Characterization and Prognosis Significance of JAK2 (V617F), MPL, and CALR Mutations in Philadelphia-Negative Myeloproliferative Neoplasms

Association of JAK2V617F allele burden and clinical correlates in polycythemia vera: a systematic review and meta-analysis

Janus kinase 2 (JAK2) V617F mutation is present in most patients with polycythemia vera (PV). One persistently puzzling aspect unresolved is the association between JAK2V617F allele burden (also known as variant allele frequency) and the relevant clinical characteristics. Numerous studies have reported associations between allele burden and both hematologic and clinical features. While there are strong indications linking high allele burden in PV patients with symptoms and clinical characteristics, not all associations are definitive, and disparate and contradictory findings have been reported. Hence, this study aimed to synthesize existing data from the literature to better understand the association between JAK2V617F allele burden and relevant clinical correlates. Out of the 1,851 studies identified, 39 studies provided evidence related to the association between JAK2V617F allele burden and clinical correlates, and 21 studies were included in meta-analyses. Meta-analyses of correlation demonstrated that leucocyte and erythrocyte counts were significantly and positively correlated with JAK2V617F allele burden, whereas platelet count was not. Meta-analyses of standardized mean difference demonstrated that leucocyte and hematocrit were significantly higher in patients with higher JAK2V617F allele burden, whereas platelet count was significantly lower. Meta-analyses of odds ratio demonstrated that patients who had higher JAK2V617F allele burden had a significantly greater odds ratio for developing pruritus, splenomegaly, thrombosis, myelofibrosis, and acute myeloid leukemia. Our study integrates data from approximately 5,462 patients, contributing insights into the association between JAK2V617F allele burden and various hematological parameters, symptomatic manifestations, and complications. However, varied methods of data presentation and statistical analyses prevented the execution of high-quality meta-analyses.

JAK2, CALR, and MPL Mutation Profiles in Colombian patients with BCR-ABL Negative Myeloproliferative Neoplasms

Background

Among the chronic myeloproliferative neoplasms (MPNs) not associated with BCR-ABL mutations are polycythemia vera, primary myelofibrosis, and essential thrombocythemia. These diseases are caused by mutations in genes, such as the JAK2, MPL, and CALR genes, which participate in regulating the JAK-STAT signaling pathway.

Objective

This study aimed to establish the frequencies of mutations in the JAK2, MPL, and CALR genes in a group of Colombian patients with a negative clinical diagnosis of BCR-ABL chronic myeloproliferative neoplasms.

Methods

The JAK2 V617F and MPL W515K mutations and deletions or insertions in exon 9 of the CALR gene were analyzed in 52 Colombian patients with polycythemia vera, primary myelofibrosis, and essential thrombocythemia.

Results

The JAK2V617F mutation was carried by 51.9% of the patients, the CALR mutation by 23%, and the MPL mutation by 3.8%; 23% were triple-negative for the mutations analyzed. In these neoplasms, 6 mutation types in CALR were identified, one of which has not been previously reported. Additionally, one patient presented a double mutation in both the CALR and JAK2 genes. Regarding the hematological results for the mutations, significant differences were found in the hemoglobin level, hematocrit level, and platelet count among the three neoplasms.

Conclusion

Thus, this study demonstrates the importance of the molecular characterization of the JAK2, CALR and MPL mutations in Colombian patients (the genetic context of which remains unclear in the abovementioned neoplasms) to achieve an accurate diagnosis, a good prognosis, adequate management, and patient survival.

A customized mass array panel for BCR::ABL1 tyrosine kinase domain mutation screening in chronic myeloid leukemia

Introduction

The therapeutic strategy and management of chronic myeloid leukemia (CML) have rapidly improved with the discovery of effective tyrosine kinase inhibitors (TKIs) to target BCR::ABL1 oncoprotein. However, nearly 30% of patients develop TKI resistance due to acquired mutations on the tyrosine kinase domain (TKD) of BCR::ABL1.

Methods

We customized a mass array panel initially intended to detect and monitor the mutational burden of hotspot BCR::ABL1 TKD mutations accumulated in our database, including key mutations recently recommended by European LeukemiaNet. Additionally, we extended the feasibility of using the assay panel for the molecular classification of myeloproliferative neoplasms (MPNs) by incorporating primer sets specific for analyzing JAK2 V617F, MPL 515 K/L, and CALR types 1 and 2.

Results

We found that the developed mass array panel was superior for detecting and monitoring clinically significant BCR::ABL1 TKD mutations, especially in cases with low mutational burden and harboring compound/polyclonal mutations, compared with direct sequencing. Moreover, our customized mass array panel detected common genetic alterations in MPNs, and the findings were consistent with those of other comparable assays available in our laboratory.

Conclusions

Our customized mass array panel was practicably used as a routine robust assay for screening and monitoring BCR::ABL1 TKD mutations in patients with CML undergoing TKI treatment and feasible for analyzing common genetic mutations in MPNs.

JAK2 p.(V617F) mutation in Tunisian myeloproliferative neoplasms and its genotype-phenotype correlation

Myeloproliferative neoplasms (MPNs) comprise polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). The relationship between JAK2 p.(V617F) mutation and MPNs was first described in 2005. The purpose of this study was to determine the prevalence of JAK2 p.(V617F) mutation in Tunisian patients assessed for MPNs and try to set a genotype-phenotype correlation. A retrospective study was conducted between January 2015 and April 2019. We collected the clinical data of all patients with MPNs suspicion or atypical splanchnic vein thrombosis (SVT). JAK2 p.(V617F) mutation was detected by allele specific real-time quantitative fluorescence PCR (AS-qPCR). We gathered 974 patients who underwent molecular analysis, 55.5% of them were male and 44.5% were female. The median age of all studied patients was 56 years. JAK2 p.(V617F) was found in 349 (35.8%) of total enrolled cases. It was reported in 44%, 37%, 29% and 25% of all patients diagnosed as having respectively ET, PV, PMF and atypical SVT. JAK2 p.(V617F) was negative in 62.2% of patients addressed for suspicion of PV. There was a significant positive correlation between the JAK2 p.(V617F) mutation status, age, gender, white blood cell counts and platelet counts. To our best knowledge, this is the first vast investigation of JAK2 p.(V617F) variant in Tunisia and North Africa with the lowest mutation rate in entire cohort and MPNs subgroups, underlying a specific presentation of this mutation. It is considered as an essential marker of MPNs’ diagnosis and prognosis and is associated with differences in the phenotype of these disorders, helpful for the follow-up of these patients.

Splenic and Portal Vein Thrombosis With Concurrent Splenic Infarction: A Rare Manifestation of Essential Thrombocythemia

Mesenteric venous thrombosis (MVT) presents with a wide range of clinical presentations depending on the vessel involved, degree of thrombosis, and the extent of bowel wall ischemia. MVT usually has an insidious presentation and is often a forerunner of an underlying disorder. Essential thrombocythemia (ET) presenting itself as MVT along with splenic infarction is a rare presentation. Here, we report the case of a 54-year-old female with massive splenomegaly, thrombocytosis, and acute splenic and portal venous thrombosis along with multiple splenic infarcts. Bone marrow suggested ET with JAK2V617F mutation positivity. She was managed conservatively and made an uneventful recovery.

Relationship of JAK2 (V617F) Allelic Burden with Clinico- Haematological Manifestations of Philadelphia-Negative Myeloproliferative Neoplasms

JAK2 (V617F) allelic burden is the main genetic driver behind and a potential differentiator between individual myeloproliferative neoplasm (MPN) subtypes. This study aimed to explore the relationship between JAK2 (V617F) allelic burden, MPN subtypes and their clinico-haematological manifestations in a Singapore-based cohort. Analysis was performed on a retrospectively collected dataset of 128 patients diagnosed with JAK2 (V617F) positive Philadelphia-negative MPNs between 2016 to 2017 in Singapore. Genomic analysis was conducted on blood samples via DNA extraction and Droplet Digital Polymerase Chain Reaction (ddPCR). The mean age was 62.4 (SD=14.1). 85 out of the 128 (66.4%) patients were male. There was a statistically significant difference in allelic burdens between the different MPN disease subtypes χ2(3) = 9.064, p=0.028, with essential thrombocytosis (ET) patients having the lowest mean JAK2 percentage allelic burden (26.5%). Patients with an allelic burden >50% had higher leukocyte counts (MWU 1016.5, p=0.001), haemoglobin levels (MWU 1287.0, p=0.045), lactate dehydrogenase levels (MWU 611.5, p=0.001), and lower platelet levels (MWU 1164.0, p=0.008). Subgroup analysis revealed none of these correlations was significant in the ET subgroup. The results are largely in concordance with previous research in Asian cohorts demonstrating the association between allelic burden and clinico-haematological manifestations of MPN. However, in the ET subgroup, the JAK2 (V617F) allelic burden do not correlate positively for haematological parameters which is only seen in Asian patients.<br />.

Evaluation of the JAK2V617F Mutational Burden in Patients with Philadelphia Chromosome Negative Myeloproliferative Neoplasms: A Single-center Experience

The identification of the JAK2V617F mutation in several distinct myeloproliferative neoplasms (MPNs) raised the question how one single mutation incites expression of at least three different clinical phenotypes, i.e., polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). In order to further evaluate already published data on the correlation between mutant JAK2V617F allele burden and specific hematological and clinical parameters, we tested the level of the JAK2 mutation in 134 JAK2+ patients with different MPNs. The patients were diagnosed according to the 2008 WHO criteria and followed for a median of 48 months. The JAK2 V617F quantification was done with a real time polymerase chain reaction (real time-PCR) method. The median allele burden was lowest in ET (25.8%), followed by 34.6% in PV and 51.8% in PMF patients (p<0.01). There was statistically significant association between the mutational load of 10.0-50.0% and blood count parameters in the PV patients (p<0.05). In PMF patients the mutational load was in correlation with older age and leukocyte count that were higher in patients with the mutational load of 10.0-50.0% and >50.0% compared to those with a mutational load of <10.0%. There were no statistically significant associations between the allele burden and blood counts in the ET cohort. Our study confirmed an association between the JAK2V617F allele burden and the distinct MPN phenotypes, indicating unfavorable prognosis in patients with a higher JAK2 allele burden. Our results suggest that JAK2 quantification should be incorporated in the diagnostic work-up of MPN patients as a useful tool for optimal treatment decision.