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

Advances in Molecular Understanding of Polycythemia Vera, Essential Thrombocythemia, and Primary Myelofibrosis: Towards Precision Medicine

Myeloproliferative neoplasms (MPNs), including Polycythemia Vera (PV), Essential Thrombocythemia (ET), and Primary Myelofibrosis (PMF), are characterized by the clonal proliferation of hematopoietic stem cells leading to an overproduction of hematopoietic cells. The last two decades have seen significant advances in our understanding of the molecular pathogenesis of these diseases, with the discovery of key mutations in the JAK2, CALR, and MPL genes being pivotal. This review provides a comprehensive update on the molecular landscape of PV, ET, and PMF, highlighting the diagnostic, prognostic, and therapeutic implications of these genetic findings. We delve into the challenges of diagnosing and treating patients with prognostic mutations, clonal evolution, and the impact of emerging technologies like next-generation sequencing and single-cell genomics on the field. The future of MPN management lies in leveraging these molecular insights to develop personalized treatment strategies, aiming for precision medicine that optimizes outcomes for patients. This article synthesizes current knowledge on molecular diagnostics in MPNs, underscoring the critical role of genetic profiling in enhancing patient care and pointing towards future research directions that promise to further refine our approach to these complex disorders.

Exploring the Molecular Landscape of Myelofibrosis, with a Focus on Ras and Mitogen-Activated Protein (MAP) Kinase Signaling

Myelofibrosis (MF) is a clonal myeloproliferative neoplasm (MPN) characterized clinically by cytopenias, fatigue, and splenomegaly stemming from extramedullary hematopoiesis. MF commonly arises from mutations in JAK2, MPL, and CALR, which manifests as hyperactive Jak/Stat signaling. Triple-negative MF is diagnosed in the absence of JAK2, MPL, and CALR but when clinical, morphologic criteria are met and other mutation(s) is/are present, including ASXL1, EZH2, and SRSF2. While the clinical and classic molecular features of MF are well-established, emerging evidence indicates that additional mutations, specifically within the Ras/MAP Kinase signaling pathway, are present and may play important role in disease pathogenesis and treatment response. KRAS and NRAS mutations alone are reportedly present in up to 15 and 14% of patients with MF (respectively), and other mutations predicted to activate Ras signaling, such as CBL, NF1, BRAF, and PTPN11, collectively exist in as much as 21% of patients. Investigations into the prevalence of RAS and related pathway mutations in MF and the mechanisms by which they contribute to its pathogenesis are critical in better understanding this condition and ultimately in the identification of novel therapeutic targets.

Clinicopathologic characteristics of myeloproliferative neoplasms with JAK2 exon 12 mutation

The presence of JAK2 exon 12 mutation was included by the 2016 World Health Organization (WHO) Classification as one of the major criteria for diagnosing polycythemia vera (PV). Few studies have evaluated the clinical presentation and bone marrow morphology of these patients and it is unclear if these patients fulfill the newly published criteria of 5th edition WHO or The International Consensus Classification (ICC) criteria for PV. Forty-three patients with JAK2 exon 12 mutations were identified from the files of 7 large academic institutions. Twenty patients had complete CBC and BM data at disease onset. Fourteen patients met the diagnostic criteria for PV and the remaining six patients were diagnosed as MPN-U. At diagnosis, 9/14 patients had normal WBC and platelet counts (isolated erythrocytosis/IE subset); while 5/14 had elevated WBC and/or platelets (polycythemic /P subset). We found that hemoglobin and hematocrit tended to be lower in the polycythemia group. Regardless of presentation (P vs IE), JAK2 deletion commonly occurred in amino acids 541-544 (62 %). MPN-U patients carried JAK2 exon 12 mutation, but did not fulfill the criteria for PV. Half of the patients had hemoglobin/hematocrit below the diagnostic threshold for PV, but showed increased red blood cell count with low mean corpuscular volume (56-60 fL). Three cases lacked evidence of bone marrow hypercellularity. In summary, the future diagnostic criteria for PV may require a modification to account for the variant CBC and BM findings in some patients with JAK2 exon 12 mutation.

Genetic and Clinical Characteristics of Patients with Philadelphia-Negative Myeloproliferative Neoplasm Carrying Concurrent Mutations in JAK2V617F, CALR, and MPL

Simultaneous mutations in Janus kinase 2 (JAK2), calreticulin, and myeloproliferative leukemia (MPL) genes are generally not considered for characterizing Philadelphia-negative myeloproliferative neoplasms (MPNs), leading to misdiagnosis. Sanger sequencing and quantitative polymerase chain reaction were used to detect gene mutations in patients with MPN. We retrospectively screened the data of patients with double mutations in our center and from the PubMed database. Two patients tested positive for both JAK2V617F and CALR mutations (2/352 0.57%) in our center, while data of 35 patients from the PubMed database, including 26 patients with essential thrombocythemia (ET), 6 with primary myelofibrosis (PMF), 2 with unexplained thrombosis, and 1 with polycythemia vera were screened for double mutations. Among these mutations, co-mutation of JAKV617F-CALR constituted the majority (80.0%), when compared with JAKV617F-MPL (17.1%) and CALR-MPL (2.9%) mutations. Moreover, patients with concurrent mutational myeloproliferative neoplasm (MPN) were relatively older (P  =  .010) with significantly higher platelet counts than their counterparts with single gene mutations (P < .001). The occurrence of palpable splenomegaly (P < .001) and leukocyte count (P  =  .041) were also significantly different between patients with single and simultaneous gene mutations. These 4 risk factors also showed significant test effectiveness in the ET and PMF cohorts (P < .05). In terms of clinical characteristics of patients with ET, those with JAK2V617F-CALR mutation had higher but normal hemoglobin levels (P  =  .0151) than those carrying JAK2V617F-MPL mutation. From a clinical perspective, patients with multiple mutational MPN are different from those with single gene mutations. The poor treatment response by patients in our center and unfavorable indicators for patients with co-mutations in published literature indicate that customized treatment may be the best choice for patients with MPN carrying co-mutations.

A facile and high-sensitive bio-sensing of the V617F mutation in JAK2 gene by GSH-CdTe-QDs FRET-based sensor

This study aimed to directly detect the V617F point mutation of the Janus kinase 2 (JAK2) gene in the target DNA using a FRET-based biosensor. The water-soluble GSH-CdTe-QDs were synthesized by a one-step process, then GSH-QD conjugated to the termini amino-modified oligonucleotides target via carboxylic groups on the QD surface. The prepared QDs-DNA biosensor was applied in the quantitative and rapid detection of V617F mutation with a detection limit of 3 × 10^-9 mol L^-1 based on the FRET mechanism. In other words, detecting the V617F mutation by bio-sensing technology would be much simpler, cheaper, time-saving, highly sensitive, and more convenient than molecular diagnostic tools. Furthermore, the nano-biosensor was applied to detect the V617F mutation in clinical samples compared to the common ARMS-PCR (Amplification Refractory Mutation System-Polymerase Chain Reaction) standard method. The results revealed that the GSH-capped biosensors would be effective for V617F mutation detection in samples distinguished with satisfactory analytical outcomes. Therefore, the designed fluorescence nanoprobe is suitable for the specific detection of V617F mutation of the JAK2 gene in clinical samples.

[Clinical and laboratory features compared between JAK2 exon12 and JAK2 V617F mutated polycythemia vera]

Objective: To compare clinical and laboratory features between JAK2 exon12 and JAK2 V617F mutated polycythemia vera (PV) . Method: We collected data from 570 consecutive newly-diagnosed subjects with PV and JAK2 mutation, and compared clinical and laboratory features between patients with JAK2 exon12 and JAK2 V617F mutation. Results: 543 (95.3%) subjects harboured JAK2 V617F mutation (JAK2 V617F cohort) , 24 (4.2%) harboured JAK2 exon12 mutations (JAK2 exon12 cohort) , and 3 (0.5%) harboured JAK2 exon12 and JAK2 V617F mutations. The mutations in JAK2 exon12 including deletion (n=10, 37.0%) , deletion accompanied insertion (n=10, 37.0%) , and missense mutations (n=7, 25.9%) . Comparing with JAK2 V617F cohort, subjects in JAK2 exon12 cohort were younger [median age 50 (20-73) years versus 59 (25-91) years, P=0.040], had higher RBC counts [8.19 (5.88-10.94) ×10(12)/L versus 7.14 (4.11-10.64) ×10(12)/L, P<0.001] and hematocrit [64.1% (53.7-79.0%) versus 59.6% (47.2%-77.1%) , P=0.001], but lower WBC counts [8.29 (3.2-18.99) ×10(9)/L versus 12.91 (3.24-38.3) ×10(9)/L, P<0.001], platelet counts [313 (83-1433) ×10(9)/L versus 470 (61-2169) ×10(9)/L, P<0.001] and epoetin [0.70 (0.06-3.27) versus 1.14 (0.01-10.16) IU/L, P=0.002] levels. We reviewed bone marrow histology at diagnosis in 20 subjects with each type of mutation matched for age and sex. Subjects with JAK2 exon12 mutations had fewer loose megakaryocyte cluster (40% versus 80%, P=0.022) compared with subjects with JAK2 V617F. The median follow-ups were 30 months (range 4-83) and 37 months (range 1-84) for cohorts with JAK2 V617F and JAK2 exon12, respectively. There was no difference in overall survival (P=0.422) and thrombosis-free survival (P=0.900) . Conclusions: Compared with patients with JAK2 V617F mutation, patients with JAK2 exon12 mutation were younger, and had more obvious erythrocytosis and less loose cluster of megakaryocytes.

Diagnostic Performance of Erythropoietin Levels in Polycythemia Vera: Experience at a Comprehensive Cancer Center

INTRODUCTION

Considering the evolving diagnostic criteria of polycythemia vera (PV), we analyzed the utility of serum erythropoietin (EPO) as a predictive marker for differentiating polycythemia vera (PV) from other etiologies of erythrocytosis.

PATIENTS AND METHODS

We conducted a retrospective study after a review of electronical medical records from January 2005 to December 2016 with diagnosis of erythrocytosis using International Classification of Disease-specific codes. To evaluate the diagnostic performance of EPO levels and JAK2-V617F mutation, we constructed a receiver-operated characteristic curve of sensitivity versus 1-specificity for serum EPO levels and JAK2-V617F mutation as predictive markers for differentiating PV from other causes of erythrocytosis.

RESULTS

We surveyed 577 patients with erythrocytosis. Median patient age was 59.2 years, 57.72% (n = 329) were male, 86.3% (n = 491) were white, and only 3.3% (n = 19) were African American. A total of 80.88% (n = 351) of those diagnosed with PV had a JAK2-V617F mutation compared to only 1.47% (n = 2) whose primary diagnosis was secondary polycythemia. When comparing JAK2-V617 mutation to the EPO level, the area under the curve of JAK2-V617 (0.8970) was statistically larger than that of EPO test (0.6765). Therefore, the PV diagnostic methodology using JAK2-V617 is better than the EPO test. An EPO level of < 2 mIU/mL was > 99% specific to predict PV but was only 12% sensitive.

CONCLUSION

In the appropriate clinical setting, cytogenetic and molecular studies such as JAK2 mutation status prevail as the most useful tools for PV case identification. The use of isolated EPO to screen patients with erythrocytosis is not a good diagnostic approach.

Mutation profile in BCR-ABL1-negative myeloproliferative neoplasms: A single-center experience from India

OBJECTIVE/BACKGROUND

Recurrent somatic mutations in the JAK2, calreticulin (CALR), and the MPL genes are described as drivers of BCR-ABL1-negative myeloproliferative neoplasms (MPN) that includes polycythemia vera (PV), essential thrombocytosis (ET), primary myelofibrosis (PMF), and MPN unclassified (MPN-U).

METHODS

We describe the mutation profile and clinical features of MPN cases diagnosed at a tertiary care center. JAK2V617F and MPL (S505/W515) mutations were screened by allele-specific polymerase chain reaction, while CALR exon 9 and JAK2 exon 12 mutations were screened by fragment analysis/Sanger sequencing. Among the 1,570 patients tested for these mutations during the study period, 407 were classified as MPN with a diagnosis of PV, ET, PMF, and MPN-U seen in 30%, 17%, 36%, and 17%, respectively, screened.

RESULTS

Similar to previous reports from Asian countries, the incidence of PMF was the highest among the classic MPN. JAK2V617F mutation was detected in 90% of PV, 38% of ET, 48% of PMF, and 65% of MPN-U. JAK2 exon 12 mutations were seen in 5.7% of PV and 1.4% of PMF. CALR exon 9 mutations were seen in 33% of ET, 33% of PMF, and 12% of MPN-U. MPL mutations were detected in 2.8%, 2.7%, and 2.9% of ET, PMF, and MPN-U, respectively. Fifteen % of PMF, 26% of ET, and 22% of MPN-U were triple negative.

CONCLUSION

There was a significantly higher incidence of CALR mutation in PMF and ET cases. Our study highlights the challenges in the diagnosis of JAK2-negative PV and the need for harmonization of criteria for the same.