Caduc, M. J. | Search bioRxiv

bioRxiv2025

The V617F mutation in JAK2 renders myeloid cells more sensitive to IL-6-mediated gp130 signaling

The somatic V617F mutation in the pseudokinase domain of JAK2 (JAK2VF) causes various phenotypes of myeloproliferative neoplasms (MPN). By interacting with cytokine receptors such as those for erythropoietin (EPO) or thrombopoietin (TPO), JAK2VF induces ligand-independent dimerization and activation, leading to deregulated blood cell production, cytokine hypersensitivity, and inflammatory cytokine release. Interleukin-6 (IL-6), a key mediator of inflammatory symptoms in MPN, signals via homodimers of the gp130 receptor. We investigated whether JAK2VF alters gp130 dimerization and IL-6 sensitivity. Molecular dynamics simulations demonstrated that the JAK2VF pseudokinase domain forms more stable dimers than wild-type (WT) JAK2, potentially supporting gp130 tetramerization. In cell-based assays, IL-6 stimulation of JAK2VF+ cells induced stronger STAT3 activation than in JAK2-WT cells, reflecting enhanced IL-6 sensitivity. Moreover, JAK2VF expression elevated gp130 surface levels, dependent on the JAK2-binding motif in gp130. These findings indicate that JAK2VF promotes gp130 expression and dimerization, sensitizing mutant cells to IL-6. Thus, JAK2VF-driven amplification of IL-6/gp130 signaling may foster chronic inflammation and disease progression in MPN, representing a potential therapeutic target.

cancer biology↗

bioRxiv2024

IFNα Inhibits JAK2V617F-Driven Neoplastic Vasculogenesis and Endothelial-to-Mesenchymal Transition in a 3D iPSC-Based Bone Marrow Niche Model

The vascular niche is a critical regulator of hematopoiesis and disease progression in myeloproliferative neoplasms (MPN). The presence of JAK2V617F+ endothelial cells (EC) in MPN patients and their association with cardiovascular complications highlight the need to understand and therapeutically target this compartment. Using patient-specific induced pluripotent stem cells (iPSC) harboring JAK2WT or the MPN-driver JAK2V617F (heterozygous, JAK2V617FHET, or homozygous, JAK2V617FHOM), we identified zygosity-dependent transcriptional profiles in iPSC-derived EC (iEC) at baseline and following interferon-alpha (IFN) treatment. JAK2V617FHET iEC exhibited an endothelial-to-mesenchymal transition (EndMT) signature, while JAK2V617FHOM iEC showed suppression of translation and ribosome biogenesis. Leveraging iPSC-based 3D assembloids that mimic the bone marrow (BM) niche, we showed that JAK2V617F-driven EndMT is inhibited by tyrosine kinase inhibitors and IFN. In both JAK2V617F-driven polycythemia vera and TPO-driven myelofibrosis murine models, scRNA-seq analysis of the BM vascular niche consistently revealed inflammatory and EndMT-associated signatures in arterial and arteriolar EC. Notably, dysregulation of ribosome- and translation-related pathways emerged in the myelofibrosis model and at advanced disease stages in JAK2V617F-driven polycythemia vera, indicating progressive vascular remodeling with disease evolution. Chronic pegylated IFN treatment in vivo effectively reversed these pathological changes. IFNs anti-EndMT activity was further validated in BM biopsies from MPN patients undergoing IFN therapy. This is the first study to define MPN stage-dependent vascular remodeling and zygosity-specific endothelial effects of JAK2V617F, and to directly link IFN-mediated EndMT inhibition as a novel antifibrotic mechanism. Our 3D assembloids provide a translational platform for mechanistic studies and therapeutic targeting of the BM microenvironment in MPN. Bullet PointsO_LIArterial vascular remodeling emerges as a novel hallmark of MPN, characterized by TNF-inflammation, ribosomal dysregulation and EndMT. C_LIO_LIIFN restores neoplastic endothelial dysfunction, highlighting its role as a vascular niche-modulating and anti-fibrotic agent in MPN. C_LI

cancer biology↗