JAK2 inhibition mediates clonal selection of RAS pathway mutations in myeloproliferative neoplasms.

JAK (Janus Kinase) inhibitors, such as ruxolitinib, were introduced a decade ago for treatment of myeloproliferative neoplasms (MPN). To evaluate ruxolitinib's impact on MPN clonal evolution, we interrogate a myelofibrosis patient cohort with longitudinal molecular evaluation and discover that ruxolitinib is associated with clonal outgrowth of RAS pathway mutations. Single-cell DNA sequencing combined with ex vivo treatment of RAS mutated CD34 primary patient cells, demonstrates that ruxolitinib induces RAS clonal selection both in a JAK/STAT wild-type and hyper-activated context.

Expanding the phenotypic and genetic landscape of congenital neutropenia through whole-exome and genome sequencing.

Congenital neutropenia (CN) comprises a heterogeneous group of rare genetic disorders. While some CN cases present only with neutropenia, others present with additional extra-hematological manifestations. The most common cause of CN is variants in ; however, approximately 30 other genes have been implicated.

Type 2 calreticulin mutations activate ATF6 to promote BCL-xL-mediated survival in myeloproliferative neoplasms.

Most calreticulin (CALR) mutations in myeloproliferative neoplasms are classified as either type 1, a 52-base pair deletion (CALRdel52); or type 2, a 5-base pair insertion (CALRins5). Both are gain-of-function (GOF) mutations that generate an identical mutant C-terminal tail, which mediates the binding to, and activation of, the thrombopoietin receptor myeloproliferative leukemia protein (MPL). We recently reported that despite this shared GOF, CALRdel52 but not CALRins5 mutations cause loss of calcium binding function, leading to activation of, and dependency on, the inositol-requiring enzyme 1/X-box binding protein 1 pathway of the unfolded protein response (UPR).

Identification of Hepatic-like EPO as a Cause of Polycythemia.

Background: Secondary erythrocytosis often results from conditions that cause tissue hypoxia or an improper increase in erythropoietin (EPO) production. EPO, the major regulator of erythropoiesis, has a complex and tightly regulated expression during development, with a liver-to-kidney switch shortly after birth.

Methods: We identified six families with erythrocytosis that was associated with circulating EPO levels within the normal range and characterized as a novel molecular and functional entity.

Increased RhoA pathway activation downstream of αIIbβ3/SRC contributes to heterozygous Bernard Soulier syndrome.

Bernard Soulier syndrome (BSS) is a severe bleeding disorder with moderate to severe thrombocytopenia, giant platelets, and platelet dysfunction, caused by biallelic mutations in GP1BA, GP1BB, or GP9 genes. We generated induced pluripotent stem cells (iPSC) from a BSS patient with a novel heterozygous GP1BA p.N103D mutation, resulting in moderate macrothrombocytopenia.

Monocytes generated by interleukin-6-treated human hematopoietic stem and progenitor cells secrete calprotectin that inhibits erythropoiesis.

Elevated circulating levels of calprotectin (CAL), the S100A8/A9 heterodimer, are biomarkers of severe systemic inflammation. Here, we investigate the effects of CAL on early human hematopoiesis. CAL demonstrates limited impact on gene expression in stem and progenitor cells, in contrast with interleukin-6 (IL6), which promotes the expression of the and genes in hematopoietic progenitors and the generation of monocytes that release CAL.

New approaches to standard of care in early-phase myeloproliferative neoplasms: can interferon-α alter the natural history of the disease?

The classical BCR::ABL-negative myeloproliferative neoplasms (MPN) include polycythemia vera, essential thrombocythemia, and primary myelofibrosis. They are acquired clonal disorders of hematopoietic stem cells leading to hyperplasia of one or several myeloid lineages. MPN are caused by three main recurrent mutations, JAK2V617F and mutations in the calreticulin (CALR) and thrombopoietin receptor (MPL) genes.

Impaired fibrinolysis in JAK2V617F-related myeloproliferative neoplasms.

Background: Myeloproliferative neoplasms (MPNs) are characterized by a high rate of thrombotic complications that contribute to morbidity and mortality. MPN-related thrombogenesis is assumed to be multifactorial, involving both procoagulant and proinflammatory processes. Whether impaired fibrinolysis also participates in the prothrombotic phenotype of MPN has been poorly investigated.

Mathematical modelling, selection and hierarchical inference to determine the minimal dose in IFNα therapy against myeloproliferative neoplasms.

Myeloproliferative neoplasms (MPN) are blood cancers that appear after acquiring a driver mutation in a hematopoietic stem cell. These hematological malignancies result in the overproduction of mature blood cells and, if not treated, induce a risk of cardiovascular events and thrombosis. Pegylated IFN$\alpha $ is commonly used to treat MPN, but no clear guidelines exist concerning the dose prescribed to patients.

Optimizing IFN Alpha Therapy against Myeloproliferative Neoplasms.

Myeloproliferative neoplasms (MPNs) are hematologic malignancies that result from acquired driver mutations in hematopoietic stem cells (HSCs), causing overproduction of blood cells and an increased risk of thrombohemorrhagic events. The most common MPN driver mutation affects the gene ( ). Interferon alpha (IFN) is a promising treatment against MPNs by inducing a hematologic response and molecular remission for some patients.

SRSF2-P95H decreases JAK/STAT signaling in hematopoietic cells and delays myelofibrosis development in mice.

Heterozygous mutation targeting proline 95 in Serine/Arginine-rich Splicing Factor 2 (SRSF2) is associated with V617F mutation in Janus Activated Kinase 2 (JAK2) in some myeloproliferative neoplasms (MPNs), most commonly primary myelofibrosis. To explore the interaction of Srsf2 with Jak2, we generated Cre-inducible knock-in mice expressing these mutants under control of the stem cell leukemia (Scl) gene promoter. In transplantation experiments, Srsf2 unexpectedly delayed myelofibrosis induced by Jak2 and decreased TGFβ1 serum level.

ANKRD26 is a new regulator of type I cytokine receptor signaling in normal and pathological hematopoiesis.

Sustained ANKRD26 expression associated with germline ANKRD26 mutations causes thrombocytopenia 2 (THC2), an inherited platelet disorder associated with a predisposition to leukemia. Some patients also present with erythrocytosis and/or leukocytosis. Using multiple human-relevant in vitro models (cell lines, primary patients' cells and patient-derived induced pluripotent stem cells) we demonstrate for the first time that ANKRD26 is expressed during the early steps of erythroid, megakaryocyte and granulocyte differentiation, and is necessary for progenitor cell proliferation.

Secreted mutant calreticulins as rogue cytokines in myeloproliferative neoplasms.

Mutant calreticulin (CALR) proteins resulting from a -1/+2 frameshifting mutation of the CALR exon 9 carry a novel C-terminal amino acid sequence and drive the development of myeloproliferative neoplasms (MPNs). Mutant CALRs were shown to interact with and activate the thrombopoietin receptor (TpoR/MPL) in the same cell. We report that mutant CALR proteins are secreted and can be found in patient plasma at levels up to 160 ng/mL, with a mean of 25.