The JAK inhibitor ruxolitinib impairs dendritic cell migration via off-target inhibition of ROCK

Differential properties of Janus kinase inhibitors in the treatment of immune-mediated inflammatory diseases

Janus kinases (JAKs) are a family of cytosolic tyrosine kinases that regulate cytokine signal transduction, including cytokines involved in a range of inflammatory diseases, such as RA, psoriasis, atopic dermatitis and IBD. Several small-molecule JAK inhibitors (JAKis) are now approved for the treatment of various immune-mediated inflammatory diseases. There are, however, key differences between these agents that could potentially translate into unique clinical profiles. Each JAKi has a unique chemical structure, resulting in a distinctive mode of binding within the catalytic cleft of the target JAK, and giving rise to distinct pharmacological characteristics. In addition, the available agents have differing selectivity for JAK isoforms, as well as off-target effects against non-JAKs. Other differences include effects on haematological parameters, DNA damage repair, reproductive toxicity and metabolism/elimination. Here we review the pharmacological profiles of the JAKis abrocitinib, baricitinib, filgotinib, peficitinib, tofacitinib and upadacitinib.

Cutaneous involvement in Ph-negative myeloproliferative neoplasms: from extramedullary hematopoiesis to myeloid metastasis with histiocytic differentiation. A systematic review of the literature

Myeloid neoplasms may metastasize to the skin, presenting a wide range of clinical-pathological features that often lead to a reduction in patients' survival. The presentation varies depending on the category of myeloid neoplasm and its prognostic significance. The literature has specifically focused on the features of acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and chronic myelomonocytic leukemia (CMML). In this article, we aimed to uncover the peculiarities of clonal skin proliferations in the course of Ph-negative myeloproliferative neoplasms (MPNs). We conducted a systematic review and statistical analysis of the literature data. MPN patients mainly exhibited cutaneous extramedullary hematopoiesis, while a minority displayed cutaneous histiocytic lesions. Furthermore, these patients showed lower survival rates compared to the median survival of MPN patients, especially when calculating survival from the appearance of cutaneous lesions. Our work highlights, for the first time, the prognostic relevance and histological heterogeneity of cutaneous lesions in MPN. Moreover, it emphasizes the importance of dermatological and histological examinations when cutaneous lesions are present.

Spoilt for choice: different immunosuppressive potential of anaplastic lymphoma kinase inhibitors for non small cell lung cancer

Introduction

Several anaplastic lymphoma kinase (ALK)-inhibitors (ALKi) have been approved for the treatment of ALK-translocated advanced or metastatic Non Small Cell Lung Cancer (NSCLC), amongst crizotinib and alectinib. This forces physicians to choose the most suitable compound for each individual patient on the basis of the tumor´s genetic profile, but also in regard to toxicities and potential co-treatments. Moreover, targeted therapies might be combined with or followed by immunotherapy, which underlines the importance to gain detailed knowledge about potential immunomodulatory effects of these inhibitors. We here aimed to 1.) determine whether ALKi display an immunosuppressive effect on human dendritic cells (DCs) as important mediators of antigen-specific immunity and to 2.) dissect whether this immunosuppression differs among ALKi.

Methods

We investigated the effect of alectinib and crizotinib on human monocyte-derived DCs (moDC) as most powerful antigen-presenting cells. We performed immunophenotyping by flow cytometry, migration, antigen uptake and cytokine assays.

Results

Crizotinib-treated DCs showed reduced activation markers, such as CD83, decreased chemokine-guided migration, lower antigen uptake and produced inferior levels of pro-inflammatory cytokines, especially Interleukin-12. In contrast, the immunosuppressive potential of alectinib was significantly less pronounced. This indicates that crizotinib might profoundly dampen anti-tumor immunity, while alectinib had no unfavourable immunosuppressive effects.

Conclusions

Our results implicate that current ALKi differ in their capacity to suppress the activation, migration and cytokine production of DCs as essential mediators of T cell immunity. We show that crizotinib, but not alectinib, had immunosuppressive effects on DCs phenotype and reduced DC function, thereby potentially impairing anti-tumor immunity.

Chromatin accessibility dynamics of neurogenic niche cells reveal defects in neural stem cell adhesion and migration during aging

The regenerative potential of brain stem cell niches deteriorates during aging. Yet the mechanisms underlying this decline are largely unknown. Here we characterize genome-wide chromatin accessibility of neurogenic niche cells in vivo during aging. Interestingly, chromatin accessibility at adhesion and migration genes decreases with age in quiescent neural stem cells (NSCs) but increases with age in activated (proliferative) NSCs. Quiescent and activated NSCs exhibit opposing adhesion behaviors during aging: quiescent NSCs become less adhesive, whereas activated NSCs become more adhesive. Old activated NSCs also show decreased migration in vitro and diminished mobilization out of the niche for neurogenesis in vivo. Using tension sensors, we find that aging increases force-producing adhesions in activated NSCs. Inhibiting the cytoskeletal-regulating kinase ROCK reduces these adhesions, restores migration in old activated NSCs in vitro, and boosts neurogenesis in vivo. These results have implications for restoring the migratory potential of NSCs and for improving neurogenesis in the aged brain.

Janus kinase 2 inhibition by pacritinib as potential therapeutic target for liver fibrosis

BACKGROUND AND AIMS

Janus kinase 2 (JAK2) signaling is increased in human and experimental liver fibrosis with portal hypertension. JAK2 inhibitors, such as pacritinib, are already in advanced clinical development for other indications and might also be effective in liver fibrosis. Here, we investigated the antifibrotic role of the JAK2 inhibitor pacritinib on activated hepatic stellate cells (HSCs) in vitro and in two animal models of liver fibrosis in vivo .

APPROACH AND RESULTS

Transcriptome analyses of JAK2 in human livers and other targets of pacritinib have been shown to correlate with profibrotic factors. Although transcription of JAK2 correlated significantly with type I collagen expression and other profibrotic genes, no correlation was observed for interleukin-1 receptor-associated kinase and colony-stimulating factor 1 receptor. Pacritinib decreased gene expression of fibrosis markers in mouse primary and human-derived HSCs in vitro . Moreover, pacritinib decreased the proliferation, contraction, and migration of HSCs. C 57 BL/6J mice received ethanol in drinking water (16%) or Western diet in combination with carbon tetrachloride intoxication for 7 weeks to induce alcoholic or nonalcoholic fatty liver disease. Pacritinib significantly reduced liver fibrosis assessed by gene expression and Sirius red staining, as well as HSC activation assessed by alpha-smooth muscle actin immunostaining in fibrotic mice. Furthermore, pacritinib decreased the gene expression of hepatic steatosis markers in experimental alcoholic liver disease. Additionally, pacritinib protected against liver injury as assessed by aminotransferase levels.

CONCLUSIONS

This study demonstrates that the JAK2 inhibitor pacritinib may be promising for the treatment of alcoholic and nonalcoholic liver fibrosis and may be therefore relevant for human pathology.

New Insights of CCR7 Signaling in Dendritic Cell Migration and Inflammatory Diseases

CCR7, collaborated with its ligands CCL19 and CCL21, controls extensive migratory events in the immune system. CCR7-bearing dendritic cells can swarm into T-cell zones in lymph nodes, initiating the antigen presentation and T-cell response. Abnormal expression of CCR7 in dendritic cells will cause a series of inflammatory diseases due to the chaotic dendritic cell trafficking. In this review, we take an in-depth look at the structural–functional domains of CCR7 and CCR7-bearing dendritic cell trajectory to lymph nodes. Then, we summarize the regulatory network of CCR7, including transcriptional regulation, translational and posttranslational regulation, internalization, desensitization, and recycling. Furthermore, the potential strategies of targeting the CCR7 network to regulate dendritic cell migration and to deal with inflammatory diseases are integrated, which not only emphasizes the possibility of CCR7 to be a potential target of immunotherapy but also has an implication on the homing of dendritic cells to benefit inflammatory diseases.

Immune Dysregulation and Infectious Complications in MPN Patients Treated With JAK Inhibitors

BCR-ABL1-negative myeloproliferative neoplasms are burdened by a reduced life expectancy mostly due to an increased risk of thrombo-hemorrhagic events, fibrotic progression/leukemic evolution, and infectious complications. In these clonal myeloid malignancies, JAK2V617F is the main driver mutation, leading to an aberrant activation of the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway. Therefore, its inhibition represents an attractive therapeutic strategy for these disorders. Several JAK inhibitors have entered clinical trials, including ruxolitinib, the first JAK1/2 inhibitor to become commercially available for the treatment of myelofibrosis and polycythemia vera. Due to interference with the JAK-STAT pathway, JAK inhibitors affect several components of the innate and adaptive immune systems such as dendritic cells, natural killer cells, T helper cells, and regulatory T cells. Therefore, even though the clinical use of these drugs in MPN patients has led to a dramatic improvement of symptoms control, organ involvement, and quality of life, JAK inhibitors–related loss of function in JAK-STAT signaling pathway can be a cause of different adverse events, including those related to a condition of immune suppression or deficiency. This review article will provide a comprehensive overview of the current knowledge on JAK inhibitors’ effects on immune cells as well as their clinical consequences, particularly with regards to infectious complications.

Philadelphia-Negative Chronic Myeloproliferative Neoplasms during the COVID-19 Pandemic: Challenges and Future Scenarios

An outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) started in December 2019 in China and then become pandemic in February 2020. Several publications investigated the possible increased rate of COVID-19 infection in hematological malignancies. Based on the published data, strategies for the management of chronic Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) are provided. The risk of severe COVID-19 seems high in MPN, particularly in patients with essential thrombocythemia, but not negligible in myelofibrosis. MPN patients are at high risk of both thrombotic and hemorrhagic complications and this must be accounted in the case of COVID-19 deciding on a case-by-case basis. There are currently no data to suggest that hydroxyurea or interferon may influence the risk or severity of COVID-19 infection. Conversely, while the immunosuppressive activity of ruxolitinib might pose increased risk of infection, its abrupt discontinuation during COVID-19 syndrome is associated with worse outcome. All MPN patients should receive vaccine against COVID-19; reassuring data are available on efficacy of mRNA vaccines in MPNs.

Structural Basis of Inhibition of DCLK1 by Ruxolitinib

Given the functional attributes of Doublecortin-like kinase 1 (DCLK1) in tumor growth, invasion, metastasis, cell motility, and tumor stemness, it is emerging as a therapeutic target in gastrointestinal cancers. Although a series of specific or nonspecific ATP-competitive inhibitors were identified against DCLK1, different types of scaffolds that can be utilized for the development of highly selective inhibitors or structural understanding of binding specificities of the compounds remain limited. Here, we present our work to repurpose a Janus kinase 1 inhibitor, ruxolitinib as a DCLK1 inhibitor, showing micromolar binding affinity and inhibitory activity. Furthermore, to gain an insight into its interaction mode with DCLK1, a crystal structure of the ruxolitinib-complexed DCLK1 has been determined and analyzed. Ruxolitinib as a nonspecific DCLK1 inhibitor characterized in this work is anticipated to provide a starting point for the structure-guided discovery of selective DCLK1 inhibitors.

Pacritinib protects dendritic cells more efficiently than ruxolitinib

Targeting Janus kinase (JAK) has revolutionized the treatment of myeloproliferative neoplasms. The JAK inhibitor ruxolitinib has improved the outcome and quality of life of patients dramatically at the cost of increased risk of infections. As previously reported, ruxolitinib severely impairs the differentiation of peripheral blood mononuclear cells to monocyte-derived dendritic cells and inhibits the function of dendritic cells in vitro and in vivo, which expanded its use as an immunomodulatory compound. Pacritinib is a novel JAK inhibitor that will soon be approved for the treatment of myeloproliferative neoplasms, and early results are promising. We investigated the impact of the novel JAK inhibitor pacritinib on the function of monocyte-derived dendritic cells and compared it with that of ruxolitinib. In contrast to ruxolitinib, pacritinib exhibits only mild suppressive effects on dendritic cells. The upregulation of activation markers and CCR7 after TLR4 ligation is not or is only marginally affected by pacritinib. Pacritinib, at concentrations reflecting patients' plasma levels, reduces interleukin (IL)-12 secretion, whereas IL-6 and tumor necrosis factor α levels are unchanged at this concentration. In conclusion, the immunosuppressive effect of pacritinib on dendritic cells is significantly less pronounced than the effect of ruxolitinib. Therefore, our data may help to identify those patients with myelofibrosis who may benefit from pacritinib treatment.

Untwining Anti-Tumor and Immunosuppressive Effects of JAK Inhibitors-A Strategy for Hematological Malignancies?

Simple Summary

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway is aberrantly activated in many malignancies. Inhibition of this pathway via JAK inhibitors (JAKinibs) is therefore an attractive therapeutic strategy underlined by Ruxolitinib (JAK1/2 inhibitor) being approved for the treatment of myeloproliferative neoplasms. As a consequence of the crucial role of the JAK-STAT pathway in the regulation of immune responses, inhibition of JAKs suppresses the immune system. This review article provides a thorough overview of the current knowledge on JAKinibs’ effects on immune cells in the context of hematological malignancies. We also discuss the potential use of JAKinibs for the treatment of diseases in which lymphocytes are the source of the malignancy.

Abstract

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway propagates signals from a variety of cytokines, contributing to cellular responses in health and disease. Gain of function mutations in JAKs or STATs are associated with malignancies, with JAK2^V617F being the main driver mutation in myeloproliferative neoplasms (MPN). Therefore, inhibition of this pathway is an attractive therapeutic strategy for different types of cancer. Numerous JAK inhibitors (JAKinibs) have entered clinical trials, including the JAK1/2 inhibitor Ruxolitinib approved for the treatment of MPN. Importantly, loss of function mutations in JAK-STAT members are a cause of immune suppression or deficiencies. MPN patients undergoing Ruxolitinib treatment are more susceptible to infections and secondary malignancies. This highlights the suppressive effects of JAKinibs on immune responses, which renders them successful in the treatment of autoimmune diseases but potentially detrimental for cancer patients. Here, we review the current knowledge on the effects of JAKinibs on immune cells in the context of hematological malignancies. Furthermore, we discuss the potential use of JAKinibs for the treatment of diseases in which lymphocytes are the source of malignancies. In summary, this review underlines the necessity of a robust immune profiling to provide the best benefit for JAKinib-treated patients.

Cytoskeleton Dynamics in Peripheral T Cell Lymphomas: An Intricate Network Sustaining Lymphomagenesis

Defects in cytoskeleton functions support tumorigenesis fostering an aberrant proliferation and promoting inappropriate migratory and invasive features. The link between cytoskeleton and tumor features has been extensively investigated in solid tumors. However, the emerging genetic and molecular landscape of peripheral T cell lymphomas (PTCL) has unveiled several alterations targeting structure and function of the cytoskeleton, highlighting its role in cell shape changes and the aberrant cell division of malignant T cells. In this review, we summarize the most recent evidence about the role of cytoskeleton in PTCLs development and progression. We also discuss how aberrant signaling pathways, like JAK/STAT3, NPM-ALK, RhoGTPase, and Aurora Kinase, can contribute to lymphomagenesis by modifying the structure and the signaling properties of cytoskeleton.

The Effectiveness of Ruxolitinib for Acute/Chronic Graft-versus-Host Disease in Children: A Retrospective Study

Objective

This study aimed to evaluate the effectiveness of Ruxolitinib for acute/chronic graft-versus-host disease in children.

Methods

This study was a retrospective trial. We analyzed the clinical characteristics of children who responded poorly to previous treatment for graft-versus-host disease (GVHD) and received ruxolitinib treatment after allogeneic hematopoietic stem cell transplantation (allo-HSCT) as an additional or replacement therapy.

Results

A total of 53 patients were analyzed: aGVHD and cGVHD. The overall response rate (ORR) to ruxolitinib was 75.5%. The ORR was 64.7% (11/17) in the aGVHD group including 6, 5, and 6 patients with partial responses (PRs), complete responses (CRs), and treatment failure, respectively. The ORR was 80.6% (29/36) in the cGVHD group including 10 with CRs and 19 with PRs. Five and 2 patients showed no response and treatment failure, respectively. Four and 14 patients were GVHD recurrence in aGVHD and cGVHD respectively. A total of 14 patients (39%) discontinued steroids and 8 patients (22.2%) reduced steroids. The incidence of obvious adverse events was 94.1% (16/17) in the aGVHD group, which was higher than that in the cGVHD group. Meanwhile, the prognosis of children with cGVHD was superior to that of children with aGVHD after treatment with ruxolitinib. During the ruxolitinib treatment, only 1 patient suffered a relapse of the primary tumor. Eleven patients also suffered transplantation-associated thrombotic microangiopathy (TA-TMA) after allo-HSCT.

Conclusion

Pediatric patients with GVHD (especially cGVHD) responded well to ruxolitinib treatment. Ruxolitinib can also be used as an alternative treatment for patients with TMA.

JAK-Inhibitoren für die Behandlung hämatoonkologischer Erkrankungen

Die konstitutive Aktivierung des JAK-STAT-Signalwegs ist charakteristisch für die Pathogenese der myeloproliferativen Neoplasien, speziell der primären Myelofibrose, der Polycythaemia vera und der essentiellen Thrombozythämie. Die Einführung von oral verfügbaren JAK-Inhibitoren in die Klinik brachte einen entscheidenden Fortschritt für die pharmakologische Behandlung der Myelofibrose und der Polycythaemia vera, wenngleich damit noch keine Heilung verbunden ist. Im Vordergrund steht die Verbesserung der Lebensqualität der meist älteren Patienten durch Kontrolle krankheitsbedingter konstitutioneller Symptome, Reduktion einer bestehenden Splenomegalie und Vermeidung insbesondere von thromboembolischen Folgekomplikationen. Darüber hinaus kann die Therapie von Myelofibrose-Patienten mit JAK-Inhibitoren jedoch auch deren Krankheitsverlauf verlangsamen und ihr Gesamtüberleben verlängern. Der bislang einzige in Europa zugelassene JAK-Inhibitor Ruxolitinib hemmt die Isoformen JAK1 und JAK2 und besitzt sowohl antiinflammatorisches als auch antiproliferatives Potenzial. Damit zeigt dieser Inhibitor überdies eine gute Wirkung in der Therapie der Graft-versus-Host-Erkrankung nach allogener hämatopoetischer Stammzelltransplantation. Mit Fedratinib, Pacritinib und Momelatinib befinden sich derzeit 3 weitere vielversprechende JAK-Inhibitoren mit etwas unterschiedlichen Wirkprofilen in der klinischen Phase III-Testung. Diese zeigen auch bei Patienten mit unwirksamer oder unverträglicher Vorbehandlung mit Ruxolitinib Wirksamkeit, sodass eine kontinuierliche Weiterentwicklung der entsprechenden Therapiestrategien abzusehen ist.

Ruxolitinib-Associated Infections in Polycythemia Vera: Review of the Literature, Clinical Significance, and Recommendations

Simple Summary

Polycythemia vera (PV) is a chronic blood disease characterized by elevated red blood cells and splenomegaly. About 98% of all PV patients harbor the JAK2 mutation. Ruxolitinib (RUX), a JAK1/JAK2 inhibitor, received approval as a second-line indication in PV patients who are resistant or intolerant to standard therapy hydroxyurea in both the United States (2014) and Europe (2015). In the studies relevant to approval, RUX achieved excellent PV control. Due to its mechanism of action, RUX also has immunosuppressive effects. As expected, an increased rate of infection was observed in clinical studies and in practical application. In this overview, we have compiled all previous literature references on RUX and infections in PV. However, apart from a few individual cases with special infections and an increased rate of zoster infections, there are no exceptional high infection problems. Recommendations are given on how infections in RUX treated PV patients can be avoided.

Abstract

Ruxolitinib (RUX), a JAK1/JAK2 inhibitor, is approved for second-line therapy in patients with polycythemia vera (PV) who are resistant or intolerant to hydroxyurea. Due to the immunomodulatory and immunosuppressive effect of RUX, there is an increased susceptibility to infections. However, an increased risk of infection is inherent to even untreated myeloproliferative neoplasms (MPN). To obtain more information on the clinical significance of RUX-associated infections in PV, we reviewed the available literature. There is no evidence-based approach to managing infection risks. Most data on RUX-associated infections are available for MF. In all studies, the infection rates in the RUX and control groups were fairly similar, with the exception of infections with the varicella zoster virus (VZV). However, individual cases of bilateral toxoplasmosis retinitis, disseminated molluscum contagiosum, or a mycobacterium tuberculosis infection or a hepatitis B reactivation are reported. A careful assessment of the risk of infection for PV patients is required at the initial presentation and before the start of RUX. Screening for hepatitis B is recommended in all patients. The risk of RUX-associated infections is lower with PV than with MF, but compared to a normal population there is an increased risk of VZV infection. However, primary VZV prophylaxis for PV patients is not recommended, while secondary prophylaxis can be considered individually. As early treatment is most effective for VZV, patients should be properly informed and trained to seek medical advice immediately if cutaneous signs of VZV develop. Vaccination against influenza, herpes zoster, and pneumococci should be considered in all PV patients at risk of infection, especially if RUX treatment is planned. Current recommendations do not support adjusting or discontinuing JAK inhibition in MPN patients to reduce the risk of COVID-19.

Tuberculosis in Patients with Primary Myelofibrosis During Ruxolitinib Therapy: Case Series and Literature Review

Background

The selective Janus-activated kinase inhibitor ruxolitinib (rux) is now widely used to treat myelofibrosis and polycythemia vera due to its remarkable effect of reducing splenomegaly and improving constitutional symptoms. With opportunistic infections secondary to rux constantly reported; however, an increasing number of studies have begun to investigate the mechanism and underlying immunosuppressive effect of rux.

Case Presentation

We report two cases of tuberculosis (TB) in primary myelofibrosis patients during rux therapy. The first patient received rux soon after diagnosis, and tracheobronchial TB (TBTB) and bronchoesophageal fistula were found after 4 months. After discontinuation of rux, antituberculosis therapy (ATT) was introduced. The second patient initiated rux due to progressive splenomegaly after 7.5 years of interferon therapy and was diagnosed with disseminated TB after 2 months. He received ATT as well. His rux was maintained due to the high burden of systematic symptoms and splenomegaly. Both myelofibrosis and TB were well controlled in these patients.

Conclusion

This is the first case report that describes rux-related TBTB accompanied by a bronchoesophageal fistula. Through a review of the literature, we provide supporting evidence to the finding that intrinsic disorders of myeloproliferative neoplasms and rux-induced immunologic deregulation together lead to TB. We highlight the importance of screening for latent TB infection and timely chemoprophylaxis before rux therapy. Once TB is diagnosed during treatment, rux is recommended to be stopped and active ATT should begin quickly.

The Rationale for Immunotherapy in Myeloproliferative Neoplasms

PURPOSE OF REVIEW

The classic, chronic Philadelphia chromosome negative myeloproliferative neoplasms (MPN)-essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF)-are clonal malignancies of hematopoietic stem cells and are associated with myeloproliferation, organomegaly, and constitutional symptoms. Expanding knowledge that chronic inflammation and a dysregulated immune system are central to the pathogenesis and progression of MPNs serves as a driving force for the development of agents affecting the immune system as therapy for MPN. This review describes the rationale and potential impact of anti-inflammatory, immunomodulatory, and targeted agents in MPNs.

RECENT FINDINGS

The advances in molecular insights, especially the discovery of the Janus kinase 2 (JAK2) V617F mutation and its role in JAK-STAT pathway dysregulation, led to the development of the JAK inhibitor ruxolitinib, which currently represents the cornerstone of medical therapy in MF and hydroxyurea-resistant/intolerant PV. However, there remain significant unmet needs in the treatment of these patients, and many agents continue to be investigated. Novel, more selective JAK inhibitors might offer reduced myelosuppression or even improvement of blood counts. The recent approval of a novel, long-acting interferon for PV patients in Europe, might eventually lead to its broader clinical use in all MPNs. Targeted immunotherapy involving monoclonal antibodies, checkpoint inhibitors, or therapeutic vaccines against selected MPN epitopes could further enhance tumor-specific immune responses. Immunotherapeutic approaches are expanding and hopefully will extend the therapeutic armamentarium in patients with myeloproliferative neoplasms.

Small-Molecule Fms-like Tyrosine Kinase 3 Inhibitors: An Attractive and Efficient Method for the Treatment of Acute Myeloid Leukemia

Fms-like tyrosine kinase 3 (FLT3) is an important member of the class III receptor tyrosine kinase (RTK) family, which is involved in the proliferation of hematopoietic cells and lymphocytes. In recent years, increasing evidence have demonstrated that the activation and mutation of FLT3 is closely implicated in the occurrence and development of acute myeloid leukemia (AML). The exploration of small-molecule inhibitors targeting FLT3 has aroused wide interest of pharmaceutical chemists and is expected to bring new hope for AML therapy. In this review, we specifically highlighted FLT3 mediated JAK/STAT, RAS/MAPK, and PI3K/AKT/mTOR signaling. The structural properties and biological activities of representative FLT3 inhibitors reported from 2014 to the present were also summarized. In addition, the major challenges in the current advance of novel FLT3 inhibitors were further analyzed, with the aim to guide future drug discovery.

Defective migration and dysmorphology of neutrophil granulocytes in atypical chronic myeloid leukemia treated with ruxolitinib

BACKGROUND

The identification of pathologically altered neutrophil granulocyte migration patterns bears strong potential for surveillance and prognostic scoring of diseases. We recently identified a strong correlation between impaired neutrophil motility and the disease stage of myelodysplastic syndrome (MDS). Here, we apply this assay to study quantitively increased neutrophils of a patient suffering from a rare leukemia subtype, atypical chronic myeloid leukemia (aCML).

METHODS

A 69-year-old male was analyzed in this study. Besides routine analyses, we purified the patient's neutrophils from peripheral whole blood and studied their migration behavior using time-lapse video microscopy in a standardized assay. These live cell migration analyses also allowed for the quantification of cell morphology. Furthermore, the cells were stained for the markers CD15, CD16, fMLPR, CXCR1 and CXCR2.

RESULTS

Despite cytoreductive therapy with hydroxyurea, the patient's WBC and ANC were poorly controlled and severe dysgranulopoiesis with hypogranularity was observed. Neutrophils displayed strongly impaired migration when compared to healthy controls and migrating cells exhibited a more flattened-out morphology than control neutrophils. Because of a detected CSF3R (p.T618I) mutation and constitutional symptoms treatment with ruxolitinib was initiated. Within 1 week of ruxolitinib treatment, the cell shape normalized and remained indistinguishable from healthy control neutrophils. However, neutrophil migration did not improve over the course of ruxolitinib therapy but was strikingly altered shortly before a sinusitis with fever and bleeding from a gastric ulcer. Molecular work-up revealed that under ruxolitinib treatment, the CSF3R clone was depleted, yet the expansion of a NRAS mutated subclone was promoted.

CONCLUSION

These results demonstrate the usefulness of neutrophil migration analyses to uncover corresponding alterations of neutrophil migration in rare myeloid neoplasms. Furthermore, in addition to monitoring migration the determination of morphological features of live neutrophils might represent a useful tool to monitor the effectiveness of therapeutic approaches.

Immunotherapy in Myeloproliferative Diseases

Myeloproliferative diseases, including myeloproliferative neoplasms (MPN) and myelodysplastic syndromes (MDS), are driven by genetic abnormalities and increased inflammatory signaling and are at high risk to transform into acute myeloid leukemia (AML). Myeloid-derived suppressor cells were reported to enhance leukemia immune escape by suppressing an effective anti-tumor immune response. MPNs are a potentially immunogenic disease as shown by their response to interferon-α treatment and allogeneic hematopoietic stem-cell transplantation (allo-HSCT). Novel immunotherapeutic approaches such as immune checkpoint inhibition, tumor vaccination, or cellular therapies using target-specific lymphocytes have so far not shown strong therapeutic efficacy. Potential reasons could be the pro-inflammatory and immunosuppressive microenvironment in the bone marrow of patients with MPN, driving tumor immune escape. In this review, we discuss the biology of MPNs with respect to the pro-inflammatory milieu in the bone marrow (BM) and potential immunotherapeutic approaches.

The role of circulating monocytes and JAK inhibition in the infectious-driven inflammatory response of myelofibrosis

Myelofibrosis (MF) is characterized by chronic inflammation and hyper-activation of the JAK-STAT pathway. Infections are one of the main causes of morbidity/mortality. Therapy with Ruxolitinib (RUX), a JAK1/2 inhibitor, may further increase the infectious risk. Monocytes are critical players in inflammation/immunity through cytokine production and release of bioactive extracellular vesicles. However, the functional behavior of MF monocytes, particularly during RUX therapy, is still unclear. In this study, we found that monocytes from JAK2V617F-mutated MF patients show an altered expression of chemokine (CCR2, CXCR3, CCR5) and cytokine (TNF-α-R, IL10-R, IL1β-R, IL6-R) receptors. Furthermore, their ability to produce and secrete free and extracellular vesicles-linked cytokines (IL1β, TNF-α, IL6, IL10) under lipopolysaccharides (LPS) stimulation is severely impaired. Interestingly, monocytes from RUX-treated patients show normal level of chemokine, IL10, IL1β, and IL6 receptors together with a restored ability to produce intracellular and to secrete extracellular vesicles-linked cytokines after LPS stimulation. Conversely, RUX therapy does not normalize TNF-R1/2 receptors expression and the LPS-driven secretion of free pro/anti-inflammatory cytokines. Accordingly, upon LPS stimulation, in vitro RUX treatment of monocytes from MF patients increases their secretion of extracellular vesicles-linked cytokines but inhibits the secretion of free pro/anti-inflammatory cytokines. In conclusion, we demonstrated that in MF the infection-driven response of circulating monocytes is defective. Importantly, RUX promotes their infection-driven cytokine production suggesting that infections following RUX therapy may not be due to monocyte failure. These findings contribute to better interpreting the immune vulnerability of MF and to envisaging strategies to improve the infection-driven immune response.

Myeloproliferative and lymphoproliferative disorders: State of the art

Myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), are clonal disorders complicated mainly by vascular events and transformation to myelofibrosis (for PV and ET) or leukemia. Although secondary malignancies, in particular, lymphoproliferative disorders (LPNs), are rare, they occur at a higher frequency than found in the general population, and there has been recent scientific discussion regarding a hypothetical relationship between treatment with JAK inhibitors in MPN and the risk of development of LPN. This has prompted increased interest regarding the coexistence of MPN and LPN. This review focuses on the role of JAK2 and the JAK/STAT pathway in MPN and LPN, whether there is a role for the genetic background in the occurrence of both MPN and LPN and whether there is a role for cytoreductive drugs in the occurrence of both MPN and LPN. Furthermore, whether an increased risk of lymphoma development is limited to patients who receive the JAK inhibitor ruxolitinib, is a more general phenomenon that occurs following JAK1/2 inhibition or is associated with preferential JAK1 or JAK2 targeting is discussed.

Targeting senescent cells: approaches, opportunities, challenges

Cellular senescence is a hallmark of aging, whose onset is linked to a series of both cell and non-cell autonomous processes, leading to several consequences for the organism. To date, several senescence routes have been identified, which play a fundamental role in development, tumor suppression and aging, among other processes. The positive and/or negative effects of senescent cells are directly related to the time that they remain in the organism. Short-term (acute) senescent cells are associated with positive effects; once they have executed their actions, immune cells are recruited to remove them. In contrast, long-term (chronic) senescent cells are associated with disease; they secrete pro-inflammatory and pro-tumorigenic factors in a state known as senescence-associated secretory phenotype (SASP). In recent years, cellular senescence has become the center of attention for the treatment of aging-related diseases. Current therapies are focused on elimination of senescent cell functions in three main ways: i) use of senolytics; ii) inhibition of SASP; and iii) improvement of immune system functions against senescent cells (immunosurveillance). In addition, some anti-cancer therapies are based on the induction of senescence in tumor cells. However, these senescent-like cancer cells must be subsequently cleared to avoid a chronic pro-tumorigenic state. Here is a summary of different scenarios, depending on the therapy used, with a discussion of the pros and cons of each scenario.

Mechanisms Underlying the Anti-inflammatory and Immunosuppressive Activity of Ruxolitinib

The JAK-STAT signaling pathway plays a central role in signal transduction in hematopoietic cells, as well as in cells of the immune system. The occurrence in most patients affected by myeloproliferative neoplasms (MPNs) of driver mutations resulting in the constitutive activation of JAK2-dependent signaling identified the deregulated JAK-STAT signal transduction pathway as the major pathogenic mechanism of MPNs. It also prompted the development of targeted drugs for MPNs. Ruxolitinib is a potent and selective oral inhibitor of both JAK2 and JAK1 protein kinases. Its use in patients with myelofibrosis is associated with a substantial reduction in spleen volume, attenuation of symptoms and decreased mortality. With growing clinical experience, concerns about infectious complications, and increased risk of B-cell lymphoma, presumably caused by the effects of JAK1/2 inhibition on immune response and immunosurveillance, have been raised. Evidence shows that ruxolitinib exerts potent anti-inflammatory and immunosuppressive effects. Cellular targets of ruxolitinib include various components of both the innate and adaptive immune system, such as natural killer cells, dendritic cells, T helper, and regulatory T cells. On the other hand, immunomodulatory properties have proven beneficial in some instances, as highlighted by the successful use of ruxolitinib in corticosteroid-resistant graft vs. host disease. The objective of this article is to provide an overview of published evidence addressing the key question of the mechanisms underlying ruxolitinib-induced immunosuppression.

Potent repression of C-reactive protein (CRP) expression by the JAK1/2 inhibitor ruxolitinib in inflammatory human hepatocytes

OBJECTIVE AND DESIGN

To determine whether inflammatory hepatocytes may constitute primary targets for ruxolitinib, a Janus kinase (JAK) inhibitor, its effects towards expression of hepatic acute-phase proteins, especially C-reactive protein (CRP), were assessed.

MATERIALS

Ruxolitinib effects were analysed in primary human hepatocytes and human hepatoma HepaRG cells exposed to various inflammatory stimuli.

RESULTS

Ruxolitinib was found to fully inhibit lipopolysaccharide (LPS)-induced CRP secretion and mRNA expression, at concentrations (IC₅₀ = 12.9 nM) achievable in human blood. It similarly repressed CRP up-regulation due to several Toll-like receptor agonists or pro-inflammatory cytokines [interleukin (IL) 1β, IL6 and tumour necrosis factor α] and counteracted LPS-mediated induction of serum amyloid A, fibrinogen, haptoglobin and serpin. Ruxolitinib was additionally found to block the activation of the IL6/JAK/signal transducer and activator of transcription (STAT) pathway triggered by LPS and whose inhibition by the neutralizing anti-IL6 receptor antibody tocilizumab prevented CRP induction.

CONCLUSION

Ruxolitinib can potently repress induction of CRP in inflammatory human hepatocytes, most likely through targeting the IL6/JAK/STAT signalling cascade. Hepatic production of acute-phase proteins during liver inflammation may, therefore, constitute a target for ruxolitinib.

A journey through infectious risk associated with ruxolitinib

Ruxolitinib has proved to be effective for the treatment of patients with myelofibrosis (either primary or secondary) and polycythaemia vera, and its approval led to a significant change in the current treatment algorithm. Despite its efficacy and beyond its well described haematological toxicity, a peculiar immunosuppressive effect emerged as our clinical experience grew, both within and outside of a clinical trial setting. Definite and negative interactions with multiple pathways of the immune system of patients have been reported so far, involving both adaptive and innate immune responses. These pathophysiological mechanisms may contribute to the increased risk of reactivation of silent infections (e.g., tuberculosis, hepatitis B virus and varicella zoster virus) that have been associated with the drug. Even though such infectious events may be fatal or may lead to significant impairment of organ function, compromising the eligibility of patients for an allotransplant procedure, there are no dedicated guidelines that may help us in assessing and managing the risk of developing serious infections. On this basis, our aim for the present work was to review the current knowledge on the pathophysiological mechanisms through which ruxolitinib may exert its immunosuppressive effect, and to illustrate our personal approach to the management of three peculiar clinical scenarios, for which a risk-based algorithm is suggested.

Tumor-related interleukins: old validated targets for new anti-cancer drug development

In-depth knowledge of cancer molecular and cellular mechanisms have revealed a strong regulation of cancer development and progression by the inflammation which orchestrates the tumor microenvironment. Immune cells, residents or recruited, in the inflammation milieu can have rather contrasting effects during cancer development. Accumulated clinical and experimental data support the notion that acute inflammation could exert an immunoprotective effect leading to tumor eradication. However, chronic immune response promotes tumor growth and invasion. These reactions are mediated by soluble mediators or cytokines produced by either host immune cells or tumor cells themselves. Herein, we provide an overview of the current understanding of the role of the best-validated cytokines involved in tumor progression, IL-1, IL-4 and IL-6; in addition to IL-2 cytokines family, which is known to promote tumor eradication by immune cells. Furthermore, we summarize the clinical attempts to block or bolster the effect of these tumor-related interleukins in anti-cancer therapy development.

JAK/STAT disruption induces immuno-deficiency: Rationale for the development of JAK inhibitors as immunosuppressive drugs

Cytokines are mediating immune cells responses through the activation of the JAK/STAT signaling pathway. Being critical for immune cells, a defective JAK/STAT signaling leads to various immune disorders, such as immunodeficiency. In contrast, hyperactivation of JAK/STAT signaling is linked to autoimmunity and cancer. Targeting the JAK/STAT proteins by small protein inhibitors impedes immune cell function by uncoupling cells from cytokine effects and by interfering with functional immune cell hallmarks, such as cell migration. This review will explore immune syndromes driven by JAK/STAT deregulation and discuss the emerging role of JAK inhibitors as immunosuppressive drugs used in autoimmunity and transplantation medicine.

Ruxolitinib in myelofibrosis: to be or not to be an immune disruptor

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm classified according to the 2016 revision of World Health Organization Classification of Tumors and Haematopoietic and Lymphoid Tissue. Ruxolitinib is an oral inhibitor of Janus kinase approved in the USA for the treatment of intermediate or high-risk PMF and approved in Europe for the treatment of splenomegaly and constitutional symptoms of the disease. More recently, case reports described serious opportunistic infections in this neoplasm treated with ruxolitinib. Research studies demonstrated the immunological derangement of this compound mainly based on T, dendritic, and natural killer cell defects. The purpose of this review of the literature was to analyze the relationship among ruxolitinib, immune system and bacterial, viral, fungal, and protozoan infections. A literature search was conducted using PubMed articles published between January 2010 and November 2016. The efficacy of drug in patients with PMF was demonstrated in two phase III studies, Controlled MyeloFibrosis Study with ORal Jak inhibitor Treatment (COMFORT-I and COMFORT-II). Grade 3 and 4 neutropenia were recognized in 7.1% and 2% of patients in the ruxolitinib and placebo arm of COMFORT-I. Grade 3 or 4 neutropenia or leukopenia were observed in 8.9% and 6.3% of ruxolitinib treated patients of 5-year follow-up of COMFORT-II. In addition, leukocyte subpopulations, lymphocyte functions, or antibody deficiency were not documented in either of the studies. The complex interactions between ruxolitinib, bone marrow, immune system, and infections in PMF need further investigation, robust data from a randomized clinical trial, registry, or large case-series.

Primary myelofibrosis: 2017 update on diagnosis, risk-stratification, and management

Disease overview: Primary myelofibrosis (PMF) is a myeloproliferative neoplasm (MPN) characterized by stem cell-derived clonal myeloproliferation that is often but not always accompanied by JAK2, CALR or MPL mutation, abnormal cytokine expression, bone marrow fibrosis, anemia, splenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression and shortened survival.

DIAGNOSIS

Diagnosis is based on bone marrow morphology. The presence of JAK2, CALR or MPL mutation is supportive but not essential for diagnosis; approximately 90% of patients carry one of these mutations and 10% are "triple-negative." None of these mutations are specific to PMF and are also seen in essential thrombocythemia (ET). According to the revised 2016 World Health Organization (WHO) classification and diagnostic criteria, "prefibrotic" PMF (pre-PMF) is distinguished from "overtly fibrotic" PMF; the former might mimic ET in its presentation and it is prognostically relevant to distinguish the two. Risk stratification: The Dynamic International Prognostic Scoring System-plus (DIPSS-plus) uses eight predictors of inferior survival: age >65 years, hemoglobin <10 g/dL, leukocytes >25 × 10⁹ /L, circulating blasts ≥1%, constitutional symptoms, red cell transfusion dependency, platelet count <100 × 10⁹ /L and unfavorable karyotype (i.e., complex karyotype or sole or two abnormalities that include +8, -7/7q-, i(17q), inv(3), 5/5q-, 12p-, or 11q23 rearrangement). The presence of 0, 1, "2 or 3" and ≥4 adverse factors defines low, intermediate-1, intermediate-2 and high-risk disease with median survivals of approximately 15.4, 6.5, 2.9 and 1.3 years, respectively. Most recently, DIPSS-plus-independent adverse prognostic relevance has been demonstrated for certain mutations including ASXL1 and SRSF2 whereas patients with type 1/like CALR mutations, compared to their counterparts with other driver mutations, displayed significantly better survival. Risk-adapted therapy: Observation alone is a reasonable treatment strategy for asymptomatic low or intermediate-1 DIPSS-plus risk disease, especially in the absence of high-risk mutations. All other patients with high or intermediate-2 risk disease, or those harboring high-risk mutations such as ASXL1 or SRSF2, should be considered for stem cell transplant, which is currently the only treatment modality with the potential to favorably modify the natural history of the disease. Non-transplant candidates should be encouraged to participate in clinical trials, since the value of conventional drug therapy, including the use of JAK2 inhibitors, is limited to symptoms palliation and reduction in spleen size. Specifically, JAK2 inhibitors have not been shown to induce complete clinical or cytogenetic remissions or significantly affect JAK2/CALR/MPL mutant allele burden. Splenectomy is considered for drug-refractory splenomegaly. Involved field radiotherapy is most useful for post-splenectomy hepatomegaly, non-hepatosplenic EMH, PMF-associated pulmonary hypertension and extremity bone pain. Am. J. Hematol. 91:1262-1271, 2016. © 2016 Wiley Periodicals, Inc.