JAK2-V617F and interferon-α induce megakaryocyte-biased stem cells characterized by decreased long-term functionality

Abstract

We studied a subset of hematopoietic stem cells (HSCs) that are defined by elevated expression of CD41 (CD41hi) and show bias for differentiation towards megakaryocytes (Mk). Mouse models of myeloproliferative neoplasms (MPN) expressing JAK2-V617F (VF) or a JAK2 exon 12 mutation (E12) displayed increased frequencies and percentages of the CD41hi versusCD41lo HSCs compared to wildtype controls. An increase in CD41hi HSCs that correlated with JAK2-V617F mutant allele burden was also found in bone marrow from MPN patients. CD41hi HSCs produced higher numbers of Mk-colonies HSC in single cell cultures in vitro, but showed reduced long-term reconstitution potential compared to CD41lo HSCs in competitive transplantations in vivo. RNA expression profiling showed upregulated cell cycle, Myc, and oxidative phosphorylation gene signatures in CD41hi HSCs, while CD41lo HSCs showed higher gene expression of interferon, JAK/STAT and TNFα/NFkB signaling pathways. Higher cell cycle activity and elevated levels of reactive oxygen species were confirmed in CD41hi HSCs by flow cytometry. Expression of Epcr, a marker for quiescent HSCs inversely correlated with expression of CD41 in mice, but did not show such reciprocal expression pattern in MPN patients. Treatment with interferon-α further increased the frequency and percentage of CD41hi HSCs and reduced the numbers of JAK2-V617F positive HSCs in mice and patients with MPN. The shift towards the CD41hi subset of HSCs by interferon-α provides a possible mechanism of how interferon-α preferentially targets the JAK2 mutant clone.

Inflammation as a regulator of hematopoietic stem cell function in disease, aging, and clonal selection

“…JAK2 V617F HSPCs proliferate and exhaust after IFN-α treatment, losing disease initiation capacity in secondary transplantation (Hasan et al, 2013;Mullally et al, 2013). In agreement, JAK2 V617F megakaryocyte-biased CD41 hi HSCs were recently shown to exhaust after IFN-α treatment (Rao et al, 2021). On the other hand, JAK2 V617F HSCs exhibit increased IL-1β secretion, which induces MSC death, resulting in mutant HSC expansion and accelerated myeloproliferative neoplasm progression (Arranz et al, 2014).…”

Inferring the dynamics of mutated hematopoietic stem and progenitor cells induced by IFNα in myeloproliferative neoplasms

“…The treatment would also preferentially favor the exit from quiescence of homozygous JAK2 V617F HSC. Similarly, in the JAK2 V617F mouse model, IFNα has been shown to enhance mutated HSC proliferation and exit from quiescence, resulting in an increase in total number of progenitors 22,35,36 . Although the main mechanism of IFNα inferred by the mathematical model is HSC exhaustion by differentiation for both JAK2 V617F and type 2 CALR m HSC, several other mechanisms might be considered.…”

MAPK14 over-expression is a transcriptomic feature of polycythemia vera and correlates with adverse clinical outcomes

“…Interferon-alpha (IFNα) is an effective treatment for MPN patients, including PV. IFNα promoted the shift towards CD41(ITGA2B) high subset of hematopoietic stem cells in JAK2V617F clones [ 34 ], exerting therapeutic effects. Notably, CD41 and MAPK14 were significantly co-expressed (Pearson’s coefficient = 0.25, p = 2.85e−4), and MAPK14 expression positively correlated with IFNα response pathway (Fig.…”