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Published on: December 7, 2014
JAK2 inhibition has different therapeutic effects according to myeloproliferative neoplasm development in mice
Franck Debeurme1, Catherine Lacout1, Claudine Moratal2
1Inserm, U.1009, Institut Gustave Roussy (IGR), Université Paris XI, Villejuif, France.
Abstract:
JAK2 inhibition therapy is used to treat patients suffering from myeloproliferative neoplasms (MPN). Conflicting data on this therapy are reported possibly linked to the types of inhibitors or disease type. Therefore, we decided to compare in mice the effect of a JAK2 inhibitor, Fedratinib, in MPN models of increasing severity: polycythemia vera (PV), post-PV myelofibrosis (PPMF) and rapid post-essential thrombocythemia MF (PTMF). The models were generated through JAK2 activation by the JAK2(V617F) mutation or MPL constant stimulation. JAK2 inhibition induced a correction of splenomegaly, leucocytosis and microcytosis in all three MPN models. However, the effects on fibrosis, osteosclerosis, granulocytosis, erythropoiesis or platelet counts varied according to the disease severity stage. Strikingly, complete blockade of fibrosis and osteosclerosis was observed in the PPMF model, linked to correction of MK hyper/dysplasia, but not in the PTMF model, suggesting that MF development may also become JAK2-independent. Interestingly, we originally found a decreased in the JAK2(V617F) allele burden in progenitor cells from the spleen but not in other cell types. Overall, this study shows that JAK2 inhibition has different effects according to disease phenotypes and can (i) normalize platelet counts, (ii) prevent the development of marrow fibrosis/osteosclerosis at an early stage and (iii) reduce splenomegaly through blockage of stem cell mobilization in the spleen.
Insights
JAK2 inhibition therapy effectively treats myeloproliferative neoplasms (MPN) by correcting splenomegaly and leucocytosis. However, its impact on fibrosis and osteosclerosis varies with disease severity, suggesting JAK2 independence in advanced myelofibrosis.
Area of Science:
- Hematology
- Oncology
- Pharmacology
Background:
- Myeloproliferative neoplasms (MPN) are a group of blood cancers.
- JAK2 inhibition therapy is a treatment for MPN, but its efficacy can vary.
- Conflicting data suggest treatment outcomes may depend on the specific inhibitor or disease subtype.
Purpose of the Study:
- To compare the effects of Fedratinib, a JAK2 inhibitor, across MPN models of increasing severity.
- To investigate the impact of JAK2 inhibition on disease progression, fibrosis, and osteosclerosis.
- To understand the role of JAK2 signaling in different MPN phenotypes.
Main Methods:
- Utilized mouse models of polycythemia vera (PV), post-PV myelofibrosis (PPMF), and post-essential thrombocythemia myelofibrosis (PTMF).
- Induced MPN models via JAK2 activation (JAK2(V617F) mutation) or MPL stimulation.
- Administered Fedratinib and assessed effects on splenomegaly, leucocytosis, microcytosis, fibrosis, osteosclerosis, and JAK2 allele burden.
Main Results:
- JAK2 inhibition corrected splenomegaly, leucocytosis, and microcytosis in all tested MPN models.
- Effects on fibrosis, osteosclerosis, and platelet counts differed based on disease severity.
- Complete blockade of fibrosis and osteosclerosis was observed in PPMF but not PTMF, suggesting JAK2-independent myelofibrosis progression.
- A decrease in JAK2(V617F) allele burden was noted in splenic progenitor cells.
Conclusions:
- JAK2 inhibition demonstrates variable efficacy depending on MPN disease phenotype.
- The therapy can normalize platelet counts and reduce splenomegaly by inhibiting stem cell mobilization.
- Early-stage myelofibrosis may be preventable with JAK2 inhibition, but advanced stages might involve JAK2-independent mechanisms.
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