutation previously described, evidencing an atypical clinical phenotype.

Myelodysplastic Syndrome, Unclassifiable (MDS-U) With 1% Blasts Is a Distinct Subgroup of MDS-U With a Poor Prognosis

OBJECTIVES

Three situations qualify as myelodysplastic syndrome, unclassifiable (MDS-U): (1) refractory cytopenia with dysplasia and 1% blasts in peripheral blood (BL), (2) pancytopenia with unilineage dysplasia (Pan), and (3) persistent cytopenia, less than 5% bone marrow blasts, and less than 10% dysplastic cells and presence of MDS-defining cytogenetic abnormalities (CG). We compared the clinicopathologic features and mutational profiles for these three groups.

METHODS

MDS-U cases were reviewed at four major academic institutions. Targeted next-generation sequencing for genes implicated in myeloid neoplasms was performed in a subset of cases.

RESULTS

Twenty-seven patients were identified (six MDS-U BL, 13 MDS-U Pan, and eight MDS-U CG). Clonal cytogenetic abnormalities were found in six of six, seven of 13, and eight of eight cases in MDS-U BL, Pan, and CG, respectively (P > .05). Overall, four of six patients with MDS-U BL progressed to acute myeloid leukemia; no MDS-U Pan or CG patients did. The rates of progression-free survival and mortality (overall survival) were significantly higher in MDS-U BL compared with Pan and CG (P < .001 for both).

CONCLUSIONS

We find that MDS-U BL is a distinct subset of MDS-U with a poor prognosis, while MDS-U Pan and CG are relatively indolent. Evaluation of peripheral blood smears in patients with MDS is essential for accurate classification and prognosis.

JAK2, MPL, and CALR mutations in Chinese Han patients with essential thrombocythemia

BACKGROUND

Mutations in Janus kinase 2 (JAK2), myeloproliferative leukemia (MPL), and CALR are highly relevant to Philadelphia chromosome (Ph)-negative myeloproliferative neoplasms.

METHODS

Assessing the prevalence of molecular mutations in Chinese Han patients with essential thrombocythemia (ET), and correlating their mutational profile with disease characteristics/phenotype.

RESULTS

Of the 110 subjects studied, 62 carried the JAK2 V617F mutation, 21 had CALR mutations, one carried an MPL (W515) mutation, and 28 had non-mutated JAK2, CALR, and MPL (so-called triple-negative ET). Mutations in JAK2 exon 12 were not detected in any patient. Two ET patients had both CALR and JAK2 V617F mutations. Comparing the hematological parameters of the patients with JAK2 mutations with those of the patients with CALR mutations showed that the ET patients with CALR mutations were younger (p = 0.045) and had higher platelet counts (p = 0.043).

CONCLUSION

Genotyping for CALR could be a useful diagnostic tool for JAK2/MPL-negative ET, since the data suggest that CALR is much more prevalent than MPL, therefore testing for CALR should be considered in patients who are JAK2 negative as its frequency is almost 20 times that of MPL mutation.

CALR gene mutational profile in myeloproliferative neoplasms with non-mutated JAK2 in Moroccan patients: A case series and germline in-frame deletion

BACKGROUND

The discovery of somatic mutations within the gene encoding calreticulin (CALR) in 2013 represented a major milestone in the molecular diagnosis of BCR-ABL negative myeloproliferative neoplasms (MPN). In fact, exome sequencing revealed that most patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF) lacking JAK2 or MPL mutations, harbor somatic insertion and/or deletion in exon 9 of CALR gene. In this study, we identified the first CALR gene mutational landscape in Moroccan patients with MPN nonmutated for the JAK2 gene.

METHODS

We performed Sanger sequencing of exon 9 of CALR gene in blood samples obtained from 33 Moroccan patients with ET or PMF non-mutated for JAK2.

RESULTS

Of the 33 patients analyzed, we detected eight distinct variants in 15 patients (45.4%); six indel mutations, five with type 1 recurrent 52bp deletion, four with type 2 recurrent 5bp insertion and one in frame deletion which was found to be a germline variant suggesting a very rare condition in MPN.

CONCLUSION

This is the first cohort reported in CALR gene mutation analysis in Morocco. Our results were concordant with studies reported up to date and very encouraging in promoting the molecular diagnosis of myeloproliferative neoplasms in Moroccan patients. Moreover, the presence of a germline in frame deletion in a symptomatic patient should undermine the effectiveness of sizing assays without DNA sequencing in the diagnosis of CALR mutations.

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.

Frequencies, Laboratory Features, and Granulocyte Activation in Chinese Patients with CALR-Mutated Myeloproliferative Neoplasms

Somatic mutations in the CALR gene have been recently identified as acquired alterations in myeloproliferative neoplasms (MPNs). In this study, we evaluated mutation frequencies, laboratory features, and granulocyte activation in Chinese patients with MPNs. A combination of qualitative allele-specific polymerase chain reaction and Sanger sequencing was used to detect three driver mutations (i.e., CALR, JAK2V617F, and MPL). CALR mutations were identified in 8.4% of cases with essential thrombocythemia (ET) and 5.3% of cases with primary myelofibrosis (PMF). Moreover, 25% of polycythemia vera, 29.5% of ET, and 48.1% of PMF were negative for all three mutations (JAK2V617F, MPL, and CALR). Compared with those patients with JAK2V617F mutation, CALR-mutated ET patients displayed unique hematological phenotypes, including higher platelet counts, and lower leukocyte counts and hemoglobin levels. Significant differences were not found between Chinese PMF patients with mutants CALR and JAK2V617F in terms of laboratory features. Interestingly, patients with CALR mutations showed markedly decreased levels of leukocyte alkaline phosphatase (LAP) expression, whereas those with JAK2V617F mutation presented with elevated levels. Overall, a lower mutant rate of CALR gene and a higher triple-negative rate were identified in the cohort of Chinese patients with MPNs. This result indicates that an undiscovered mutant gene may have a significant role in these patients. Moreover, these pathological features further imply that the disease biology varies considerably between mutants CALR and JAK2V617F.

Calreticulin (CALR) mutation in myeloproliferative neoplasms (MPNs)

As a heterogeneous group of disease, myeloproliferative neoplasms (MPNs) have confused hematologists and hematopathologists with their protean clinical presentations and myriads of morphologies. A thought of classifying MPNs based on molecular alterations has gained popularity because there is increasing evidence that molecular or chromosomal alterations have a better correlation with clinical presentation, response to therapies, and prognosis than conventional morphological classification. This type of efforts has been facilitated by the advancement of molecular technologies. A significant number of gene mutations have been identified in MPNs with JAK2 and MPL being the major ones. However, a significant gap is present in that many cases of MPNs do not harbor any of these mutations. This gap is recently filled by the discovery of Calreticulin (CALR) mutation in MPNs without JAK2 or MPL mutation and since then, the clinical and molecular correlation in MPNs has become a hot research topic. There seems to be a fairly consistent correlation between CALR mutation and certain hematological parameters such as a high platelet count and a better prognosis in MPNs with CALR mutation. However, controversies are present regarding the risks of thrombosis, interactions of CALR with other gene mutation, the role of CALR in the pathogenesis, and the optimal treatment strategies. In addition, there are many questions remain to be answered, which all boiled down to the molecular mechanisms by which CALR causes or contributes to MPNs. Here, we summarized current published literatures on CALR mutations in MPNs with an emphasis on the clinical-molecular correlation. We also discussed the controversies and questions remain to be answered.

The Mutation Profile of Calreticulin in Patients with Myeloproliferative Neoplasms and Acute Leukemia

OBJECTIVE

Calreticulin (CALR) plays important roles in cell proliferation, apoptosis, and immune responses. CALR mutations were described recently in Janus kinase 2 gene (JAK2)-negative or MPL-negative primary myelofibrosis (PMF) and essential thrombocythemia (ET) patients. CALR trails JAK2 as the second most mutated gene in myeloproliferative neoplasms (MPNs). However, little is known about CALR mutation in Chinese patients with leukemia. In the present study, a cohort of 305 Chinese patients with hematopoietic neoplasms was screened for CALR mutations, with the aim of uncovering the frequency of CALR mutations in leukemia and MPNs.

MATERIALS AND METHODS

Polymerase chain reaction and direct sequencing were performed to analyze mutations of CALR in 305 patients with hematopoietic malignancies, including 135 acute myeloid leukemia patients, 57 acute lymphoblastic leukemia patients, and 113 MPN patients.

RESULTS

CALR mutations were found in 10.6% (12 of 113) of samples from patients with MPNs. CALR mutations were determined in 11.3% (6 of 53), 21.7% (5 of 23), and 9.1% (1/11) of patients with ET, PMF, and unclassifiable MPN, respectively.

CONCLUSION

We showed that MPN patients carrying CALR mutations presented with higher platelet counts and lower hemoglobin levels compared to those with mutated JAK2. However, all of the leukemia patients had negative results for CALR mutations.

CALR mutations screening in wild type JAK2(V617F) and MPL(W515K/L) Brazilian myeloproliferative neoplasm patients

Some myeloproliferative neoplasm (MPN) patients harbor JAK2(V617F) mutation, and CALR mutations were recently discovered in wild type (WT) JAK2(V617F). We evaluated the frequency and type of CALR mutations, and clinical and hematological characteristics in WT JAK2(V617F) and MPL(W515K/L) MPN patients. Sixty-five patients were included: 21 with primary myelofibrosis (PMF), 21 with myelofibrosis post-essential thrombocythemia (MPET) and 23 with essential thrombocythemia (ET). Screening for JAK2(V617F) and MPL(W515K/L) were performed using real-time PCR, while CALR mutations were analyzed by fragment analysis and Sanger sequencing. JAK2(V617F) was the most frequent mutation (54.5%) and one patient (1.5%) harbored MPL(W515L). CALR mutations were present in 38.1% of PMF, 12.5% of ET and 33.3% of MPET patients. Five types of CALR mutations were detected, among which type 1 (32.1%) and type 2 (21.4%) were found to be the most common. A novel CALR mutation in a PMF patient was found. Patients carrying CALR mutations had higher platelet count and less presence of splenomegaly than JAK2(V617F), while triple negatives had higher C-reactive protein levels than CALR mutant carriers. Screening for CALR mutations and its correlation with clinical features could be useful for the characterization of MPN patients and result in its incorporation into a new prognostic score.

JAK2 V617F, MPL, and CALR Mutations in Korean Patients with Essential Thrombocythemia and Primary Myelofibrosis

Mutations in the calreticulin gene, CALR, have recently been discovered in subsets of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF). We investigated Korean patients with ET and PMF to determine the prevalence, and clinical and laboratory correlations of CALR/JAK2/MPL mutations. Among 84 ET patients, CALR mutations were detected in 23 (27.4%) and were associated with higher platelet counts (P=0.006) and lower leukocyte counts (P=0.035) than the JAK2 V617F mutation. Among 50 PMF patients, CALR mutations were detected in 11 (22.0%) and were also associated with higher platelet counts (P=0.035) and trended to a lower rate of cytogenetic abnormalities (P=0.059) than the JAK2 V617F mutation. By multivariate analysis, triple-negative status was associated with shorter overall survival (HR, 7.0; 95% CI, 1.6-31.1, P=0.01) and leukemia-free survival (HR, 6.3; 95% CI, 1.8-22.0, P=0.004) in patients with PMF. The type 1 mutation was the most common (61.1%) type among all patients with CALR mutations, and tended toward statistical predominance in PMF patients. All 3 mutations were mutually exclusive and were never detected in patients with other myeloid neoplasms showing thrombocytosis. CALR mutations characterize a distinct group of Korean ET and PMF patients. Triple-negative PMF patients in particular have an unfavorable prognosis, which supports the idea that triple-negative PMF is a molecularly high-risk disease.

The Prevalence of JAK2, MPL, and CALR Mutations in Chinese Patients With BCR-ABL1-Negative Myeloproliferative Neoplasms

OBJECTIVES

To evaluate the mutation frequency of JAK2 V617F, JAK2 exon 12, MPL exon 10, and CALR exon 9 and the value of the combined tests in the diagnosis of BCR-ABL1-negative myeloproliferative neoplasms (MPNs).

METHODS

In the current study, mutations of JAK2 V617F, JAK2 exon 12, MPL exon 10, and CALR exon 9 were analyzed in 929 Chinese patients with BCR-ABL1-negative MPN, including 234 cases of polycythemia vera (PV), 428 ETs, 187 PMFs, and 80 unclassifiable MPNs (MPN-Us).

RESULTS

Our result showed that the positive rate of any of four mutations in patients with PV, ET, PMF, and MPN-U was 89.3%, 83.4%, 87.2%, and 77.5%, respectively, which significantly improved the diagnostic rate, especially in ET and PMF. Meanwhile, we also found that the patients without any of four mutations were younger than those with one or more mutations. Unexpectedly, the coexistence of JAK2 V617F and CALR exon 9 was identified in six (0.6%) patients, and JAK2 V617F and MPL exon 10 were present simultaneously in two (0.2%) patients. In addition, we also identified several novel mutation types in CALR exon 9.

CONCLUSIONS

The combined genetic tests of JAK2 V617F, JAK2 exon 12, MPL exon 10, and CALR exon 9 help improve the diagnostic rate for BCR-ABL1-negative MPN.

[CALR gene mutation detection and clinical observation of 150 essential thrombocythemia patients]

OBJECTIVE

To explore the prevalence of CARL gene mutations and the mutation types in patients with essential thrombocythemia (ET), and to compare the patients clinical characteristics of CALR mutation with JAK2 V617F, MPL W515K mutation patients and triple negative group.

METHODS

The mutations of CALR gene at extron 9 and MPL W515K in 150 ET patients were detected by PCR amplification followed by direct sequencing of genomic DNA, the JAK2 V617F mutation by using allele specific PCR.

RESULTS

(1)The CALR mutations were found in 38 patients (25.3%) of 150 ET patients. A total of 4 types of CALR mutations were identified (type Ic.1092_1143del52bp, n=17; type II c.1154_1155insTTGTC, n=16; type III c.1094_1139del46bp, n=4; type IV c.1103_1136del34bp, n=1). (2)The incidence of JAK2 V617F and MPL W515K was 61.3% (92/150) and 2.7% (4/150), respectively. The frequency of CALR mutation was 70.4% (38/54) in 54 ET patients without JAK2 V617F and MPL W515K mutations. The co-occurrence of any two kinds of gene mutations was not detected. (3)The hemoglobin level and leukocyte counts of patients with CARL mutations were significantly lower than that in patients with JAK2 V617F mutations (P<0.05). The median age of patients with CALR mutation was significantly higher than that of triple negative patients (59 years vs 29.5 years, P<0.01). Cytogenetic analysis was performed in 147 patients, and there were 4 abnormal karyotype cases. CALR mutation incidence was significantly higher in abnormal karyotype cases than that in normal ones (75% vs 24.5%, P=0.019).

CONCLUSION

The incidence of CALR mutations is high in ET patients without JAK2 V617F and MPL W515K mutations, and is associated with abnormal karyotype. CARL-mutated cases showed a significantly lower leucocyte and hemoglobin levels compared with JAK2 V617F mutated cases.

Frequency and allele burden of CALR mutations in Chinese with essential thrombocythemia and primary myelofibrosis without JAK2(V617F) or MPL mutations

CALR mutations are detected in about 50% of persons of predominately European descent with essential thrombocythemia (ET) or primary myelofibrosis (PMF) with wild-type alleles of JAK2 and MPL. We studied 1088 Chinese with diverse myeloproliferative neoplasms including ET (N=234) and PMF (N=50) without JAK2(V617F) or MPL exon 10 mutations. CALR mutation was detected in 53% (95% CI, 46-60%) of subjects with ET and 56% (95% CI, 41-70%) of subjects with PMF. 152 CALR mutations were identified clustering into 15 types including deletions (N=8), insertions (N=3) and complex indels (N=4). We also identified 9 new mutations. Mean (±SD) mutant allele burden was 31±12% (range, 0.5-69%). Persons with PMF had higher CALR mutant allele burdens than those with ET (38±8% vs. 29±12%; P<0.001). Amongst persons with CALR mutations, those with PMF had different clinical features from those with ET. These data may be useful for diagnosing ET and PMF in Chinese who are about 40% of all persons with ET and PMF and for monitoring therapy-response. They also highlight similarities and differences in CALR mutations between Chinese and persons of predominately European descent with these diseases.

The mutation profile of JAK2, MPL and CALR in Mexican patients with Philadelphia chromosome-negative myeloproliferative neoplasms

CONTEXT AND OBJECTIVE

By using molecular markers, it is possible to gain information on both the classification and etiopathogenesis of chronic myeloproliferative neoplasias (MPN).

METHODS

In a group of 27 Mexican mestizo patients with MPNs, we studied seven molecular markers: the BCR/ABL1 fusion gene, the JAK2 V617F mutation, the JAK2 exon 12 mutations, the MPL W515L mutation, the MPL W515K mutation, and the calreticulin (CALR) exon 9 deletion or insertion. Patients with the BCR/ABL1 fusion gene were excluded. We studied 14 patients with essential thrombocythemia (ET), eight with polycythemia vera (PV), four with primary myelofibrosis (MF), and one with undifferentiated MPN.

RESULTS

We found twelve individuals with the JAK2 V617F mutation; five of them had been clinically classified as PV, five as ET, and one as MF. One patient with the MPL W515L was identified with a clinical picture of ET. Five patients with the CALR mutation were identified, four ET and one MF. No individuals with either the MPL W515K mutation or the JAK2 exon 12 mutations were identified. The most consistent relationship was that between PV and the JAK2 V617F mutation (p=.01).

CONCLUSIONS

Despite its small size, the study shows much less prevalence of JAK2 mutation in PV, ET and MF, which does not match international data.

Clinical relevance between CALR mutation and myeloproliferative neoplasms

In late 2013, somatic mutations in calreticulin (CALR), mainly those involving insertions and deletions in exon 9, attracted the great attention of hematologists and researchers. These JAK2- and MPL- mutual exclusive mutations enjoy a favorable specificity and prevalence (20-30%) in patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF), suggesting promise for these mutations in disease management. Moreover, these genetic variations are now also considered as a group of independent risk factors for disease prognosis. In this mini-review, we will document the value of CALR mutations in disease diagnosis, prognosis, and therapeutic strategy selection, and we will discuss current advances in methods to detect these mutations.

[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.

Rapid and sensitive detection of CALR exon 9 mutations using high-resolution melting analysis

BACKGROUND

Somatic CALR exon 9 mutations have recently been identified in patients with JAK2/MPL-unmutated myeloproliferative neoplasm, and have become an important clonal marker for the diagnosis of essential thrombocythemia (ET) and primary myelofibrosis. In the present study, we sought to use high-resolution melting analysis (HRMA) as a screening method for the detection of CALR mutations.

METHODS

32 JAK2/MPL-unmutated ET patients were retrospectively enrolled and 8 healthy adults were used as wild-type control. CALR exon 9 mutation was independently screened by HRMA with the CFX Connect real-time system and Sanger sequencing. TA-cloning was used to detect CALR exon 9 mutations in patients suspected to have low mutant allele burden.

RESULTS

The maximal sensitivity of HRMA in identifying both CALR type 1 and type 2 mutants from patients' genomic DNA was 2.5%. Twenty-two samples were found to have distinct melting curves from wild-type. The presence of CALR mutations in 16 of these 22 samples was confirmed by Sanger sequencing, while the other 6 samples were wild-type by sequencing. After TA-cloning, CALR mutations were detected in 5 of 6 patients from 1 (6%) of 16 clones to 1 (2%) of 50 clones. Therefore, HRMA identified CALR mutations in 21 (65.6%) of 32 ET patients compared to 16 (50%) patients by Sanger sequencing, with a false positive rate of 3% and no false negative.

CONCLUSION

The HRMA developed in our system is a rapid and sensitive technique for the detection of CALR exon 9 mutations.