Platelet-derived growth factor mediates survival of leukemic large granular lymphocytes via an autocrine regulatory pathway

Large Granular Lymphocytic Leukemia: Clinical Features, Molecular Pathogenesis, Diagnosis and Treatment

Large granular lymphocytic (LGL) leukemia is a lymphoproliferative disorder characterized by persistent clonal expansion of mature T- or natural killer cells in the blood via chronic antigenic stimulation. LGL leukemia is associated with specific immunophenotypic and molecular features, particularly STAT3 and STAT5 mutations and activation of the JAK-STAT3, Fas/Fas-L and NF-κB signaling pathways. Disease-related deaths are mainly due to recurrent infections linked to severe neutropenia. The current treatment is based on immunosuppressive therapies, which frequently produce unsatisfactory long-term responses, and for this reason, personalized approaches and targeted therapies are needed. Here, we discuss molecular pathogenesis, clinical presentation, associated autoimmune disorders, and the available treatment options, including emerging therapies.

Pro-inflammatory cells sustain leukemic clonal expansion in T-cell large granular lymphocyte leukemia

T-cell large granular lymphocyte leukemia (T-LGLL) is a chronic lymphoproliferative disorder characterized by the clonal expansion of T-cell large granular lymphocytes (T-LGL). Immunophenotypic and genotypic features contribute to discriminate symptomatic (CD8+ STAT3-mutated T-LGLL) from clinically indolent patients, this latter group including CD8+ wildtype (wt), CD4+ STAT5B-mutated and wt cases. T-LGL lymphoproliferation is sustained both by somatic gain-offunction mutations (i.e., STAT3 and STAT5B) and by pro-inflammatory cytokines, but little information is available on the activity of T-LGLL non-leukemic cells. In this study, we characterized pro-inflammatory cells in the peripheral blood of T-LGLL patients and analyzed their role in supporting the leukemic growth. In symptomatic patients we found that cell populations not belonging to the leukemic component showed a discrete pro-inflammatory pattern. In particular, CD8+ STAT3-mutated cases showed a skewed Th17/Treg ratio and an abnormal distribution of monocyte populations characterized by increased intermediate and non-classical monocytes. We also demonstrated that monocytes released high levels of interleukin-6 after CCL5 stimulation, a chemokine specifically expressed only by leukemic LGL. Conversely, in asymptomatic cases an altered distribution of monocyte populations was not detected. Moreover, T-LGLL patients' monocytes showed abnormal activation of signaling pathways, further supporting the different pathogenic role of monocytes in patients in discrete clinical settings. Altogether, our data contribute to deepening the knowledge on the different cell subtypes in T-LGLL, focusing particularly on non-leukemic cell populations and thus offering the rationale for new therapeutic strategies.

Sclerotome-derived PDGF signaling functions as a niche cue responsible for primitive erythropoiesis

Primitive erythropoiesis serves a vital role in embryonic development, generating primitive red blood cells responsible for transportation of oxygen throughout the body. Although diverse niche factors are known to function in definitive hematopoiesis, the microenvironment contributing to primitive hematopoiesis remains largely elusive. Here, we report that platelet-derived growth factor (PDGF) signaling is required for erythroid progenitor differentiation in zebrafish. Ablating pdgfαa (also known as pdgfaa) and pdgfαb (also known as pdgfab) or blocking PDGF signaling with an inhibitor impairs erythroid progenitor differentiation, thus resulting in a significant decrease in the number of erythrocytes. We reveal that pdgfαb is expressed in sclerotomal cells, and that its receptor genes, pdgfra and pdgfrb, are expressed in the adjacent erythroid progenitor cells. Sclerotome-specific overexpression of pdgfαb effectively restores primitive erythropoiesis in pdgfαa-/-;pdgfαb-/- mutant embryos. In addition, we have defined ERK1/2 signaling as a downstream pathway of PDGF signaling during embryonic erythropoiesis. Taken together, our findings indicate that PDGF signaling derived from sclerotome functions as a niche cue for primitive erythropoiesis.

Not all LGL leukemias are created equal

Large Granular Lymphocyte (LGL) Leukemia is a rare, heterogeneous even more that once thought, chronic lymphoproliferative disorder characterized by the clonal expansion of T- or NK-LGLs that requires appropriate immunophenotypic and molecular characterization. As in many other hematological conditions, genomic features are taking research efforts one step further and are also becoming instrumental in refining discrete subsets of LGL disorders. In particular, STAT3 and STAT5B mutations may be harbored in leukemic cells and their presence has been linked to diagnosis of LGL disorders. On clinical grounds, a correlation has been established in CD8+ T-LGLL patients between STAT3 mutations and clinical features, in particular neutropenia that favors the onset of severe infections. Revisiting biological aspects, clinical features as well as current and predictable emerging treatments of these disorders, we will herein discuss why appropriate dissection of different disease variants is needed to better manage patients with LGL disorders.

Large granular lymphocyte leukemia: An indolent clonal proliferative disease associated with an array of various immunologic disorders

Large granular lymphocyte leukemia (LGLL) is a chronic lymphoproliferative disorder characterized by the proliferation of T or NK cytotoxic cells in the peripheral blood, the spleen and the bone marrow. Neutropenia leading to recurrent infections represents the main manifestation of LGLL. One specificity of LGLL is its frequent association with auto-immune disorders, among them first and foremost rheumatoid arthritis, and other hematologic diseases, including pure red cell aplasia and bone marrow failure. The large spectrum of manifestations and the classical indolent course contribute to the diagnosis difficulties and the frequency of underdiagnosed cases. Of importance, the dysimmune manifestations disappear with the treatment of LGLL as the blood cell counts normalize, giving a strong argument for a pathological link between the two entities. The therapeutic challenge results from the high rate of relapses following the first line of immunosuppressive drugs. New targeted agents, some of which are currently approved in autoimmune diseases, appear to be relevant therapeutic strategies to treat LGLL, by targeting key activated pathways involved in the pathogenesis of the disease, including JAK-STAT signaling.

Genomic landscape of TCRαβ and TCRγδ T-large granular lymphocyte leukemia

Large granular lymphocyte (LGL) leukemia comprises a group of rare lymphoproliferative disorders whose molecular landscape is incompletely defined. We leveraged paired whole-exome and transcriptome sequencing in the largest LGL leukemia cohort to date, which included 105 patients (93 T-cell receptor αβ [TCRαβ] T-LGL and 12 TCRγδ T-LGL). Seventy-six mutations were observed in 3 or more patients in the cohort, and out of those, STAT3, KMT2D, PIK3R1, TTN, EYS, and SULF1 mutations were shared between both subtypes. We identified ARHGAP25, ABCC9, PCDHA11, SULF1, SLC6A15, DDX59, DNMT3A, FAS, KDM6A, KMT2D, PIK3R1, STAT3, STAT5B, TET2, and TNFAIP3 as recurrently mutated putative drivers using an unbiased driver analysis approach leveraging our whole-exome cohort. Hotspot mutations in STAT3, PIK3R1, and FAS were detected, whereas truncating mutations in epigenetic modifying enzymes such as KMT2D and TET2 were observed. Moreover, STAT3 mutations co-occurred with mutations in chromatin and epigenetic modifying genes, especially KMT2D and SETD1B (P < .01 and P < .05, respectively). STAT3 was mutated in 50.5% of the patients. Most common Y640F STAT3 mutation was associated with lower absolute neutrophil count values, and N647I mutation was associated with lower hemoglobin values. Somatic activating mutations (Q160P, D170Y, L287F) in the STAT3 coiled-coil domain were characterized. STAT3-mutant patients exhibited increased mutational burden and enrichment of a mutational signature associated with increased spontaneous deamination of 5-methylcytosine. Finally, gene expression analysis revealed enrichment of interferon-γ signaling and decreased phosphatidylinositol 3-kinase-Akt signaling for STAT3-mutant patients. These findings highlight the clinical and molecular heterogeneity of this rare disorder.

Cytokines in the Pathogenesis of Large Granular Lymphocytic Leukemia

Large granular lymphocytic leukemia (LGLL) is a lymphoproliferative disorder of older adults characterized by the clonal expansion of cytotoxic T/natural killer cells due to constitutive pro-survival signaling. In recent years, it has become clear that cytokines and their receptors are aberrantly expressed in LGLL cells. The exact initiation process of LGLL is unknown, although several cytokine-driven mechanisms have emerged. Elevated levels of several cytokines, including interleukin-15 (IL-15) and platelet-derived growth factor (PDGF), have been described in LGLL patients. Evidence from humans and animal models has shown that cytokines may also contribute to the co-occurrence of a wide range of autoimmune diseases seen in patients with LGLL. The goal of this review is to provide a comprehensive analysis of the link between cytokines and pro-survival signaling in LGLL and to discuss the various strategies and research approaches that are being utilized to study this link. This review will also highlight the importance of cytokine-targeted therapeutics in the treatment of LGLL.

Toward a Better Classification System for NK-LGL Disorders

Large granular lymphocytic leukemia is a rare lymphoproliferative disorder characterized by a clonal expansion of T-lineage lymphocyte or natural killer (NK) cells in 85 and 15% of cases respectively. T and NK large granular leukemia share common pathophysiology, clinical and biological presentation. The disease is characterized by cytopenia and a frequent association with autoimmune manifestations. Despite an indolent course allowing a watch and wait attitude in the majority of patients at diagnosis, two third of the patient will eventually need a treatment during the course of the disease. Unlike T lymphocyte, NK cells do not express T cell receptor making the proof of clonality difficult. Indeed, the distinction between clonal and reactive NK-cell expansion observed in several situations such as autoimmune diseases and viral infections is challenging. Advances in our understanding of the pathogenesis with the recent identification of recurrent mutations provide new tools to prove the clonality. In this review, we will discuss the pathophysiology of NK large granular leukemia, the recent advances in the diagnosis and therapeutic strategies.

Large granular lymphocytic leukemia: a brief review

LGL leukemia is a rare chronic lymphoproliferative disorder of cytotoxic lymphocytes which can be immunophenotypically either T cell or NK cell-derived. According to the World Health Organization classification, it can be divided into three subtypes: chronic T-cell leukemia and chronic natural killer cell lymphocytosis, and aggressive natural killer cell LGL leukemia. Clonal proliferation of large granular lymphocytes can be because of stimulation of various molecular pathways namely JAK-STAT3 pathway, FAS/FAS-L pathway, RAS-RAF-1-MEK1-ERK pathway, PI3K/AKT pathway, NF-KB pathway, and Sphingolipid Rheostat pathways. The most common clinical features presenting with this leukemia are neutropenia, anemia, thrombocytopenia. This leukemia is also associated with various autoimmune conditions. It usually has an indolent course except for the aggressive NK cell LGL leukemia. The cause of death in the indolent cases was mostly due to infectious complications related to the neutropenia associated with the disease. The rarity of the disease coupled with the availability of only a handful of clinical trials has been a hindrance to the development of a specific treatment. Most of the cases are managed with immunomodulators. The advances in the knowledge of molecular pathways associated with the disease have brought few targeted therapies into the limelight. We discuss here the evolution, epidemiology, demographic profile, pathophysiology, differential diagnosis, the available treatment options along with the survival and prognostic variables which may help us in better understanding and better management of the disease and hopefully, paving the way for a targeted clinical approach.

Case Report: Endocapillary Glomerulopathy Associated With Large Granular T Lymphocyte Leukemia

Large granular T lymphocyte leukemia (T-LGLL) is a rare indolent lymphocyte leukemia. The clonal proliferation of T cells, which is related to STAT3 gene mutation and abnormal Fas-mediated apoptosis pathway after cell activation, plays a major role in disease progression. Some studies have found that the exogenous and continuous stimulation of endogenous antigens, such as virus infection, is related to the pathogenesis of T-LGLL. The renal pathological manifestations of T-LGLL have rarely been described. In this study, we report a case of T-LGLL with kidney involvement as proteinuria, acute kidney injury, with the appearance of circulating T-LGL infiltrating intra-glomerular capillaries, and endocapillary glomerulopathy. We also summarize reported cases of renal injury associated with LGLL.

PDGF-D-PDGFRβ signaling enhances IL-15-mediated human natural killer cell survival

Natural killer (NK) cells belong to a critical innate arm of host immunity against viral infection and malignancies. However, limited expansion and persistence of NK cells in vivo remain major challenges for NK cell-based therapy. Here, we show that platelet-derived growth factor (PDGF)-D−PDGF receptor-beta signaling—a potent stimulator of cell growth and motility—activates NK cells in an autocrine manner and contributes to interleukin-15–mediated NK cell survival but not effector functions, the latter of which were previously shown to depend on the binding of PDGF-D to the NKp44 receptor. Therefore, selectively introducing PDGF signaling into NK cells should benefit NK cell expansion and persistence and/or enhance effector function in NK cell-based immunotherapies.

The axis of platelet-derived growth factor (PDGF) and PDGF receptor-beta (PDGFRβ) plays prominent roles in cell growth and motility. In addition, PDGF-D enhances human natural killer (NK) cell effector functions when binding to the NKp44 receptor. Here, we report an additional but previously unknown role of PDGF-D, whereby it mediates interleukin-15 (IL-15)–induced human NK cell survival but not effector functions via its binding to PDGFRβ but independent of its binding to NKp44. Resting NK cells express no PDGFRβ and only a low level of PDGF-D, but both are significantly up-regulated by IL-15, via the nuclear factor κB signaling pathway, to promote cell survival in an autocrine manner. Both ectopic and IL-15–induced expression of PDGFRβ improves NK cell survival in response to treatment with PDGF-D. Our results suggest that the PDGF-D−PDGFRβ signaling pathway is a mechanism by which IL-15 selectively regulates the survival of human NK cells without modulating their effector functions.

Angiogenic factors could help us to define patients obtaining complete response with undetectable minimal residual disease in untreated CLL patients treated by FCR: results from the CLL2010FMP, a FILO study

Angiogenesis is in a constant balance between pro and anti-angiogenic factors. Neoangiogenesis, implicated in metastatic spreading is characterized in solid cancers, but fairly new in chronic lymphocytic leukemia (CLL). We hypothesize that secretion of angiogenic factors could be correlated to the pathogenesis of CLL, and therefore predict the outcome of patients. We investigated concentrations of 22 cytokines and chemokines in 137 non-del 17p B-CLL patients, treated with a fludarabine-cyclophosphamide-rituximab (FCR)-based regimen. We constructed a biomarker index defining different risk groups based on lymphocyte count, the intensity of CD20 antigen on CD19⁺ cells, Ang-2, and PDGF-BB plasma concentrations at diagnosis. Four groups were defined, exhibiting specific molecular signatures and correlated with progression-free survival of patients. Our results suggest that we can determine at diagnosis of non-del 17p B-CLL patients, those with a very high probability of progression-free survival, independently of IGVH mutational status and residual disease at the end of treatment.

Immunological effects of cerebral palsy and rehabilitation exercises in children

Cerebral palsy (CP) is a group of motor disorders caused by non-progressive lesions of the premature brain with lifelong pathophysiological consequences that include dysregulation of innate immunity. Persistent inflammation with increased levels of circulating pro-inflammatory tumor necrosis factor alpha (TNF-a) is negatively associated with rehabilitation outcome in children with CP. Because of the crosstalk between innate and adaptive immunity, we investigated the effect of CP and rehabilitation exercises on the adaptive immune system in children with CP by measuring the levels of CD3⁺, CD4⁺, CD8⁺ Т-cells, and CD22⁺ B-cells and the levels of immunoglobulins. Children with CP had higher levels of CD3⁺, CD4⁺, CD8⁺ Т-cells, and CD22⁺ B-cells compared to healthy children, and the rehabilitation exercise programs produced better outcomes in terms of increased gains in motor function at an earlier age. Rehabilitation exercises performed over a month resulted in significantly decreased levels of IgA in serum and reduced numbers of B-lymphocytes and reduced IgM levels. Our study suggests that rehabilitation programs with a focus on neuroplasticity and physical exercises in children with CP can reduce both cellular and humoral immune responses.

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Children with CP demonstrate increased levels of T and B cells.

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Rehabilitation exercises helped balance immune responses.

Neutropenia and Large Granular Lymphocyte Leukemia: From Pathogenesis to Therapeutic Options

Large granular lymphocyte leukemia (LGLL) is a rare lymphoproliferative disorder characterized by the clonal expansion of cytotoxic T-LGL or NK cells. Chronic isolated neutropenia represents the clinical hallmark of the disease, being present in up to 80% of cases. New advances were made in the biological characterization of neutropenia in these patients, in particular STAT3 mutations and a discrete immunophenotype are now recognized as relevant features. Nevertheless, the etiology of LGLL-related neutropenia is not completely elucidated and several mechanisms, including humoral abnormalities, bone marrow infiltration/substitution and cell-mediated cytotoxicity might cooperate to its pathogenesis. As a consequence of the multifactorial nature of LGLL-related neutropenia, a targeted therapeutic approach for neutropenic patients has not been developed yet; moreover, specific guidelines based on prospective trials are still lacking, thus making the treatment of this disorder a complex and challenging task. Immunosuppressive therapy represents the current, although poorly effective, therapeutic strategy. The recent identification of a STAT3-mediated miR-146b down-regulation in neutropenic T-LGLL patients emphasized the pathogenetic role of STAT3 activation in neutropenia development. Accordingly, JAK/STAT3 axis inhibition and miR-146b restoration might represent tempting strategies and should be prospectively evaluated for the treatment of neutropenic LGLL patients.

Large Granular Lymphocytic Leukemia: From Immunopathogenesis to Treatment of Refractory Disease

Large Granular Lymphocyte Leukemia (LGLL) is a rare, chronic lymphoproliferative disorder of effector cytotoxic T-cells, and less frequently, natural killer (NK) cells. The disease is characterized by an indolent and often asymptomatic course. However, in roughly 50% of cases, treatment is required due to severe transfusion-dependent anemia, severe neutropenia, or moderate neutropenia with associated recurrent infections. LGLL represents an interesting disease process at the intersection of a physiological immune response, autoimmune disorder, and malignant (clonal) proliferation, resulting from the aberrant activation of cellular pathways promoting survival, proliferation, and evasion of apoptotic signaling. LGLL treatment primarily consists of immunosuppressive agents (methotrexate, cyclosporine, and cyclophosphamide), with a cumulative response rate of about 60% based on longitudinal expertise and retrospective studies. However, refractory cases can result in clinical scenarios characterized by transfusion-dependent anemia and severe neutropenia, which warrant further exploration of other potential targeted treatment modalities. Here, we summarize the current understanding of the immune-genomic profiles of LGLL, its pathogenesis, and current treatment options, and discuss potential novel therapeutic agents, particularly for refractory disease.

Immunologic effects on the haematopoietic stem cell in marrow failure

Acquired bone marrow failure (BMF) syndromes comprise a diverse group of diseases with variable clinical manifestations but overlapping features of immune activation, resulting in haematopoietic stem and progenitor cells (HSPC) damage and destruction. This review focuses on clinical presentation, pathophysiology, and treatment of four BMF: acquired aplastic anaemia, large granular lymphocytic leukaemia, paroxysmal nocturnal haemoglobinuria, and hypoplastic myelodysplastic syndrome. Autoantigens are speculated to be the inciting event that result in immune activation in all of these diseases, but specific pathogenic antigens have not been identified. Oligoclonal cytotoxic T cell expansion and an active role of proinflammatory cytokines, primarily interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α), are two main contributors to HSPC growth inhibition and apoptosis in BMF. Emerging evidence also suggests involvement of the innate immune system.

Doppler-based predictive model for methotrexate resistance in low-risk gestational trophoblastic neoplasia with myometrial invasion: prospective study of 147 patients

OBJECTIVES

This prospective clinical study aimed to evaluate the vascularization characteristics of low-risk gestational trophoblastic neoplasia (GTN) using Doppler imaging and to develop a predictive model for resistance to methotrexate (MTX).

METHODS

Patients with low-risk GTN receiving primary MTX treatment were enrolled from the Women's Hospital, Zhejiang University School of Medicine, Hangzhou, China, from September 2012 to August 2018. The primary endpoint was to develop and internally validate a predictive model for resistance to MTX therapy in these patients. In the training set, clinical features and Doppler hemodynamic parameters before MTX therapy were analyzed using logistic regression to identify independent predictors of MTX resistance, which were integrated into the model. The predictive performance of the model was evaluated by leave-one-out cross-validation in the training dataset and internal validation in an independent-sample test dataset.

RESULTS

The entire imaging protocol was completed by 147 eligible patients, of which 110 comprised the training set and 37 the test set. In the training set, cases with myometrial invasion (81.8%; 90/110) showed vascular-enriched areas in the myometrium and high velocity and low impedance ratios of the uterine artery (UtA) compared to cases without myometrial invasion (18.2%; 20/110). On multivariate logistic regression analysis, time-averaged mean velocity in UtA (UtA-TAmean) and the International Federation of Gynecology and Obstetrics (FIGO) score were identified as independent predictors (P = 0.009 and P = 0.043, respectively) of MTX resistance. The Doppler-based predictive model, developed based on the 90 cases with myometrial invasion, was y = -2.95332 + 0.41696 × FIGO score + 0.03551 × UtA-TAmean. The model showed an area under the curve of 0.757 (95% CI, 0.653-0.862) and the optimal cut-off value was 0.50622, which had 45.2% sensitivity and 96.6% specificity. The model stratified patients with low-risk GTN into low (< 10%), intermediate (10-90%) and high (> 90%) probability of MTX resistance, based on the threshold values of -1.59544 and 0.10046. The model had an accuracy of 74.4% (95% CI, 64.5-82.3%) in the cross-validation and 72.7% (95% CI, 55.8-84.9%) in the internal validation.

CONCLUSIONS

The Doppler-based predictive model, combining a non-invasive marker of tumor vascularity with the FIGO scoring system, can differentiate cases with low from those with high probability of developing MTX resistance and therefore has the potential to guide treatment options in patients with low-risk GTN and myometrial invasion. © 2020 Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Reversible switching of leukemic cells to a drug-resistant, stem-like subset via IL-4 mediated cross-talk with mesenchymal stroma

Chemoresistance of leukemic cells has largely been attributed to clonal evolution secondary to accumulating mutations. Here, we show that a subset of leukemic blasts in contact with the mesenchymal stroma undergo cellular conversion into a distinct cell type that exhibits a stem cell-like phenotype and chemoresistance. These stroma-induced changes occur in a reversible and stochastic manner driven by cross-talk, whereby stromal contact induces interleukin-4 in leukemic cells that in turn targets the mesenchymal stroma to facilitate the development of new subset. This mechanism was dependent on interleukin-4-mediated upregulation of vascular cell adhesion molecule- 1 in mesenchymal stroma, causing tight adherence of leukemic cells to mesenchymal progenitors for generation of new subsets. Together, our study reveals another class of chemoresistance in leukemic blasts via functional evolution through stromal cross-talk, and demonstrates dynamic switching of leukemic cell fates that could cause a non-homologous response to chemotherapy in concert with the patient-specific microenvironment.

Secretome studies of mesenchymal stromal cells (MSCs) isolated from three tissue sources reveal subtle differences in potency

Human mesenchymal stromal cells (MSCs) are currently the leading candidate for cell-based therapeutics. While the use of MSCs in transplantation therapies is widely expanding, still, there is a lot of scope for better understanding of the mechanisms underlying their effects. We have generated MSCs from pre- and post-natal human tissue sources such as Wharton's jelly (WJ), stem cells from human exfoliated deciduous teeth (SHED), and bone marrow (BM). We then expanded, banked, and characterized them based on morphology, growth kinetics, senescence, immunophenotype, gene expression, and secretion of growth factors. Although the immunophenotype was very similar across MSCs from the three types of donor tissues, they showed minor variations in their growth kinetics. Further, a higher percentage of senescent cells were observed in BM-MSCs than in WJ-MSCs and SHED. Gene expression analysis showed the increased expression of INF-γ, PDGFA, VEGF, IL10, and SDF in SHED over WJ-MSC and BM-MSC. Comparative secretome profiling by ELISA demonstrated the presence of FGF-2, IL-10, PDGF, SDF-1, Ang-1, TGF-β3, HGF, INF-γ, VEGF, and IL-6 in cell culture supernatants. Based on our findings, WJ-MSC and SHED appear more potent than BM-MSC for managing inflammation, immunomodulation, angiogenesis, fibrosis, and scarring. Due to widespread application of MSCs in cell replacement therapy, these subtle differences need to be taken into consideration while designing stem cell-based clinical trials.

Advances in the Diagnosis and Treatment of Large Granular Lymphocytic Leukemia

PURPOSE OF REVIEW

The past decade in LGL leukemia research has seen increased pairing of clinical data with molecular markers, shedding new insights on LGL leukemia pathogenesis and heterogeneity. This review summarizes the current standard of care of LGL leukemia, updates from clinical trials, and our congruent improved understanding of LGL pathogenesis.

RECENT FINDINGS

Various clinical reports have identified associations between stem, bone marrow, and solid organ transplants and incidence of LGL leukemia. There is also a potential for underdiagnosis of LGL leukemia within the rheumatoid arthritis patient population, emphasizing our need for continued study. Preliminary results from the BNZ-1 clinical trial, which targets IL-15 along with IL-2 and IL-9 signaling pathways, show some evidence of clinical response. With advances in our understanding of LGL pathogenesis from both the bench and the clinic, exciting avenues for investigations lie ahead for LGL leukemia.

Pharmacokinetics of Dasatinib

Tyrosine kinase inhibitors have recently become an essential tool in management of chronic myeloid leukaemia (CML). Dasatinib, a representative of those drugs, acts by inhibiting key proteins included in CML development, predominantly Bcr-Abl and Src. Its advantage is that it shows activity in many cases where other agents bring no improvement due to resistance. Pharmacokinetics of dasatinib has specific characteristics that may play an important role in achieving sufficient exposure in patients. Therefore, the key pharmacokinetic properties are summarized in this report. For example, dasatinib absorption is significantly influenced by gastric pH and its modulation can be a source of serious interactions, as well as simultaneous administration of drugs affecting cytochrome P450.

Deregulated expression of NKL homeobox genes in T-cell lymphomas

Recently, we have presented a scheme, termed "NKL-code", which describes physiological expression patterns of NKL homeobox genes in early hematopoiesis and in lymphopoiesis including main stages of T-, B- and NK-cell development. Aberrant activity of these genes underlies the generation of hematological malignancies notably T-cell leukemia. Here, we searched for deregulated NKL homeobox genes in main entities of T-cell lymphomas comprising angioimmunoblastic T-cell lymphoma (AITL), anaplastic large cell lymphoma (ALCL), adult T-cell leukemia/lymphoma (ATLL), hepatosplenic T-cell lymphoma (HSTL), NK/T-cell lymphoma (NKTL) and peripheral T-cell lymphoma (PTCL). Our data revealed altogether 19 aberrantly overexpressed genes in these types, demonstrating deregulated NKL homeobox genes involvement in T-cell lymphomas as well. For detailed analysis we focused on NKL homeobox gene MSX1 which is normally expressed in NK-cells. MSX1 was overexpressed in subsets of HSTL patients and HSTL-derived sister cell lines DERL-2 and DERL-7 which served as models to characterize mechanisms of deregulation. We performed karyotyping, genomic and expression profiling, and whole genome sequencing to reveal mutated and deregulated gene candidates, including the fusion gene CD53-PDGFRB. Subsequent knockdown experiments allowed the reconstruction of an aberrant network involved in MSX1 deregulation, including chromatin factors AUTS2 and mutated histone HIST1H3B(K27M). The gene encoding AUTS2 is located at chromosome 7q11 and may represent a basic target of the HSTL hallmark aberration i(7q). Taken together, our findings highlight an oncogenic role for deregulated NKL homeobox genes in T-cell lymphoma and identify MSX1 as a novel player in HSTL, implicated in aberrant NK- and T-cell differentiation.

TRAIL mediates and sustains constitutive NF-κB activation in LGL leukemia

Large granular lymphocyte (LGL) leukemia results from clonal expansion of CD3⁺ cytotoxic T lymphocytes or CD3^- natural killer (NK) cells. Chronic antigen stimulation is postulated to promote long-term survival of LGL leukemia cells through constitutive activation of multiple survival pathways, resulting in global dysregulation of apoptosis and resistance to activation-induced cell death. We reported previously that nuclear factor κB (NF-κB) is a central regulator of the survival network for leukemic LGL. However, the mechanisms that trigger constitutive activation of NF-κB in LGL leukemia remain undefined. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is known to induce apoptosis in tumor cells but can also activate NF-κB through interaction with TRAIL receptors 1, 2, and 4 (also known as DR4, DR5, and DcR2, respectively). The role of TRAIL has not been studied in LGL leukemia. In this study, we hypothesized that TRAIL interaction with DcR2 contributes to NF-κB activation in LGL leukemia. We observed upregulated TRAIL messenger RNA and protein expression in LGL leukemia cells with elevated levels of soluble TRAIL protein in LGL leukemia patient sera. We also found that DcR2 is the predominant TRAIL receptor in LGL leukemia cells. We demonstrated that TRAIL-induced activation of DcR2 led to increased NF-κB activation in leukemic LGL. Conversely, interruption of TRAIL-DcR2 signaling led to decreased NF-κB activation. Finally, a potential therapeutic application of proteasome inhibitors (bortezomib and ixazomib), which are known to inhibit NF-κB, was identified through their ability to decrease proliferation and increase apoptosis in LGL leukemia cell lines and primary patient cells.

Involvement of platelet-derived growth factor ligands and receptors in tumorigenesis

Platelet-derived growth factor (PDGF) isoforms and their receptors have important roles during embryogenesis, particularly in the development of various mesenchymal cell types in different organs. In the adult, PDGF stimulates wound healing and regulates tissue homeostasis. However, overactivity of PDGF signalling is associated with malignancies and other diseases characterized by excessive cell proliferation, such as fibrotic conditions and atherosclerosis. In certain tumours, genetic or epigenetic alterations of the genes for PDGF ligands and receptors drive tumour cell proliferation and survival. Examples include the rare skin tumour dermatofibrosarcoma protuberance, which is driven by autocrine PDGF stimulation due to translocation of a PDGF gene, and certain gastrointestinal stromal tumours and leukaemias, which are driven by constitute activation of PDGF receptors due to point mutations and formation of fusion proteins of the receptors, respectively. Moreover, PDGF stimulates cells in tumour stroma and promotes angiogenesis as well as the development of cancer-associated fibroblasts, both of which promote tumour progression. Inhibitors of PDGF signalling may thus be of clinical usefulness in the treatment of certain tumours.

Chronic neutropenia in LGL leukemia and rheumatoid arthritis

This section reviews the diagnostic criteria and pathogenesis of large granular lymphocyte (LGL) leukemia. There is a particular focus on the overlap of LGL leukemia and rheumatoid arthritis (Felty's syndrome). Current understanding of the mechanisms of neutropenia in these disorders is discussed. Finally, treatment indications and therapeutic recommendations are outlined.

PDGF-C and PDGF-D in ocular diseases

PDGFs and their receptors are critical regulators of numerous tissues and organs, including the eye. Extensive studies have shown that PDGFs and their receptors play critical roles in many ocular neovascular diseases, such as neovascular age-related macular degeneration, retinopathy of prematurity, and proliferative vitreoretinopathy. In addition, PDGFs and PDGFRs are also important players in ocular diseases involving the degeneration of retinal neuronal and vascular cells, such as glaucoma and retinitis pigmentosa. Due to their critical roles in the pathogenesis of many blinding ocular diseases, the PDGFs and PDGFRs have been considered as important target molecules for the treatment of eye diseases. PDGF-C and PDGF-D are relatively new members of the PDGF family and are potent angiogenic and survival factors. Recent studies have demonstrated their important roles in different types of eye diseases. Thus, modulating PDGF-C and PDGF-D activities may have therapeutic values for the treatment of ocular neovascular and degenerative diseases. This review mainly summarizes the recent advances on PDGF-C and PDGF-D biology in relationship to some major ocular diseases.

STAT3 mediates C6-ceramide-induced cell death in chronic lymphocytic leukemia

The pathogenesis of chronic lymphocytic leukemia (CLL) is poorly understood and it remains incurable with current therapies. We have previously shown that nanoliposomal C6-ceramide (CNL) is an effective therapy in an in vivo murine model of CLL. However, the key signaling pathways mediating CNL-induced cell death in CLL remains unknown. We hypothesized that CNL targets STAT3, a critical regulator of hematopoietic biology. We observed that CNL treatment reduced phosphorylated STAT3 at both Y705 and S727 residues in CLL cell lines and patient cells. This, in turn, reduced STAT3 transcriptional activity and expression of critical STAT3-dependent survival factors like Mcl-1 and survivin. The effect of CNL on STAT3 was further confirmed ex vivo as shown by reduced STAT3 phosphorylation in xenograft tumors obtained from mice treated with CNL. CNL suppressed STAT3 phosphorylation at Y705 and S727 through reduction in BTK activity and MEK1/2 kinase/PKC activities, respectively. Moreover, a synergistic reduction in CLL cell viability was observed on co-treatment with CNL and the BTK inhibitor, ibrutinib. Expression of an oncogenic form of STAT3 conferred partial resistance to CNL, providing confirmation that STAT3 mediates CNL-induced cell death. Taken together, these findings provide the first body of evidence demonstrating ceramide regulation of STAT3 phosphorylation. These results are also the first to demonstrate an effect of ceramide on BTK, a critical kinase mediating the B-cell receptor signaling in CLL cells and suggest a novel and synergistic combination of CNL and BTK inhibitors for CLL treatment.

LGL leukemia: from pathogenesis to treatment

Large granular lymphocyte (LGL) leukemia has been recognized by the World Health Organization classifications amongst mature T-cell and natural killer (NK) cell neoplasms. There are 3 categories: chronic T-cell leukemia and NK-cell lymphocytosis, which are similarly indolent diseases characterized by cytopenias and autoimmune conditions as opposed to aggressive NK-cell LGL leukemia. Clonal LGL expansion arise from chronic antigenic stimulation, which promotes dysregulation of apoptosis, mainly due to constitutive activation of survival pathways including Jak/Stat, MapK, phosphatidylinositol 3-kinase-Akt, Ras-Raf-1, MEK1/extracellular signal-regulated kinase, sphingolipid, and nuclear factor-κB. Socs3 downregulation may also contribute to Stat3 activation. Interleukin 15 plays a key role in activation of leukemic LGL. Several somatic mutations including Stat3, Stat5b, and tumor necrosis factor alpha-induced protein 3 have been demonstrated recently in LGL leukemia. Because these mutations are present in less than half of the patients, they cannot completely explain LGL leukemogenesis. A better mechanistic understanding of leukemic LGL survival will allow future consideration of a more targeted therapeutic approach than the current practice of immunosuppressive therapy.

Cell fate reprogramming by control of intracellular network dynamics

Identifying control strategies for biological networks is paramount for practical applications that involve reprogramming a cell’s fate, such as disease therapeutics and stem cell reprogramming. Here we develop a novel network control framework that integrates the structural and functional information available for intracellular networks to predict control targets. Formulated in a logical dynamic scheme, our approach drives any initial state to the target state with 100% effectiveness and needs to be applied only transiently for the network to reach and stay in the desired state. We illustrate our method’s potential to find intervention targets for cancer treatment and cell differentiation by applying it to a leukemia signaling network and to the network controlling the differentiation of helper T cells. We find that the predicted control targets are effective in a broad dynamic framework. Moreover, several of the predicted interventions are supported by experiments.

Practical applications in modern molecular and systems biology such as the search for new therapeutic targets for diseases and stem cell reprogramming have generated a great interest in controlling the internal dynamics of a cell. Here we present a network control approach that integrates the structural and functional information of the network. We show that stabilizing the expression or activity of a few select components can drive the cell towards a desired fate or away from an undesired fate. We demonstrate our method’s effectiveness by applying it to a type of blood cell cancer and to the differentiation of a type of immune cell. Overall, our approach provides new insights into how to control the dynamics of intracellular networks.

Src family kinases and their role in hematological malignancies

The Src family protein tyrosine kinases (SFKs) are non-receptor intracellular kinases that have important roles in both hematopoiesis and leukemogenesis. The derangement of their expression or activation has been demonstrated to contribute to hematological malignancies. This review first examines the mechanisms of SFK overexpression and hyperactivation, emphasizing the dysregulation of the upstream modulators. Subsequently, the role of SFK up-regulation in the initiation, progression and therapy resistance of many hematological malignancies is also analyzed. The presented evidence endeavors to highlight the influence of SFK up-regulation on an extensive number of hematological malignancies and the need to consider them as candidates in targeted anticancer therapy.

Treating rare lymphoproliferative malignancies: a focus on indolent large granular lymphocytic leukemia

SUMMARY 

Large granular lymphocyte leukemia is a heterogeneous group of lymphoproliferative disorders that arises from mature T cells or NK cells. These disorders are relatively uncommon and usually present with cytopenias and/or autoimmune disorders. As patients often do not have symptoms warranting therapy upfront, surveillance is often employed. Common frontline therapies include cyclosphosphamide, methotrexate or cyclosporine A, however, no controlled trials or retrospective analyses have demonstrated one superior therapeutic strategy. Mechanisms of pathogenesis and survival have been identified that include abnormalities in the cell surface receptors halting apoptotic signals, dysregulation of prosurvival and apoptotic signaling pathways, and somatic mutations of the STAT3 and STAT5b genes, among others. Investigating novel therapies that target pathways shared by other neoplastic processes, as well as the identification of new agents directed toward the aberrant cellular mechanisms of large granular lymphocyte leukemia, are fundamental to moving from empiric chemotherapy to targeted therapies in the future.

Advances in diagnosis and treatment of large granular lymphocyte syndrome

PURPOSE OF REVIEW

Large granular lymphocyte (LGL) syndrome comprises a clonal spectrum of T-cell and natural killer (NK)-cell LGL lymphoproliferative disorders associated with neutropenia. This review presents advances in diagnosis and therapy of LGL syndrome.

RECENT FINDINGS

Due to the lack of a single unique genetic or phenotypic feature and clinicopathological overlap between reactive and neoplastic entities, accurate LGL syndrome diagnosis should be based on the combination of morphologic, immunophenotypic, and molecular studies as well as clinical features. For diagnosis and monitoring of LGL proliferations, it is essential to perform flow cytometric blood and/or bone marrow analysis using a panel of monoclonal antibodies to conventional and novel T-cell and NK-cell antigens such as NK-cell receptors and T-cell receptor β-chain variable region families together with TCR gene rearrangement studies. Treatment of symptomatic cytopenias in patients with indolent LGL leukemia is still based on immunosuppressive therapy. Treatment with purine analogs and alemtuzumab may be considered as an alternative option.

SUMMARY

Progress in understanding the pathogenetic mechanisms of these entities, especially resistance of clonal LGLs to apoptosis, due to constitutive activation of survival signaling pathways, has its impact on identification of potential molecular therapeutic targets.

Immunosuppressive therapy of LGL leukemia: prospective multicenter phase II study by the Eastern Cooperative Oncology Group (E5998)

Failure to undergo activation-induced cell death due to global dysregulation of apoptosis is the pathogenic hallmark of large granular lymphocyte (LGL) leukemia. Consequently, immunosuppressive agents are rational choices for treatment. This first prospective trial in LGL leukemia was a multicenter, phase 2 clinical trial evaluating methotrexate (MTX) at 10 mg/m(2) orally weekly as initial therapy (step 1). Patients failing MTX were eligible for treatment with cyclophosphamide at 100 mg orally daily (step 2). The overall response in step 1 was 38% with 95% confidence interval (CI): 26 and 53%. The overall response in step 2 was 64% with 95% CI: 35 and 87%. The median overall survival for patients with anemia was 69 months with a 95% CI lower bound of 46 months and an upper bound not yet reached. The median overall survival for patients with neutropenia has not been reached 13 years from study activation. Serum biomarker studies confirmed the inflammatory milieu of LGL but were not a priori predictive of response. We identify a gene expression signature that correlates with response and may be STAT3 mutation driven. Immunosuppressive therapies have efficacy in LGL leukemia. Gene signature and mutational profiling may be an effective tool in determining whether MTX is an appropriate therapy.

Gallium-68-labeled affibody molecule for PET imaging of PDGFRβ expression in vivo

Platelet-derived growth factor receptor β (PDGFRβ) is a transmembrane tyrosine kinase receptor involved, for example, in angiogenesis. Overexpression and excessive signaling of PDGFRβ has been observed in multiple malignant tumors and fibrotic diseases, making this receptor a pharmaceutical target for monoclonal antibodies and tyrosine kinase inhibitors. Successful targeted therapy requires identification of responding patients. Radionuclide molecular imaging would enable determination of the PDGFRβ status in all lesions using a single noninvasive repeatable procedure. Recently, we have demonstrated that the affibody molecule Z09591 labeled with (111)In can specifically target PDGFRβ-expressing tumors in vivo. The use of positron emission tomography (PET) as an imaging technique would provide superior resolution, sensitivity, and quantitation accuracy. In this study, a DOTA-conjugated Z09591 was labeled with the generator-produced positron emitting radionuclide (68)Ga (T1/2 = 67.6 min, Eβ + max = 1899 keV, 89% β(+)). (68)Ga-DOTA-Z09591 retained the capacity to specifically bind to PDGFRβ-expressing U-87 MG glioma cells. The half-maximum inhibition concentration (IC50) of (68)Ga-DOTA-Z09591 (6.6 ± 1.4 nM) was somewhat higher than that of (111)In-DOTA-Z09591 (1.4 ± 1.2 nM). (68)Ga-DOTA-Z09591 demonstrated specific (saturable) targeting of U-87 MG xenografts in immunodeficient mice. The tumor uptake at 2 h after injection was 3.7 ± 1.7% IA/g, which provided a tumor-to-blood ratio of 8.0 ± 3.1. The only organ with higher accumulation of radioactivity was the kidney. MicroPET imaging provided high-contrast imaging of U-87 MG xenografts. In conclusion, the (68)Ga-labeled affibody molecule Z09591 is a promising candidate for further development as a probe for imaging PDGFRβ expression in vivo using PET.

Template-based intervention in Boolean network models of biological systems

MOTIVATION

A grand challenge in the modeling of biological systems is the identification of key variables which can act as targets for intervention. Boolean networks are among the simplest of models, yet they have been shown to adequately model many of the complex dynamics of biological systems. In our recent work, we utilized a logic minimization approach to identify quality single variable targets for intervention from the state space of a Boolean network. However, as the number of variables in a network increases, the more likely it is that a successful intervention strategy will require multiple variables. Thus, for larger networks, such an approach is required in order to identify more complex intervention strategies while working within the limited view of the network's state space. Specifically, we address three primary challenges for the large network arena: the first challenge is how to consider many subsets of variables, the second is to design clear methods and measures to identify the best targets for intervention in a systematic way, and the third is to work with an intractable state space through sampling.

RESULTS

We introduce a multiple variable intervention target called a template and show through simulation studies of random networks that these templates are able to identify top intervention targets in increasingly large Boolean networks. We first show that, when other methods show drastic loss in performance, template methods show no significant performance loss between fully explored and partially sampled Boolean state spaces. We also show that, when other methods show a complete inability to produce viable intervention targets in sampled Boolean state spaces, template methods maintain significantly consistent success rates even as state space sizes increase exponentially with larger networks. Finally, we show the utility of the template approach on a real-world Boolean network modeling T-LGL leukemia.

CONCLUSIONS

Overall, these results demonstrate how template-based approaches now effectively take over for our previous single variable approaches and produce quality intervention targets in larger networks requiring sampled state spaces.

The pathogenesis and treatment of large granular lymphocyte leukemia

Large granular lymphocyte (LGL) leukemia is a spectrum of rare lymphoproliferative diseases of T lymphocytes and natural killer cells. These diseases frequently present with splenomegaly, neutropenia, and autoimmune diseases like rheumatoid arthritis. LGL leukemia is more commonly of a chronic, indolent nature; however, rarely, they have an aggressive course. LGL leukemia is thought to arise from chronic antigen stimulation, which drives long-term cell survival through the activation of survival signaling pathways and suppression of pro-apoptotic signals. These include Jak-Stat, Mapk, Pi3k-Akt, sphingolipid, and IL-15/Pdgf signaling. Treatment traditionally includes immunosuppression with low dose methotrexate, cyclophosphamide, and other immunosuppressive agents; however, prospective and retrospective studies reveal very limited success. New studies surrounding Jak-Stat signaling suggest this may reveal new avenues for LGL leukemia therapeutics.

Mechanical stress-induced apoptosis of nucleus pulposus cells: an in vitro and in vivo rat model

BACKGROUND

Un-physiological loads play an important role in the degenerative process of inter-vertebral discs (IVD). In this study, we used an in vitro and in vivo rat model to investigate the mechanism of nucleus pulposus (NP) cells apoptosis induced by mechanical stress.

METHODS

Static compressive load to IVDs of rat tails was used as the in vivo model. For the in vitro model, NP cells were tested under the physiological and un-physiological loading. For histological examination, apoptotic index study, and apoptotic gene expression, we also selected cytokines [bone morphogenetic protein (BMP)-2/7, insulin-like growth factor (IGF)-1, platelet-derived growth factor (PDGF)] to be analyzed.

RESULTS

Under mechanical loading, cellular density was significantly decreased, but there was an increase of TUNEL positive cells and apoptosis index. In a dose-dependent manner; the necrosis became apparent in the un-physiologic strain. The selected cytokines (BMP-2/7, IGF-1, PDGF) can significantly reduce the percentage of apoptotic and necrotic cells.

CONCLUSIONS

We conclude that the intrinsic (mitochondrial) apoptotic pathway plays an important role in the compressive load-induced apoptosis of NP cells. Combination therapy reducing the mechanical load and selected cytokines (BMP-2/7, IGF-1 and PDGF) may have considerable promise in the treatment of spine disc degeneration.

Platelet-derived growth factor-C (PDGF-C) induces anti-apoptotic effects on macrophages through Akt and Bad phosphorylation

PDGF-C, which is abundant in the malignant breast tumor microenvironment, plays an important role in cell growth and survival. Because tumor-associated macrophages (TAMs) contribute to cancer malignancy, macrophage survival mechanisms are an attractive area of research into controlling tumor progression. In this study, we investigated PDGF-C-mediated signaling pathways involved in anti-apoptotic effects in macrophages. We found that the human malignant breast cancer cell line MDA-MB-231 produced high quantities of PDGF-C, whereas benign MCF-7 cells did not. Recombinant PDGF-C induced PDGF receptor α chain phosphorylation, followed by Akt and Bad phosphorylation in THP-1-derived macrophages. MDA-MB-231 culture supernatants also activated macrophage PDGF-Rα. PDGF-C prevented staurosporine-induced macrophage apoptosis by inhibiting the activation of caspase-3, -7, -8, and -9 and cleavage of poly(ADP-ribose) polymerase. Finally, TAMs isolated from the PDGF-C knockdown murine breast cancer cell line 4T1 and PDGF-C knockdown MDA-MB-231-derived tumor mass showed higher rates of apoptosis than the respective WT controls. Collectively, our results suggest that tumor cell-derived PDGF-C enhances TAM survival, promoting tumor malignancy.

Targeting the PDGF signaling pathway in tumor treatment

Platelet-derived growth factor (PDGF) isoforms and PDGF receptors have important functions in the regulation of growth and survival of certain cell types during embryonal development and e.g. tissue repair in the adult. Overactivity of PDGF receptor signaling, by overexpression or mutational events, may drive tumor cell growth. In addition, pericytes of the vasculature and fibroblasts and myofibroblasts of the stroma of solid tumors express PDGF receptors, and PDGF stimulation of such cells promotes tumorigenesis. Inhibition of PDGF receptor signaling has proven to useful for the treatment of patients with certain rare tumors. Whether treatment with PDGF/PDGF receptor antagonists will be beneficial for more common malignancies is the subject for ongoing studies.

C6-ceramide nanoliposomes target the Warburg effect in chronic lymphocytic leukemia

Ceramide is a sphingolipid metabolite that induces cancer cell death. When C6-ceramide is encapsulated in a nanoliposome bilayer formulation, cell death is selectively induced in tumor models. However, the mechanism underlying this selectivity is unknown. As most tumors exhibit a preferential switch to glycolysis, as described in the "Warburg effect", we hypothesize that ceramide nanoliposomes selectively target this glycolytic pathway in cancer. We utilize chronic lymphocytic leukemia (CLL) as a cancer model, which has an increased dependency on glycolysis. In CLL cells, we demonstrate that C6-ceramide nanoliposomes, but not control nanoliposomes, induce caspase 3/7-independent necrotic cell death. Nanoliposomal ceramide inhibits both the RNA and protein expression of GAPDH, an enzyme in the glycolytic pathway, which is overexpressed in CLL. To confirm that ceramide targets GAPDH, we demonstrate that downregulation of GAPDH potentiates the decrease in ATP after ceramide treatment and exogenous pyruvate treatment as well as GAPDH overexpression partially rescues ceramide-induced necrosis. Finally, an in vivo murine model of CLL shows that nanoliposomal C6-ceramide treatment elicits tumor regression, concomitant with GAPDH downregulation. We conclude that selective inhibition of the glycolytic pathway in CLL cells with nanoliposomal C6-ceramide could potentially be an effective therapy for leukemia by targeting the Warburg effect.

Characterization and identification of PARM-1 as a new potential oncogene

Background

The Graffi murine retrovirus is a powerful tool to find leukemia associated oncogenes. Using DNA microarrays, we recently identified several genes specifically deregulated in T- and B-leukemias induced by this virus.

Results

In the present study, probsets associated with T-CD8⁺ leukemias were analyzed and we validated the expression profile of the Parm-1 gene. PARM-1 is a member of the mucin family. We showed that human PARM-1 is an intact secreted protein accumulating predominantly, such as murine PARM-1, at the Golgi and in the early and late endosomes. PARM-1 colocalization with α-tubulin suggests that its trafficking within the cell involves the microtubule cytoskeleton. Also, the protein co-localizes with caveolin-1 which probably mediates its internalization. Transient transfection of both mouse and human Parm-1 cDNAs conferred anchorage- and serum-independent growth and enhanced cell proliferation. Moreover, deletion mutants of human PARM-1 without either extracellular or cytoplasmic portions seem to retain the ability to induce anchorage-independent growth of NIH/3T3 cells. In addition, PARM-1 increases ERK1/2, but more importantly AKT and STAT3 phosphorylation.

Conclusions

Our results strongly suggest the oncogenic potential of PARM-1.

Multifarious functions of PDGFs and PDGFRs in tumor growth and metastasis

Platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) are frequently expressed in various tumors and their expression levels correlate with tumor growth, invasiveness, drug resistance, and poor clinical outcomes. Emerging experimental evidence demonstrates that PDGFs exhibit multiple functions in modulation of tumor growth, metastasis, and the tumor microenvironment by targeting malignant cells, vascular cells, and stromal cells. Understanding PDGF-PDGFR-mediated molecular signaling may provide new mechanistic rationales for optimizing current cancer therapies and the development of future novel therapeutic modalities.

Increased expression of miR-221 is associated with shorter overall survival in T-cell acute lymphoid leukemia

Background

CD56 expression has been associated with a poor prognosis in lymphoid neoplasms, including T-cell acute lymphoblastic leukemia (T-ALL). MicroRNAs (miRNAs) play an important role in lymphoid differentiation, and aberrant miRNA expression has been associated with treatment outcome in lymphoid malignancies. Here, we evaluated miRNA expression profiles in normal thymocytes, mature T-cells, and T-ALL samples with and without CD56 expression and correlated microRNA expression with treatment outcome.

Methods

The gene expression profile of 164 miRNAs were compared for T-ALL/CD56⁺ (n=12) and T-ALL/CD56^- (n=36) patients by Real-Time Quantitative PCR. Based on this analysis, we decided to evaluate miR-221 and miR-374 expression in individual leukemic and normal samples.

Results

miR-221 and miR-374 were expressed at significantly higher levels in T-ALL/CD56⁺ than in T-ALL/CD56^- cells and in leukemic blasts compared with normal thymocytes and peripheral blood (PB) T-cells. Age at diagnosis (15 or less vs grater than 15 years; HR: 2.19, 95% CI: 0.98-4.85; P=0.05), miR-221 expression level (median value as cut off in leukemic samples; HR: 3.17, 95% CI: 1.45-6.92; P=0.004), and the expression of CD56 (CD56^-vs CD56⁺; HR: 2.99, 95% CI: 1.37-6.51; P=0.006) were predictive factors for shorter overall survival; whereas, only CD56 expression (HR: 2.73, 95% CI: 1.03-7.18; P=0.041) was associated with a shorter disease-free survival rate.

Conclusions

miR-221 is highly expressed in T-ALL and its expression level may be associated with a poorer prognosis.

Large granular lymphocyte leukemia: from dysregulated pathways to therapeutic targets

Large granular lymphocyte (LGL) leukemia is a clonal lymphoproliferative disorder of cytotoxic lymphocytes characterized by an expansion of CD3(+) cytotoxic T lymphocytes or CD3(-) natural killer cells. Patients present with various cytopenias including neutropenia, anemia and thrombocytopenia. In addition, there is an association of T-cell large granular lymphocytic leukemia with rheumatoid arthritis. It is believed that LGL leukemia begins as an antigen-driven immune response with subsequent constitutive activation of cytotoxic T lymphocytes or natural killer cells through PDGF and IL-15 contributing to their survival. Consequently, this leads to a dysregulation of apoptosis and dysfunction of the activation-induced cell death pathway. Treatment of LGL leukemia is based on a low-dose immunosuppressive regimen using methotrexate or cyclophosphamide. However, no standard of therapy has been established, as large prospective trials have not been conducted. In addition, some patients are refractory to treatment. The lack of a curative therapy for LGL leukemia means that new treatment options are needed. Insight into the various dysregulated signaling pathways in LGL leukemia may provide novel therapeutic treatment modalities.