Myelofibrosis (MF) is the most common complication of myeloproliferative neoplasms (MPNs)，which is markedly correlated with a dismal prognosis. Murine model such as the thrombopoietin receptor (MPL)W515L-mutant MPN mouse model functions as a crucial vehicle in disease research, is widely used in basic and applied research on MPNs and MF.However, the lack of methods for dynamic observation of MF progression hinders mechanistic studies and drug development for MF. Here we develop a sensitive, stable and minimally invasive MPN evaluation system to assess the evolution of myelofibrosis in murine model.Key peripheral blood parameters (WBC, RBC, HGB, HCT, PLT, and tumor cell proportion) from MPN mice were analyzed using PCA to reduce dimensionality and generate a comprehensive evaluation score (Y). Based on peripheral blood smear observations and predefined score cut-off values (0.59 and - 0.44), MPN was classified into mild, moderate, and severe stages. Validation conducted across diverse experimental settings yielded outcomes that were in alignment with the pathological grading of myelofibrosis. This system facilitated the dynamic monitoring of MF progression in applied research on pigment epithelium-derived factor treatment for MPN and basic studies on the role of NLRP inflammasomes in the bone marrow microenvironment. We believed that this minimally invasive evaluation system for grading MF severity in MPN mouse model will provide a potential tool for MPN pathogenesis research and targeted therapy development.

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. Here, we review the general diagnosis, the complications, and the management of MPN. Second, we explain the physiopathology of the natural disease development and its regulation, which contributes to MPN heterogeneity. Thirdly, we describe the new paradigm of MPN development highlighting the early origin of driver mutations, decades before the onset of symptoms, and the consequence of early detection of MPN cases in the general population for prompt diagnosis and better medical management. Finally, we present interferon-α therapy as a potential, early disease-modifying drug after reporting its good hematologic and molecular efficacies in polycythemia vera, essential thrombocythemia, and early myelofibrosis in clinical trials as well as its mechanism of action in pre-clinical studies. As a result, we may expect that, in the future, MPN patients will be diagnosed very early during the course of disease and that new selective therapies under development, such as interferon-α, JAK2V617F inhibitors and CALRmut monoclonal antibodies, will be able to intercept the mutated clones.

Myelofibrosis (MF) is a chronic myeloid neoplasm characterized by myeloproliferation, bone marrow fibrosis, splenomegaly, and constitutional symptoms related to pro-inflammatory cytokine signaling. Biologically, MF is characterized by constitutive activation of JAK-STAT signaling; accordingly, JAK inhibitors have been rationally developed to treat MF. Following the initial approval of ruxolitinib in 2011, three additional agents have been approved: fedratinib, pacritinib, and momelotinib. As these therapies are noncurative, allogeneic stem cell transplantation remains a key treatment modality and patients with MF who are deemed candidates should be referred to a transplant center. This potentially curative but toxic approach is typically reserved for patients with higher-risk disease, and JAK inhibitors are recommended in the pretransplant setting. JAK inhibitors have proven effective at managing splenomegaly and constitutional symptoms and should be started early in the disease course in patients presenting with these clinical manifestations; asymptomatic patients may initially be followed with close surveillance. Drug-related myelosuppression has been a challenge with initial JAK inhibitors, particularly in patients presenting with a cytopenic phenotype. However, newer agents, namely pacritinib and momelotinib, have proven more effective in this setting and are approved for patients with significant thrombocytopenia and anemia, respectively. Resistance or disease progression is clinically challenging and may be defined by several possible events, such as increasing splenomegaly or progression to accelerated or blast phase disease. However, with multiple JAK inhibitors now approved, sequencing of these agents appears poised to improve outcomes. Additionally, novel JAK inhibitors and JAK inhibitor-based combinations are in clinical development.

Rusfertide, a peptide hepcidin mimetic, has shown efficacy in polycythemia vera. This trial investigated the multiple-dose pharmacokinetics, pharmacodynamics, and safety of once-weekly rusfertide 60 mg for 5 weeks in healthy subjects. Subjects were randomized to subcutaneous injection in the abdomen, upper arm, or thigh. Eighteen subjects were enrolled, and 15 completed the study. Geometric mean peak rusfertide plasma concentrations (Cmax) following the first dose were 547, 387, and 560 ng/mL following injection in the abdomen, thigh, and arm, respectively (P = .0054). There was no difference between injection sites in the rusfertide area under the plasma concentration-time curve (AUC) following the first dose (P ≥ .179) or in the Cmax or AUC during the dosing interval following the last dose (P ≥ .238). Geometric mean accumulation (Dose 5/Dose 1) for AUC and Cmax was 1.5 and 1.2, respectively, and similar across injection sites. Mechanism-based decreases in serum iron, transferrin-iron saturation, hemoglobin, and hematocrit were noted following multiple doses. There were no differences between injection sites in the pharmacodynamic effect as measured by change from baseline in hematocrit values. There were no serious adverse events. Treatment-emergent adverse events in 2 or more subjects were injection-site reactions (erythema, induration, pruritus), fatigue, and headache. There were no clinically relevant findings in the safety laboratory parameters, vital signs, electrocardiograms, or physical examination. While a higher incidence of treatment-emergent adverse events was noted in these healthy participants following multiple doses of 60 mg, rusfertide was generally well tolerated. There were no clinically meaningful differences in rusfertide pharmacokinetics or pharmacodynamics between injection sites.

The JAK pathway is central to mammalian cell communication, characterized by rapid responses, receptor versatility, and fine-tuned regulation. It involves Janus kinases (JAK1, JAK2, JAK3, TYK2), which are activated when natural ligands bind to receptors, leading to autophosphorylation and activation of STAT transcription factors [1, 2]. JAK-dependent signaling plays a pivotal role in coordinating cell communication networks across a broad spectrum of biological systems including development, immune responses, cell growth, and differentiation. JAKs are frequently mutated in the aging hematopoietic system [3, 4] and in hematopoietic cancers [5]. Thus, dysregulation of the pathway results in various diseases, including cancers and immune disorders. The binding of extracellular ligands to class I and II cytokine receptors initiates a critical signaling cascade through the activation of Janus kinases (JAKs). Upon ligand engagement, JAKs become activated and phosphorylate specific tyrosine residues on the receptor, creating docking sites for signal transducer and activator of transcription (STAT) proteins. Subsequent JAK-mediated phosphorylation of STATs enables their dimerization and nuclear translocation, where they function as transcription factors to modulate gene expression. Under physiological conditions, JAK-signaling is a tightly regulated mechanism that governs cellular responses to external cues, such as cytokines and growth factors, ensuring homeostasis and maintaining the functional integrity of tissues and organs. Highly defined regulation of JAK-signaling is essential for balancing cellular responses to inflammatory stimuli and growth signals, thus safeguarding tissue health. In contrast, dysregulated JAK-signaling results in chronic inflammation and unrestrained cellular proliferation associated with various diseases. Understanding the qualitative and quantitative differences at the interface of physiologic JAK-signaling and its aberrant activation in disease is crucial for the development of targeted therapies that precisely tune this pathway to target pathologic activation patterns while leaving homeostatic processes largely unaffected. Consequently, pharmaceutical research has targeted this pathway for drug development leading to the approval of several substances with different selectivity profiles towards individual JAKs. Yet, the precise impact of inhibitor selectivity and the complex interplay of different functional modules within normal and malignant cells remains incompletely understood. In this review, we summarize the current knowledge on JAK-signaling in health and disease and highlight recent advances and future directions in the field.

Patients with essential thrombocythemia (ET) have a chronic evolution with a risk of hematologic transformation associated with a dismal outcome. Because patients with resistance or intolerance have adverse prognosis, it is important to identify which patient will respond to first-line treatment. We, therefore, aim to describe the association between additional mutations and response to first-line treatment in patients with ET. In this retrospective study, we analyzed the molecular landscape of 121 ET patients first-line treated with hydroxyurea (HU; n = 86) or pegylated interferon (peg-IFN; n = 35). Patients undergoing peg-IFN therapy were younger and had higher proportion of low and very low risk of thrombosis recurrence. A total of 62 patients (51%) had ≥1 additional mutations at diagnosis. At 12 months of treatment, 75 patients (62%) achieved complete response (CR), 37 (31%) partial response, and 7 (6%) no response. The presence of at least 1 additional mutation at diagnosis was associated with not achieving CR (hazard ratio [HR], 0.65; P = .038), whereas treatment with peg-IFN was associated with higher CR (HR, 2.00; P = .002). The number of additional mutations at diagnosis was associated with hematologic progressions (P < .0001). None of the patients receiving peg-IFN therapy progressed to myelofibrosis, whereas 16 of 86 patients (19%) treated with HU developed secondary myelofibrosis. In conclusion, our results suggest that the presence of at least 1 additional mutation at diagnosis is associated with failure to achieve CR and also with an increased risk of hematologic evolution.

The Janus kinase/signal transducer and activator of transfection (JAK/STAT) system is comprised of multiple cell surface receptors, receptor tyrosine kinases, and signal transducers that are key components of numerous systems involved in malignancy, inflammation, immune surveillance and development, cellular proliferation, metabolism, differentiation, apoptosis, and hematologic disorders, all of which when disrupted can produce severe disease. Nevertheless, small molecule inhibitors of the four known JAKs, termed JAKinibs, have found therapeutic indications for a broad category of diseases. In this perspective, I will summarize the development of JAK inhibitors, whose origins were in antiquity, with particular attention to their use in treating patients with inflammatory bowel disease (IBD). This perspective is accompanied by a companion publication addressing how JAKinibs have forever altered the landscape of IBD therapy.

Patients with chronic, indolent myeloproliferative neoplasms (MPNs) are at risk for transformation to highly lethal leukemia, although targetable mechanisms driving progression remain elusive. We discovered that the High Mobility Group A1 (HMGA1) gene is up-regulated with MPN progression in patients and required for evolution into myelofibrosis (MF) or acute myeloid leukemia (AML) in preclinical models. HMGA1 encodes the HMGA1 epigenetic regulators that modulate the chromatin state during embryogenesis and tissue regeneration. While HMGA1 is silenced in most differentiated cells, it becomes aberrantly re-expressed in JAK2 mutant (JAK2-V617F) MPN, with the highest levels after transformation to secondary MF or AML. Here, we review recent work highlighting HMGA1 function in MPN progression. Though underlying mechanisms continue to emerge, increasing evidence suggests that HMGA1 functions as a "chromatin key" required to "unlock" regions of the genome involved in clonal expansion and progression in MPN. Together, these findings illuminate HMGA1 as a driver of MPN progression and a promising therapeutic target.

Essential thrombocythemia, a clonal myeloproliferative neoplasm with excessive platelet production, is associated with an increased risk of thrombosis and bleeding. The annual incidence rate of essential thrombocythemia in the US is 1.5/100 000 persons.

Patients with essential thrombocythemia have a persistent platelet count of 450 × 109/L or greater. The differential diagnosis includes myeloproliferative neoplasms (polycythemia vera, primary myelofibrosis, chronic myeloid leukemia); inflammatory conditions such as rheumatoid arthritis and systemic lupus erythematosus; infections; splenectomy; iron deficiency anemia; and solid tumors such as lung cancer. Approximately 90% of individuals with essential thrombocythemia have genetic variants that upregulate the JAK-STAT (signal transducer and activator of transcription 5) signaling pathway, including Janus kinase 2 (JAK2, 64%), calreticulin (CALR, 23%), and myeloproliferative leukemia virus oncogene (MPL, 4%). The median age at diagnosis of essential thrombocythemia is 59 years. The median overall survival exceeds 35 years in those diagnosed at 40 years or younger. Patients with essential thrombocythemia are at increased risk of arterial thrombosis (11%), venous thrombosis (7%), and hemorrhagic complications (8%). Thrombosis risk is increased among those with a history of thrombosis, age older than 60 years, a JAK2 gene variant, and cardiovascular risk factors (eg, hypertension, diabetes mellitus, hyperlipidemias, tobacco use). Use of aspirin (81-100 mg/d) is suggested for most patients with essential thrombocythemia to lower thrombosis risk. In a retrospective study of 300 affected patients with a low thrombosis risk (younger than 60 years with no prior thrombosis), those not taking aspirin (100 mg/d) had a risk of arterial thrombosis of 9.4/1000 patient-years and a venous thrombosis risk of 8.2/1000 patient years; cardiovascular risk factors were associated with a higher risk of arterial thrombi (incidence rate ratio, 2.5 [95% CI, 1.02-6.1]), and a JAK2 gene variant was associated with increased risk of venous thrombosis (incidence rate ratio, 4.0 [95% CI, 1.2-12.9]). In a randomized trial of 114 patients at higher risk for thrombosis (age older than 60 years or a prior thrombotic event), cytoreduction with hydroxyurea significantly lowered the risk of arterial or venous thrombotic events compared with no cytoreductive therapy (3.6% vs 24%; P < .01). At a median of 8.5 years from diagnosis, approximately 10% of patients with essential thrombocythemia develop myelofibrosis and about 3% develop acute myeloid leukemia.

Essential thrombocythemia is a rare clonal myeloproliferative neoplasm associated with an increased risk of venous and arterial thrombosis, hemorrhage, myelofibrosis, and acute myeloid leukemia. Based on individual risk factors for thrombosis, persons with essential thrombocythemia may be treated with low-dose aspirin, either alone or in combination with a cytoreductive drug such as hydroxyurea.

JAK2 exon 12 mutation status and the clinical characteristics of patients with polycythemia vera (PV) in Asia remain to be defined.

We analyzed the clinical, molecular, and genetic features and outcomes of patients with PV harboring exon 12 mutation and compared them with the JAK2V617F-mutated patients in Taiwan. JAK2V617F with allele burden was measured by pyrosequencing and/or RT/qPCR. The allele frequency of exon 12 mutation was analyzed by next-generation sequencing in JAK2V617F-negative patients.

A total of 532 patients diagnosed with PV were enrolled. The JAK2V617F mutation was present in 94.9% and exon 12 mutations in 5.1%. At diagnosis, patients with exon 12 mutation had higher hemoglobin (p = 0.012), and hematocrit levels (p = 0.003), and lower platelet (p <0.001), and leukocyte counts (p <0.001) compared to patients with JAK2V617F mutations. Patients harboring the JAK2V617F mutation had a higher incidence of high allele burden (p <0.001), disease risk (p= 0.014), and bleeding events (p= 0.013) compared to patients with PV with exon 12 mutations. These patients showed similar outcomes (overall survival, leukemia-free, myelofibrosis and thrombosis-free survival) to those with JAK2V617F mutations. An allele frequency ≥52.5% conferred an inferior overall survival compared to ≤52.5% in both exon 12-mutated (p = 0.029) and JAK2V617F patients with PV (p = 0.038).

Taiwanese patients with PV showed differences in blood count, risk group, and bleeding events between exon 12 and JAK2V617F patients. Higher mutant allele burden had a negative impact on overall survival for both mutation types.

 JAK2V617F-mutated myeloproliferative neoplasms (MPN) exhibit abnormal proliferation of bone marrow progenitors and increased risk of thrombosis, specifically in splanchnic veins (SVT). The contribution of the endothelium to the development of the prothrombotic phenotype was explored.

 Plasma and serum samples from JAK2V617F MPN patients with (n=26) or without (n=7) thrombotic debut and different treatments, were obtained (n=33). Cultured endothelial cells (ECs) were exposed to serum samples from these patients and from healthy donors as controls. Changes in markers of inflammation (VCAM-1, ICAM-1), cell permeability (VE-cadherin), production of VWF, extracellular matrix (ECM) reactivity, and activation of intracellular signaling pathways related to stress, proliferation, inflammation (Akt, p44/42, IkBa), and JAK2/STAT3 pathway, were assessed by immunofluorescence, flow adhesion, SDS-PAGE and immunoblot. Additionally, circulating markers of endothelial activation and damage (VWF, sVCAM-1, sTNFRI, thrombomodulin, angiopoietin-2, a2-antiplasmin activity, PAI-1) were evaluated in Patients' plasma.

 The in vitro studies showed that EC exposure to MPN thrombotic patients' sera resulted in increased VCAM-1 and ICAM-1, and reduced VE-cadherin expression (p<0.05) at the cell surface. Production and release of VWF to the ECM were higher (p<0.05), with increased platelet adhesion after perfusing whole blood, being more noticeable in response to sera from non-treated patients. Furthermore, intracellular activation of Akt, p44/42, IkBa and JAK2/STAT3 was observed. Moreover, plasma levels of VWF, TNF-R1, VCAM-1, thrombomodulin, and angiopoietin-2 were higher in JAK2V617F+ MPN patients with thrombosis.

 The present findings suggest that circulating factors in MPNs with SVT debut induce endothelial proinflammatory and prothrombotic phenotypes, which are modulated in vitro with MPN treatment.

Early cancer recognition is key to improving patient outcomes. Diagnosis is often delayed in patients with myeloproliferative neoplasms (MPNs), putting them at risk of thromboembolic events and other complications pre-diagnosis. A clear understanding of the barriers to presentation and diagnosis is required.

To explore barriers and factors influencing delayed presentation and diagnosis of MPNs.

A cross-sectional study of patients with MPN within the UK and the Republic of Ireland.

An online cross-sectional survey of patients with MPN was undertaken. Symptoms and factors influencing patient and GP delay were examined. Adjusted odds ratios (aORs) were calculated to explore the relationship between these factors and patient and GP delay.

Most (80.2%) of the 620 patients completing the survey reported symptomatic presentation. The most common symptoms associated with patient delay were pruritus (aOR 1.89, 95% confidence interval [CI] = 1.19 to 3.01), headaches (aOR 1.86, 95% CI = 1.13 to 2.82), and concentration difficulties (aOR 1.75, 95% CI = 1.12 to 2.76). Attributing symptoms to ageing (aOR 1.92, 95% CI = 1.19 to 3.11) and not wanting to burden the GP (2.04, 95% CI = 1.24 to 3.39) were significantly associated with patient delay. Those reporting >3 blood cancer warning signs were more likely to experience GP delay than those experiencing fewer (aOR 3.26, 95% CI = 1.75 to 6.29), and lack of relational continuity of GP care was significantly associated with GP delay (aOR 3.41, 95% CI = 1.65 to 7.28).

Debunking misconceptions around ageing, encouraging timely communication with GPs, and improving relational continuity of GP care could assist in reducing diagnostic delays, prevent potentially fatal disease complications, and ultimately improve outcomes for patients with MPN.

Polycythemia vera (PV), a myeloproliferative neoplasm characterized by an increased red blood cell mass and increased risk of thrombosis, affects approximately 65 000 people in the US, with an annual incidence of 0.5 to 4.0 cases per 100 000 persons.

Erythrocytosis (hemoglobin >16.5 mg/dL in men or >16.0 mg/dL in women) is a required diagnostic criterion, although thrombocytosis (53%) and leukocytosis (49%) are common. Patients may have pruritus (33%), erythromelalgia (5.3%), transient visual changes (14%), and splenomegaly (36%) with abdominal discomfort. More than 95% of patients have a JAK2 gene variant, which helps distinguish PV from secondary causes of erythrocytosis, such as tobacco smoking or sleep apnea. Among 7 cohorts (1545 individuals), the median survival from diagnosis was 14.1 to 27.6 years. Prior to or at the time of PV diagnosis, arterial thrombosis occurred in 16% of patients and 7% had venous thrombotic events, which could involve unusual sites, such as splanchnic veins. PV is also associated with an increased bleeding risk, especially in patients with acquired von Willebrand disease, which can occur with extreme thrombocytosis (platelet count, ≥1000 × 109/L). All patients with PV should receive therapeutic phlebotomy (goal hematocrit, <45%) and low-dose aspirin (if no contraindications). Patients who are at higher risk of thrombosis include those aged 60 years or older or with a prior thrombosis. These patients and those with persistent PV symptoms may benefit from cytoreductive therapy with hydroxyurea or interferon to lower thrombosis risk and decrease symptoms. Ruxolitinib is a Janus kinase inhibitor that can alleviate pruritus and decrease splenomegaly in patients who are intolerant of or resistant to hydroxyurea. About 12.7% of patients with PV develop myelofibrosis and 6.8% develop acute myeloid leukemia.

PV is a myeloproliferative neoplasm characterized by erythrocytosis and is almost universally associated with a JAK2 gene variant. PV is associated with an increased risk of arterial and venous thrombosis, hemorrhage, myelofibrosis, and acute myeloid leukemia. To decrease the risk of thrombosis, all patients with PV should be treated with aspirin and therapeutic phlebotomy to maintain a hematocrit of less than 45%. Cytoreductive therapies, such as hydroxyurea or interferon, are recommended for patients at high risk of thrombosis.

More than a decade following the discovery of Calreticulin (CALR) mutations as drivers of myeloproliferative neoplasms (MPN), advances in the understanding of CALR-mutant MPN continue to emerge. Here, we summarize recent advances in mehanistic understanding and in targeted therapies for CALR-mutant MPN.

Structural insights revealed that the mutant CALR-MPL complex is a tetramer and the mutant CALR C-terminus is exposed on the cell surface. Targeting mutant CALR utilizing antibodies is the leading therapeutic approach, while mutant CALR-directed vaccines are also in early clinical trials. Additionally, chimeric antigen receptor (CAR) T-cells directed against mutant CALR are under evaluation in preclinical models. Approaches addressing the cellular effects of mutant CALR beyond MPL-JAK-STAT activation, such as targeting the unfolded protein response, proteasome, and N-glycosylation pathways, have been tested in preclinical models. In CALR-mutant MPN, the path from discovery to mechanistic understanding to direct therapeutic targeting has advanced rapidly. The longer-term goal remains clonally-selective therapies that modify the disease course in patients.

Myeloid neoplasms include myeloproliferative and myelodysplastic neoplasms and acute myeloid leukaemia. Historically, these diseases have been diagnosed based on clinicopathological features with sometimes arbitrary thresholds that have persisted even as molecular features were gradually incorporated into their classification. As such, although current diagnostic approaches can classify the majority of myeloid neoplasms accurately using a combination of molecular and clinicopathological features, some areas of overlap persist and occasionally pose diagnostic challenges. These include overlap across BCR::ABL1-negative myeloproliferative neoplasms; between clonal cytopenia of undetermined significance and myelodysplastic neoplasms; myelodysplastic/myeloproliferative neoplasms; and, detection of KIT mutations in myeloid neoplasms other than mastocytosis, raising the prospect of systemic mastocytosis. Molecular testing has become state of the art in the diagnostic work-up of myeloid neoplasms, and molecular patterns can inherently help to classify overlapping entities if considered within a framework of haematological presentations. For future development, molecular testing will likely include whole genome and transcriptome sequencing, and primarily molecular classifications of myeloid neoplasms have already been suggested. As such, genetically defined groups should still constitute the basis for our understanding of disease development from early onset to progression, while clinicopathological features could then be used to describe the stage of the disease rather than the specific type of myeloid neoplasm.

The oral Janus kinase (JAK) 1/JAK2 inhibitor ruxolitinib was approved by the US Food and Drug Administration in 2014 for treatment of patients with polycythemia vera (PV) who have an inadequate response to or intolerance of hydroxyurea (HU). PV is a chronic myeloproliferative neoplasm defined by primary absolute erythrocytosis, bone marrow hypercellularity, and JAK mutations such as JAK2V617F. Patients with PV experience burdensome symptoms and are at risk of thromboembolic events, in particular those with resistance to or intolerance of initial treatments such as HU. Other risks for patients with PV include progression of disease to more aggressive forms with worse prognoses, such as myelofibrosis or blast-phase myeloproliferative neoplasms. This review summarizes the efficacy and safety of ruxolitinib from key phase 2 and 3 trials (MAJIC-PV, RESPONSE, RESPONSE-2, RELIEF, and Ruxo-BEAT), large real-world studies, and a decade of postmarketing surveillance safety data. The authors focus on improved blood count control, rates of thromboembolic events, symptom improvement, and markers of disease modification such as reduction of JAK2V617F allele burden in patients treated with ruxolitinib. They also discuss the well-characterized safety profile of ruxolitinib regarding hematologic and other adverse events of interest. In the 10 years since its approval, ruxolitinib remains a safe and effective standard-of-care treatment for PV. As the treatment landscape for PV continues to evolve in the coming years, the efficacy and safety profiles of ruxolitinib suggest it will remain a preferred treatment as monotherapy and as a potential backbone of future combination regimens.

Polycythemia vera (PV) is characterized by clonal hematopoietic stem or progenitor cells with constitutively active somatic mutation(s) in the Janus kinase 2 gene. Phlebotomy (Phl) and aspirin are often used alone for low-risk PV patients. However, data from the Low-PV study demonstrated that Phl and aspirin may not be adequate for patients. Therapeutic intervention with disease-modifying treatment appears to be beneficial for patients with PV regardless of the risk category. Ropeginterferon alfa-2b (ropeg) is a novel interferon-based therapy with favorable dosing schedules. A higher starting-dose (250 µg) regimen with simpler dose titrations was found to have a potent disease-modifying effect with respect to inducing a molecular response. PARADIGM-PV is a randomized, phase 4 study with the primary goal of assessing the efficacy of ropeg at this dosing regimen in alleviating Phl-dependence in both low- and high-risk patients with PV. The secondary endpoints include complete hematologic response, molecular response, symptom improvement, maintenance of median hematocrit (Hct) values < 45% without disease progression, and safety. Patients will be randomized equally to receive either ropeg every two weeks or to continue their current treatment with Phl or other cytoreductive agents (e.g., hydroxyurea, other interferons, or ruxolitinib) as applicable. All patients will receive Phl if their Hct values are elevated to ≥45% according to the National Comprehensive Cancer Network guidelines. The study will enroll approximately 70 patients internationally, including patients in the US. This study will provide new efficacy data, measured as the ability of ropeg to reduce Phl eligibility and modify the disease.

Extrahepatic portal vein obstruction (EHPVO) is a rare disease-causing form of portal hypertension. Myeloproliferative neoplasm (MPN) including essential thrombocythemia (ET) is a reported risk factor for EHPVO due to underlying persistent thrombophilia. A Japanese woman in her 40s was referred to our hospital with a 1-month history of gastric variceal bleeding due to EHPVO. Laboratory investigation showed thrombocytosis despite portal hypertension. She had a mutation in clonal marker JAK2V617F with EHPVO, which prompted us to consult a hematologist. A bone marrow biopsy revealed megakaryocyte lineage proliferation, which confirmed a diagnosis of ET. Esophagogastroduodenoscopy revealed esophagogastric varices (LsF2CbRC2, Lg-cF1RC1), and abdominal computed tomography and angiography revealed splenomegaly and portal vein thrombosis with cavernous transformation, which suggested EHPVO. The patient had a history of ruptured esophagogastric varices and required prophylaxis against further variceal bleeding before antithrombotic therapy for EHPVO with ET. We performed laparoscopic Hassab's operation followed by endoscopic variceal ligation (EVL) and hematological cytoreduction therapy. Laparoscopic Hassab's operation and three bi-monthly EVL procedures improved the esophagogastric varix (LmF0RC0, Lg-f F0RC0) at 6 months after surgery. Cytoreduction therapy reduced platelet count to 60.1 × 104/uL, and the patient was very healthy at 7 months after surgery. Patients with EHPVO are traditionally referred to a gastroenterologist for abdominal pain, intestinal bleeding, or refractory ascites; however, hypercoagulative disease may be occult in such patients and require the attention of a hematologist. When treating patients with EHPVO, gastroenterologists should screen for hematological disease, including MPN.

Endometrial cancer (EC) is the ninth most common malignancy among women. While mutations in JAK2 are frequently observed in EC, the specific biological functions of JAK2 in endometrial cancer are poorly understood.

The genetic alterations of JAK2 in different cancer types were explored using sequencing dataset deposited at TCGA database. JAK2 mutations were detected in EC formalin-fixed paraffin-embedded (FFPE) samples using Sanger sequencing. The expression levels of JAK2 was accessed using the TCGA database and immunohistochemistry. Furthermore, the relationships between JAK2 expression and staging and prognosis of EC patients were investigated using the TCGA database. Down-regulation of JAK2 were achieved by transient transfection with short hairpin RNAs (shRNAs). Effects of JAK2 on cancer cells proliferation and migration were evaluated by CCK8, colony formation, and transwell assay. The potential biological functions of JAK2 in EC were identified based on bioinformatics analysis. Effects of JAK2 on expression levels of target genes were detected by RT-qPCR and western blotting. Co-immunoprecipitation (co-IP) assays was used to detect the physical association between JAK2 and HIF-1α.

Frequent mutations and down-regulation of JAK2 were found in EC. Loss-of-function (LOF) assays suggested that JAK2 silencing in endometrial cancer cells promoted cell proliferation and migration, which were partially dependent on HIF-1α signaling pathway. Furthermore, our findings demonstrated that JAK2 interacted with HIF-1α and reduced HIF1α protein expression under hypoxia.

These findings revealed novel molecular mechanisms underlying JAK2 LOF mutations-driven endometrial tumorigenesis and revealed that the HIF-1α pathway may be a potential therapeutic target in JAK2-mutated endometrial cancer.

Constitutive activation of Janus kinase 2 (JAK2)/signal transducer and activator of transcription (STAT) signaling pathway is central to the pathogenesis of myeloproliferative neoplasms (MPNs). Long noncoding RNAs (lncRNAs) regulate diverse biological processes. However, the role of lncRNAs in MPN pathogenesis is not well studied.

The expression of lnc-AC004893 in MPN patients was measured by quantitative real-time PCR (qRT-PCR). Gene-specific short hairpin RNAs (shRNAs) were designed to inhibit the expression of lnc-AC004893, and western blot was performed to explore the role of lnc-AC004893 via regulating the JAK2/STAT5 signaling pathway. Furthermore, co-IP was performed to determine the binding ability of lnc-AC004893 and STAT5 protein. Finally, the BaF3-JAK2V617F-transplanted mouse model was used to assess the biological role of lnc-ac004893 in vivo.

We report that lnc-AC004893, a poorly conserved pseudogene-209, is substantially upregulated in MPN cells compared with normal controls (NCs). Knockdown of lnc-AC004893 by specific shRNAs suppressed cell proliferation and decreased colony formation. Furthermore, the knockdown of lnc-AC004893 reduced the expression of p-STAT5 but not total STAT5 in HEL and murine IL-3-dependent Ba/F3 cells, which present constitutive and inducible activation of JAK2/STAT5 signaling. In addition, inhibition of murine lnc-ac004893 attenuated BaF3-JAK2V617F-transplanted phenotypes and extended the overall survival. Mechanistically, knockdown of lnc-AC004893 enhanced the binding ability of STAT5 and protein tyrosine phosphatase SHP1. Furthermore, knockdown of lnc-AC004893 decreased STAT5-lnc-AC004893 interaction but not SHP1-lnc-AC004893 interaction.

Lnc-AC004893 regulates STAT5 phosphorylation by affecting the interaction of STAT5 and SHP1. Lnc-AC004893 might be a potential therapeutic target for MPN patients.

Hepcidin, an endogenous peptide hormone, binds to ferroportin and is the master regulator of iron trafficking. Rusfertide, a synthetic peptide, is a potent hepcidin mimetic. Clinical studies suggest rusfertide may be effective in the treatment of polycythemia vera. This study investigated the dose-ranging pharmacokinetics, pharmacodynamics, and safety of a lyophilized formulation of rusfertide.

A randomized open-label crossover study was conducted in two groups of healthy adult subjects to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of subcutaneous rusfertide doses that ranged from 10 to 60 mg of a lyophilized formulation and 20 mg of an aqueous prefilled syringe formulation that were used in clinical trials.

Rusfertide showed a rapid initial absorption. Median time to peak plasma concentrations for the lyophilized formulation was 24 h for doses of 10-30 mg and 2-4 h for doses of 45 and 60 mg. Mean terminal half-life ranged from 19.6 to 57.1 h. Rusfertide peak concentration and area under the concentration-time curve increased with an increasing dose, but in a less than dose-proportional manner. Metabolites M4 and M9 were identified as major metabolites. At the rusfertide 20-mg dose, the lyophilized formulation had an area under the concentration-time curve from time zero to infinity approximately 1.5-fold higher than the aqueous formulation. The elimination half-life was comparable for the two formulations. Dose-related decreases in serum iron and transferrin-iron saturation were seen following rusfertide treatment. The majority of treatment-emergent adverse events were mild; treatment-related treatment-emergent adverse events seen in ≥10% of subjects were injection-site erythema and injection-site pruritus.

Rusfertide was well tolerated; the pharmacokinetic and pharmacodynamic results indicate that lyophilized rusfertide is suitable for once-weekly or twice-weekly administration.

Platelets are critical for thrombosis and hemostasis. The THPO-MPL pathway is the primary pathway for generating thrombocytes. Dysregulation of thrombopoiesis results in platelet formation and/or function-related disorders, such as thrombocytopenia. Paclitaxel is an extensively utilized chemotherapeutic agent and its activity may be related to platelets, but the effect of paclitaxel on thrombocytopoiesis warrants comprehensive exploration.

We focused on identifying factors that regulate thrombocyte production and elucidating paclitaxel's regulatory mechanisms on thrombocytopoiesis, with a particular emphasis on discovering mechanisms that bypass THPO-MPL pathways.

We performed drug screenings using the Tg(mpl:eGFP) zebrafish model in vivo to identify Food and Drug Administration-approved compounds capable of boosting thrombocyte production. An injury experiment was used to evaluate thrombocyte function. Bromodeoxyuridine assays, terminal deoxynucleotidyl transferase dUTP nick-end labeling, and RNA sequencing analyses were performed to explore cytological and molecular mechanisms. Routine blood testing and flow cytometry were used to analyze mouse phenotypes.

We found that paclitaxel expands thrombocytes by accelerating the proliferation of thrombocytic lineage cells in zebrafish and elevates platelet levels in mice. This effect occurs by bypassing the thrombopoietin receptor (Mpl). We found that paclitaxel promotes thrombopoiesis, potentially involving the JAK2-ERK1/2 MAPK signaling cascade, a pathway integral to MPL and other regulators. Our results further demonstrate that ERK1/2 is at least partially downstream of JAK2 in paclitaxel-induced thrombopoiesis.

Paclitaxel could promote thrombopoiesis by bypassing Mpl but presumably via the JAK2-ERK1/2 MAPK pathways. It will aid in understanding the relationship between paclitaxel and platelets clinically, and paclitaxel may have potential value for safeguarding platelets and improving thrombocytosis in related diseases.

This study aimed to compile bioinformatic and experimental information for JAK2 missense variants previously reported in myeloproliferative neoplasms (MPN) and determine if germline JAK2-I724T, recently found to be common in New Zealand Polynesians, associates with MPN.

For all JAK2 variants found in the literature, gnomAD_exome allele frequencies were extracted and REVEL scores were calculated using the dbNSFP database. We investigated the prevalence of JAK2-I724T in a cohort of 111 New Zealand MPN patients using a TaqMan assay, examined its allelic co-occurrence with JAK2-V617F using Oxford Nanopore sequencing, and modelled the impact of I724T on JAK2 using I-Mutant and ChimeraX software.

Several non-V617F JAK2 variants previously reported in MPN had REVEL scores greater than 0.5, suggesting pathogenicity. JAK2-I724T (REVEL score 0.753) was more common in New Zealand Polynesian MPN patients (n = 2/27; 7.4%) than in other New Zealand patients (n = 0/84; 0%) but less common than expected for healthy Polynesians (n = 56/377; 14.9%). Patients carrying I724T (n = 2), one with polycythaemia vera and one with essential thrombocythaemia, had high-risk MPN. Both patients with JAK2-I724T were also positive for JAK2-V617F, found on the same allele as I724T, as well as separately. In silico modelling did not identify noticeable structural changes that would give JAK2-I724T a gain-of-function.

Several non-canonical JAK2 variants with high REVEL scores have been reported in MPN, highlighting the need to further understand their relationship with disease. The JAK2-I724T variant does not drive MPN, but additional investigations are required to exclude any potential modulatory effect on the MPN phenotype.

In this issue of Blood, Reis et al1 identify a monoclonal antibody, INCA033989, that selectively targets mutant calreticulin (mutCALR) in myeloproliferative neoplasms (MPNs), inhibiting its oncogenic activity without affecting normal hematopoiesis.

Heat shock protein 90 (HSP90) is a pivotal molecular chaperone with multifaceted roles in cellular health and disease. Herein, we explore how HSP90 orchestrates cellular stress responses, particularly through its partnership with heat shock factor 1 (HSF-1). PU-H71, a selective inhibitor of HSP90, demonstrates significant potential in cancer therapy by targeting a wide array of oncogenic pathways. By inducing the degradation of multiple client proteins, PU-H71 disrupts critical signaling pathways such as MAPK, PI3K/Akt, JAK/STAT, EGFR, and mTOR, which are essential for cancer cell survival, proliferation, and metastasis. We examined its impact on combating triple-negative breast cancer and enhancing the effectiveness of carbon-ion beam therapy, offering new avenues for cancer treatment. Furthermore, the dual inhibition of HSP90A and HSP90B1 by PU-H71 proves highly effective in the context of myeloma, providing fresh hope for patients with this challenging malignancy. We delve into its potential to induce apoptosis in B-cell lymphomas that rely on Bcl6 for survival, highlighting its relevance in the realm of hematologic cancers. Shifting our focus to hepatocellular carcinoma, we explore innovative approaches to chemotherapy. Moreover, the current review elucidates the potential capacity of PU-H71 to suppress glial cell activation paving the way for developing novel therapeutic strategies for neuroinflammatory disorders. Additionally, the present report also suggests the promising role of PU-H71 in JAK2-dependent myeloproliferative neoplasms. Eventually, our report sheds more light on the multiple functions of HSP90 protein as well as the potential therapeutic benefit of its selective inhibitor PU-H71 in the context of an array of diseases, laying the foundations for the development of novel therapeutic approaches that could achieve better treatment outcomes.

Scleroderma and other fibrotic diseases have been investigated using single-cell RNA sequencing (scRNA-Seq), which has demonstrated enrichment in myeloid cell populations in multiple tissues. However, scRNA-Seq studies are inconsistent in their nomenclature of myeloid cell types, including dendritic cells, monocytes, and macrophages. Using cell type-defining gene signatures, I propose a unified nomenclature through analysis of myeloid cell enrichment across fibrotic tissues.

scRNA-Seq of human blood and skin identified a new subset of dendritic cells called DC3. DC3 express similar inflammatory genes to monocytes, including FCN1 , IL1B, VCAN, S100A8, S100A9 , and S100A12 . DC3 can be distinguished from monocytes by expression of EREG and Fc receptor genes such as FCER1A and FCGR2B . scRNA-Seq analyses of scleroderma skin and lung, idiopathic pulmonary fibrosis (IPF), COVID-19 lung fibrosis, myelofibrosis, and liver, kidney, and cardiac fibrosis all showed enrichment in myeloid cell types. Although they were called different names, studies of scleroderma skin and lung as well as liver cirrhosis datasets demonstrated enrichment in DC3. By contrast, lung, heart, and kidney fibrosis were enriched in SPP1 macrophages. High numbers of DC3 in the skin was associated with worse SSc skin and lung fibrosis severity.

scRNA-Seq of multiple diseases showed enrichment of DC3 in fibrotic skin, lung, and liver, whereas SPP1 macrophages occurred in fibrotic lung, heart, and kidney. Because DC3 and SPP1 macrophages showed organ-specific enrichment, understanding their signaling mechanisms across tissues will be important for future investigation.

There has been remarkable progress in the development of novel therapeutic approaches for patients with polycythemia vera (PV). Historically, therapy goals in PV were to mitigate thrombotic risks and control blood counts and symptoms. There is now increased focus on disease modification through progressive attrition of JAK2-mutant stem/progenitor cells. The approval of ropeginterferon, a novel monoPEGylated interferon, coupled with findings from LOW-PV and longer-term data from CONTINUATION-PV that strongly support a disease-modifying effect for interferon therapy, have transformed the treatment paradigm for this disorder. Results from MAJIC-PV demonstrate that disease modification can also be induced with JAK inhibitors, suggesting an urgent need to incorporate prospective molecular monitoring into PV trials. Novel agents, such as hepcidin mimetics, aim to help patients with PV restore normal hematocrit levels and become phlebotomy-free. In this review, we will summarize past, current and future approaches to PV management and highlight findings from key clinical studies.

Clonal hematopoiesis (CH), the expansion of hematopoietic stem cells and their progeny driven by somatic mutations in leukemia-associated genes, is a common phenomenon that rises in prevalence with advancing age to affect most people older than 70 years. CH remains subclinical in most carriers, but, in a minority, it progresses to a myeloid neoplasm, such as acute myeloid leukemia, myelodysplastic syndrome, or myeloproliferative neoplasm. Over the last decade, advances in our understanding of CH, its molecular landscape, and the risks associated with different driver gene mutations have culminated in recent developments that allow for a more precise estimation of myeloid neoplasia risk in CH carriers. In turn, this is leading to the development of translational and clinical programs to intercept and prevent CH from developing into myeloid neoplasia. Here, we give an overview of the spectrum of CH driver mutations, what is known about their pathophysiology, and how this informs the risk of incident myeloid malignancy.

Ropeginterferon alfa-2b (Ropeg) is approved for the treatment of adults with polycythemia vera (PV). This report aims to analyze the ethnic sensitivity of Ropeg for the treatment of PV, comparing the pharmacokinetics (PK), efficacy, and safety profiles across diverse ethnic groups. We conducted a relevant review of PV and analysis of data obtained from clinical studies involving Ropeg. The PK behavior of ropeg showed no significant differences between Chinese and overseas populations. Their efficacy and safety profiles were similar across the ethnic groups. The analyses indicated that the dose-exposure-response profile of Ropeg was consistent irrespective of ethnic variations. The results suggest that Ropeg exhibits a consistent PK and pharmacodynamics profile and a similar therapeutic effect across different ethnic groups, confirming its efficacy and safety in the global treatment of PV. More generally, these findings support the broader application of Ropeg in diverse patient populations and emphasize the need for an inclusive clinical practice.

Myeloproliferative neoplasms (MPNs) are characterized by increased proliferation of myeloid lineages in the bone marrow. Calreticulin (CALR) 52 bp deletion and CALR 5 bp insertion have been identified in essential thrombocythemia (ET) and primary myelofibrosis (PMF). There is not much data on the crosstalk between mutated CALR and MPN-related signaling pathways, such as JAK/STAT, PI3K/Akt/mTOR, and Hedgehog. Calreticulin, a multifunctional protein, takes part in many cellular processes. Nevertheless, there is little data on how mutated CALR affects the oxidative stress response and oxidative stress-induced DNA damage, apoptosis, and cell cycle progression. We aimed to investigate the role of the CALR 52 bp deletion and 5 bp insertion in the pathogenesis of MPN, including signaling pathway activation and functional analysis in CALR-mutated cells. Our data indicate that the JAK/STAT and PI3K/Akt/mTOR pathways are activated in CALR-mutated cells, and this activation does not necessarily depend on the CALR and MPL interaction. Moreover, it was found that CALR mutations impair calreticulin function, leading to reduced responses to oxidative stress and DNA damage. It was revealed that the accumulation of G2/M-CALR-mutated cells indicates that oxidative stress-induced DNA damage is difficult to repair. Taken together, this study contributes to a deeper understanding of the specific molecular mechanisms underlying CALR-mutated MPNs.

Cancer remains one of the leading diseases of mortality worldwide. Janus kinases 2/3 (JAK2/3) have been considered a drug target for the development of drugs to treat different types of cancer. JAK2/3 play a critical role in innate immunity, inflammation, and hematopoiesis by mediating the signaling of numerous cytokines, growth factors, and interferons. The current focus is to develop new selective inhibitors for each JAK type. In this review, the current strategies of computer-aided studies, and biological evaluations against JAK2/3 are addressed. We found that the new synthesized JAK2/3 inhibitors are prone to containing heterocyclic aromatic rings such as pyrimidine, pyridine, and pyrazolo [3,4-d]pyrimidine. Moreover, inhibitors of natural origin derived from plant extracts and insects have shown suitable inhibitory capacities. Computer-assisted studies have shown the important features of inhibitors for JAK2/3 binding. Biological evaluations showed that the inhibition of the JAK receptor affects its related signaling pathway. Although the reviewed compounds showed good inhibitory capacity in vitro and in vivo, more in-depth studies are needed to advance toward full approval of cancer treatments in humans.

Despite increased understanding of the genomic landscape of Myeloproliferative Neoplasms (MPNs), the pathological mechanisms underlying abnormal megakaryocyte (Mk)-stromal crosstalk and fibrotic progression in MPNs remain unclear. We conducted mass spectrometry-based proteomics on mice with Romiplostim-dependent myelofibrosis to reveal alterations in signaling pathways and protein changes in Mks, platelets, and bone marrow (BM) cells. The chemokine Platelet Factor 4 (PF4)/Cxcl4 was up-regulated in all proteomes and increased in plasma and BM fluids of fibrotic mice. High TPO concentrations sustained in vitro PF4 synthesis and secretion in cultured Mks, while Ruxolitinib restrains the abnormal PF4 expression in vivo. We discovered that PF4 is rapidly internalized by stromal cells through surface glycosaminoglycans (GAGs) to promote myofibroblast differentiation. Cxcl4 gene silencing in Mks mitigated the profibrotic phenotype of stromal cells in TPO-saturated co-culture conditions. Consistently, extensive stromal PF4 uptake and altered GAGs deposition were detected in Romiplostim-treated, JAK2V617F mice and BM biopsies of MPN patients. BM PF4 levels and Mk/platelet CXCL4 expression were elevated in patients, exclusively in overt fibrosis. Finally, pharmacological inhibition of GAGs ameliorated in vivo fibrosis in Romiplostim-treated mice. Thus, our findings highlight the critical role of PF4 in the fibrosis progression of MPNs and substantiate the potential therapeutic strategy of neutralizing PF4-GAGs interaction.

Extrahepatic portal vein obstruction (EHPVO) is a rare disease with myeloproliferative neoplasm (MPN) as the most common cause. We report that hypersplenic hematologic changes in EHPVO might be eliminated by MPN. Through experience with splenectomy for variceal control with EHPVO, we suspected that spleen might mask MPN-induced thrombocytosis, and that MPN might have a significant influence on excessive thrombocytosis after splenectomy. To clarify the influence of MPN and spleen on platelet trends, we conducted a retrospective hospital database analysis, evaluating 8 EHPVO patients with splenectomy (2 males, 6 females; from 17 years to 64 years, mean 38.3 years). Three (37.5%) of 8 were diagnosed as MPN by JAK2V617F mutation. The perioperative serum platelet counts in EHPVO without MPN were 10.5, 35.4, and 36.6 (x104/μL) preoperatively, after 1 week and 3 weeks, respectively. The platelet counts in EHPVO with MPN were 34.2, 86.4, and 137.0 (x104/μL), respectively. Splenectomy and MPN showed positive interaction on platelet increasing with statistical significance. We also examined the spleen volume index (SpVI: splenic volume (cm3) / body surface area (m2) and postoperative platelet elevations ratio (PER: 3-week postoperative platelet counts / preoperative platelet counts). However, both SpVI and PER showed no significant difference with or without MPN. Histological examination revealed splenic congestion in all 8 EHPVO cases, and splenic extramedullary hematopoiesis in 2 of 3 MPN. In EHPVO with MPN, hypersplenism causes feigned normalization of platelet count by masking MPN-induced thrombocytosis; however, splenectomy unveils postoperative thrombocytosis. Spleen in EHPVO with MPN also participates in extramedullary hematopoiesis.

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway serves as a paradigm for signal transduction from the extracellular environment to the nucleus. It plays a pivotal role in physiological functions, such as hematopoiesis, immune balance, tissue homeostasis, and surveillance against tumors. Dysregulation of this pathway may lead to various disease conditions such as immune deficiencies, autoimmune diseases, hematologic disorders, and cancer. Due to its critical role in maintaining human health and involvement in disease, extensive studies have been conducted on this pathway, ranging from basic research to medical applications. Advances in the structural biology of this pathway have enabled us to gain insights into how the signaling cascade operates at the molecular level, laying the groundwork for therapeutic development targeting this pathway. Various strategies have been developed to restore its normal function, with promising therapeutic potential. Enhanced comprehension of these molecular mechanisms, combined with advances in protein engineering methodologies, has allowed us to engineer cytokines with tailored properties for targeted therapeutic applications, thereby enhancing their efficiency and safety. In this review, we outline the structural basis that governs key nodes in this pathway, offering a comprehensive overview of the signal transduction process. Furthermore, we explore recent advances in cytokine engineering for therapeutic development in this pathway.

Receptor tyrosine kinases (RTKs), a category of transmembrane receptors, have gained significant clinical attention in oncology due to their central role in cancer pathogenesis. Genetic alterations, including mutations, amplifications, and overexpression of certain RTKs, are critical in creating environments conducive to tumor development. Following their discovery, extensive research has revealed how RTK dysregulation contributes to oncogenesis, with many cancer subtypes showing dependency on aberrant RTK signaling for their proliferation, survival and progression. These findings paved the way for targeted therapies that aim to inhibit crucial biological pathways in cancer. As a result, RTKs have emerged as primary targets in anticancer therapeutic development. Over the past two decades, this has led to the synthesis and clinical validation of numerous small molecule tyrosine kinase inhibitors (TKIs), now effectively utilized in treating various cancer types. In this manuscript we aim to provide a comprehensive understanding of the RTKs in the context of cancer. We explored the various alterations and overexpression of specific receptors across different malignancies, with special attention dedicated to the examination of current RTK inhibitors, highlighting their role as potential targeted therapies. By integrating the latest research findings and clinical evidence, we seek to elucidate the pivotal role of RTKs in cancer biology and the therapeutic efficacy of RTK inhibition with promising treatment outcomes.

The treatment landscape of polycythemia vera (PV) has seen major advancements within the last decade including approval of ruxolitinib in the second line setting after hydroxyurea, ropegylated interferon-α2b, and advanced clinical development of a novel class of agents called hepcidin mimetics.

We provide a comprehensive review of the evidence discussing the risk stratification, treatment indications, role and limitations of phlebotomy only approach and pivotal trials covering nuances related to the use of interferon-α (IFN-α), ruxolitinib, hepcidin mimetics, and upcoming investigational agents including HDAC and LSD1 inhibitors.

The research paradigm in PV is slowly shifting from the sole focus on hematocrit control and moving toward disease modification. The discovery of hepcidin mimetics has come as a breakthrough in restoring iron homeostasis, achieving phlebotomy-independence and may lead to improved thrombosis-free survival with stricter hematocrit control. On the other hand, emerging data with IFN- α and ruxolitinib as well as combination of the two agents suggests the potential for achieving molecular remission in a subset of PV patients and long-term follow-up is awaited to validate the correlation of molecular responses with clinically relevant outcomes of progression-free and thrombosis-free survival.

We report a case of acute myocardial infarction in a patient with polycythemia rubra vera, who has been treated with hydroxyurea. The patient presented with chest pain extending to both arms accompanied by nausea and sweating. Hemoglobin was 18.1 mg/dL, hematocrit 53.2%, white blood cells 9600/mm³, and platelets 745,000/mm³. The levels of specific cardiac injury markers were increased, troponin I increased to 110 ng/mL and creatine kinase-MB to 361 U/l, respectively. Electrocardiography showed sinus rhythm with ST-segment elevation in leads V2-6, D1, and aVL as well as ST depression in D2, D3 and aVF. Echocardiography demonstrated hypokinesis of the interventricular septum and lateral wall with mildly reduced left ventricle (LV) ejection fraction (EF≈45%). Coronary angiography revealed proximal-LAD subtotal occlusion and 80% mid-LAD stenosis with distal-LAD vasospasm. Percutaneous coronary intervention was performed with a drug-eluting stent in mid- and proximal-LAD. Hypercoagulable state of polycythemia rubra vera may be complicated with acute myocardial infarction, in addition to the vasospastic effect and endothelium lesions of hydroxyurea regardless its favorable effect as a standard therapy.

Leukemia represents a diverse group of hematopoietic neoplasms that can be classified into different subtypes based on the molecular aberration in the affected cell population. Identification of these molecular classification is required to identify specific targeted therapeutic approaches for each leukemic subtype. In general, targeted therapy approaches achieve good responses in some leukemia subgroups, however, resistance against these targeted therapies is common. In this review, we summarize molecular drug resistance biomarkers in targeted therapies in BCR::ABL1-driven chronic myeloid leukemia (CML) and JAK2-driven myeloproliferative neoplasms (MPNs). While acquisition of secondary mutations in the BCR::ABL1 kinase domain is the a common mechanism associated with TKI resistance in CML, in JAK2-driven MPNs secondary mutations in JAK2 are rare. Due to high prevalence and lack of specific therapy approaches in MPNs compared to CML, identification of crucial pathways leading to inhibitor persistence in MPN model is utterly important. In this review, we focus on different alternative signaling pathways activated in both, BCR::ABL1-mediated CML and JAK2-mediated MPNs, by combining data from in vitro and in vivo-studies that could be used as potential biomarkers of drug resistance. In a nutshell, some common similarities, especially activation of PDGFR, Ras, PI3K/Akt signaling pathways, have been demonstrated in both leukemias. In addition, induction of the nucleoprotein YBX1 was shown to be involved in TKI-resistant JAK2-mediated MPN, as well as TKI-resistant CML highlighting deubiquitinating enzymes as potential biomarkers of TKI resistance. Taken together, whole exome sequencing of cell-based or patients-derived samples are highly beneficial to define specific resistance markers. Additionally, this might be helpful for the development of novel diagnostic tools, e.g., liquid biopsy, and novel therapeutic agents, which could be used to overcome TKI resistance in molecularly distinct leukemia subtypes.

Ruxolitinib has been approved by the US FDA for the treatment of myeloproliferative neoplasms such as polycythemia vera and primary myelofibrosis. Ruxolitinib will remain a main stay in the treatment of MPN patients due to its effective therapeutic benefits. However, there have been instances of ruxolitinib resistance in MPN patients. As JAK2 is a direct target of ruxolitinib, we generated ruxolitinib-resistant clones to find out the mechanism of resistance.

Cell-based screening strategy was used to detect the ruxolitinib-resistant mutations in JAK2. The Sanger sequencing method was used to detect the point mutations in JAK2. Mutations were re-introduced using the site-directed mutagenesis method and stably expressed in Ba/F3 cells. Drug sensitivities against the JAK2 inhibitors were measured using an MTS-based assay. JAK2 and STAT5 activation levels and total proteins were measured using immunoblotting. Computational docking studies were performed using the Glide module of Schrodinger Maestro software.

In this study, we have recovered seven residues in the kinase domain of JAK2 that affect ruxolitinib sensitivity. All these mutations confer cross-resistance across the panel of JAK2 kinase inhibitors except JAK2-L983F. JAK2-L983F reduces the sensitivity towards ruxolitinib. However, it is sensitive towards fedratinib indicating that our screen identifies the drug-specific resistance profiles. All the ruxolitinib-resistant JAK2 variants displayed sensitivity towards type II JAK2 inhibitor CHZ-868. In this study, we also found that JAK1-L1010F (homologous JAK2-L983F) is highly resistant towards ruxolitinib suggesting the possibility of JAK1 escape mutations in JAK2-driven MPNs and JAK1 mutated ALL. Finally, our study also shows that HSP90 inhibitors are potent against ruxolitinib-resistant variants through the JAK2 degradation and provides the rationale for clinical evaluation of potent HSP90 inhibitors in genetic resistance driven by JAK2 inhibitors.

Our study identifies JAK1 and JAK2 resistance variants against the type I JAK2 inhibitors ruxolitinib, fedratinib, and lestaurtinib. The sensitivity of these resistant variants towards the type II JAK2 inhibitor CHZ-868 indicates that this mode of type II JAK2 inhibition is a potential therapeutic approach against ruxolitinib refractory leukemia. This also proposes the development of potent and specific type II JAK2 inhibitors using ruxolitinib-resistance variants as a prototype.

Polycythemia vera (PV) is a clonal disorder arising from the acquired somatic mutations of the JAK2 gene, including JAK2V617F or several others in exon 12. A 38-year-old female had a stroke at age 32 and found to have elevated hemoglobin, normal leukocytes, normal platelets, and tested negative for JAK2V617F and exon 12 mutations. Next generation sequencing revealed a novel mutation: JAK2R715T in the pseudokinase domain (JH2) at 47.5%. Its presence in her nail DNA confirmed a germline origin. Her mother and her son similarly had erythrocytosis and a JAK2R715T mutation. Computer modeling indicated gain-of-function JAK2 activity. The propositus and her mother had polyclonal myelopoiesis, ruling out another somatic mutation-derived clonal hematopoiesis. Some erythroid progenitors of all three generations grew without erythropoietin, a hallmark of PV. The in vitro reporter assay confirmed increased activity of the JAK2R715T kinase. Similar to PV, the JAK2R715T native cells have increased STAT5 phosphorylation, augmented transcripts of prothrombotic and inflammatory genes, and decreased KLF2 transcripts. The propositus was not controlled by hydroxyurea, and JAK2 inhibitors were not tolerated; however, Ropeginterferon-alfa-2b (Ropeg-IFN-α) induced a remission. Ropeg-IFN-α treatment also reduced JAK2 activity in the propositus, her mother and JAK2V617F PV subjects. We report dominantly inherited erythrocytosis secondary to a novel germline JAK2R715T gain-of-function mutation with many but not all comparable molecular features to JAK2V617F PV. We also document a previously unreported inhibitory mechanism of JAK2 signaling by Ropeg-IFN-α.