Evaluation of JAK2 in B and T cell neoplasms: identification of JAK2(V617F) mutation of undetermined significance (JMUS) in the bone marrow of three individuals

Expression of CD markers in JAK2V617F positive myeloproliferative neoplasms: Prognostic significance

Myeloproliferative neoplasms (MPNs) are clonal stem cell disorders characterized by the presence of JAK2^V617F mutation. Thrombohemorrhagic as well as autoimmune or inflammatory phenomena are common clinical outcomes of these disorders. Recent studies have shown that abnormality in frequency and function of blood cells manifested by an alteration in CD markers' expression patterns play a key role in these complications. So, there may be a relationship between CD markers' expressions and prognosis of JAK2^V617F positive MPNs. Therefore, in this review, we have focused on these abnormalities from the perspective of changing expressions of CD markers and assessment of the relationship between these changes with prognosis of JAK2^V617F positive MPNs. It can be stated that the abnormal expression of a large number of CD markers can be used as a prognostic biomarker for clinical outcomes including thrombohememorrhagic events, as well as autoimmune and leukemic transformation in JAK2^V617F positive MPNs. Considering the possible role of CD markers' expressions in JAK2^V617F MPNs prognosis, further studies are needed to confirm the relationship between the expression of CD markers with prognosis to be able to find an appropriate therapeutic approach via targeting CD markers.

Bone marrow fibrosis in chronic myelomonocytic leukemia is associated with increased megakaryopoiesis, splenomegaly and with a shorter median time to disease progression

Bone marrow (BM) fibrosis is an adverse prognostic marker in several myeloid neoplasms, particularly in myelodysplastic syndrome (MDS) with fibrosis; however, its significance in chronic myelomonoctyic leukemia (CMML) has not been evaluated. We performed a retrospective analysis to investigate the prognostic and clinicopathological features of CMML with and without BM fibrosis. The study included specimens from a total of 83 untreated CMML patients from 2 large institutions. Patients with any amount of BM fibrosis (MF-1 or higher; MF1+) had significantly shorter progression-free survival (MF1+, 28.3 months vs MF0, not reached; p = 0.001, log rank test), splenomegaly (p = 0.016), and increased BM megakaryocytes (p = 0.04) compared to patients without BM fibrosis (MF-0). No association was observed between fibrosis and peripheral blood parameters, presence of JAK2 V617F mutation, BM blasts, or overall survival. Our study demonstrates the importance of assessing BM fibrosis in CMML. Similar to MDS, the presence of BM fibrosis may identify a distinct subgroup of CMML patients (CMML-F) with a more aggressive clinical course.

JAK2 V617F detected in two B-cell chronic lymphocytic leukemia patients without coexisting Philadelphia chromosome-negative myeloproliferative neoplasms: A report of two cases

The JAK2 V617F mutation has been observed in patients with Philadelphia chromosome-negative myeloproliferative neoplasms (Ph-MPNs), including polycythemia vera, essential thrombocythemia and idiopathic myelofibrosis. This mutation has also been observed in a small number of other myeloid malignancies, such as acute myeloid leukemia, chronic myeloid leukemia and myelodysplastic syndrome. The JAK2 V617F allele has rarely been evaluated in lymphoproliferative disorders. In total, 28 JAK2 V617F-positive B-cell lymphocytic leukemia (B-CLL) patients have previously been reported and all presented with Ph-MPN concomitantly. However, following investigation of the JAK2 V617F mutation in 63 B-CLL patients at the Shanghai First People’s Hospital (Shanghai, China) between January 2008 and December 2012 via allele-specific polymerase chain reaction, two B-CLL patients without a history of Ph-MPN were identified to carry the JAK2 V617F allele.

A rare case of primary cutaneous follicle centre lymphoma presenting as a giant tumour of the scalp and combined with JAK2V617F positive essential thrombocythaemia

Primary cutaneous follicle centre lymphoma (PCFCL) is a rare cutaneous B cell lymphoma in middle-age adults with excellent prognosis. Here we present a case of a patient with a PCFCL in the form of a giant tumour of the scalp in combination with a myeloproliferative neoplasm, JAK2V617F positive essential thrombocythaemia. This case may be of interest because of the favourable outcome in spite of the large size of the PCFCL, the rare combination with essential thrombocythaemia and because it contributes to discussion on the role of JAK2 mutation in such patients.

Laboratory detection of JAK2V617F in human myeloproliferative neoplasms

Recently, a point mutation in the JAK2 gene, JAK2 (V617F) , was discovered in several myeloid proliferative neoplasms including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Demonstration of the mutation and other similar mutations has now become one of the major criteria in the diagnosis of these neoplasms in the revised World Health Organization Classification of Tumors of Hematopoietic Tissues. In this chapter, we compared the advantages and disadvantages of five commonly used methods for the detection of JAK2 (V617F) . We explained, based on the current literature, why analytic sensitivity of the methodology is of particular importance for the detection of JAK2 (V617F) . A detailed laboratory procedure for the performance of an extensively optimized ARMS-PCR assay was presented. The assay shows distinct patterns for normal, mutant, and mixed genotypes. Diagnostically, it is highly sensitive, highly specific, and simple to perform with no need for any specialized equipment other than thermocyclers.

Simultaneous and sequential concurrent myeloproliferative and lymphoproliferative neoplasms

Concurrent manifestation of two chronic-stage myeloid and lymphoid/plasmacytoid neoplasms in one patient is rare and occurs in ≤1% of patients. There has been no systematic analysis of which combinations are frequent/infrequent and whether two concurrent diseases in one patient are clonally related or represent independent diseases. We therefore characterised a series of cases from our own archive (n = 65) and collected a large number of previously reported cases of patients in whom myeloid and lymphoid/plasmacytoid neoplasms co-occurred (n = 185). The most frequent combination was Philadelphia chromosome-negative myeloproliferative neoplasm with concurrent B cell chronic lymphocytic leukaemia, accounting for approximately 50% of double-disease patients. We compared the quantity of unsorted bone marrow cell-derived JAK2(V617F) and KIT(D816V) alleles with the quantity of the lymphoid/plasmacytoid compartment and analysed a subfraction of cases with fluorescence in situ hybridisation. Although a common aberrant progenitor has been reported in some cases in the literature, we found evidence of two independent chronic-stage myeloid and lymphoid/plasmacytoid neoplasms.

The role of molecular genetic analysis within the diagnostic haemato-oncology laboratory

The identification of the molecular genetic basis to many haematological malignancies along with the increased use of molecularly targeted therapy has heralded an increasing role for molecular genetic-based techniques. Demonstration of acquired changes such as the JAK2 V617F mutation within myeloproliferative neoplasms has quickly moved from a research setting to the diagnostic laboratory. Disease-specific genetic markers, such as the BCR-ABL1 fusion gene in chronic myeloid leukaemia, enable sensitive molecular genetic methods to be applied for the detection and quantification of low-level residual disease, allowing early identification of relapse. Consequently, molecular genetics now plays a crucial role in diagnosis, the identification of prognostic markers and monitoring of haematological malignancies. The development of high-throughput whole-genome approaches offers the potential to rapidly screen newly diagnosed patients for all disease-associated molecular genetic changes.

JAK2(V617F) allele burden in polycythemia vera correlates with grade of myelofibrosis, but is not substantially affected by therapy

In a series of 105 patients with polycythemia vera, we retrospectively determined whether the JAK2(V617F) mutation correlated with severity of disease phenotype. Higher JAK2(V617F) allele burden correlated with more advanced myelofibrosis, greater splenomegaly, and higher white blood cell count, but not with age, gender, hematocrit level, or frequency of phlebotomy prior to cytoreductive therapy. Although a subgroup at increased risk for thrombosis was not clearly defined, there was a suggestion that frequency of thrombosis increased as the JAK2(V617F) allele burden increased. The JAK2(V617F) allele burden did not change significantly in treated patients with serial JAK2 analyses.

Distinct patterns of cytogenetic and clinical progression in chronic myeloproliferative neoplasms with or without JAK2 or MPL mutations

Chronic myeloproliferative neoplasms (MPN), including essential thrombocythemia (ET) and primary myelofibrosis (PMF), result from interactions between initiating growth factor mutations and secondary genomic changes. Codon 617 mutation of the JAK2 kinase is found in 40-50% of ET/PMF, whereas the mutation of codon 515 in the JAK2-linked thrombopoietin receptor MPL is found in approximately 20% of JAK2-unmutated cases of ET and PMF. Using quantitative mutation assays, we compared patterns of clinical and cytogenetic progression in MPL-mutated MPN (n=21) to those with JAK2 V617F mutation (n=383) or neither mutation (n=109). Among patients with MPL mutations, ET was seen in 9 and PMF in 12. Median mutation levels in pretreatment ET samples were significantly higher for MPL-mutated cases (60%) than for JAK2-mutated cases (24%; P=0.01), as was presentation with anemia. Differential genomic changes included +9 in JAK2-mutated cases and chromosome 1 alterations in MPL-mutated ones, implicating dosage effects related to gene copy number. Decreases in the levels of MPL mutation were seen in sequential marrow samples from some patients under treatment with biologic therapies, but not in those treated with kinase inhibitors, consistent with selective response of the MPL-mutated clone similar to the responses seen in JAK2-mutated MPN.

Comparison of mutated ABL1 and JAK2 as oncogenes and drug targets in myeloproliferative disorders

Constitutively activated mutants of the non-receptor tyrosine kinases (TK) ABL1 (Abelson murine leukemia viral (v-abl) homolog (1) protein) and JAK2 (JAnus Kinase 2 or Just Another Kinase 2) play a central role in the pathogenesis of clinically and morphologically distinct chronic myeloproliferative disorders but are also found in some cases of de novo acute leukemia and lymphoma. Ligand-independent activation occurs as a consequence of point mutations or insertions/deletions within functionally relevant regulatory domains (JAK2) or the creation of TK fusion proteins by balanced reciprocal translocations, insertions or episomal amplification (ABL1 and JAK2). Specific abnormalities are correlated with clinical phenotype, although some are broad and encompass several World Health Organization-defined entities. TKs are excellent drug targets as exemplified by the activity of imatinib in BCR-ABL1-positive disease, particularly chronic myeloid leukemia. Resistance to imatinib is seen in a minority of cases and is often associated with the appearance of secondary point mutations within the TK domain of BCR-ABL1. These mutations are highly variable in their sensitivity to increased doses of imatinib or alternative TK inhibitors such as nilotinib or dasatinib. Selective and non-selective inhibitors of JAK2 are currently being developed, and encouraging data from pre-clinical experiments and initial phase-I studies regarding efficacy and potential toxicity of these compounds have already been reported.