Activated IL-6 signaling contributes to the pathogenesis of, and is a novel therapeutic target for, CALR-mutated MPNs

Non-canonical Hedgehog signaling mediates profibrotic hematopoiesis-stroma crosstalk in myeloproliferative neoplasms

The role of hematopoietic Hedgehog signaling in myeloproliferative neoplasms (MPNs) remains incompletely understood despite data suggesting that Hedgehog (Hh) pathway inhibitors have therapeutic activity in patients. We aim to systematically interrogate the role of canonical vs. non-canonical Hh signaling in MPNs. We show that Gli1 protein levels in patient peripheral blood mononuclear cells (PBMCs) mark fibrotic progression and that, in murine MPN models, absence of hematopoietic Gli1, but not Gli2 or Smo, significantly reduces MPN phenotype and fibrosis, indicating that GLI1 in the MPN clone can be activated in a non-canonical fashion. Additionally, we establish that hematopoietic Gli1 has a significant effect on stromal cells, mediated through a druggable MIF-CD74 axis. These data highlight the complex interplay between alterations in the MPN clone and activation of stromal cells and indicate that Gli1 represents a promising therapeutic target in MPNs, particularly that Hh signaling is dispensable for normal hematopoiesis.

Whole blood transcriptional profiling reveals highly deregulated atherosclerosis genes in Philadelphia-chromosome negative myeloproliferative neoplasms

BACKGROUND

The Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) are associated with a huge comorbidity burden, including an increased risk of cardiovascular diseases. Recently, chronic inflammation has been suggested to be the driving force for clonal evolution and disease progression in MPN but also potentially having an impact upon the development of accelerated (premature) atherosclerosis.

OBJECTIVES

Since chronic inflammation, atherosclerosis, and atherothrombosis are prevalent in MPNs and we have previously shown oxidative stress genes to be markedly upregulated in MPNs, we hypothesized that genes linked to development of atherosclerosis might be highly deregulated as well.

METHODS

Using whole blood gene expression profiling in patients with essential thrombocythemia (ET; n = 19), polycythemia vera (PV; n = 41), or primary myelofibrosis (PMF; n = 9), we herein for the first time report aberrant expression of several atherosclerosis genes.

RESULTS

Of 84 atherosclerosis genes, 45, 56, and 46 genes were deregulated in patients with ET, PV, or PMF, respectively. Furthermore, BCL2L1, MMP1, PDGFA, PTGS1, and THBS4 were progressively significantly upregulated and BCL2 progressively significantly downregulated from ET over PV to PMF (all FDR <0.05).

CONCLUSIONS

We have for the first time shown massive deregulation of atherosclerosis genes in MPNs, likely reflecting the inflammatory state in MPNs in association with in vivo activation of leukocytes, platelets, and endothelial cells being deeply involved in the atherosclerotic process.

Pronounced gut microbiota signatures in patients with JAK2V617F-positive essential thrombocythemia

Essential thrombocythemia (ET) is part of the Philadelphia chromosome-negative myeloproliferative neoplasms. It is characterized by an increased risk of thromboembolic events and also to a certain degree hypermetabolic symptoms. The gut microbiota is an important initiator of hematopoiesis and regulation of the immune system, but in patients with ET, where inflammation is a hallmark of the disease, it is vastly unexplored. In this study, we compared the gut microbiota via amplicon-based 16S rRNA gene sequencing of the V3-V4 region in 54 patients with ET according to mutation status Janus-kinase 2 (JAK2V617F)-positive vs JAK2V617F-negative patients with ET, and in 42 healthy controls (HCs). Gut microbiota richness was higher in patients with ET (median-observed richness, 283.5; range, 75-535) compared with HCs (median-observed richness, 191.5; range, 111-300; P < 0.001). Patients with ET had a different overall bacterial composition (beta diversity) than HCs (analysis of similarities [ANOSIM]; R = 0.063, P = 0.004). Patients with ET had a significantly lower relative abundance of taxa within the Firmicutes phylum compared with HCs (51% vs 59%, P = 0.03), and within that phylum, patients with ET also had a lower relative abundance of the genus Faecalibacterium (8% vs 15%, P < 0.001), an important immunoregulative bacterium. The microbiota signatures were more pronounced in patients harboring the JAK2V617F mutation, and highly similar to patients with polycythemia vera as previously described. These findings suggest that patients with ET may have an altered immune regulation; however, whether this dysregulation is induced in part by, or is itself inducing, an altered gut microbiota remains to be investigated. IMPORTANCE Essential thrombocythemia (ET) is a cancer characterized by thrombocyte overproduction. Inflammation has been shown to be vital in both the initiation and progression of other myeloproliferative neoplasms, and it is well known that the gut microbiota is important in the regulation of our immune system. However, the gut microbiota of patients with ET remains uninvestigated. In this study, we characterized the gut microbiota of patients with ET compared with healthy controls and thereby provide new insights into the field. We show that the gut microbiota of patients with ET differs significantly from that of healthy controls and the patients with ET have a lower relative abundance of important immunoregulative bacteria. Furthermore, we demonstrate that patients with JAK2V617F-positive ET have pronounced gut microbiota signatures compared with JAK2V617F-negative patients. Thereby confirming the importance of the underlying mutation, the immune response as well as the composition of the microbiota.

Inhibition of ERK1/2 signaling prevents bone marrow fibrosis by reducing osteopontin plasma levels in a myelofibrosis mouse model

Clonal myeloproliferation and development of bone marrow (BM) fibrosis are the major pathogenetic events in myelofibrosis (MF). The identification of novel antifibrotic strategies is of utmost importance since the effectiveness of current therapies in reverting BM fibrosis is debated. We previously demonstrated that osteopontin (OPN) has a profibrotic role in MF by promoting mesenchymal stromal cells proliferation and collagen production. Moreover, increased plasma OPN correlated with higher BM fibrosis grade and inferior overall survival in MF patients. To understand whether OPN is a druggable target in MF, we assessed putative inhibitors of OPN expression in vitro and identified ERK1/2 as a major regulator of OPN production. Increased OPN plasma levels were associated with BM fibrosis development in the Romiplostim-induced MF mouse model. Moreover, ERK1/2 inhibition led to a remarkable reduction of OPN production and BM fibrosis in Romiplostim-treated mice. Strikingly, the antifibrotic effect of ERK1/2 inhibition can be mainly ascribed to the reduced OPN production since it could be recapitulated through the administration of anti-OPN neutralizing antibody. Our results demonstrate that OPN is a novel druggable target in MF and pave the way to antifibrotic therapies based on the inhibition of ERK1/2-driven OPN production or the neutralization of OPN activity.

Clonal haematopoiesis of indeterminate potential and impaired kidney function-A Danish general population study with 11 years follow-up

The myeloproliferative neoplasms are associated with chronic kidney disease but whether clonal haematopoiesis of indeterminate potential (CHIP) is associated with impaired kidney function is unknown. In the Danish General Suburban Population Study (N = 19 958) from 2010 to 2013, 645 individuals were positive for JAK2V617F (N = 613) or CALR (N = 32) mutations. Mutation-positive individuals without haematological malignancy were defined as having CHIP (N = 629). We used multiple and inverse probability weighted (IPW)-adjusted linear regression analysis to estimate adjusted mean (95% confidence interval) differences in estimated glomerular filtration rate (eGFR; ml/min/1.73 m² ) by mutation status, variant allele frequency (VAF%), blood cell counts, and neutrophil-to-lymphocyte ratio (NLR). We performed 11-year longitudinal follow-up of eGFR in all individuals. Compared to CHIP-negative individuals, the mean differences in eGFR were -5.6 (-10.3, -0.8, p = .02) for CALR, -11.9 (-21.4, -2.4, p = 0.01) for CALR type 2, and -10.1 (-18.1, -2.2, p = .01) for CALR with VAF ≥ 1%. The IPW-adjusted linear regression analyses showed similar results. NLR was negatively associated with eGFR. Individuals with CALR type 2 had a worse 11-year longitudinal follow-up on eGFR compared to CHIP-negative individuals (p = .004). In conclusion, individuals with CALR mutations, especially CALR type 2, had impaired kidney function compared to CHIP-negative individuals as measured by a lower eGFR at baseline and during 11-year follow-up.

Interferon-alpha2 treatment of patients with polycythemia vera and related neoplasms favorably impacts deregulation of oxidative stress genes and antioxidative defense mechanisms

Chronic inflammation is considered a major driving force for clonal expansion and evolution in the Philadelphia-negative myeloproliferative neoplasms, which include essential thrombocythemia, polycythemia vera and primary myelofibrosis (MPNs). One of the key mutation drivers is the JAK2V617F mutation, which has been shown to induce the generation of reactive oxygen species (ROS). Using whole blood gene expression profiling, deregulation of several oxidative stress and anti-oxidative defense genes has been identified in MPNs, including significant downregulation of TP53, the NFE2L2 or NRF2 genes. These genes have a major role for maintaining genomic stability, regulation of the oxidative stress response and in modulating migration or retention of hematopoietic stem cells. Therefore, their deregulation might give rise to increasing genomic instability, increased chronic inflammation and disease progression with egress of hematopoietic stem cells from the bone marrow to seed in the spleen, liver and elsewhere. Interferon-alpha2 (rIFNα) is increasingly being recognized as the drug of choice for the treatment of patients with MPNs. Herein, we report the first gene expression profiling study on the impact of rIFNα upon oxidative stress and antioxidative defense genes in patients with MPNs (n = 33), showing that rIFNα downregulates several upregulated oxidative stress genes and upregulates downregulated antioxidative defense genes. Treatment with rIFNα induced upregulation of 19 genes in ET and 29 genes in PV including CXCR4 and TP53. In conclusion, this rIFNα- mediated dampening of genotoxic damage to hematopoietic cells may ultimately diminish the risk of additional mutations and accordingly clonal evolution and disease progression towards myelofibrotic and leukemic transformation.

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs): A continuum of different disease entities

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell-derived disorders characterized by uncontrolled proliferation of differentiated myeloid cells and close pathobiologic and clinical features. According to the 2016 World Health Organization (WHO) classification, MPNs include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The 2016 revision aimed in particular at strengthening the distinction between masked PV and JAK2-mutated ET, and between prefibrotic/early (pre-PMF) and overt PMF. Clinical manifestations in MPNs include constitutional symptoms, microvascular disorders, thrombosis and bleeding, splenomegaly secondary to extramedullary hematopoiesis, cytopenia-related symptoms, and progression to overt MF and acute leukemia. A dysregulation of the JAK/STAT pathway is the unifying mechanistic hallmark of MPNs, and is guided by somatic mutations in driver genes including JAK2, CALR and MPL. Additional mutations in myeloid neoplasm-associated genes have been also identified, with established prognostic relevance, particularly in PMF. Prognostication of MPN patients relies on disease-specific clinical models. The increasing knowledge of MPN biology led to the development of integrated clinical and molecular prognostic scores that allow a more refined stratification. Recently, the therapeutic landscape of MPNs has been revolutionized by the introduction of potent, selective JAK inhibitors (ruxolitinib, fedratinib), that proved effective in controlling disease-related symptoms and splenomegaly, yet leaving unmet critical needs, owing the lack of disease-modifying activity. In this review, we will deal with molecular, clinical, and therapeutic aspects of the three classical MPNs aiming at highlighting either shared characteristics, that overall define a continuum within a single disease family, and uniqueness, at the same time.

Clinical Relevance of VEGFA (rs3025039) +936 C>T Polymorphism in Primary Myelofibrosis: Susceptibility, Clinical Co-Variates, and Outcomes

We evaluated the association of VEGFA rs3025039 polymorphism with clinical co-variates and outcomes in 849 subjects with primary myelofibrosis (PMF) and 250 healthy controls. Minor T-allele frequency was higher in subjects with JAK2^V617F compared with those without JAK2^V617F (18% vs. 13%; p = 0.014). In subjects with JAK2^V617F, the TT genotype was associated at diagnosis with lower platelet concentrations (p = 0.033), higher plasma LDH concentration (p = 0.005), higher blood CD34-positive cells (p = 0.027), lower plasma cholesterol concentration (p = 0.046), and higher concentration of high-sensitivity C-reactive protein (p = 0.018). These associations were not found in subjects with PMF without JAK2^V617F. In subjects with the TT genotype, risk of death was higher compared with subjects with CC/CT genotypes (HR = 2.12 [1.03, 4.35], p = 0.041). Finally, the TT genotype was associated with higher frequency of deep vein thrombosis in typical sites (12.5% vs. 2.5%; OR = 5.46 [1.51, 19.7], p = 0.009). In conclusion, in subjects with PMF, the VEGFA rs3025039 CT or TT genotypes are more common in those with JAK2^V617F than in those without JAK2^V67F mutation and are associated with disease severity, poor prognosis, and risk of deep vein thrombosis.

Integration of Molecular Information in Risk Assessment of Patients with Myeloproliferative Neoplasms

Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) are clonal disorders of a hematopoietic stem cell, characterized by an abnormal proliferation of largely mature cells driven by mutations in JAK2, CALR, and MPL. All these mutations lead to a constitutive activation of the JAK-STAT signaling, which represents a target for therapy. Beyond driver ones, most patients, especially with myelofibrosis, harbor mutations in an array of "myeloid neoplasm-associated" genes that encode for proteins involved in chromatin modification and DNA methylation, RNA splicing, transcription regulation, and oncogenes. These additional mutations often arise in the context of clonal hematopoiesis of indeterminate potential (CHIP). The extensive characterization of the pathologic genome associated with MPN highlighted selected driver and non-driver mutations for their clinical informativeness. First, driver mutations are enlisted in the WHO classification as major diagnostic criteria and may be used for monitoring of residual disease after transplantation and response to treatment. Second, mutation profile can be used, eventually in combination with cytogenetic, histopathologic, hematologic, and clinical variables, to risk stratify patients regarding thrombosis, overall survival, and rate of transformation to secondary leukemia. This review outlines the molecular landscape of MPN and critically interprets current information for their potential impact on patient management.