The JAK2 V617F mutation involves B‐ and T‐lymphocyte lineages in a subgroup of patients with Philadelphia‐chromosome negative chronic myeloproliferative disorders

Abstract

Summary The JAK2 V617F mutation is a frequent genetic event in the three classical Philadelphia‐chromosome negative chronic myeloproliferative disorders (Phneg.‐CMPD), polycythemia vera (PV), essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF). Its occurrence varies in frequency in regards to phenotype. The mutation is found in the majority of patients with PV and about half of the patients with ET and IMF. These diseases are clonal stem cell disorders arising in an early stem cell progenitor. The level in the stem cell hierarchy on which the initiating genetic events and the JAK2 V617F mutation occurs is not known. The mutation has so far been detected in all cells of the myeloid lineage, whereas the potential clonal involvement of the lymphoid lineage is controversial. In this study, we detected the JAK2 V617F mutation by real‐time quantitative PCR (qPCR) in both B‐lymphocytes and T‐lymphocytes in a subgroup of patients with Phneg.‐CMPDs. These results demonstrate the origin of the JAK2 V617F positive disorders in an early stem cell with both lymphoid and myeloid differentiation potential.

JAK2V617F monitoring in polycythemia vera and essential thrombocythemia: Clinical usefulness for predicting myelofibrotic transformation and thrombotic events

“…In our hands, this technique reached a sensitivity of 2%. In cases with JAK2V617F below 5%, we applied the Larsen assay that is composed of two allele-specific PCR reactions; one for the JAK2V617F mutated allele and one for the wild type allele [19]. In both assays standard curves for the wild type and the V617F JAK2 were used (Ipsogen, Marseille, France).…”

Quantitative assessment of the JAK2 V617F allele burden: equivalent levels in peripheral blood and bone marrow

“…The quantification of the JAK2 V617F mutant clone in PB unfractionized WBCs is an exact and reliable determinant of disease burden at diagnosis. As the clonal involvement of various mature hematopoietic cells is very heterogenous and varies between patients, and a separation of, for example, granulocytes is sometimes difficult because of in vivo and in vitro aggregation of monocytes, granulocytes and platelets, 8 the use of unfractionized WBC as DNA source seems rational. Hereby the timeto-time uncertainty and potential bias from an unsuccessful separation procedure are eliminated.…”

“…qPCR was performed as described previously. 8 Briefly, two realtime qPCRs were performed in parallel with a common forward primer and a Taqman probe and only differed in the use of a reverse primer specific for the JAK2 wild type and the V617F mutated DNA respectively. The JAK2 V617F proportion was calculated from standard curves and end point determination from limiting dilution series of JAK2 wild-type donor DNA and the homozygous JAK2 cell line HEL.…”

Two novel JAK2 exon 12 mutations in JAK2V617F-negative polycythaemia vera patients

“…In this patient, the eBFUE as well as the mature monocyte and lymphocyte populations may be carrying the heterozygous change leading to full penetration of the disease clone in all haematopoietic lineages, as previously reported in a small number of JAK2V617F-positive MPD patients. 8 In support of this, early BM pathology obtained three years before PV diagnosis suggests that PV63 may have had long-standing disease, allowing time for full clonal haematopoiesis to have occurred (see below). Additional mutational events in this patient may be associated with amplification of additional cellular compartments.…”