Recurrent numerical aberrations of JAK2 and deregulation of the JAK2-STAT cascade in lymphomas

Molecular Biomarkers in Prediction of High-Grade Transformation and Outcome in Patients with Follicular Lymphoma: A Comprehensive Systemic Review

Follicular lymphoma (FL) is the most prevalent indolent B-cell lymphoma entity, often characterized by the t(14;18) BCL2-IGH translocation. The malignancy represents a clinically and biologically highly heterogeneous disease. Most patients have favorable prognoses; however, despite therapeutic advancements, the disease remains incurable, with recurrent relapses or early disease progression. Moreover, transformation to an aggressive histology, most often diffuse large-B-cell lymphoma, remains a critical event in the disease course, which is associated with poor outcomes. Understanding the individual patient's risk of transformation remains challenging, which has motivated much research on novel biomarkers within the past four decades. This review systematically assessed the research on molecular biomarkers in FL transformation and outcome. Following the PRISMA guidelines for systemic reviews, the PubMed database was searched for English articles published from January 1984 through September 2024, yielding 6769 results. The identified publications were carefully screened and reviewed, of which 283 original papers met the inclusion criteria. The included studies focused on investigating molecular biomarkers as predictors of transformation or as prognostic markers of time-related endpoints (survival, progression, etc.). The effects of each biomarker were categorized based on their impact on prognosis or risk of transformation as none, favorable, or inferior. The biomarkers included genetic abnormalities, gene expression, microRNAs, markers of B cells/FL tumor cells, markers of the tumor microenvironment, and soluble biomarkers. This comprehensive review provides an overview of the research conducted in the past four decades, underscoring the persistent challenge in risk anticipation of FL patients.

Emerging drug profile: JAK inhibitors

Dysregulated JAK/STAT hyperactivity is essential to the pathogenesis of myelofibrosis, and JAK inhibitors are the first-line treatment option for many patients. There are four FDA-approved JAK inhibitors for patients with myelofibrosis. Single-agent JAK inhibition can improve splenomegaly, symptom burden, cytopenias, and possibly survival in patients with myelofibrosis. Despite their efficacy, JAK inhibitors produce variable or short-lived responses, in part due to the large network of cooperating signaling pathways and downstream targets of JAK/STAT, which mediates upfront or acquired resistance to JAK inhibitors. Synergistic inhibition of JAK/STAT accessory pathways can increase the rates and duration of response for patients with myelofibrosis. Two recently reported, placebo-controlled phase III trials of novel agents added to JAK inhibition met their primary endpoint, and additional late-stage studies are ongoing. This paper will review role of dysregulated JAK/STAT signaling, biological plausible additional therapeutic targets and the recent advancements in combination strategies with JAK inhibitors for myelofibrosis.

A first-in-class inhibitor of HSP110 to potentiate XPO1-targeted therapy in primary mediastinal B-cell lymphoma and classical Hodgkin lymphoma

BACKGROUND

Primary mediastinal B-cell lymphoma (PMBL) and classical Hodgkin lymphoma (cHL) are distinct hematological malignancies of B-cell origin that share many biological, molecular, and clinical characteristics. In particular, the JAK/STAT signaling pathway is a driver of tumor development due to multiple recurrent mutations, particularly in STAT6. Furthermore, the XPO1 gene that encodes exportin 1 (XPO1) shows a frequent point mutation (E571K) resulting in an altered export of hundreds of cargo proteins, which may impact the success of future therapies in PMBL and cHL. Therefore, targeted therapies have been envisioned for these signaling pathways and mutations.

METHODS

To identify novel molecular targets that could overcome the treatment resistance that occurs in PMBL and cHL patients, we have explored the efficacy of a first-in-class HSP110 inhibitor (iHSP110-33) alone and in combination with selinexor, a XPO1 specific inhibitor, both in vitro and in vivo.

RESULTS

We show that iHSP110-33 decreased the survival of several PMBL and cHL cell lines and the size of tumor xenografts. We demonstrate that HSP110 is a cargo of XPO1wt as well as of XPO1E571K. Using immunoprecipitation, proximity ligation, thermophoresis and kinase assays, we showed that HSP110 directly interacts with STAT6 and favors its phosphorylation. The combination of iHSP110-33 and selinexor induces a synergistic reduction of STAT6 phosphorylation and of lymphoma cell growth in vitro and in vivo. In biopsies from PMBL patients, we show a correlation between HSP110 and STAT6 phosphorylation levels.

CONCLUSIONS

These findings suggest that HSP110 could be proposed as a novel target in PMBL and cHL therapy.

Cytokine profiles in patients with newly diagnosed diffuse large B-cell lymphoma: IL-6 and IL-10 levels are associated with adverse clinical features and poor outcomes

BACKGROUND

The development of diffuse large B-cell lymphoma (DLBCL), a prevalent subgroup of non-Hodgkin lymphoma (NHL), potentially involves various cytokines. We aimed to determine the correlation between deregulated serum levels of cytokines and clinical features and investigate their impact on the prognosis of patients with DLBCL.

METHODS

We conducted a retrospective study of 77 patients with newly diagnosed DLBCL to explore the relationships between different cytokines, adverse clinical features, and poor outcomes. The Mann-Whitney U test was used to compare the cytokine profiles between patients with DLBCL and healthy controls. The Kaplan-Meier method was used to analyze the probability of survival, and the log-rank tests were used to evaluate the differences between survival curves. The Cox proportional hazards regression model was used to performed univariate and multivariate analyses to evaluate prognostic variables for survival analyze.

RESULTS

Serum levels of interleukin-2 (IL-2), tumor necrosis factor (TNF)-α, IL-6, IL-10, and IFN-γ were significantly elevated in patients with untreated DLBCL. Serum levels of IL-6 and IL-10 were significantly higher in patients with an International Prognostic Index (IPI) of 3-5, bone marrow involvement, serum levels of LDH ≥ 250 U/L, and β2-microglobulin (β2-MG) levels ≥ 2.3 mg/L. Patients with B symptoms only had higher serum IL-10 levels, whereas patients with a partial response or no response to treatment had significantly elevated serum levels of IL-6 as well as IL-10. Significant positive correlations were observed between the levels of IL-6 and IL-10 with those of β2-MG and LDH. Patients with levels of IL-6 ≥ 4.5 or IL-10 ≥ 5.0 pg/mL, as well as combined elevated IL-6 and IL-10 levels, exhibited shorter progression-free survival and overall survival. Additionally, univariate and multivariate analyses revealed that serum levels of IL-6 ≥ 4.5 pg/mL and IL-10 ≥ 5.0 pg/mL and IPI 3-5 were independent prognostic factors for relapse and survival in patients with DLBCL.

CONCLUSIONS

Pre-treatment serum IL-6 and IL-10 levels in patients with newly diagnosed DLBCL might be powerful markers for determining treatment response and predicting the prognosis of DLBCL.

Advances in the treatment of Hodgkin's lymphoma (Review)

Hodgkin's lymphoma (HL) is a unique B‑cell lymphoproliferative malignancy that has a critical pathogenesis characterized by a sparse population of Hodgkin and Reed‑Sternberg cells surrounded by numerous dysfunctional immune cells. Although systemic chemotherapy with or without radiotherapy, has significantly improved the prognosis of the majority of patients with HL, a subset of patients remains refractory to first‑line therapy or relapse after achieving an initial response. With the increased understanding of the biology and microenvironment of HL, novel strategies with notable efficacy and manageable toxicity, including targeted therapies, immunotherapy and cell therapy have emerged. The present review summarizes the progress made in developing novel therapies for HL and discusses future research directions in HL therapy.

Hodgkin Lymphoma: Biology and Differential Diagnostic Problem

Hodgkin lymphomas (HLs) are lymphoid neoplasms that are morphologically defined as being composed of dysplastic cells, namely, Hodgkin and Reed–Sternberg cells, in a reactive inflammatory background. The biological nature of HLs has long been unclear; however, our understanding of HL-related genetics and tumor microenvironment interactions is rapidly expanding. For example, cell surface overexpression of programmed cell death 1 ligand 1 (CD274/PD-L1) is now considered a defining feature of an HL subset, and targeting such immune checkpoint molecules is a promising therapeutic option. Still, HLs comprise multiple disease subtypes, and some HL features may overlap with its morphological mimics, posing challenging diagnostic and therapeutic problems. In this review, we summarize the recent advances in understanding the biology of HLs, and discuss approaches to differentiating HL and its mimics.

An Update on the Pathology and Molecular Features of Hodgkin Lymphoma

Simple Summary

Hodgkin lymphomas (HLs) include two main types, classic HL (CHL) and nodular lymphocyte predominant HL (NLPHL). Recent molecular findings in HLs have contributed to dramatic changes in the treatment and identification of tumor characteristics. For example, PD-1/PD-L1 blockade and brentuximab vedotin, an anti-CD30 antibody bearing a cytotoxic compound, are now widely used in patients with CHL. Biological continuity between NLPHL and T-cell/histiocyte-rich large B-cell lymphoma has been highlighted. An era of novel therapeutics for HL has begun. The aim of this paper is to review the morphologic, immunophenotypic, and molecular features of CHL and NLPHL, which must be understood for the development of novel therapeutics.

Abstract

Hodgkin lymphomas (HLs) are lymphoid neoplasms derived from B cells and consist histologically of large neoplastic cells known as Hodgkin and Reed–Sternberg cells and abundant reactive bystander cells. HLs include two main types, classic HL (CHL) and nodular lymphocyte predominant HL (NLPHL). Recent molecular analyses have revealed that an immune evasion mechanism, particularly the PD-1/PD-L1 pathway, plays a key role in the development of CHL. Other highlighted key pathways in CHL are NF-κB and JAK/STAT. These advances have dramatically changed the treatment for CHL, particularly relapsed/refractory CHL. For example, PD-1 inhibitors are now widely used in relapsed/refractory CHL. Compared with CHL, NLPHL is more characterized by preserved B cell features. Overlapping morphological and molecular features between NLPHL and T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) have been reported, and biological continuity between these two entities has been highlighted. Some THRLBCLs are considered to represent progression from NLPHLs. With considerable new understanding becoming available from molecular studies in HLs, therapies and classification of HLs are continually evolving. This paper offers a summary of and update on the pathological and molecular features of HLs for a better understanding of the diseases.

Tumor cell-derived IL-10 promotes cell-autonomous growth and immune escape in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy arising from germinal center or post-germinal center B-cells that retain many of the properties of normal B-cells. Here we show that a subset of DLBCL express the cytokine IL-10 and its receptor. The genetic ablation of IL-10 receptor signaling abrogates the autocrine STAT3 phosphorylation triggered by tumor cell-intrinsic IL-10 expression and impairs growth of DLBCL cell lines in subcutaneous and orthotopic xenotransplantation models. Furthermore, we demonstrate using an immunocompetent Myc-driven model of DLBCL that neutralization of IL-10 signaling reduces tumor growth, which can be attributed to reduced Treg infiltration, stronger intratumoral effector T-cell responses, and restored tumor-specific MHCII expression. The effects of IL-10R neutralization were phenocopied by the genetic ablation of IL-10 signaling in the Treg compartment and could be reversed by MHCII blockade. The BTK inhibitor ibrutinib effectively blocked tumor cell-intrinsic IL-10 expression and tumor growth in this Myc-driven model. Tumors from patients with high IL-10RA expression are infiltrated by higher numbers of Tregs than IL-10RA^low patients. Finally, we show in 16 cases of DLBCL derived from transplant patients on immunosuppressive therapy that IL-10RA expression is less common in this cohort, and Treg infiltration is not observed.

GM-CSF mediates immune evasion via upregulation of PD-L1 expression in extranodal natural killer/T cell lymphoma

Background

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a cytokine that is used as an immunopotentiator for anti-tumor therapies in recent years. We found that some of the extranodal natural killer/T cell lymphoma (ENKTL) patients with the treatment of hGM-CSF rapidly experienced disease progression, but the underlying mechanisms remain to be elucidated. Here, we aimed to explore the mechanisms of disease progression triggered by GM-CSF in ENKTL.

Methods

The mouse models bearing EL4 cell tumors were established to investigate the effects of GM-CSF on tumor growth and T cell infiltration and function. Human ENKTL cell lines including NK-YS, SNK-6, and SNT-8 were used to explore the expression of programmed death-ligand 1 (PD-L1) induced by GM-CSF. To further study the mechanisms of disease progression of ENKTL in detail, the mutations and gene expression profile were examined by next-generation sequence (NGS) in the ENKTL patient’s tumor tissue samples.

Results

The mouse-bearing EL4 cell tumor exhibited a faster tumor growth rate and poorer survival in the treatment with GM-CSF alone than in treatment with IgG or the combination of GM-CSF and PD-1 antibody. The PD-L1 expression at mRNA and protein levels was significantly increased in ENKTL cells treated with GM-CSF. STAT5A high-frequency mutation including p.R131G, p.D475N, p.F706fs, p.V707E, and p.S710F was found in 12 ENKTL cases with baseline tissue samples. Importantly, STAT5A-V706fs mutation tumor cells exhibited increased activation of STAT5A pathway and PD-L1 overexpression in the presence of GM-CSF.

Conclusions

These findings demonstrate that GM-CSF potentially triggers the loss of tumor immune surveillance in ENKTL patients and promotes disease progression, which is associated with STAT5 mutations and JAK2 hyperphosphorylation and then upregulates the expression of PD-L1. These may provide new concepts for GM-CSF application and new strategies for the treatment of ENKTL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01374-y.

Genomic Landscape of Hodgkin Lymphoma

Simple Summary

Hodgkin lymphoma (HL) is composed of many reactive and only a few cancer cells, so-called Hodgkin and Reed-Sternberg (HRS) or lymphocyte predominant (LP) cells. Due to the scarcity of these cells, it was difficult to perform high-throughput molecular investigations on them for a long time. With the help of recently developed methods, it is now possible to analyze their genomes. This review summarizes the genetic alterations found in HRS and LP cells that impact immune evasion, proliferation and circumvention of programmed cell death in HL. Understanding these underlying molecular mechanisms is essential, as they may be of prognostic and predictive value and help to improve the therapy especially for patients with recurrent or treatment-resistant disease.

Abstract

Background: Hodgkin lymphoma (HL) is predominantly composed of reactive, non-neoplastic cells surrounding scarcely distributed tumor cells, that is, so-called Hodgkin and Reed-Sternberg (HRS) or lymphocyte predominant (LP) cells. This scarcity impeded the analysis of the tumor cell genomes for a long time, but recently developed methods (especially laser capture microdissection, flow cytometry/fluorescence-activated cell sorting) facilitated molecular investigation, elucidating the pathophysiological principles of “Hodgkin lymphomagenesis”. Methods: We reviewed the relevant literature of the last three decades focusing on the genomic landscape of classic and nodular lymphocyte predominant HL (NLPHL) and summarized molecular cornerstones. Results: Firstly, the malignant cells of HL evade the immune system by altered expression of PDL1/2, B2M and MHC class I and II due to various genetic alterations. Secondly, tumor growth is promoted by permanently activated JAK/STAT signaling due to pervasive mutations of multiple genes involved in the pathway. Thirdly, apoptosis of neoplastic cells is prevented by alterations of NF-κB compounds and the PI3K/AKT/mTOR axis. Additionally, Epstein-Barr virus infection can simultaneously activate JAK/STAT and NF-κB, similarly leading to enhanced survival and evasion of apoptosis. Finally, epigenetic phenomena such as promoter hypermethylation lead to the downregulation of B-lineage-specific, tumor-suppressor and immune regulation genes. Conclusion: The blueprint of HL genomics has been laid, paving the way for future investigations into its complex pathophysiology.

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.

The IL-6 signaling complex is a critical driver, negative prognostic factor, and therapeutic target in diffuse large B-cell lymphoma

Interleukin-6 (IL-6) is a growth factor for normal B cells and plasma cell-derived malignancies. Here, we show that the IL-6 signaling pathway is also active in a subset of diffuse large B-cell lymphoma (DLBCL) patients with particularly poor prognosis. Primary DLBCL cells and DLBCL cell lines expressing IL-6R engraft and form orthotopic lymphomas in humanized mice that ectopically produce human IL-6, and in mice reconstituted with a human immune system. We show that a subset of DLBCL cases have evolved mechanisms that ensure constitutive activation of the IL-6 signaling pathway, i.e., the expression of both chains of the IL-6R, the expression of the cytokine itself, and the mutational inactivation of a negative regulator of IL-6 signaling, SOCS1. IL-6 signaling promotes MYC-driven lymphomagenesis in a genetically engineered model, and treatment with the IL-6R-specific antibody tocilizumab reduces growth of primary DLBCL cells and of DLBCL cell lines in various therapeutic settings. The combined results uncover the IL-6 signaling pathway as a driver and negative prognosticator in aggressive DLBCL that can be targeted with a safe and well-tolerated biologic.

Targeting the Immune Microenvironment in Lymphomas of B-Cell Origin: From Biology to Clinical Application

In lymphomas of B-cell origin, cancer cells orchestrate an inflammatory microenvironment of immune and stromal cells that sustain the tumor cell survival and growth, known as a tumor microenvironment (TME). The features of the TME differ between the different lymphoma types, ranging from extremely inflammatory, such as in Hodgkin lymphoma, to anergic, leading to immune deficiency and susceptibility to infections, such as in chronic lymphocytic leukemia. Understanding the characteristic features of the TME as well as the interactions between cancer and TME cells has given insight into the pathogenesis of most lymphomas and contributed to identify novel therapeutic targets. Here, we summarize the preclinical data that contributed to clarifying the role of the immune cells in the TME of different types of lymphomas of B-cell origin, and explain how the understanding of the biological background has led to new clinical applications. Moreover, we provide an overview of the clinical results of trials that assessed the safety and efficacy of drugs directly targeting TME immune cells in lymphoma patients.

Novel cell enrichment technique for robust genetic analysis of archival classical Hodgkin lymphoma tissues

Approximately 15% of patients with classical Hodgkin lymphoma (cHL) die after relapse or progressive disease. Comprehensive genetic characterization is required to better understand its molecular pathology and improve management. However, genetic information on cHL is hard to obtain mainly due to rare malignant Hodgkin- and Reed-Sternberg cells (HRSC), whose overall frequencies in the affected tissues ranges from 0.1 to 10%. Therefore, enrichment of neoplastic cells is necessary for the majority of genetic investigations. We have developed a new high-throughput method for marker-based enrichment of archival formalin-fixed and paraffin-embedded (FFPE) tissue-derived HRSC nuclei by fluorescence-assisted flow sorting (FACS) and successfully applied it on ten cHL cases. Genomic DNA extracted from sorted nuclei was used for targeted high-throughput sequencing (HTS) of 68 genes that are frequently affected in lymphomas. Chromosomal copy number aberrations were investigated by the Agilent SurePrint 180k microarray. Our method enabled HRSC nuclei enrichment to 40-90% in sorted populations. This level of enrichment was sufficient for reliable identification of tumor-specific mutations and copy number aberrations. Genetic analysis revealed that components of JAK-STAT signaling pathway were affected in all investigated tumors by frequent mutations of SOCS1 and STAT6 as well as copy number gains of JAK2. Involvement of nuclear factor-κB (NF-κB) pathway compounds was evident from recurrent gains of the locus containing the REL gene and mutations in TNFAIP3 and CARD11. Finally, genetic alterations of PD-L1 and B2M suggested immune evasion as mechanisms of oncogenesis in some patients. In this work, we present a new method for HRSC enrichment from FFPE tissue blocks by FACS and demonstrate the feasibility of a wide-scale genetic analysis by cutting-edge molecular methods. Our work opens the door to a large resource of archived clinical cHL samples and lays foundation to more complex studies aimed to answer important biological and clinical questions that are critical to improve cHL management.

TIRAP p.R81C is a novel lymphoma risk variant which enhances cell proliferation via NF-κB mediated signaling in B-cells

Diffuse large B-cell lymphoma is the most common malignant lymphoma in adults. By gene-expression profiling, this lymphoma is divided in three cell-of-origin subtypes with distinct molecular and clinical features. Most lymphomas arise sporadically, yet familial clustering is known, suggesting a genetic contribution to disease risk. Familial lymphoma cases are a valuable tool to investigate risk genes. We studied a Swiss/Japanese family with 2 sisters affected by a primary mediastinal B-cell lymphoma and a non-germinal center diffuse large B-cell lymphoma not otherwise specified, respectively. The somatic landscape of both lymphomas was marked by alterations affecting multiple components of the JAK-STAT pathway. Consequently, this pathway was constitutively activated as evidenced by high pJAK2 as well as increased nuclear pSTAT3 and pSTAT6 in malignant cells. Potential lymphoma risk variants were identified by whole exome sequencing of the germline DNA derived from siblings and unaffected family members. This analysis revealed a pathogenic variant in TIRAP, an upstream regulator of NF-κB, in both affected siblings and their mother. We observed increased B-cell proliferation in family members harboring the TIRAP p.R81C variant. B-cell proliferation correlated with TIRAP and NF-κB target gene expression, suggesting enhanced NF-κB pathway activity in TIRAP p.R81C individuals. TIRAP knockdown reduced B-cell survival and NF-κB target gene expression, particularly in individuals with TIRAP p.R81C. Functional studies revealed significantly increased NF-κB activity and resistance to stress-induced cell-death by TIRAP p.R81C. The identification of an inherited TIRAP variant provides evidence for a novel link between genetic alterations affecting the NF-κB pathway and lymphomagenesis.

Inhibiting Janus Kinase 1 and BCL-2 to treat T cell acute lymphoblastic leukemia with IL7-Rα mutations

Acute lymphoblastic leukemia (ALL) is the most common cancer in children. Current chemotherapy is quite toxic in growing children and more directed therapeutics are being sought. The IL-7R pathway is a major driver of ALL and here we evaluate two drugs directed to that pathway using a model of T cell ALL. Mutant gain-of-function IL-7Rα was transduced into an IL-7-dependent murine thymocyte line conferring ligand-independent survival and growth. JAK1 is associated with IL-7Rα and mediates signaling from the mutant receptor. In vitro, treating the transformed cell line with the JAK1/2 inhibitor ruxolitinib inhibited ligand-independent signaling and induced cell death. Transfer of the transformed cell line into mice resulted in aggressive leukemia and untreated mice succumbed in about three weeks. Treatment with ruxolitinib incorporated into chow showed a potent therapeutic benefit with reduction in leukemic burden and extension of survival. BCL-2 is an anti-apoptotic downstream mediator of the IL-7R survival mechanism. Venetoclax, an inhibitor of BCL-2, showed activity against the transformed cell line in vitro and could be combined with ruxolitinib in vivo. These findings support the therapeutic potential of treating T-ALL by targeting the IL-7R pathway.

Somatic IL4R mutations in primary mediastinal large B-cell lymphoma lead to constitutive JAK-STAT signaling activation

Primary mediastinal large B-cell lymphoma (PMBCL) is a distinct subtype of diffuse large B-cell lymphoma thought to arise from thymic medullary B cells. Gene mutations underlying the molecular pathogenesis of the disease are incompletely characterized. Here, we describe novel somatic IL4R mutations in 15 of 62 primary cases of PMBCL (24.2%) and in all PMBCL-derived cell lines tested. The majority of mutations (11/21; 52%) were hotspot single nucleotide variants in exon 8, leading to an I242N amino acid change in the transmembrane domain. Functional analyses establish this mutation as gain of function leading to constitutive activation of the JAK-STAT pathway and upregulation of downstream cytokine expression profiles and B cell-specific antigens. Moreover, expression of I242N mutant IL4R in a mouse xenotransplantation model conferred growth advantage in vivo. The pattern of concurrent mutations within the JAK-STAT signaling pathway suggests additive/synergistic effects of these gene mutations contributing to lymphomagenesis. Our data establish IL4R mutations as novel driver alterations and provide a strong preclinical rationale for therapeutic targeting of JAK-STAT signaling in PMBCL.

A phase II study of the oral JAK1/JAK2 inhibitor ruxolitinib in advanced relapsed/refractory Hodgkin lymphoma

JAK2 constitutive activation/overexpression is common in classical Hodgkin lymphoma, and several cytokines stimulate Hodgkin lymphoma cells by recognizing JAK1-/JAK2-bound receptors. JAK blockade may thus be therapeutically beneficial in Hodgkin lymphoma. In this phase II study we assessed the safety and efficacy of ruxolitinib, an oral JAK1/2 inhibitor, in patients with relapsed/refractory Hodgkin lymphoma. The primary objective was overall response rate according to the International Harmonization Project 2007 criteria. Thirty-three patients with advanced disease (median number of prior lines of treatment: 5; refractory: 82%) were included; nine (27.3%) received at least six cycles of ruxolitinib and six (18.2%) received more than six cycles. The overall response rate after six cycles was 9.4% (3/32 patients). All three responders had partial responses; another 11 patients had transient stable disease. Best overall response rate was 18.8% (6/32 patients). Rapid alleviation of B-symptoms was common. The median duration of response was 7.7 months, median progression-free survival 3.5 months (95% CI: 1.9–4.6), and the median overall survival 27.1 months (95% CI: 14.4–27.1). Forty adverse events were reported in 14/33 patients (42.4%). One event led to treatment discontinuation, while 87.5% of patients recovered without sequelae. Twenty-five adverse events were grade 3 or higher. These events were mostly anemia (n=11), all considered related to ruxolitinib. Other main causes of grade 3 or higher adverse events included lymphopenia and infections. Of note, no cases of grade 4 neutropenia or thrombocytopenia were observed. Ruxolitinib shows signs of activity, albeit short-lived, beyond a simple anti-inflammatory effect. Its limited toxicity suggests that it has the potential to be combined with other therapeutic modalities. ClinicalTrials.gov: NCT01877005

HiJAKing the epigenome in leukemia and lymphoma

The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is central to signaling by receptors of diverse cytokines, growth factors, and other related molecules. Many of these receptors transmit anti-apoptosis, proliferation, and differentiation signals that are critical for normal hematopoiesis and immune response. However, the JAK/STAT signaling pathway is deregulated in many hematologic malignancies, and as such is co-opted by malignant cells to promote their survival and proliferation. It has recently come to light that an alternative mechanism, wherein nuclear JAKs epigenetically modify the chromatin to increase gene expression independent of STATs, also plays an important role in the pathogenesis of many hematologic malignancies. In this review, we will focus on common genetic alterations of the JAK family members in leukemia and lymphoma, and provide examples in which JAKs regulate gene expression by targeting the cancer epigenome.

The promise of Janus kinase inhibitors in the treatment of hematological malignancies

The Janus kinases (JAK) are a family of kinases that play an essential role in cytokine signaling and are implicated in the pathogenesis of autoimmune diseases and hematological malignancies. As a result, the JAKs have become attractive therapeutic targets. The discovery of a JAK2 point mutation (JAK2 V617F) as the main cause of polycythemia vera lead to the development and FDA approval of a JAK1/2 inhibitor, ruxolitinib, in 2011. This review focuses on the various JAK and associated components aberrations implicated in myeloproliferative neoplasms, leukemias, and lymphomas. In addition to ruxolitinib, other JAK inhibitors are currently being evaluated in clinical trials for treating hematological malignancies. The use of JAK inhibitors alone or in combination therapy should be considered as a way to deliver targeted therapy to patients.

Decreased NK-cell tumour immunosurveillance consequent to JAK inhibition enhances metastasis in breast cancer models

The JAK/STAT pathway is an attractive target for breast cancer therapy due to its frequent activation, and clinical trials evaluating JAK inhibitors (JAKi) in advanced breast cancer are ongoing. Using patient biopsies and preclinical models of breast cancer, we demonstrate that the JAK/STAT pathway is active in metastasis. Unexpectedly, blocking the pathway with JAKi enhances the metastatic burden in experimental and orthotopic models of breast cancer metastasis. We demonstrate that this prometastatic effect is due to the immunosuppressive activity of JAKi with ensuing impairment of NK-cell-mediated anti-tumour immunity. Furthermore, we show that immunostimulation with IL-15 overcomes the enhancing effect of JAKi on metastasis formation. Our findings highlight the importance of evaluating the effect of targeted therapy on the tumour environment. The impact of JAKi on NK cells and the potential value of immunostimulators to overcome the weakened tumour immunosurveillance, are worthwhile considering in the clinical setting of breast cancer.

JAK inhibitors are currently undergoing evaluation in clinical trials for advanced breast cancer. Here, the authors show that JAK pathway inhibition increases metastasis in mouse models of breast cancer by impairing NK anti-tumour activity and that these side effects can be overcome by addition of IL-15.

Expression of PD-L1 Identifies a Subgroup of More Aggressive Non-Small Cell Carcinomas of the Lung

OBJECTIVES

In light of various trials showing impressive response rates when treating non-small cell lung cancer (NSCLC) patients with anti PD-1/PD-L1 antibodies, the currently equivocal role of PD-L1 expression in NSCLC is in need of further clarification.

METHODS

We therefore analyzed the expression of PD-L1 on 293 well-documented NSCLC cases and correlated the results with clinical, histopathological and immunohistochemical characteristics.

RESULTS

The expression of PD-L1 on NSCLC was a poor prognostic factor for patients with nodal-negative adenocarcinoma (ACA) and, independent of other covariates, in tumors with increased CD8+ tumor-infiltrating lymphocytes (TILs). Expression of PD-L1 was more commonly seen in ACA and in male patients with a past and current smoking history. Finally, PD-L1+ TILs were more often found in squamous and large cell carcinomas.

CONCLUSIONS

Should the expression of PD-L1 be on the verge of becoming an additional biomarker for routine diagnostics in NSCLC, our findings will provide important further insight and could contribute towards more effectively stratifying patients. These results may single out certain patient groups with a potential for increased benefit from anti PD-1/PD-L1 treatment strategies and should be considered in future trials.

Molecular genetics of childhood, adolescent and young adult non-Hodgkin lymphoma

Molecular genetic abnormalities are ubiquitous in non-Hodgkin lymphoma (NHL), but genetic changes are not yet used to define specific lymphoma subtypes. Certain recurrent molecular genetic abnormalities in NHL underlie molecular pathogenesis and/or are associated with prognosis or represent potential therapeutic targets. Most molecular genetic studies of B- and T-NHL have been performed on adult patient samples, and the relevance of many of these findings for childhood, adolescent and young adult NHL remains to be demonstrated. In this review, we focus on NHL subtypes that are most common in young patients and emphasize features actually studied in younger NHL patients. This approach highlights what is known about NHL genetics in young patients but also points to gaps that remain, which will require cooperative efforts to collect and share biological specimens for genomic and genetic analyses in order to help predict outcomes and guide therapy in the future.

Genomic alterations of the JAK2 and PDL loci occur in a broad spectrum of lymphoid malignancies

The recurrent 9p24.1 aberrations in lymphoid malignancies potentially involving four cancer-related and druggable genes (JAK2, CD274/PDL1, PDCD1LG2/PDL2, and KDM4C/JMJD2Cl) are incompletely characterized. To gain more insight into the anatomy of these abnormalities, at first we studied 9p24.1 alterations in 18 leukemia/lymphoma cases using cytogenetic and molecular techniques. The aberrations comprised structural (nine cases) and numerical (nine cases) alterations. The former lesions were heterogeneous but shared a common breakpoint region of 200 kb downstream of JAK2. The rearrangements predominantly targeted the PDL locus. We have identified five potential partner genes of PDL1/2: PHACTR4 (1p34), N4BP2 (4p14), EEF1A1 (6q13), JAK2 (9p24.1), and IGL (22q11). Interestingly, the cryptic JAK2-PDL1 rearrangement was generated by a microdeletion spanning the 3'JAK2-5'PDL1 region. JAK2 was additionally involved in a cytogenetically cryptic IGH-mediated t(9;14)(p24.1;q32) found in two patients. This rare but likely underestimated rearrangement highlights the essential role of JAK2 in B-cell neoplasms. Cases with amplification of 9p24.1 were diagnosed as primary mediastinal B-cell lymphoma (five cases) and T-cell lymphoma (four cases). The smallest amplified 9p24.1 region was restricted to the JAK2-PDL1/2-RANBP6 interval. In the next step, we screened 200 cases of classical Hodgkin lymphoma by interphase FISH and identified PDL1/2 rearrangement (CIITA- and IGH-negative) in four cases (2%), what is a novel finding. Forty (25%) cases revealed high level amplification of 9p24.1, including four cases with a selective amplification of PDL1/2. Altogether, the majority of 9p24.1 rearrangements occurring in lymphoid malignancies seem to target the programmed death-1 ligands, what potentiates the therapeutic activity of PD-1 blockade in these tumors. © 2016 Wiley Periodicals, Inc.

A single-institution retrospective analysis of outcomes for stage I-II primary mediastinal large B-cell lymphoma treated with immunochemotherapy with or without radiotherapy

As the optimal treatment for primary mediastinal large B-cell lymphoma (PMBCL) remains undefined, we evaluated outcomes of patients treated with standard and dose-intense rituximab-chemotherapy (R-CT) with and without radiotherapy (RT). We retrospectively identified 28 patients with stage I-II PMBCL in our lymphoma database, re-reviewed pathology slides and scored interim or post-chemotherapy PET/CTs using the Deauville scale. Fourteen patients received RT (36-45 Gy) preceded by either six cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) or 12 weeks of rituximab, etoposide, doxorubicin, cyclophosphamide, vincristine, prednisone and bleomycin (R-VACOP-B) with median follow-up of 94 months. Fourteen patients received 4-8 cycles of dose-adjusted etoposide, vincristine, doxorubicin, cyclophosphamide and rituximab (DA-EPOCH-R) with median follow-up of 38 months; one of these received RT (36 Gy) due to post-chemotherapy PET/CT Deauville score 4. Following R-CT and RT or DA-EPOCH-R, 5-year and 3-year FFP and OS were both 100%. Both R-CHOP/R-VACOP-B with RT and DA-EPOCH-R demonstrate excellent outcomes.

Deregulated JAK/STAT signalling in lymphomagenesis, and its implications for the development of new targeted therapies

Gene expression profiling has implicated several intracellular signalling cascades, including the JAK/STAT pathway, in the pathogenesis of particular subtypes of lymphoma. In marked contrast to the situation in patients with either acute lymphoblastic leukaemia or a myeloproliferative neoplasm, JAK2 coding sequence mutations are rare in lymphoma patients with an activated JAK/STAT "signature". This is instead the consequence of mutational events that result in the increased expression of non-mutated JAK2; positively or negatively affect the activity of other components of the JAK/STAT pathway; or establish an autocrine signalling loop that drives JAK-mediated cytokine-independent proliferation. Here, we detail these genetic lesions, their functional consequences, and impact on patient outcome. In light of the approval of a JAK1/JAK2 inhibitor for the treatment of myelofibrosis, and preliminary studies evaluating the efficacy of other JAK inhibitors, the therapeutic potential of compounds that target JAK/STAT signalling in the treatment of patients with lymphoma is also discussed.

Malignant hematopoietic cell lines: in vitro models for the study of primary mediastinal B-cell lymphomas

Primary mediastinal B-cell lymphoma (PMBL) is a highly aggressive disease with a unique set of biological, clinical, morphological, immunological and in particular genetic features that in the molecular era of defining lymphomas clearly distinguishes it as a separate entity from other diffuse large B-cell lymphomas (DLBCL). A precise molecular diagnosis of PMBL can be achieved by gene expression profiling. The signature gene expression profile of PMBL is more closely related to classic Hodgkin lymphoma (cHL) than to other DLBCL subgroups. A number of common genetic aberrations in PMBL and cHL further underscore their close relationship. To investigate the pathobiology of lymphomas in depth, many groups have turned to cell lines that are suitable models facilitating molecular studies and providing unique insights. For the purposes of the current perspective, we focus on four bona fide PMBL-derived cell lines (FARAGE, KARPAS-1106, MEDB-1, U-2940) that we identified and validated as such through hierarchical cluster analysis among a large collection of leukemia-lymphoma cell lines. These gene expression profiles showed that the four PMBL cell lines represent a distinct entity and are most similar to cHL cell lines, confirming derivation from a related cell type. A validated cell line resource for PMBL should assist those seeking druggable targets in this entity. This review aims to provide a comprehensive overview of the currently available cellular models for the study of PMBL.

Clinical implications of phosphorylated STAT3 expression in De Novo diffuse large B-cell lymphoma

PURPOSE

Activated signal transducer and activator of transcription 3 (STAT3) regulates tumor growth, invasion, cell proliferation, angiogenesis, immune response, and survival. Data regarding expression of phosphorylated (activated) STAT3 in diffuse large B-cell lymphoma (DLBCL) and the impact of phosphorylated STAT3 (pSTAT3) on prognosis are limited.

EXPERIMENTAL DESIGN

We evaluated expression of pSTAT3 in de novo DLBCL using immunohistochemistry, gene expression profiling (GEP), and gene set enrichment analysis (GSEA). Results were analyzed in correlation with cell-of-origin (COO), critical lymphoma biomarkers, and genetic translocations.

RESULTS

pSTAT3 expression was observed in 16% of DLBCL and was associated with advanced stage, multiple extranodal sites of involvement, activated B-cell-like (ABC) subtype, MYC expression, and MYC/BCL2 expression. Expression of pSTAT3 predicted inferior overall survival (OS) and progression-free survival (PFS) in patients with de novo DLBCL. When DLBCL cases were stratified according to COO or MYC expression, pSTAT3 expression did not predict inferior outcome, respectively. Multivariate analysis showed that the prognostic predictability of pSTAT3 expression was due to its association with the ABC subtype, MYC expression, and adverse clinical features. GEP demonstrated upregulation of genes, which can potentiate function of STAT3. GSEA showed the JAK-STAT pathway to be enriched in pSTAT3(+) DLBCL.

CONCLUSIONS

The results of this study provide a rationale for the ongoing successful clinical trials targeting the JAK-STAT pathway in DLBCL.

Selective JAK2 inhibition specifically decreases Hodgkin lymphoma and mediastinal large B-cell lymphoma growth in vitro and in vivo

PURPOSE

Classical Hodgkin lymphoma (cHL) and primary mediastinal large B-cell lymphoma (MLBCL) share similar histologic, clinical, and genetic features. In recent studies, we found that disease-specific chromosome 9p24.1/JAK2 amplification increased JAK2 expression and activity in both cHL and MLBCL. This prompted us to assess the activity of a clinical grade JAK2 selective inhibitor, fedratinib (SAR302503/TG101348), in in vitro and in vivo model systems of cHL and MLBCL with defined JAK2 copy numbers.

EXPERIMENTAL DESIGN

We used functional and immunohistochemical analyses to investigate the preclinical activity of fedratinib and associated biomarkers in cell lines and murine xenograft models of cHL and MLBCL with known 9p24.1/JAK2 copy number.

RESULTS

Chemical JAK2 inhibition decreased the cellular proliferation of cHL and MLBCL cell lines and induced their apoptosis. There was an inverse correlation between 9p24.1/JAK2 copy number and the EC50 of fedratinib. Chemical JAK2 inhibition decreased phosphorylation of JAK2, STAT1, STAT3, and STAT6 and reduced the expression of additional downstream targets, including PD-L1, in a copy number-dependent manner. In murine xenograft models of cHL and MLBCL with 9p24.1/JAK2 amplification, chemical JAK2 inhibition significantly decreased JAK2/STAT signaling and tumor growth and prolonged survival. In in vitro and in vivo studies, pSTAT3 was an excellent biomarker of baseline JAK2 activity and the efficacy of chemical JAK2 inhibition.

CONCLUSIONS

In in vitro and in vivo analyses, cHL and MLBCL with 9p24.1/JAK2 copy gain are sensitive to chemical JAK2 inhibition suggesting that clinical evaluation of JAK2 blockade is warranted.

JAK-STAT in lipid metabolism of adipocytes

JAK-STAT signaling pathway plays an important role in the cells' development and homeostasis. Over the past decades, the studies have identified the role of the JAK-STAT pathway in cell proliferation and apoptosis. Here, we want to discuss that whether and how the JAK-STAT pathway affects the lipid metabolism of adipose tissue. A host of cytokines and hormones can regulate lipid metabolism through activating the JAK-STAT signaling pathway. Activated STATs can regulate lipid metabolism directly by influencing the expression of enzymes. We have summarized the relevant research and articles of JAK-STAT during the recent years. Within this review, we will introduce you the recent research and highlight the unresolved problems in understanding how JAK-STAT signaling pathway contribute to the lipid metabolism in mature adipocytes and preadipocytes. Dysregulation of the JAK-STAT pathway would lead to a multiple metabolism disorders and medicines for this signaling pathway maybe become a new idea for diseases such as metabolic syndrome, especially in children.

Histone H2AX suppresses translocations in lymphomas of Eμ-c-Myc transgenic mice that contain a germline amplicon of tumor-promoting genes

The DNA damage response (DDR) can restrain the ability of oncogenes to cause genomic instability and drive malignant transformation. The gene encoding the histone H2AX DDR factor maps to 11q23, a region frequently altered in human cancers. Since H2ax functions as a haploinsufficient suppressor of B lineage lymphomas with c-Myc amplification and/or translocation, we determined the impact of H2ax expression on the ability of deregulated c-Myc expression to cause genomic instability and drive transformation of B cells. Neither H2ax deficiency nor haploinsufficiency affected the rate of mortality of Eμ-c-Myc mice from B lineage lymphomas with genomic deletions and amplifications. Yet H2ax functioned in a dosage-dependent manner to prevent unbalanced translocations in Eμ-c-Myc tumors, demonstrating that H2ax functions in a haploinsufficient manner to suppress allelic imbalances and limit molecular heterogeneity within and among Eμ-c-Myc lymphomas. Regardless of H2ax copy number, all Eμ-c-Myc tumors contained identical amplification of chromosome 19 sequences spanning 20 genes. Many of these genes encode proteins with tumor-promoting activities, including Cd274, which encodes the PD-L1 programmed death ligand that induces T cell apoptosis and enables cancer cells to escape immune surveillance. This amplicon was in non-malignant B and T cells and non-lymphoid cells, linked to the Eμ-c-Myc transgene, and associated with overexpression of PD-L1 on non-malignant B cells. Our data demonstrate that, in addition to deregulated c-Myc expression, non-malignant B lineage lymphocytes of Eμ-c-Myc transgenic mice may have constitutive amplification and increased expression of other tumor-promoting genes.

The role of the JAK-STAT pathway and related signal cascades in telomerase activation during the development of hematologic malignancies

Telomerase, comprising a reverse transcriptase protein (TERT) and an RNA template, plays a critical role during senescence and carcinogenesis; however, the mechanisms by which telomerase is regulated remain to be elucidated. Several signaling pathways are involved in the activation of TERT at multistep levels. The JAK-STAT pathway is indispensable for mediating signals through growth factor and cytokine receptors during the development of hematopoietic cells, and its activity is frequently upregulated in hematological malignancies. Here, we review the role of the JAK-STAT pathway and related signaling cascades in the regulation of telomerase in hematological malignancies.

Dysregulation of JAK-STAT pathway in hematological malignancies and JAK inhibitors for clinical application

JAK-STAT (Janus associated kinase-signal transducer and activator of transcription) pathway plays a critical role in transduction of extracellular signals from cytokines and growth factors involved in hematopoiesis, immune regulation, fertility, lactation, growth and embryogenesis. JAK family contains four cytoplasmic tyrosine kinases, JAK1-3 and Tyk2. Seven STAT proteins have been identified in human cells, STAT1-6, including STAT5a and STAT5b. Negative regulators of JAK-STAT pathways include tyrosine phosphatases (SHP1 and 2, CD45), protein inhibitors of activated STATs (PIAS), suppressors of cytokine signaling (SOCS) proteins, and cytokine-inducible SH2-containing protein (CIS). Dysregulation of JAK-STAT pathway have been found to be key events in a variety of hematological malignancies. JAK inhibitors are among the first successful agents reaching clinical application. Ruxolitinib (Jakafi), a non-selective inhibitor of JAK1 & 2, has been approved by FDA for patients with intermediate to high risk primary or secondary myelofibrosis. This review will also summarize early data on selective JAK inhibitors, including SAR302503 (TG101348), lestaurtinib (CEP701), CYT387, SB1518 (pacritinib), LY2784544, XL019, BMS-911543, NS-018, and AZD1480.

PIM kinases are progression markers and emerging therapeutic targets in diffuse large B-cell lymphoma

Background:

PIM serine/threonine kinases are often highly expressed in haematological malignancies. We have shown that PIM inhibitors reduced the survival and migration of leukaemic cells. Here, we investigated PIM kinases in diffuse large B-cell lymphoma (DLBCL) biopsy samples and DLBCL cell lines.

Methods:

Immunohistochemical staining for PIM kinases and CXCR4 was performed on tissue microarrays from a cohort of 101 DLBCL cases, and the effects of PIM inhibitors on the survival and migration of DLBCL cell lines were determined.

Results:

PIM1 expression significantly correlated with the activation of signal transducer and activator of transcription (STAT) 3 and 5, P-glycoprotein expression, CXCR4-S339 phosphorylation, and cell proliferation. Whereas most cases exhibited cytoplasmic or cytoplasmic and nuclear PIM1 and PIM2 expression, 12 cases (10 of the non-germinal centre DLBCL type) expressed PIM1 predominately in the nucleus. Interestingly, nuclear expression of PIM1 significantly correlated with disease stage. Exposure of DLBCL cell lines to PIM inhibitors modestly impaired cellular proliferation and CXCR4-mediated migration.

Conclusion:

This work demonstrates that PIM expression in DLBCL is associated with activation of the JAK/STAT signalling pathway and with the proliferative activity. The correlation of nuclear PIM1 expression with disease stage and the modest response to small-molecule inhibitors suggests that PIM kinases are progression markers rather than primary therapeutic targets in DLBCL.

Pathogenesis of human B cell lymphomas

The mechanisms that drive normal B cell differentiation and activation are frequently subverted by B cell lymphomas for their unlimited growth and survival. B cells are particularly prone to malignant transformation because the machinery used for antibody diversification can cause chromosomal translocations and oncogenic mutations. The advent of functional and structural genomics has greatly accelerated our understanding of oncogenic mechanisms in lymphomagenesis. The signaling pathways that normal B cells utilize to sense antigens are frequently derailed in B cell malignancies, leading to constitutive activation of prosurvival pathways. These malignancies co-opt transcriptional regulatory systems that characterize their normal B cell counterparts and frequently alter epigenetic regulators of chromatin structure and gene expression. These mechanistic insights are ushering in an era of targeted therapies for these cancers based on the principles of pathogenesis.

Proliferation centers in chronic lymphocytic leukemia: correlation with cytogenetic and clinicobiological features in consecutive patients analyzed on tissue microarrays

To better define the significance of proliferation centers (PCs), the morphological hallmark of chronic lymphocytic leukemia (CLL), lymph node biopsies taken from 183 patients were submitted to histopathologic and fluorescence in situ hybridization (FISH) studies using a 5-probe panel on tissue microarrays. Seventy-five cases (40.9%) with confluent PCs were classified as 'PCs-rich' and 108 cases (59.1%) with scattered PCs were classified as 'typical'. Complete FISH data were obtained in 101 cases (55.1%), 79 of which (78.2%) displayed at least one chromosomal aberration. The incidence of each aberration was: 13q- 36,7%, 14q32 translocations 30.8%, 11q- 24.7%, trisomy 12 19.5% and 17p- 15.6%. Five cases showed extra copies of the 14q32 region. The 'PCs-rich' group was associated with 17p-, 14q32/IgH translocation, +12, Ki-67>30%. The median survival from the time of tissue biopsy for PCs-rich and typical groups was 11 and 64 months, respectively (P=0.00001). The PCs-rich pattern was the only predictive factor of an inferior survival at multivariate analysis (P=0.022). These findings establish an association between cytogenetic profile and the amount of PC in CLL, and show that this histopathologic characteristic is of value for risk assessment in patients with clinically significant adenopathy.

Nuclear JAK2: form and function in cancer

The conventional view of Janus kinase 2 (JAK2) is a nonreceptor tyrosine kinase which transmits information to the nucleus via the signal transducer and activator of transcriptions (STATs) without leaving the cytoplasm. However, accumulating data suggest that JAK2 may signal by exporting from cytoplasm to nucleus, where it guides the transcriptional machinery independent of STATs protein. Recent studies demonstrated that JAK2 is a crucial component of signaling pathways operating in the nucleus. Especially the latest landmark discovery confirmed that JAK2 goes into the nucleus and directly interacts with nucleoproteins, such as histone H3 at tyrosine 41 (H3Y41), nuclear factor 1-C2 (NF1-C2) and SWI/SNF-related helicases/ATPases (RUSH)-1α, indicating that JAK2 has a fresh nuclear function. Nuclear JAK2 is linked to a variety of cellular functions, such as cell cycle progression, apoptosis and genetic instability. The balance between these functions is an essential factor in determining whether a cell remains benign or becomes malignant. The aim of this review is intended to summarize the state of our knowledge on nuclear localization of JAK2 and nuclear JAK2 pathways, and to highlight the emerging roles for nuclear JAK2 in carcinogenesis.

Monocytes and T cells cooperate to favor normal and follicular lymphoma B-cell growth: role of IL-15 and CD40L signaling

Interleukin-15 (IL-15) has been extensively studied for its role in the survival and proliferation of NK and T cells through a unique mechanism of trans-presentation by producer cells. Conversely, whereas activated B cells have been described as IL-15-responding cells, the cellular and molecular context sustaining this effect remains unexplored. In this study, we found that, whereas human B cells could not respond to soluble IL-15, monocytes and lymphoid tissue-derived macrophages but not stromal cells efficiently trans-present IL-15 to normal B cells and cooperate with T-cell-derived CD40L to promote IL-15-dependent B-cell proliferation. Furthermore, CD40L signaling triggers a Src-independent upregulation of STAT5 expression and favors a Src-dependent phosphorylation of STAT5 in response to IL-15. In follicular lymphoma (FL), immunohistochemical studies reported a strong relationship between malignant B cells, infiltrating macrophages and T cells. We show here an overexpression of IL-15 in purified tumor-associated macrophages, and STAT5A in purified tumor B cells. Moreover, FL B cells respond to IL-15 trans-presented by monocytes/macrophages, in particular, in the presence of CD40L-mediated signaling. This cooperation between IL-15 and CD40L reinforces the importance of tumor microenvironment and unravels a mechanism of FL growth that should be considered if using IL-15 as a drug in this disease.

Lestaurtinib inhibition of the Jak/STAT signaling pathway in hodgkin lymphoma inhibits proliferation and induces apoptosis

Standard cytotoxic chemotherapy for Hodgkin Lymphoma (HL) has changed little in 30 years; the treatment for patients with relapsed or refractory disease remains challenging and novel agents are under development. JAK/STAT constitutive activation plays an important role in the pathogenesis of HL. Lestaurtinib is an orally bioavailable multikinase inhibitor that has recently been shown to inhibit JAK2 in myeloproliferative disorders. The potential role of Lestaurtinib in HL therapy is unknown. We have analyzed the effect of Lestaurtinib treatment in five HL cell lines from refractory patients, L-428, L-1236, L-540, HDML-2 and HD-MY-Z. At 48 h, a dose-dependent cell growth inhibition (23%–66% at 300 nM) and apoptotic increment (10%–64% at 300 nM) were observed. Moreover, Lestaurtinib inhibited JAK2, STAT5 and STAT3 phosphorylation and reduced the mRNA expression of its downstream antiapoptotic target Bcl-xL. In addition, we have analyzed the effect of Lestaurtinib treatment in lymph nodes from four classic HL patients. We observed a decrease in cell viability at 24 hours of treatment in three patients (mean decrease of 27% at 300 nM). Our findings provide, for the first time, a molecular rationale for testing JAK2 inhibitors, specifically Lestaurtinib, in HL patients.

JAK2 rearrangements, including the novel SEC31A-JAK2 fusion, are recurrent in classical Hodgkin lymphoma

The genetics of classical Hodgkin lymphoma (cHL) is poorly understood. The finding of a JAK2-involving t(4;9)(q21;p24) in 1 case of cHL prompted us to characterize this translocation on a molecular level and to determine the prevalence of JAK2 rearrangements in cHL. We showed that the t(4;9)(q21;p24) leads to a novel SEC31A-JAK2 fusion. Screening of 131 cHL cases identified 1 additional case with SEC31A-JAK2 and 2 additional cases with rearrangements involving JAK2. We demonstrated that SEC31A-JAK2 is oncogenic in vitro and acts as a constitutively activated tyrosine kinase that is sensitive to JAK inhibitors. In vivo, SEC31A-JAK2 was found to induce a T-lymphoblastic lymphoma or myeloid phenotype in a murine bone marrow transplantation model. Altogether, we identified SEC31A-JAK2 as a chromosomal aberration characteristic for cHL and provide evidence that JAK2 rearrangements occur in a minority of cHL cases. Given the proven oncogenic potential of this novel fusion, our studies provide new insights into the pathogenesis of cHL and indicate that in at least some cases, constitutive activation of the JAK/STAT pathway is caused by JAK2 rearrangements. The finding that SEC31A-JAK2 responds to JAK inhibitors indicates that patients with cHL and JAK2 rearrangements may benefit from targeted therapies.

Cooperative epigenetic modulation by cancer amplicon genes

Chromosome band 9p24 is frequently amplified in primary mediastinal B cell lymphoma (PMBL) and Hodgkin lymphoma (HL). To identify oncogenes in this amplicon, we screened an RNA interference library targeting amplicon genes and thereby identified JAK2 and the histone demethylase JMJD2C as essential genes in these lymphomas. Inhibition of JAK2 and JMJD2C cooperated in killing these lymphomas by decreasing tyrosine 41 phosphorylation and increasing lysine 9 trimethylation of histone H3, promoting heterochromatin formation. MYC, a major target of JAK2-mediated histone phosphorylation, was silenced after JAK2 and JMJD2C inhibition, with a corresponding increase in repressive chromatin. Hence, JAK2 and JMJD2C cooperatively remodel the PMBL and HL epigenome, offering a mechanistic rationale for the development of JAK2 and JMJD2C inhibitors in these diseases.